;************************************************************************ ;** An assembly file listing to generate a 16K Rom for the ZX Spectrum ** ;************************************************************************ ; ; Copyright (c) Amstrad plc. All rights reserved. ; ; Acknowledgements ; ----------------- ; Sean Irvine for default list of section headings ; (author unknown). ; Dr. Ian Logan for labels and functional disassembly. ; Dr. Frank O'Hara for labels and functional disassembly. ; ; Credits ; ------- ; Alex Pallero Gonzales for corrections. ; Mike Dailly for comments. ; Alvin Albrecht for comments. ; Hob of c.s.s for full relocatability implementation and testing. ; ; z00m^SinDiKAT sjasmplus adaptation and dirty reformat. ; ; obsolete labels ; L1C16 JUMP-C-R OUTPUT "zx-spectrum-rom.bin" ; System variables definitions include "zx-spectrum-rom-sysvars.i.asm" ;***************************************** ;** Part 1. RESTART ROUTINES AND TABLES ** ;***************************************** ;------ ; Start ;------ ; At switch on, the Z80 chip is in interrupt mode 0. ; This location can also be 'called' to reset the machine. ; Typically with PRINT USR 0. ORG $0000 ;;;$0000 START: DI ; disable interrupts. XOR A ; signal coming from START. LD DE,$FFFF ; top of possible physical RAM. JP START_NEW ; jump forward to common code at START_NEW. ;-------------- ; Error restart ;-------------- ; The error pointer is made to point to the position of the error to enable ; the editor to show the error if it occurred during syntax checking. ; It is used at 37 places in the program. ; An instruction fetch on address $0008 may page in a peripheral ROM ; although this was not an original design concept. ;;;$0008 ERROR_1: LD HL,(CH_ADD) ; fetch the character address from CH_ADD. LD (X_PTR),HL ; copy it to the error pointer X_PTR. JR ERROR_2 ; forward to continue at ERROR_2. ;------------------ ; Print a character ;------------------ ; The A register holds the code of the character that is to be sent to ; the output stream of the current channel. ; The alternate register set is used to output a character in the A register ; so there is no need to preserve any of the current registers. ; This restart occurs 21 times. ;;;$0010 PRINT_A: JP PRINT_A_2 ; jump forward to continue at PRINT_A_2. DEFB $FF, $FF, $FF ; five unused locations. DEFB $FF, $FF ;-------------------- ; Collect a character ;-------------------- ; The contents of the location currently addressed by CH_ADD are fetched. ; A return is made if the value represents a character that has ; relevance to the BASIC parser. Otherwise CH_ADD is incremented and the ; tests repeated. CH_ADD will be addressing somewhere - ; 1) in the basic program area during line execution. ; 2) in workspace if evaluating, for example, a string expression. ; 3) in the edit buffer if parsing a direct command or a new basic line. ; 4) in workspace if accepting input but not that from INPUT LINE. ;;;$0018 GET_CHAR: LD HL,(CH_ADD) ; fetch the address from CH_ADD. LD A,(HL) ; use it to pick up current character. ;;;$001C TEST_CHAR: CALL SKIP_OVER ; routine SKIP_OVER tests if the character RET NC ; is relevant. Return if it is so. ;----------------------- ; Collect next character ;----------------------- ; As the BASIC commands and expressions are interpreted, this routine is ; called repeatedly to step along the line. It is used 83 times. ;;;$0020 NEXT_CHAR: CALL CH_ADD_1 ; routine CH_ADD_1 fetches the next immediate character. JR TEST_CHAR ; jump back to TEST_CHAR until a valid ; character is found. DEFB $FF, $FF, $FF ; unused ;------------------- ; Calculator restart ;------------------- ; This restart enters the Spectrum's internal, floating-point, ; stack-based, FORTH-like language. ; It is further used recursively from within the calculator. ; It is used on 77 occasions. ;;;$0028 FP_CALC: JP CALCULATE ; jump forward to the CALCULATE routine. DEFB $FF, $FF, $FF ; spare - note that on the ZX81, space being a DEFB $FF, $FF ; little cramped, these same locations were ; used for the five-byte END_CALC literal. ;------------------------------------ ; Create free locations in work space ;------------------------------------ ; This restart is used on only 12 occasions to create BC spaces ; between workspace and the calculator stack. ;;;$0030 BC_SPACES: PUSH BC ; save number of spaces. LD HL,(WORKSP) ; fetch WORKSP. PUSH HL ; save address of workspace. JP RESERVE ; jump forward to continuation code RESERVE. ;--------------------------- ; Maskable interrupt routine ;--------------------------- ; This routine increments the Spectrum's three-byte FRAMES counter ; fifty times a second (sixty times a second in the USA ). ; Both this routine and the called KEYBOARD subroutine use ; the IY register to access system variables and flags so a user-written ; program must disable interrupts to make use of the IY register. ;;;$0038 MASK_INT: PUSH AF ; save the registers. PUSH HL ; but not IY unfortunately. LD HL,(FRAMES1) ; fetch two bytes at FRAMES1. INC HL ; increment lowest two bytes of counter. LD (FRAMES1),HL ; place back in FRAMES1. LD A,H ; test if the result OR L ; was zero. JR NZ,KEY_INT ; forward to KEY_INT if not. INC (IY+$40) ; otherwise increment FRAMES3 the third byte. ; now save the rest of the main registers and read and decode the keyboard. ;;;$0048 KEY_INT: PUSH BC ; save the other PUSH DE ; main registers. CALL KEYBOARD ; routine KEYBOARD executes a stage in the process of reading a key-press. POP DE POP BC ; restore registers. POP HL POP AF EI ; enable interrupts. RET ; return. ;---------------- ; ERROR_2 routine ;---------------- ; A continuation of the code at 0008. ; The error code is stored and after clearing down stacks, ; an indirect jump is made to MAIN_4, etc. to handle the error. ;;;$0053 ERROR_2: POP HL ; drop the return address - the location ; after the RST 08H instruction. LD L,(HL) ; fetch the error code that follows. ; (nice to see this instruction used.) ; Note. this entry point is used when out of memory at REPORT_4. ; The L register has been loaded with the report code but X_PTR ; is not updated. ;;;$0055 ERROR_3: LD (IY+$00),L ; store it in the system variable ERR_NR. LD SP,(ERR_SP) ; ERR_SP points to an error handler on the ; machine stack. There may be a hierarchy ; of routines. ; to MAIN_4 initially at base. ; or REPORT_G on line entry. ; or ED_ERROR when editing. ; or ED_FULL during ED_ENTER. ; or IN_VAR_1 during runtime input etc. JP SET_STK ; jump to SET_STK to clear the calculator ; stack and reset MEM to usual place in the ; systems variables area. ; and then indirectly to MAIN_4, etc. DEFB $FF, $FF, $FF ; unused locations DEFB $FF, $FF, $FF ; before the fixed-position DEFB $FF ; NMI routine. ;------------------------------- ; Non-maskable interrupt routine ;------------------------------- ; There is no NMI switch on the standard Spectrum. ; When activated, a location in the system variables is tested ; and if the contents are zero a jump made to that location else ; a return is made. Perhaps a disabled development feature but ; if the logic was reversed, no program would be safe from ; copy-protection and the Spectrum would have had no software base. ; The location NMIADD was later used by Interface 1 for other purposes ; ironically to make use of the Spectrum's RS232 TAB character ; which was not understood when the Interface was designed. ; On later Spectrums, and the Brazilian Spectrum, the logic of this ; routine was reversed. ;;;$0066 RESET: PUSH AF ; save the PUSH HL ; registers. LD HL,(NMIADD) ; fetch the system variable NMIADD. LD A,H ; test address OR L ; for zero. JR NZ,NO_RESET ; skip to NO_RESET if NOT ZERO JP (HL) ; jump to routine ( i.e. START ) ;;;$0070 NO_RESET: POP HL ; restore the POP AF ; registers. RETN ; return to previous interrupt state. ;---------------------- ; CH ADD + 1 subroutine ;---------------------- ; This subroutine is called from RST 20, and three times from elsewhere ; to fetch the next immediate character following the current valid character ; address and update the associated system variable. ; The entry point TEMP_PTR1 is used from the SCANNING routine. ; Both TEMP_PTR1 and TEMP_PTR2 are used by the READ command routine. ;;;$0074 CH_ADD_1: LD HL,(CH_ADD) ; fetch address from CH_ADD. ;;;$0077 TEMP_PTR1: INC HL ; increase the character address by one. ;;;$0078 TEMP_PTR2: LD (CH_ADD),HL ; update CH_ADD with character address. LD A,(HL) ; load character to A from HL. RET ; and return. ;---------- ; Skip over ;---------- ; This subroutine is called once from RST 18 to skip over white-space and ; other characters irrelevant to the parsing of a basic line etc. . ; Initially the A register holds the character to be considered ; and HL holds it's address which will not be within quoted text ; when a basic line is parsed. ; Although the 'tab' and 'at' characters will not appear in a basic line, ; they could be present in a string expression, and in other situations. ; Note. although white-space is usually placed in a program to indent loops ; and make it more readable, it can also be used for the opposite effect and ; spaces may appear in variable names although the parser never sees them. ; It is this routine that helps make the variables 'Anum bEr5 3BUS' and ; 'a number 53 bus' appear the same to the parser. ;;;$007D SKIP_OVER: CP $21 ; test if higher than space. RET NC ; return with carry clear if so. CP $0D ; carriage return ? RET Z ; return also with carry clear if so. ; all other characters have no relevance ; to the parser and must be returned with ; carry set. CP $10 ; test if 0-15d RET C ; return, if so, with carry set. CP $18 ; test if 24-32d CCF ; complement carry flag. RET C ; return with carry set if so. ; now leaves 16d-23d INC HL ; all above have at least one extra character ; to be stepped over. CP $16 ; controls 22d ('at') and 23d ('tab') have two. JR C,SKIPS ; forward to SKIPS with ink, paper, flash, ; bright, inverse or over controls. ; Note. the high byte of tab is for RS232 only. ; it has no relevance on this machine. INC HL ; step over the second character of 'at'/'tab'. ;;;$0090 SKIPS: SCF ; set the carry flag LD (CH_ADD),HL ; update the CH_ADD system variable. RET ; return with carry set. ;------------- ; Token tables ;------------- ; The tokenized characters 134d (RND) to 255d (COPY) are expanded using ; this table. The last byte of a token is inverted to denote the end of ; the word. The first is an inverted step-over byte. ;;;$0095 TKN_TABLE: DEFB '?'+$80 DEFB "RN",'D'+$80 DEFB "INKEY",'$'+$80 DEFB "P",'I'+$80 DEFB "F",'N'+$80 DEFB "POIN",'T'+$80 DEFB "SCREEN",'$'+$80 DEFB "ATT",'R'+$80 DEFB "A",'T'+$80 DEFB "TA",'B'+$80 DEFB "VAL",'$'+$80 DEFB "COD",'E'+$80 DEFB "VA",'L'+$80 DEFB "LE",'N'+$80 DEFB "SI",'N'+$80 DEFB "CO",'S'+$80 DEFB "TA",'N'+$80 DEFB "AS",'N'+$80 DEFB "AC",'S'+$80 DEFB "AT",'N'+$80 DEFB "L",'N'+$80 DEFB "EX",'P'+$80 DEFB "IN",'T'+$80 DEFB "SQ",'R'+$80 DEFB "SG",'N'+$80 DEFB "AB",'S'+$80 DEFB "PEE",'K'+$80 DEFB "I",'N'+$80 DEFB "US",'R'+$80 DEFB "STR",'$'+$80 DEFB "CHR",'$'+$80 DEFB "NO",'T'+$80 DEFB "BI",'N'+$80 ; The previous 32 function-type words are printed without a leading space ; The following have a leading space if they begin with a letter DEFB "O",'R'+$80 DEFB "AN",'D'+$80 DEFB $3C,'='+$80 ; <= DEFB $3E,'='+$80 ; >= DEFB $3C,$3E+$80 ; <> DEFB "LIN",'E'+$80 DEFB "THE",'N'+$80 DEFB "T",'O'+$80 DEFB "STE",'P'+$80 DEFB "DEF F",'N'+$80 DEFB "CA",'T'+$80 DEFB "FORMA",'T'+$80 DEFB "MOV",'E'+$80 DEFB "ERAS",'E'+$80 DEFB "OPEN ",'#'+$80 DEFB "CLOSE ",'#'+$80 DEFB "MERG",'E'+$80 DEFB "VERIF",'Y'+$80 DEFB "BEE",'P'+$80 DEFB "CIRCL",'E'+$80 DEFB "IN",'K'+$80 DEFB "PAPE",'R'+$80 DEFB "FLAS",'H'+$80 DEFB "BRIGH",'T'+$80 DEFB "INVERS",'E'+$80 DEFB "OVE",'R'+$80 DEFB "OU",'T'+$80 DEFB "LPRIN",'T'+$80 DEFB "LLIS",'T'+$80 DEFB "STO",'P'+$80 DEFB "REA",'D'+$80 DEFB "DAT",'A'+$80 DEFB "RESTOR",'E'+$80 DEFB "NE",'W'+$80 DEFB "BORDE",'R'+$80 DEFB "CONTINU",'E'+$80 DEFB "DI",'M'+$80 DEFB "RE",'M'+$80 DEFB "FO",'R'+$80 DEFB "GO T",'O'+$80 DEFB "GO SU",'B'+$80 DEFB "INPU",'T'+$80 DEFB "LOA",'D'+$80 DEFB "LIS",'T'+$80 DEFB "LE",'T'+$80 DEFB "PAUS",'E'+$80 DEFB "NEX",'T'+$80 DEFB "POK",'E'+$80 DEFB "PRIN",'T'+$80 DEFB "PLO",'T'+$80 DEFB "RU",'N'+$80 DEFB "SAV",'E'+$80 DEFB "RANDOMIZ",'E'+$80 DEFB "I",'F'+$80 DEFB "CL",'S'+$80 DEFB "DRA",'W'+$80 DEFB "CLEA",'R'+$80 DEFB "RETUR",'N'+$80 DEFB "COP",'Y'+$80 ;----------- ; Key tables ;----------- ; These six look-up tables are used by the keyboard reading routine ; to decode the key values. ; The first table contains the maps for the 39 keys of the standard ; 40-key Spectrum keyboard. The remaining key [SHIFT $27] is read directly. ; The keys consist of the 26 upper-case alphabetic characters, the 10 digit ; keys and the space, ENTER and symbol shift key. ; Unshifted alphabetic keys have $20 added to the value. ; The keywords for the main alphabetic keys are obtained by adding $A5 to ; the values obtained from this table. ;;;$0205 MAIN_KEYS: DEFB $42 ; B DEFB $48 ; H DEFB $59 ; Y DEFB $36 ; 6 DEFB $35 ; 5 DEFB $54 ; T DEFB $47 ; G DEFB $56 ; V DEFB $4E ; N DEFB $4A ; J DEFB $55 ; U DEFB $37 ; 7 DEFB $34 ; 4 DEFB $52 ; R DEFB $46 ; F DEFB $43 ; C DEFB $4D ; M DEFB $4B ; K DEFB $49 ; I DEFB $38 ; 8 DEFB $33 ; 3 DEFB $45 ; E DEFB $44 ; D DEFB $58 ; X DEFB $0E ; SYMBOL SHIFT DEFB $4C ; L DEFB $4F ; O DEFB $39 ; 9 DEFB $32 ; 2 DEFB $57 ; W DEFB $53 ; S DEFB $5A ; Z DEFB $20 ; SPACE DEFB $0D ; ENTER DEFB $50 ; P DEFB $30 ; 0 DEFB $31 ; 1 DEFB $51 ; Q DEFB $41 ; A ;;;$022C ; The 26 unshifted extended mode keys for the alphabetic characters. ; The green keywords on the original keyboard. E_UNSHIFT: DEFB $E3 ; READ DEFB $C4 ; BIN DEFB $E0 ; LPRINT DEFB $E4 ; DATA DEFB $B4 ; TAN DEFB $BC ; SGN DEFB $BD ; ABS DEFB $BB ; SQR DEFB $AF ; CODE DEFB $B0 ; VAL DEFB $B1 ; LEN DEFB $C0 ; USR DEFB $A7 ; PI DEFB $A6 ; INKEY$ DEFB $BE ; PEEK DEFB $AD ; TAB DEFB $B2 ; SIN DEFB $BA ; INT DEFB $E5 ; RESTORE DEFB $A5 ; RND DEFB $C2 ; CHR$ DEFB $E1 ; LLIST DEFB $B3 ; COS DEFB $B9 ; EXP DEFB $C1 ; STR$ DEFB $B8 ; LN ;;;$0246 ; The 26 shifted extended mode keys for the alphabetic characters. ; The red keywords below keys on the original keyboard. EXT_SHIFT: DEFB $7E ; ~ DEFB $DC ; BRIGHT DEFB $DA ; PAPER DEFB $5C ; \ ; DEFB $B7 ; ATN DEFB $7B ; { DEFB $7D ; } DEFB $D8 ; CIRCLE DEFB $BF ; IN DEFB $AE ; VAL$ DEFB $AA ; SCREEN$ DEFB $AB ; ATTR DEFB $DD ; INVERSE DEFB $DE ; OVER DEFB $DF ; OUT DEFB $7F ; (Copyright character) DEFB $B5 ; ASN DEFB $D6 ; VERIFY DEFB $7C ; | DEFB $D5 ; MERGE DEFB $5D ; ] DEFB $DB ; FLASH DEFB $B6 ; ACS DEFB $D9 ; INK DEFB $5B ; [ DEFB $D7 ; BEEP ;;;$0260 ; The ten control codes assigned to the top line of digits when the shift ; key is pressed. CTL_CODES: DEFB $0C ; DELETE DEFB $07 ; EDIT DEFB $06 ; CAPS LOCK DEFB $04 ; TRUE VIDEO DEFB $05 ; INVERSE VIDEO DEFB $08 ; CURSOR LEFT DEFB $0A ; CURSOR DOWN DEFB $0B ; CURSOR UP DEFB $09 ; CURSOR RIGHT DEFB $0F ; GRAPHICS ;;;$026A ; The 26 red symbols assigned to the alphabetic characters of the keyboard. ; The ten single-character digit symbols are converted without the aid of ; a table using subtraction and minor manipulation. SYM_CODES: DEFB $E2 ; STOP DEFB $2A ; * DEFB $3F ; ? DEFB $CD ; STEP DEFB $C8 ; >= DEFB $CC ; TO DEFB $CB ; THEN DEFB $5E ; ^ DEFB $AC ; AT DEFB $2D ; - DEFB $2B ; + DEFB $3D ; = DEFB $2E ; . DEFB $2C ; , DEFB $3B ; ; DEFB $22 ; " DEFB $C7 ; <= DEFB $3C ; < DEFB $C3 ; NOT DEFB $3E ; > DEFB $C5 ; OR DEFB $2F ; / DEFB $C9 ; <> DEFB $60 ; pound DEFB $C6 ; AND DEFB $3A ; : ;;;$0284 ; The ten keywords assigned to the digits in extended mode. ; The remaining red keywords below the keys. E_DIGITS: DEFB $D0 ; FORMAT DEFB $CE ; DEF FN DEFB $A8 ; FN DEFB $CA ; LINE DEFB $D3 ; OPEN# DEFB $D4 ; CLOSE# DEFB $D1 ; MOVE DEFB $D2 ; ERASE DEFB $A9 ; POINT DEFB $CF ; CAT ;******************************* ;** Part 2. KEYBOARD ROUTINES ** ;******************************* ; Using shift keys and a combination of modes the Spectrum 40-key keyboard ; can be mapped to 256 input characters ;---------------------------------------------------------------------------- ; ; 0 1 2 3 4 -Bits- 4 3 2 1 0 ; PORT PORT ; ; F7FE [ 1 ] [ 2 ] [ 3 ] [ 4 ] [ 5 ] | [ 6 ] [ 7 ] [ 8 ] [ 9 ] [ 0 ] EFFE ; ^ | v ; FBFE [ Q ] [ W ] [ E ] [ R ] [ T ] | [ Y ] [ U ] [ I ] [ O ] [ P ] DFFE ; ^ | v ; FDFE [ A ] [ S ] [ D ] [ F ] [ G ] | [ H ] [ J ] [ K ] [ L ] [ ENT ] BFFE ; ^ | v ; FEFE [SHI] [ Z ] [ X ] [ C ] [ V ] | [ B ] [ N ] [ M ] [sym] [ SPC ] 7FFE ; ^ $27 $18 v ; Start End ; 00100111 00011000 ; ;---------------------------------------------------------------------------- ; The above map may help in reading. ; The neat arrangement of ports means that the B register need only be ; rotated left to work up the left hand side and then down the right ; hand side of the keyboard. When the reset bit drops into the carry ; then all 8 half-rows have been read. Shift is the first key to be ; read. The lower six bits of the shifts are unambiguous. ;------------------ ; Keyboard scanning ;------------------ ; from keyboard and S_INKEY ; returns 1 or 2 keys in DE, most significant shift first if any ; key values 0-39 else 255 ;;;$028E KEY_SCAN: LD L,$2F ; initial key value ; valid values are obtained by subtracting ; eight five times. LD DE,$FFFF ; a buffer to receive 2 keys. LD BC,$FEFE ; the commencing port address ; B holds 11111110 initially and is also ; used to count the 8 half-rows ;;;$0296 KEY_LINE: IN A,(C) ; read the port to A - bits will be reset ; if a key is pressed else set. CPL ; complement - pressed key-bits are now set AND $1F ; apply 00011111 mask to pick up the ; relevant set bits. JR Z,KEY_DONE ; forward to KEY_DONE if zero and therefore ; no keys pressed in row at all. LD H,A ; transfer row bits to H LD A,L ; load the initial key value to A ;;;$029F KEY_3KEYS: INC D ; now test the key buffer RET NZ ; if we have collected 2 keys already ; then too many so quit. ;;;$02A1 KEY_BITS: SUB $08 ; subtract 8 from the key value ; cycling through key values (top = $27) ; e.g. 2F> 27>1F>17>0F>07 ; 2E> 26>1E>16>0E>06 SRL H ; shift key bits right into carry. JR NC,KEY_BITS ; back to KEY_BITS if not pressed ; but if pressed we have a value (0-39d) LD D,E ; transfer a possible previous key to D LD E,A ; transfer the new key to E JR NZ,KEY_3KEYS ; back to KEY_3KEYS if there were more ; set bits - H was not yet zero. ;;;$02AB KEY_DONE: DEC L ; cycles 2F>2E>2D>2C>2B>2A>29>28 for ; each half-row. RLC B ; form next port address e.g. FEFE > FDFE JR C,KEY_LINE ; back to KEY_LINE if still more rows to do. LD A,D ; now test if D is still FF ? INC A ; if it is zero we have at most 1 key ; range now $01-$28 (1-40d) RET Z ; return if one key or no key. CP $28 ; is it capsshift (was $27) ? RET Z ; return if so. CP $19 ; is it symbol shift (was $18) ? RET Z ; return also LD A,E ; now test E LD E,D ; but first switch LD D,A ; the two keys. CP $18 ; is it symbol shift ? RET ; return (with zero set if it was). ; but with symbol shift now in D ;------------------------------- ; Scan keyboard and decode value ;------------------------------- ; from interrupt 50 times a second ;;;$02BF KEYBOARD: CALL KEY_SCAN ; routine KEY_SCAN RET NZ ; return if invalid combinations ; then decrease the counters within the two key-state maps ; as this could cause one to become free. ; if the keyboard has not been pressed during the last five interrupts ; then both sets will be free. LD HL,KSTATE_0 ; point to KSTATE_0 ;;;$02C6 K_ST_LOOP: BIT 7,(HL) ; is it free ? ($FF) JR NZ,K_CH_SET ; forward to K_CH_SET if so INC HL ; address 5-counter DEC (HL) ; decrease counter DEC HL ; step back JR NZ,K_CH_SET ; forward to K_CH_SET if not at end of count LD (HL),$FF ; else mark it free. ;;;$02D1 K_CH_SET: LD A,L ; store low address byte. LD HL,KSTATE_4 ; point to KSTATE_4 ; (ld l, $04) CP L ; have 2 been done ? JR NZ,K_ST_LOOP ; back to K_ST_LOOP to consider this 2nd set ; now the raw key (0-38) is converted to a main key (uppercase). CALL K_TEST ; routine K_TEST to get main key in A RET NC ; return if single shift LD HL,KSTATE_0 ; point to KSTATE_0 CP (HL) ; does it match ? JR Z,K_REPEAT ; forward to K_REPEAT if so ; if not consider the second key map. EX DE,HL ; save KSTATE_0 in DE LD HL,KSTATE_4 ; point to KSTATE_4 CP (HL) ; does it match ? JR Z,K_REPEAT ; forward to K_REPEAT if so ; having excluded a repeating key we can now consider a new key. ; the second set is always examined before the first. BIT 7,(HL) ; is it free ? JR NZ,K_NEW ; forward to K_NEW if so. EX DE,HL ; bring back KSTATE_0 BIT 7,(HL) ; is it free ? RET Z ; return if not. ; as we have a key but nowhere to put it yet. ; continue or jump to here if one of the buffers was free. ;;;$02F1 K_NEW: LD E,A ; store key in E LD (HL),A ; place in free location INC HL ; advance to interrupt counter LD (HL),$05 ; and initialize to 5 INC HL ; advance to delay LD A,(REPDEL) ; pick up system variable REPDEL LD (HL),A ; and insert that for first repeat delay. INC HL ; advance to last location of state map. LD C,(IY+$07) ; pick up MODE (3 bytes) LD D,(IY+$01) ; pick up FLAGS (3 bytes) PUSH HL ; save state map location ; Note. could now have used. ; ld l,$41; ld c,(hl); ld l,$3B; ld d,(hl). ; six and two threes of course. CALL K_DECODE ; routine K_DECODE POP HL ; restore map pointer LD (HL),A ; put decoded key in last location of map. ;;;$0308 K_END: LD (LASTK),A ; update LASTK system variable. SET 5,(IY+$01) ; update FLAGS - signal new key. RET ; done ;------------------- ; Repeat key routine ;------------------- ; A possible repeat has been identified. HL addresses the raw (main) key. ; The last location holds the decoded key (from the first context). ;;;$0310 K_REPEAT: INC HL ; advance LD (HL),$05 ; maintain interrupt counter at 5 INC HL ; advance DEC (HL) ; decrease REPDEL value. RET NZ ; return if not yet zero. LD A,(REPPER) ; REPPER LD (HL),A ; but for subsequent repeats REPPER will be used. INC HL ; advance LD A,(HL) ; pick up the key decoded possibly in another context. JR K_END ; back to K_END ;--------------- ; Test key value ;--------------- ; also called from S_INKEY ; begin by testing for a shift with no other. ;;;$031E K_TEST: LD B,D ; load most significant key to B ; will be $FF if not shift. LD D,$00 ; and reset D to index into main table LD A,E ; load least significant key from E CP $27 ; is it higher than 39d i.e. FF RET NC ; return with just a shift (in B now) CP $18 ; is it symbol shift ? JR NZ,K_MAIN ; forward to K_MAIN if not ; but we could have just symbol shift and no other BIT 7,B ; is other key $FF (ie not shift) RET NZ ; return with solitary symbol shift ;;;$032C K_MAIN: LD HL,MAIN_KEYS ; address: MAIN_KEYS ADD HL,DE ; add offset 0-38 LD A,(HL) ; pick up main key value SCF ; set carry flag RET ; return (B has other key still) ;------------------ ; Keyboard decoding ;------------------ ; also called from S_INKEY ;;;$0333 K_DECODE: LD A,E ; pick up the stored main key CP $3A ; an arbitrary point between digits and letters JR C,K_DIGIT ; forward to K_DIGIT with digits,space,enter DEC C ; decrease MODE ( 0='KLC', 1='E', 2='G') JP M,K_KLC_LET ; to K_KLC_LET if was zero JR Z,K_E_LET ; to K_E_LET if was 1 for extended letters. ; proceed with graphic codes. ; Note. should selectively drop return address if code > 'U' ($55). ; i.e. abort the KEYBOARD call. ; e.g. cp 'V'; jr c addit; pop af; ;;addit etc. (5 bytes of instruction). ; (S_INKEY never gets into graphics mode.) ;; addit ADD A,$4F ; add offset to augment 'A' to graphics A say. RET ; return. ; Note. ( but [GRAPH] V gives RND, etc ). ; the jump was to here with extended mode with uppercase A-Z. ;;;$0341 K_E_LET: LD HL,E_UNSHIFT-$41; base address of E_UNSHIFT-$41 ; ( $01EB in standard ROM ) INC B ; test B is it empty i.e. not a shift JR Z,K_LOOK_UP ; forward to K_LOOK_UP if neither shift LD HL,EXT_SHIFT-$41; Address: $0205 EXT_SHIFT-$41 base ;;;$034A K_LOOK_UP: LD D,$00 ; prepare to index ADD HL,DE ; add the main key value LD A,(HL) ; pick up other mode value RET ; return ; the jump was here with mode = 0 ;;;$034F K_KLC_LET: LD HL,SYM_CODES-$41; prepare base of SYM_CODES BIT 0,B ; shift=$27 sym-shift=$18 JR Z,K_LOOK_UP ; back to K_LOOK_UP with symbol-shift BIT 3,D ; test FLAGS is it 'K' mode (from OUT_CURS) JR Z,K_TOKENS ; skip to K_TOKENS if so BIT 3,(IY+$30) ; test FLAGS2 - consider CAPS LOCK ? RET NZ ; return if so with main code. INC B ; is shift being pressed ? ; result zero if not RET NZ ; return if shift pressed. ADD A,$20 ; else convert the code to lower case. RET ; return. ; the jump was here for tokens ;;;$0364 K_TOKENS: ADD A,$A5 ; add offset to main code so that 'A' ; becomes 'NEW' etc. RET ; return ; the jump was here with digits, space, enter and symbol shift (< $xx) ;;;$0367 K_DIGIT: CP $30 ; is it '0' or higher ? RET C ; return with space, enter and symbol-shift DEC C ; test MODE (was 0='KLC', 1='E', 2='G') JP M,K_KLC_DGT ; jump to K_KLC_DGT if was 0. JR NZ,K_GRA_DGT ; forward to K_GRA_DGT if mode was 2. ; continue with extended digits 0-9. LD HL,E_DIGITS-$30 ; $0254 - base of E_DIGITS BIT 5,B ; test - shift=$27 sym-shift=$18 JR Z,K_LOOK_UP ; to K_LOOK_UP if sym-shift CP $38 ; is character '8' ? JR NC,K_8_AND_9 ; to K_8_AND_9 if greater than '7' SUB $20 ; reduce to ink range $10-$17 INC B ; shift ? RET Z ; return if not. ADD A,$08 ; add 8 to give paper range $18 - $1F RET ; return ; 89 ;;;$0382 K_8_AND_9: SUB $36 ; reduce to 02 and 03 bright codes INC B ; test if shift pressed. RET Z ; return if not. ADD A,$FE ; subtract 2 setting carry RET ; to give 0 and 1 flash codes. ; graphics mode with digits ;;;$0389 K_GRA_DGT: LD HL,CTL_CODES-$30; $0230 base address of CTL_CODES CP $39 ; is key '9' ? JR Z,K_LOOK_UP ; back to K_LOOK_UP - changed to $0F, GRAPHICS. CP $30 ; is key '0' ? JR Z,K_LOOK_UP ; back to K_LOOK_UP - changed to $0C, delete. ; for keys '0' - '7' we assign a mosaic character depending on shift. AND $07 ; convert character to number. 0 - 7. ADD A,$80 ; add offset - they start at $80 INC B ; destructively test for shift RET Z ; and return if not pressed. XOR $0F ; toggle bits becomes range $88-$8F RET ; return. ; now digits in 'KLC' mode ;;;$039D K_KLC_DGT: INC B ; return with digit codes if neither RET Z ; shift key pressed. BIT 5,B ; test for caps shift. LD HL,CTL_CODES-$30; prepare base of table CTL_CODES. JR NZ,K_LOOK_UP ; back to K_LOOK_UP if shift pressed. ; must have been symbol shift SUB $10 ; for ascii most will now be correct ; on a standard typewriter. CP $22 ; but '@' is not - see below. JR Z,K_AT_CHAR ; forward to to K_AT_CHAR if so CP $20 ; '_' is the other one that fails RET NZ ; return if not. LD A,$5F ; substitute ascii '_' RET ; return. ;;;$03B2 K_AT_CHAR: LD A,$40 ; substitute ascii '@' RET ; return. ;------------------------------------------------------------------------- ; The Spectrum Input character keys. One or two are abbreviated. ; From $00 Flash 0 to $FF COPY. The routine above has decoded all these. ; | 00 Fl0| 01 Fl1| 02 Br0| 03 Br1| 04 In0| 05 In1| 06 CAP| 07 EDT| ; | 08 LFT| 09 RIG| 0A DWN| 0B UP | 0C DEL| 0D ENT| 0E SYM| 0F GRA| ; | 10 Ik0| 11 Ik1| 12 Ik2| 13 Ik3| 14 Ik4| 15 Ik5| 16 Ik6| 17 Ik7| ; | 18 Pa0| 19 Pa1| 1A Pa2| 1B Pa3| 1C Pa4| 1D Pa5| 1E Pa6| 1F Pa7| ; | 20 SP | 21 ! | 22 " | 23 # | 24 $ | 25 % | 26 & | 27 ' | ; | 28 ( | 29 ) | 2A * | 2B + | 2C , | 2D - | 2E . | 2F / | ; | 30 0 | 31 1 | 32 2 | 33 3 | 34 4 | 35 5 | 36 6 | 37 7 | ; | 38 8 | 39 9 | 3A : | 3B ; | 3C < | 3D = | 3E > | 3F ? | ; | 40 @ | 41 A | 42 B | 43 C | 44 D | 45 E | 46 F | 47 G | ; | 48 H | 49 I | 4A J | 4B K | 4C L | 4D M | 4E N | 4F O | ; | 50 P | 51 Q | 52 R | 53 S | 54 T | 55 U | 56 V | 57 W | ; | 58 X | 59 Y | 5A Z | 5B [ | 5C \ | 5D ] | 5E ^ | 5F _ | ; | 60 ukp| 61 a | 62 b | 63 c | 64 d | 65 e | 66 f | 67 g | ; | 68 h | 69 i | 6A j | 6B k | 6C l | 6D m | 6E n | 6F o | ; | 70 p | 71 q | 72 r | 73 s | 74 t | 75 u | 76 v | 77 w | ; | 78 x | 79 y | 7A z | 7B { | 7C | | 7D } | 7E ~ | 7F (c)| ; | 80 128| 81 129| 82 130| 83 131| 84 132| 85 133| 86 134| 87 135| ; | 88 136| 89 137| 8A 138| 8B 139| 8C 140| 8D 141| 8E 142| 8F 143| ; | 90 [A]| 91 [B]| 92 [C]| 93 [D]| 94 [E]| 95 [F]| 96 [G]| 97 [H]| ; | 98 [I]| 99 [J]| 9A [K]| 9B [L]| 9C [M]| 9D [N]| 9E [O]| 9F [P]| ; | A0 [Q]| A1 [R]| A2 [S]| A3 [T]| A4 [U]| A5 RND| A6 IK$| A7 PI | ; | A8 FN | A9 PNT| AA SC$| AB ATT| AC AT | AD TAB| AE VL$| AF COD| ; | B0 VAL| B1 LEN| B2 SIN| B3 COS| B4 TAN| B5 ASN| B6 ACS| B7 ATN| ; | B8 LN | B9 EXP| BA INT| BB SQR| BC SGN| BD ABS| BE PEK| BF IN | ; | C0 USR| C1 ST$| C2 CH$| C3 NOT| C4 BIN| C5 OR | C6 AND| C7 <= | ; | C8 >= | C9 <> | CA LIN| CB THN| CC TO | CD STP| CE DEF| CF CAT| ; | D0 FMT| D1 MOV| D2 ERS| D3 OPN| D4 CLO| D5 MRG| D6 VFY| D7 BEP| ; | D8 CIR| D9 INK| DA PAP| DB FLA| DC BRI| DD INV| DE OVR| DF OUT| ; | E0 LPR| E1 LLI| E2 STP| E3 REA| E4 DAT| E5 RES| E6 NEW| E7 BDR| ; | E8 CON| E9 DIM| EA REM| EB FOR| EC GTO| ED GSB| EE INP| EF LOA| ; | F0 LIS| F1 LET| F2 PAU| F3 NXT| F4 POK| F5 PRI| F6 PLO| F7 RUN| ; | F8 SAV| F9 RAN| FA IF | FB CLS| FC DRW| FD CLR| FE RET| FF CPY| ; Note that for simplicity, Sinclair have located all the control codes ; below the space character. ; ascii DEL, $7F, has been made a copyright symbol. ; Also $60, '`', not used in Basic but used in other languages, has been ; allocated the local currency symbol for the relevant country - ; ukp in most Spectrums. ;------------------------------------------------------------------------- ;********************************** ;** Part 3. LOUDSPEAKER ROUTINES ** ;********************************** ; Documented by Alvin Albrecht. ;------------------------------- ; Routine to control loudspeaker ;------------------------------- ; Outputs a square wave of given duration and frequency ; to the loudspeaker. ; Enter with: DE = #cycles - 1 ; HL = tone period as described next ; ; The tone period is measured in T states and consists of ; three parts: a coarse part (H register), a medium part ; (bits 7..2 of L) and a fine part (bits 1..0 of L) which ; contribute to the waveform timing as follows: ; ; coarse medium fine ; duration of low = 118 + 1024*H + 16*(L>>2) + 4*(L&0x3) ; duration of hi = 118 + 1024*H + 16*(L>>2) + 4*(L&0x3) ; Tp = tone period = 236 + 2048*H + 32*(L>>2) + 8*(L&0x3) ; = 236 + 2048*H + 8*L = 236 + 8*HL ; ; As an example, to output five seconds of middle C (261.624 Hz): ; (a) Tone period = 1/261.624 = 3.822ms ; (b) Tone period in T-States = 3.822ms*fCPU = 13378 ; where fCPU = clock frequency of the CPU = 3.5MHz ; (c) Find H and L for desired tone period: ; HL = (Tp - 236) / 8 = (13378 - 236) / 8 = 1643 = 0x066B ; (d) Tone duration in cycles = 5s/3.822ms = 1308 cycles ; DE = 1308 - 1 = 0x051B ; ; The resulting waveform has a duty ratio of exactly 50%. ;;;$03B5 BEEPER: DI ; Disable Interrupts so they don't disturb timing LD A,L SRL L SRL L ; L = medium part of tone period CPL AND $03 ; A = 3 - fine part of tone period LD C,A LD B,$00 LD IX,BE_IX_3 ; Address: BE_IX_3 ADD IX,BC ; IX holds address of entry into the loop ; the loop will contain 0-3 NOPs, implementing ; the fine part of the tone period. LD A,(BORDCR) ; BORDCR AND $38 ; bits 5..3 contain border colour RRCA ; border colour bits moved to 2..0 RRCA ; to match border bits on port #FE RRCA OR $08 ; bit 3 set (tape output bit on port #FE) ; for loud sound output ;;;$03D1 BE_IX_3: NOP ;(4) ; optionally executed NOPs for small ; adjustments to tone period ;;;$03D2 BE_IX_2: NOP ;(4) ;;;$03D3 BE_IX_1: NOP ;(4) ;;;$03D4 BE_IX_0: INC B ;(4) INC C ;(4) ;;;$03D6 BE_HL_LP: DEC C ;(4) ; timing loop for duration of JR NZ,BE_HL_LP ;(12/7) ; high or low pulse of waveform LD C,$3F ;(7) DEC B ;(4) JP NZ,BE_HL_LP ;(10) ; to BE_HL_LP XOR $10 ;(7) ; toggle output beep bit OUT ($FE),A ;(11) ; output pulse LD B,H ;(4) ; B = coarse part of tone period LD C,A ;(4) ; save port #FE output byte BIT 4,A ;(8) ; if new output bit is high, go JR NZ,BE_AGAIN ;(12/7) ; to BE_AGAIN LD A,D ;(4) ; one cycle of waveform has completed OR E ;(4) ; (low->low). if cycle countdown = 0 JR Z,BE_END ;(12/7) ; go to BE_END LD A,C ;(4) ; restore output byte for port #FE LD C,L ;(4) ; C = medium part of tone period DEC DE ;(6) ; decrement cycle count JP (IX) ;(8) ; do another cycle ;;;$03F2; halfway through cycle BE_AGAIN: LD C,L ;(4) ; C = medium part of tone period INC C ;(4) ; adds 16 cycles to make duration of high = duration of low JP (IX) ;(8) ; do high pulse of tone ;;;$03F6 BE_END: EI ; Enable Interrupts RET ;-------------------- ; Handle BEEP command ;-------------------- ; BASIC interface to BEEPER subroutine. ; Invoked in BASIC with: ; BEEP dur,pitch ; where dur = duration in seconds ; pitch = # of semitones above/below middle C ; ; Enter with: pitch on top of calculator stack ; duration next on calculator stack ;;;$03F8 BEEP: RST 28H ;; FP_CALC DEFB $31 ;;DUPLICATE ; duplicate pitch DEFB $27 ;;INT ; convert to integer DEFB $C0 ;;st-mem-0 ; store integer pitch to memory 0 DEFB $03 ;;SUBTRACT ; calculate fractional part of pitch = fp_pitch - int_pitch DEFB $34 ;;STK_DATA ; push constant DEFB $EC ;;Exponent: $7C, Bytes: 4 ; constant = 0.05762265 DEFB $6C,$98,$1F,$F5 ;;($6C,$98,$1F,$F5) DEFB $04 ;;MULTIPLY ; compute: DEFB $A1 ;;STK_ONE ; 1 + 0.05762265 * fraction_part(pitch) DEFB $0F ;;ADDITION DEFB $38 ;;END_CALC ; leave on calc stack LD HL,MEM_0 ; MEM_0: number stored here is in 16 bit integer format (pitch) ; 0, 0/FF (pos/neg), LSB, MSB, 0 ; LSB/MSB is stored in two's complement ; In the following, the pitch is checked if it is in the range -128<=p<=127 LD A,(HL) ; First byte must be zero, otherwise AND A ; error in integer conversion JR NZ,REPORT_B ; to REPORT_B INC HL LD C,(HL) ; C = pos/neg flag = 0/FF INC HL LD B,(HL) ; B = LSB, two's complement LD A,B RLA SBC A,A ; A = 0/FF if B is pos/neg CP C ; must be the same as C if the pitch is -128<=p<=127 JR NZ,REPORT_B ; if no, error REPORT_B INC HL ; if -128<=p<=127, MSB will be 0/FF if B is pos/neg CP (HL) ; verify this JR NZ,REPORT_B ; if no, error REPORT_B ; now we know -128<=p<=127 LD A,B ; A = pitch + 60 ADD A,$3C ; if -60<=pitch<=67, JP P,BE_I_OK ; goto BE_I_OK JP PO,REPORT_B ; if pitch <= 67 goto REPORT_B ; lower bound of pitch set at -60 ;;;$0425; here, -60<=pitch<=127 ; and A=pitch+60 -> 0<=A<=187 BE_I_OK: LD B,$FA ; 6 octaves below middle C ;;;$0427 ; A=# semitones above 5 octaves below middle C BE_OCTAVE: INC B ; increment octave SUB $0C ; 12 semitones = one octave JR NC,BE_OCTAVE ; to BE_OCTAVE ADD A,$0C ; A = # semitones above C (0-11) PUSH BC ; B = octave displacement from middle C, 2's complement: -5<=B<=10 LD HL,SEMI_TONE ; Address: SEMI_TONE CALL LOC_MEM ; routine LOC_MEM ; HL = 5*A + $046E CALL STACK_NUM ; routine STACK_NUM ; read FP value (freq) from semitone table (HL) and push onto calc stack RST 28H ;; FP_CALC DEFB $04 ;;MULTIPLY mult freq by 1 + 0.0576 * fraction_part(pitch) stacked earlier ;; thus taking into account fractional part of pitch. ;; the number 0.0576*frequency is the distance in Hz to the next ;; note (verify with the frequencies recorded in the semitone ;; table below) so that the fraction_part of the pitch does ;; indeed represent a fractional distance to the next note. DEFB $38 ;;END_CALC HL points to first byte of fp num on stack = middle frequency to generate POP AF ; A = octave displacement from middle C, 2's complement: -5<=A<=10 ADD A,(HL) ; increase exponent by A (equivalent to multiplying by 2^A) LD (HL),A RST 28H ;; FP_CALC DEFB $C0 ;;st-mem-0 ; store frequency in memory 0 DEFB $02 ;;DELETE ; remove from calc stack DEFB $31 ;;DUPLICATE ; duplicate duration (seconds) DEFB $38 ;;END_CALC CALL FIND_INT1 ; routine FIND_INT1 ; FP duration to A CP $0B ; if dur > 10 seconds, JR NC,REPORT_B ; goto REPORT_B ;;; The following calculation finds the tone period for HL and the cycle count ;;; for DE expected in the BEEPER subroutine. From the example in the BEEPER comments, ;;; ;;; HL = ((fCPU / f) - 236) / 8 = fCPU/8/f - 236/8 = 437500/f -29.5 ;;; DE = duration * frequency - 1 ;;; ;;; Note the different constant (30.125) used in the calculation of HL ;;; below. This is probably an error. RST 28H ;; FP_CALC DEFB $E0 ;;get-mem-0 ; push frequency DEFB $04 ;;MULTIPLY ; result1: #cycles = duration * frequency DEFB $E0 ;;get-mem-0 ; push frequency DEFB $34 ;;STK_DATA ; push constant DEFB $80 ;;Exponent $93, Bytes: 3 ; constant = 437500 DEFB $43,$55,$9F,$80 ;;($55,$9F,$80,$00) DEFB $01 ;;EXCHANGE ; frequency on top DEFB $05 ;;DIVISION ; 437500 / frequency DEFB $34 ;;STK_DATA ; push constant DEFB $35 ;;Exponent: $85, Bytes: 1 ; constant = 30.125 DEFB $71 ;;($71,$00,$00,$00) DEFB $03 ;;SUBTRACT ; result2: tone_period(HL) = 437500 / freq - 30.125 DEFB $38 ;;END_CALC CALL FIND_INT2 ; routine FIND_INT2 PUSH BC ; BC = tone_period(HL) CALL FIND_INT2 ; routine FIND_INT2, BC = #cycles to generate POP HL ; HL = tone period LD D,B LD E,C ; DE = #cycles LD A,D OR E RET Z ; if duration = 0, skip BEEP and avoid 65536 cycle ; boondoggle that would occur next DEC DE ; DE = #cycles - 1 JP BEEPER ; to BEEPER ;;;$046C REPORT_B: RST 08H ; ERROR_1 DEFB $0A ; Error Report: Integer out of range ;---------------- ; Semi-tone table ;---------------- ; ; Holds frequencies corresponding to semitones in middle octave. ; To move n octaves higher or lower, frequencies are multiplied by 2^n. ;;;$046E five byte fp decimal freq note (middle) SEMI_TONE: DEFB $89, $02, $D0, $12, $86; 261.625565290 C DEFB $89, $0A, $97, $60, $75; 277.182631135 C# DEFB $89, $12, $D5, $17, $1F; 293.664768100 D DEFB $89, $1B, $90, $41, $02; 311.126983881 D# DEFB $89, $24, $D0, $53, $CA; 329.627557039 E DEFB $89, $2E, $9D, $36, $B1; 349.228231549 F DEFB $89, $38, $FF, $49, $3E; 369.994422674 F# DEFB $89, $43, $FF, $6A, $73; 391.995436072 G DEFB $89, $4F, $A7, $00, $54; 415.304697513 G# DEFB $89, $5C, $00, $00, $00; 440.000000000 A DEFB $89, $69, $14, $F6, $24; 466.163761616 A# DEFB $89, $76, $F1, $10, $05; 493.883301378 B ;**************************************** ;** Part 4. CASSETTE HANDLING ROUTINES ** ;**************************************** ; These routines begin with the service routines followed by a single ; command entry point. ; The first of these service routines is a curiosity. ;------------------ ; ZX81_NAME routine ;------------------ ; This routine fetches a filename in ZX81 format. ; and is not used by the cassette handling routines in this ROM. ;;;$04AA ZX81_NAME: CALL SCANNING ; routine SCANNING to evaluate expression. LD A,(FLAGS) ; fetch system variable FLAGS. ADD A,A ; test bit 7 - syntax, bit 6 - result type. JP M,REPORT_C ; to REPORT_C if not string result ; 'Nonsense in Basic'. POP HL ; drop return address. RET NC ; return early if checking syntax. PUSH HL ; re-save return address. CALL STK_FETCH ; routine STK_FETCH fetches string parameters. LD H,D ; transfer start of filename LD L,E ; to the HL register. DEC C ; adjust to point to last character and RET M ; return if the null string. ; or multiple of 256! ADD HL,BC ; find last character of the filename. ; and also clear carry. SET 7,(HL) ; invert it. RET ; return. ; ========================================= ; ; PORT 254 ($FE) ; ; spk mic { border } ; ___ ___ ___ ___ ___ ___ ___ ___ ; PORT | | | | | | | | | ; 254 | | | | | | | | | ; $FE |___|___|___|___|___|___|___|___| ; 7 6 5 4 3 2 1 0 ; ;----------------------------------- ; Save header and program/data bytes ;----------------------------------- ; This routine saves a section of data. It is called from SA-CTRL to save the ; seventeen bytes of header data. It is also the exit route from that routine ; when it is set up to save the actual data. ; On entry - ; HL points to start of data. ; IX points to descriptor. ; The accumulator is set to $00 for a header, $FF for data. ;;;$04C2 SA_BYTES: LD HL,SA_LD_RET ; address: SA_LD_RET PUSH HL ; is pushed as common exit route. ; however there is only one non-terminal exit point. LD HL,$1F80 ; a timing constant H=$1F, L=$80 ; inner and outer loop counters ; a five second lead-in is used for a header. BIT 7,A ; test one bit of accumulator. ; (AND A ?) JR Z,SA_FLAG ; skip to SA_FLAG if a header is being saved. ; else is data bytes and a shorter lead-in is used. LD HL,$0C98 ; another timing value H=$0C, L=$98. ; a two second lead-in is used for the data. ;;;$04D0 SA_FLAG: EX AF,AF' ; save flag INC DE ; increase length by one. DEC IX ; decrease start. DI ; disable interrupts LD A,$02 ; select red for border, microphone bit on. LD B,A ; also does as an initial slight counter value. ;;;$04D8 SA_LEADER: DJNZ SA_LEADER ; self loop to SA_LEADER for delay. ; after initial loop, count is $A4 (or $A3) OUT ($FE),A ; output byte $02/$0D to tape port. XOR $0F ; switch from RED (mic on) to CYAN (mic off). LD B,$A4 ; hold count. also timed instruction. DEC L ; originally $80 or $98. ; but subsequently cycles 256 times. JR NZ,SA_LEADER ; back to SA_LEADER until L is zero. ; the outer loop is counted by H DEC B ; decrement count DEC H ; originally twelve or thirty-one. JP P,SA_LEADER ; back to SA_LEADER until H becomes $FF ; now send a synch pulse. At this stage mic is off and A holds value ; for mic on. ; A synch pulse is much shorter than the steady pulses of the lead-in. LD B,$2F ; another short timed delay. ;;;$04EA SA_SYNC_1: DJNZ SA_SYNC_1 ; self loop to SA_SYNC_1 OUT ($FE),A ; switch to mic on and red. LD A,$0D ; prepare mic off - cyan LD B,$37 ; another short timed delay. ;;;$04F2 SA_SYNC_2: DJNZ SA_SYNC_2 ; self loop to SA_SYNC_2 OUT ($FE),A ; output mic off, cyan border. LD BC,$3B0E ; B=$3B time(*), C=$0E, YELLOW, MIC OFF. EX AF,AF' ; restore saved flag ; which is 1st byte to be saved. LD L,A ; and transfer to L. ; the initial parity is A, $FF or $00. JP SA_START ; jump forward to SA_START -> ; the mid entry point of loop. ; ------------------------- ; During the save loop a parity byte is maintained in H. ; the save loop begins by testing if reduced length is zero and if so ; the final parity byte is saved reducing count to $FFFF. ;;;$04FE SA_LOOP: LD A,D ; fetch high byte OR E ; test against low byte. JR Z,SA_PARITY ; forward to SA_PARITY if zero. LD L,(IX+$00) ; load currently addressed byte to L. ;;;$0505 SA_LOOP_P: LD A,H ; fetch parity byte. XOR L ; exclusive or with new byte. ; -> the mid entry point of loop. ;;;$0507 SA_START: LD H,A ; put parity byte in H. LD A,$01 ; prepare blue, mic=on. SCF ; set carry flag ready to rotate in. JP SA_8_BITS ; jump forward to SA_8_BITS -8-> ;;;$050E SA_PARITY: LD L,H ; transfer the running parity byte to L and JR SA_LOOP_P ; back to SA_LOOP_P ; to output that byte before quitting normally. ;-------------------------- ; entry point to save yellow part of bit. ; a bit consists of a period with mic on and blue border followed by ; a period of mic off with yellow border. ; Note. since the DJNZ instruction does not affect flags, the zero flag is used ; to indicate which of the two passes is in effect and the carry maintains the ; state of the bit to be saved. ;;;$0511 SA_BIT_2: LD A,C ; fetch 'mic on and yellow' which is held permanently in C. BIT 7,B ; set the zero flag. B holds $3E. ; entry point to save 1 entire bit. For first bit B holds $3B(*). ; Carry is set if saved bit is 1. zero is reset NZ on entry. ;;;$0514 SA_BIT_1: DJNZ SA_BIT_1 ; self loop for delay to SA_BIT_1 JR NC,SA_OUT ; forward to SA_OUT if bit is 0. ; but if bit is 1 then the mic state is held for longer. LD B,$42 ; set timed delay. (66 decimal) ;;;$051A SA_SET: DJNZ SA_SET ; self loop to SA_SET ; (roughly an extra 66*13 clock cycles) ;;;$051C SA_OUT: OUT ($FE),A ; blue and mic on OR yellow and mic off. LD B,$3E ; set up delay JR NZ,SA_BIT_2 ; back to SA_BIT_2 if zero reset NZ (first pass) ; proceed when the blue and yellow bands have been output. DEC B ; change value $3E to $3D. XOR A ; clear carry flag (ready to rotate in). INC A ; reset zero flag ie. NZ. ; -8-> ;;;$0525 SA_8_BITS: RL L ; rotate left through carry ; C<76543210 ; now test if byte counter has reached $FFFF. LD A,D ; fetch high byte INC A ; increment. JP NZ,SA_LOOP ; jump to SA_LOOP if more bytes. LD B,$3B ; a final delay. ;;;$053C SA_DELAY: DJNZ SA_DELAY ; self loop to SA_DELAY RET ; return - - > ;--------------------------------------------------- ; Reset border and check BREAK key for LOAD and SAVE ;--------------------------------------------------- ; the address of this routine is pushed on the stack prior to any load/save ; operation and it handles normal completion with the restoration of the ; border and also abnormal termination when the break key, or to be more ; precise the space key is pressed during a tape operation. ; - - > ;;;$053F SA_LD_RET: PUSH AF ; preserve accumulator throughout. LD A,(BORDCR) ; fetch border colour from BORDCR. AND $38 ; mask off paper bits. RRCA ; rotate RRCA ; to the RRCA ; range 0-7. OUT ($FE),A ; change the border colour. LD A,$7F ; read from port address $7FFE the IN A,($FE) ; row with the space key at outside. RRA ; test for space key pressed. EI ; enable interrupts JR C,SA_LD_END ; forward to SA_LD_END if not ;;;$0552 REPORT_DA: RST 08H ; ERROR_1 DEFB $0C ; Error Report: BREAK - CONT repeats ;;;$0554 SA_LD_END: POP AF ; restore the accumulator. RET ; return. ;------------------------------------- ; Load header or block of information ;------------------------------------- ; This routine is used to load bytes and on entry A is set to $00 for a ; header or to $FF for data. IX points to the start of receiving location ; and DE holds the length of bytes to be loaded. If, on entry the carry flag ; is set then data is loaded, if reset then it is verified. ;;;$0556 LD_BYTES: INC D ; reset the zero flag without disturbing carry. EX AF,AF' ; preserve entry flags. DEC D ; restore high byte of length. DI ; disable interrupts LD A,$0F ; make the border white and mic off. OUT ($FE),A ; output to port. LD HL,SA_LD_RET ; Address: SA_LD_RET PUSH HL ; is saved on stack as terminating routine. ; the reading of the EAR bit (D6) will always be preceded by a test of the ; space key (D0), so store the initial post-test state. IN A,($FE) ; read the ear state - bit 6. RRA ; rotate to bit 5. AND $20 ; isolate this bit. OR $02 ; combine with red border colour. LD C,A ; and store initial state long-term in C. CP A ; set the zero flag. ;;;$056B LD_BREAK: RET NZ ; return if at any time space is pressed. ;;;$056C LD_START: CALL LD_EDGE_1 ; routine LD_EDGE_1 JR NC,LD_BREAK ; back to LD_BREAK with time out and no ; edge present on tape. ; but continue when a transition is found on tape. LD HL,$0415 ; set up 16-bit outer loop counter for ; approx 1 second delay. ;;;$0574 LD_WAIT: DJNZ LD_WAIT ; self loop to LD_WAIT (for 256 times) DEC HL ; decrease outer loop counter. LD A,H ; test for OR L ; zero. JR NZ,LD_WAIT ; back to LD_WAIT, if not zero, with zero in B. ; continue after delay with H holding zero and B also. ; sample 256 edges to check that we are in the middle of a lead-in section. CALL LD_EDGE_2 ; routine LD_EDGE_2 JR NC,LD_BREAK ; back to LD_BREAK ; if no edges at all. ;;;$0580 LD_LEADER: LD B,$9C ; set timing value. CALL LD_EDGE_2 ; routine LD_EDGE_2 JR NC,LD_BREAK ; back to LD_BREAK if time-out LD A,$C6 ; two edges must be spaced apart. CP B ; compare JR NC,LD_START ; back to LD_START if too close together for a ; lead-in. INC H ; proceed to test 256 edged sample. JR NZ,LD_LEADER ; back to LD_LEADER while more to do. ; sample indicates we are in the middle of a two or five second lead-in. ; Now test every edge looking for the terminal synch signal. ;;;$058F LD_SYNC: LD B,$C9 ; initial timing value in B. CALL LD_EDGE_1 ; routine LD_EDGE_1 JR NC,LD_BREAK ; back to LD_BREAK with time-out. LD A,B ; fetch augmented timing value from B. CP $D4 ; compare JR NC,LD_SYNC ; back to LD_SYNC if gap too big, that is, ; a normal lead-in edge gap. ; but a short gap will be the synch pulse. ; in which case another edge should appear before B rises to $FF CALL LD_EDGE_1 ; routine LD_EDGE_1 RET NC ; return with time-out. ; proceed when the synch at the end of the lead-in is found. ; We are about to load data so change the border colours. LD A,C ; fetch long-term mask from C XOR $03 ; and make blue/yellow. LD C,A ; store the new long-term byte. LD H,$00 ; set up parity byte as zero. LD B,$B0 ; timing. JR LD_MARKER ; forward to LD_MARKER ; the loop mid entry point with the alternate ; zero flag reset to indicate first byte ; is discarded. ; the loading loop loads each byte and is entered at the mid point. ;;;$05A9 LD_LOOP: EX AF,AF' ; restore entry flags and type in A. JR NZ,LD_FLAG ; forward to LD_FLAG if awaiting initial flag ; which is to be discarded. JR NC,LD_VERIFY ; forward to LD_VERIFY if not to be loaded. LD (IX+$00),L ; place loaded byte at memory location. JR LD_NEXT ; forward to LD_NEXT ;;;$05B3 LD_FLAG: RL C ; preserve carry (verify) flag in long-term ; state byte. Bit 7 can be lost. XOR L ; compare type in A with first byte in L. RET NZ ; return if no match e.g. CODE vs DATA. ; continue when data type matches. LD A,C ; fetch byte with stored carry RRA ; rotate it to carry flag again LD C,A ; restore long-term port state. INC DE ; increment length ?? JR LD_DEC ; forward to LD_DEC. ; but why not to location after ? ; for verification the byte read from tape is compared with that in memory. ;;;$05BD LD_VERIFY: LD A,(IX+$00) ; fetch byte from memory. XOR L ; compare with that on tape RET NZ ; return if not zero. ;;;$05C2 LD_NEXT: INC IX ; increment byte pointer. ;;;$05C4 LD_DEC: DEC DE ; decrement length. EX AF,AF' ; store the flags. LD B,$B2 ; timing. ; when starting to read 8 bits the receiving byte is marked with bit at right. ; when this is rotated out again then 8 bits have been read. ;;;$05C8 LD_MARKER: LD L,$01 ; initialize as %00000001 ;;;$05CA LD_8_BITS: CALL LD_EDGE_2 ; routine LD_EDGE_2 increments B relative to ; gap between 2 edges. RET NC ; return with time-out. LD A,$CB ; the comparison byte. CP B ; compare to incremented value of B. ; if B is higher then bit on tape was set. ; if <= then bit on tape is reset. RL L ; rotate the carry bit into L. LD B,$B0 ; reset the B timer byte. JP NC,LD_8_BITS ; jump back to LD_8_BITS ; when carry set then marker bit has been passed out and byte is complete. LD A,H ; fetch the running parity byte. XOR L ; include the new byte. LD H,A ; and store back in parity register. LD A,D ; check length of OR E ; expected bytes. JR NZ,LD_LOOP ; back to LD_LOOP ; while there are more. ; when all bytes loaded then parity byte should be zero. LD A,H ; fetch parity byte. CP $01 ; set carry if zero. RET ; return ; in no carry then error as checksum disagrees. ;-------------------------- ; Check signal being loaded ;-------------------------- ; An edge is a transition from one mic state to another. ; More specifically a change in bit 6 of value input from port $FE. ; Graphically it is a change of border colour, say, blue to yellow. ; The first entry point looks for two adjacent edges. The second entry point ; is used to find a single edge. ; The B register holds a count, up to 256, within which the edge (or edges) ; must be found. The gap between two edges will be more for a '1' than a '0' ; so the value of B denotes the state of the bit (two edges) read from tape. ; -> ;;;$05E3 LD_EDGE_2: CALL LD_EDGE_1 ; call routine LD_EDGE_1 below. RET NC ; return if space pressed or time-out. ; else continue and look for another adjacent ; edge which together represent a bit on the ; tape. ; -> ; this entry point is used to find a single edge from above but also ; when detecting a read-in signal on the tape. ;;;$05E7 LD_EDGE_1: LD A,$16 ; a delay value of twenty two. ;;;$05E9 LD_DELAY: DEC A ; decrement counter JR NZ,LD_DELAY ; loop back to LD_DELAY 22 times. AND A ; clear carry. ;;;$05ED LD_SAMPLE: INC B ; increment the time-out counter. RET Z ; return with failure when $FF passed. LD A,$7F ; prepare to read keyboard and EAR port IN A,($FE) ; row $7FFE. bit 6 is EAR, bit 0 is SPACE key. RRA ; test outer key the space. (bit 6 moves to 5) RET NC ; return if space pressed. >>> XOR C ; compare with initial long-term state. AND $20 ; isolate bit 5 JR Z,LD_SAMPLE ; back to LD_SAMPLE if no edge. ; but an edge, a transition of the EAR bit, has been found so switch the ; long-term comparison byte containing both border colour and EAR bit. LD A,C ; fetch comparison value. CPL ; switch the bits LD C,A ; and put back in C for long-term. AND $07 ; isolate new colour bits. OR $08 ; set bit 3 - MIC off. OUT ($FE),A ; send to port to effect change of colour. SCF ; set carry flag signalling edge found within ; time allowed. RET ; return. ;---------------------------------- ; Entry point for all tape commands ;---------------------------------- ; This is the single entry point for the four tape commands. ; The routine first determines in what context it has been called by examining ; the low byte of the Syntax table entry which was stored in T_ADDR. ; Subtracting $EO (the present arrangement) gives a value of ; $00 - SAVE ; $01 - LOAD ; $02 - VERIFY ; $03 - MERGE ; As with all commands the address STMT_RET is on the stack. ;;;$0605 SAVE_ETC: POP AF ; discard address STMT_RET. LD A,(T_ADDR) ; fetch T_ADDR ; Now reduce the low byte of the Syntax table entry to give command. SUB $E0 ; subtract the known offset - giving 0 for SAVE, ; 1 for LOAD, 2 for VERIFY and 3 for MERGE LD (T_ADDR),A ; and put back in T_ADDR as 0,1,2, or 3 ; for future reference. CALL EXPT_EXP ; routine EXPT_EXP checks that a string ; expression follows and stacks the ; parameters in run-time. CALL SYNTAX_Z ; routine SYNTAX_Z JR Z,SA_DATA ; forward to SA_DATA if checking syntax. LD BC,$0011 ; presume seventeen bytes for a header. LD A,(T_ADDR) ; fetch command from T_ADDR. AND A ; test for zero - SAVE. JR Z,SA_SPACE ; forward to SA_SPACE if so. LD C,$22 ; else double length to thirty four. ;;;$0621 SA_SPACE: RST 30H ; BC_SPACES creates 17/34 bytes in workspace. PUSH DE ; transfer the start of new space to POP IX ; the available index register. ; ten spaces are required for the default filename but it is simpler to ; overwrite the first file-type indicator byte as well. LD B,$0B ; set counter to eleven. LD A,$20 ; prepare a space. ;;;$0629 SA_BLANK: LD (DE),A ; set workspace location to space. INC DE ; next location. DJNZ SA_BLANK ; loop back to SA_BLANK till all eleven done. LD (IX+$01),$FF ; set first byte of ten character filename ; to $FF as a default to signal null string. CALL STK_FETCH ; routine STK_FETCH fetches the filename ; parameters from the calculator stack. ; length of string in BC. ; start of string in DE. LD HL,$FFF6 ; prepare the value minus ten. DEC BC ; decrement length. ; ten becomes nine, zero becomes $FFFF. ADD HL,BC ; trial addition. INC BC ; restore true length. JR NC,SA_NAME ; forward to SA_NAME if length is one to ten. ; the filename is more than ten characters in length or the null string. LD A,(T_ADDR) ; fetch command from T_ADDR. AND A ; test for zero - SAVE. JR NZ,SA_NULL ; forward to SA_NULL if not the SAVE command. ; but no more than ten characters are allowed for SAVE. ; The first ten characters of any other command parameter are acceptable. ; Weird, but necessary, if saving to sectors. ; Note. the golden rule that there are no restriction on anything is broken. ;;;$0642 REPORT_FA: RST 08H ; ERROR_1 DEFB $0E ; Error Report: Invalid file name ; continue with LOAD, MERGE, VERIFY and also SAVE within ten character limit. ;;;$0644 SA_NULL: LD A,B ; test length of filename OR C ; for zero. JR Z,SA_DATA ; forward to SA_DATA if so using the 255 ; indicator followed by spaces. LD BC,$000A ; else trim length to ten. ; other paths rejoin here with BC holding length in range 1 - 10. ;;;$064B SA_NAME: PUSH IX ; push start of file descriptor. POP HL ; and pop into HL. INC HL ; HL now addresses first byte of filename. EX DE,HL ; transfer destination address to DE, start ; of string in command to HL. LDIR ; copy up to ten bytes ; if less than ten then trailing spaces follow. ; the case for the null string rejoins here. ;;;$0652 SA_DATA: RST 18H ; GET_CHAR CP $E4 ; is character after filename the token 'DATA' ? JR NZ,SA_SCR ; forward to SA_SCR to consider SCREEN$ if not. ; continue to consider DATA. LD A,(T_ADDR) ; fetch command from T_ADDR CP $03 ; is it 'VERIFY' ? JP Z,REPORT_C ; jump forward to REPORT_C if so. ; 'Nonsense in basic' ; VERIFY "d" DATA is not allowed. ; continue with SAVE, LOAD, MERGE of DATA. RST 20H ; NEXT_CHAR CALL LOOK_VARS ; routine LOOK_VARS searches variables area ; returning with carry reset if found or ; checking syntax. SET 7,C ; this converts a simple string to a ; string array. The test for an array or string ; comes later. JR NC,SA_V_OLD ; forward to SA_V_OLD if variable found. LD HL,$0000 ; set destination to zero as not fixed. LD A,(T_ADDR) ; fetch command from T_ADDR DEC A ; test for 1 - LOAD JR Z,SA_V_NEW ; forward to SA_V_NEW with LOAD DATA. ; to load a new array. ; otherwise the variable was not found in run-time with SAVE/MERGE. ;;;$0670 REPORT_2A: RST 08H ; ERROR_1 DEFB $01 ; Error Report: Variable not found ; continue with SAVE/LOAD DATA ;;;$0672 SA_V_OLD: JP NZ,REPORT_C ; to REPORT_C if not an array variable. ; or erroneously a simple string. ; 'Nonsense in basic' CALL SYNTAX_Z ; routine SYNTAX_Z JR Z,SA_DATA_1 ; forward to SA_DATA_1 if checking syntax. INC HL ; step past single character variable name. LD A,(HL) ; fetch low byte of length. LD (IX+$0B),A ; place in descriptor. INC HL ; point to high byte. LD A,(HL) ; and transfer that LD (IX+$0C),A ; to descriptor. INC HL ; increase pointer within variable. ;;;$0685 SA_V_NEW: LD (IX+$0E),C ; place character array name in header. LD A,$01 ; default to type numeric. BIT 6,C ; test result from LOOK_VARS. JR Z,SA_V_TYPE ; forward to SA_V_TYPE if numeric. INC A ; set type to 2 - string array. ;;;$068F SA_V_TYPE: LD (IX+$00),A ; place type 0, 1 or 2 in descriptor. ;;;$0692 SA_DATA_1: EX DE,HL ; save var pointer in DE RST 20H ; NEXT_CHAR CP $29 ; is character ')' ? JR NZ,SA_V_OLD ; back if not to SA_V_OLD to report ; 'Nonsense in basic' RST 20H ; NEXT_CHAR advances character address. CALL CHECK_END ; routine CHECK_END errors if not end of the statement. EX DE,HL ; bring back variables data pointer. JP SA_ALL ; jump forward to SA_ALL ; the branch was here to consider a 'SCREEN$', the display file. ;;;$06A0 SA_SCR: CP $AA ; is character the token 'SCREEN$' ? JR NZ,SA_CODE ; forward to SA_CODE if not. LD A,(T_ADDR) ; fetch command from T_ADDR CP $03 ; is it MERGE ? JP Z,REPORT_C ; jump to REPORT_C if so. ; 'Nonsense in basic' ; continue with SAVE/LOAD/VERIFY SCREEN$. RST 20H ; NEXT_CHAR CALL CHECK_END ; routine CHECK_END errors if not at end of ; statement. ; continue in runtime. LD (IX+$0B),$00 ; set descriptor length LD (IX+$0C),$1B ; to $1b00 to include bitmaps and attributes. LD HL,$4000 ; set start to display file start. LD (IX+$0D),L ; place start in LD (IX+$0E),H ; the descriptor. JR SA_TYPE_3 ; forward to SA_TYPE_3 ; the branch was here to consider CODE. ;;;$06C3 SA_CODE: CP $AF ; is character the token 'CODE' ? JR NZ,SA_LINE ; forward if not to SA_LINE to consider an ; auto-started basic program. LD A,(T_ADDR) ; fetch command from T_ADDR CP $03 ; is it MERGE ? JP Z,REPORT_C ; jump forward to REPORT_C if so. ; 'Nonsense in basic' RST 20H ; NEXT_CHAR advances character address. CALL PR_ST_END ; routine PR_ST_END checks if a carriage ; return or ':' follows. JR NZ,SA_CODE_1 ; forward to SA_CODE_1 if there are parameters. LD A,(T_ADDR) ; else fetch the command from T_ADDR. AND A ; test for zero - SAVE without a specification. JP Z,REPORT_C ; jump to REPORT_C if so. ; 'Nonsense in basic' ; for LOAD/VERIFY put zero on stack to signify handle at location saved from. CALL USE_ZERO ; routine USE_ZERO JR SA_CODE_2 ; forward to SA_CODE_2 ; if there are more characters after CODE expect start and possibly length. ;;;$06E1 SA_CODE_1: CALL EXPT_1NUM ; routine EXPT_1NUM checks for numeric ; expression and stacks it in run-time. RST 18H ; GET_CHAR CP $2C ; does a comma follow ? JR Z,SA_CODE_3 ; forward if so to SA_CODE_3 ; else allow saved code to be loaded to a specified address. LD A,(T_ADDR) ; fetch command from T_ADDR. AND A ; is the command SAVE which requires length ? JP Z,REPORT_C ; jump to REPORT_C if so. ; 'Nonsense in basic' ; the command LOAD code may rejoin here with zero stacked as start. ;;;$06F0 SA_CODE_2: CALL USE_ZERO ; routine USE_ZERO stacks zero for length. JR SA_CODE_4 ; forward to SA_CODE_4 ; the branch was here with SAVE CODE start, ;;;$06F5 SA_CODE_3: RST 20H ; NEXT_CHAR advances character address. CALL EXPT_1NUM ; routine EXPT_1NUM checks for expression ; and stacks in run-time. ; paths converge here and nothing must follow. ;;;$06F9 SA_CODE_4: CALL CHECK_END ; routine CHECK_END errors with extraneous ; characters and quits if checking syntax. ; in run-time there are two 16-bit parameters on the calculator stack. CALL FIND_INT2 ; routine FIND_INT2 gets length. LD (IX+$0B),C ; place length LD (IX+$0C),B ; in descriptor. CALL FIND_INT2 ; routine FIND_INT2 gets start. LD (IX+$0D),C ; place start LD (IX+$0E),B ; in descriptor. LD H,B ; transfer the LD L,C ; start to HL also. ;;;$0710 SA_TYPE_3: LD (IX+$00),$03 ; place type 3 - code in descriptor. JR SA_ALL ; forward to SA_ALL. ; the branch was here with basic to consider an optional auto-start line number. ;;;$0716 SA_LINE: CP $CA ; is character the token 'LINE' ? JR Z,SA_LINE_1 ; forward to SA_LINE_1 if so. ; else all possibilities have been considered and nothing must follow. CALL CHECK_END ; routine CHECK_END ; continue in run-time to save basic without auto-start. LD (IX+$0E),$80 ; place high line number in descriptor to disable auto-start. JR SA_TYPE_0 ; forward to SA_TYPE_0 to save program. ; the branch was here to consider auto-start. ;;;$0723 SA_LINE_1: LD A,(T_ADDR) ; fetch command from T_ADDR AND A ; test for SAVE. JP NZ,REPORT_C ; jump forward to REPORT_C with anything else. ; 'Nonsense in basic' RST 20H ; NEXT_CHAR CALL EXPT_1NUM ; routine EXPT_1NUM checks for numeric ; expression and stacks in run-time. CALL CHECK_END ; routine CHECK_END quits if syntax path. CALL FIND_INT2 ; routine FIND_INT2 fetches the numeric expression. LD (IX+$0D),C ; place the auto-start LD (IX+$0E),B ; line number in the descriptor. ; Note. this isn't checked, but is subsequently handled by the system. ; If the user typed 40000 instead of 4000 then it won't auto-start ; at line 4000, or indeed, at all. ; continue to save program and any variables. ;;;$073A SA_TYPE_0: LD (IX+$00),$00 ; place type zero - program in descriptor. LD HL,(E_LINE) ; fetch E_LINE to HL. LD DE,(PROG) ; fetch PROG to DE. SCF ; set carry flag to calculate from end of ; variables E_LINE -1. SBC HL,DE ; subtract to give total length. LD (IX+$0B),L ; place total length LD (IX+$0C),H ; in descriptor. LD HL,(VARS) ; load HL from system variable VARS SBC HL,DE ; subtract to give program length. LD (IX+$0F),L ; place length of program LD (IX+$10),H ; in the descriptor. EX DE,HL ; start to HL, length to DE. ;;;$075A SA_ALL: LD A,(T_ADDR) ; fetch command from T_ADDR AND A ; test for zero - SAVE. JP Z,SA_CONTRL ; jump forward to SA_CONTRL with SAVE -> ; continue with LOAD, MERGE and VERIFY. PUSH HL ; save start. LD BC,$0011 ; prepare to add seventeen ADD IX,BC ; to point IX at second descriptor. ;;;$0767 LD_LOOK_H: PUSH IX ; save IX LD DE,$0011 ; seventeen bytes XOR A ; reset zero flag SCF ; set carry flag CALL LD_BYTES ; routine LD_BYTES loads a header from tape ; to second descriptor. POP IX ; restore IX. JR NC,LD_LOOK_H ; loop back to LD_LOOK_H until header found. LD A,$FE ; select system channel 'S' CALL CHAN_OPEN ; routine CHAN_OPEN opens it. LD (IY+$52),$03 ; set SCR_CT to 3 lines. LD C,$80 ; C has bit 7 set to indicate type mismatch as ; a default startpoint. LD A,(IX+$00) ; fetch loaded header type to A CP (IX-$11) ; compare with expected type. JR NZ,LD_TYPE ; forward to LD_TYPE with mis-match. LD C,$F6 ; set C to minus ten - will count characters up to zero. ;;;$078A LD_TYPE: CP $04 ; check if type in acceptable range 0 - 3. JR NC,LD_LOOK_H ; back to LD_LOOK_H with 4 and over. ; else A indicates type 0-3. LD DE,TAPE_MSGS2 ; address base of last 4 tape messages PUSH BC ; save BC CALL PO_MSG ; routine PO_MSG outputs relevant message. ; Note. all messages have a leading newline. POP BC ; restore BC PUSH IX ; transfer IX, POP DE ; the 2nd descriptor, to DE. LD HL,$FFF0 ; prepare minus seventeen. ADD HL,DE ; add to point HL to 1st descriptor. LD B,$0A ; the count will be ten characters for the filename. LD A,(HL) ; fetch first character and test for INC A ; value 255. JR NZ,LD_NAME ; forward to LD_NAME if not the wildcard. ; but if it is the wildcard, then add ten to C which is minus ten for a type ; match or -128 for a type mismatch. Although characters have to be counted ; bit 7 of C will not alter from state set here. LD A,C ; transfer $F6 or $80 to A ADD A,B ; add $0A LD C,A ; place result, zero or -118, in C. ; At this point we have either a type mismatch, a wildcard match or ten ; characters to be counted. The characters must be shown on the screen. ;;;$07A6 LD_NAME: INC DE ; address next input character LD A,(DE) ; fetch character CP (HL) ; compare to expected INC HL ; address next expected character JR NZ,LD_CH_PR ; forward to LD_CH_PR with mismatch INC C ; increment matched character count ;;;$07AD LD_CH_PR: RST 10H ; PRINT_A prints character DJNZ LD_NAME ; loop back to LD_NAME for ten characters. ; if ten characters matched and the types previously matched then C will ; now hold zero. BIT 7,C ; test if all matched JR NZ,LD_LOOK_H ; back to LD_LOOK_H if not ; else print a terminal carriage return. LD A,$0D ; prepare carriage return. RST 10H ; PRINT_A outputs it. ; The various control routines for LOAD, VERIFY and MERGE are executed ; during the one-second gap following the header on tape. POP HL ; restore xx LD A,(IX+$00) ; fetch incoming type CP $03 ; compare with CODE JR Z,VR_CONTROL ; forward to VR_CONTROL if it is CODE. ; type is a program or an array. LD A,(T_ADDR) ; fetch command from T_ADDR DEC A ; was it LOAD ? JP Z,LD_CONTRL ; jump forward to LD_CONTRL if so to ; load BASIC or variables. CP $02 ; was command MERGE ? JP Z,ME_CONTRL ; jump forward to ME_CONTRL if so. ; else continue into VERIFY control routine to verify. ;---------------------- ; Handle VERIFY control ;---------------------- ; There are two branches to this routine. ; 1) From above to verify a program or array ; 2) from earlier with no carry to load or verify code. ;;;$07CB VR_CONTROL: PUSH HL ; save pointer to data. LD L,(IX-$06) ; fetch length of old data LD H,(IX-$05) ; to HL. LD E,(IX+$0B) ; fetch length of new data LD D,(IX+$0C) ; to DE. LD A,H ; check length of old OR L ; for zero. JR Z,VR_CONT_1 ; forward to VR_CONT_1 if length unspecified ; e.g LOAD "x" CODE ; as opposed to, say, LOAD 'x' CODE 32768,300. SBC HL,DE ; subtract the two lengths. JR C,REPORT_R ; forward to REPORT_R if the length on tape is ; larger than that specified in command. ; 'Tape loading error' JR Z,VR_CONT_1 ; forward to VR_CONT_1 if lengths match. ; a length on tape shorter than expected is not allowed for CODE LD A,(IX+$00) ; else fetch type from tape. CP $03 ; is it CODE ? JR NZ,REPORT_R ; forward to REPORT_R if so ; 'Tape loading error' ;;;$07E9 VR_CONT_1: POP HL ; pop pointer to data LD A,H ; test for zero OR L ; e.g. LOAD 'x' CODE JR NZ,VR_CONT_2 ; forward to VR_CONT_2 if destination specified. LD L,(IX+$0D) ; else use the destination in the header LD H,(IX+$0E) ; and load code at address saved from. ;;;$07F4 VR_CONT_2: PUSH HL ; push pointer to start of data block. POP IX ; transfer to IX. LD A,(T_ADDR) ; fetch reduced command from T_ADDR CP $02 ; is it VERIFY ? SCF ; prepare a set carry flag JR NZ,VR_CONT_3 ; skip to VR_CONT_3 if not AND A ; clear carry flag for VERIFY so that ; data is not loaded. ;;;$0800 VR_CONT_3: LD A,$FF ; signal data block to be loaded ;------------------ ; Load a data block ;------------------ ; This routine is called from 3 places other than above to load a data block. ; In all cases the accumulator is first set to $FF so the routine could be ; called at the previous instruction. ;;;$0802 LD_BLOCK: CALL LD_BYTES ; routine LD_BYTES RET C ; return if successful. ;;;$0806 REPORT_R: RST 08H ; ERROR_1 DEFB $1A ; Error Report: Tape loading error ;-------------------- ; Handle LOAD control ;-------------------- ; This branch is taken when the command is LOAD with type 0, 1 or 2. ;;;$0808 LD_CONTRL: LD E,(IX+$0B) ; fetch length of found data block LD D,(IX+$0C) ; from 2nd descriptor. PUSH HL ; save destination LD A,H ; test for zero OR L JR NZ,LD_CONT_1 ; forward if not to LD_CONT_1 INC DE ; increase length INC DE ; for letter name INC DE ; and 16-bit length EX DE,HL ; length to HL, JR LD_CONT_2 ; forward to LD_CONT_2 ;;;$0819 LD_CONT_1: LD L,(IX-$06) ; fetch length from LD H,(IX-$05) ; the first header. EX DE,HL SCF ; set carry flag SBC HL,DE JR C,LD_DATA ; to LD_DATA ;;;$0825 LD_CONT_2: LD DE,$0005 ; allow overhead of five bytes. ADD HL,DE ; add in the difference in data lengths. LD B,H ; transfer to LD C,L ; the BC register pair CALL TEST_ROOM ; routine TEST_ROOM fails if not enough room. ;;;$082E LD_DATA: POP HL ; pop destination LD A,(IX+$00) ; fetch type 0, 1 or 2. AND A ; test for program and variables. JR Z,LD_PROG ; forward if so to LD_PROG ; the type is a numeric or string array. LD A,H ; test the destination for zero OR L ; indicating variable does not already exist. JR Z,LD_DATA_1 ; forward if so to LD_DATA_1 ; else the destination is the first dimension within the array structure DEC HL ; address high byte of total length LD B,(HL) ; transfer to B. DEC HL ; address low byte of total length. LD C,(HL) ; transfer to C. DEC HL ; point to letter of variable. INC BC ; adjust length to INC BC ; include these INC BC ; three bytes also. LD (X_PTR),IX ; save header pointer in X_PTR. CALL RECLAIM_2 ; routine RECLAIM_2 reclaims the old variable ; sliding workspace including the two headers downwards. LD IX,(X_PTR) ; reload IX from X_PTR which will have been ; adjusted down by POINTERS routine. ;;;$084C LD_DATA_1: LD HL,(E_LINE) ; address E_LINE DEC HL ; now point to the $80 variables end-marker. LD C,(IX+$0B) ; fetch new data length LD B,(IX+$0C) ; from 2nd header. PUSH BC ; * save it. INC BC ; adjust the INC BC ; length to include INC BC ; letter name and total length. LD A,(IX-$03) ; fetch letter name from old header. PUSH AF ; preserve accumulator though not corrupted. CALL MAKE_ROOM ; routine MAKE_ROOM creates space for variable ; sliding workspace up. IX no longer addresses ; anywhere meaningful. INC HL ; point to first new location. POP AF ; fetch back the letter name. LD (HL),A ; place in first new location. POP DE ; * pop the data length. INC HL ; address 2nd location LD (HL),E ; store low byte of length. INC HL ; address next. LD (HL),D ; store high byte. INC HL ; address start of data. PUSH HL ; transfer address POP IX ; to IX register pair. SCF ; set carry flag indicating load not verify. LD A,$FF ; signal data not header. JP LD_BLOCK ; jump back to LD_BLOCK ; the branch is here when a program as opposed to an array is to be loaded. ;;;$0873 LD_PROG: EX DE,HL ; transfer dest to DE. LD HL,(E_LINE) ; address E_LINE DEC HL ; now variables end-marker. LD (X_PTR),IX ; place the IX header pointer in X_PTR LD C,(IX+$0B) ; get new length LD B,(IX+$0C) ; from 2nd header PUSH BC ; and save it. CALL RECLAIM_1 ; routine RECLAIM_1 reclaims program and vars. ; adjusting X_PTR. POP BC ; restore new length. PUSH HL ; * save start PUSH BC ; ** and length. CALL MAKE_ROOM ; routine MAKE_ROOM creates the space. LD IX,(X_PTR) ; reload IX from adjusted X_PTR INC HL ; point to start of new area. LD C,(IX+$0F) ; fetch length of BASIC on tape LD B,(IX+$10) ; from 2nd descriptor ADD HL,BC ; add to address the start of variables. LD (VARS),HL ; set system variable VARS LD H,(IX+$0E) ; fetch high byte of autostart line number. LD A,H ; transfer to A AND $C0 ; test if greater than $3F. JR NZ,LD_PROG_1 ; forward to LD_PROG_1 if so with no autostart. LD L,(IX+$0D) ; else fetch the low byte. LD (NEWPPC),HL ; set sytem variable to line number NEWPPC LD (IY+$0A),$00 ; set statement NSPPC to zero. ;;;$08AD LD_PROG_1: POP DE ; ** pop the length POP IX ; * and start. SCF ; set carry flag LD A,$FF ; signal data as opposed to a header. JP LD_BLOCK ; jump back to LD_BLOCK ;--------------------- ; Handle MERGE control ;--------------------- ; the branch was here to merge a program and it's variables or an array. ;;;$08B6 ME_CONTRL: LD C,(IX+$0B) ; fetch length LD B,(IX+$0C) ; of data block on tape. PUSH BC ; save it. INC BC ; one for the pot. RST 30H ; BC_SPACES creates room in workspace. ; HL addresses last new location. LD (HL),$80 ; place end-marker at end. EX DE,HL ; transfer first location to HL. POP DE ; restore length to DE. PUSH HL ; save start. PUSH HL ; and transfer it POP IX ; to IX register. SCF ; set carry flag to load data on tape. LD A,$FF ; signal data not a header. CALL LD_BLOCK ; routine LD_BLOCK loads to workspace. POP HL ; restore first location in workspace to HL. LD DE,(PROG) ; set DE from system variable PROG. ; now enter a loop to merge the data block in workspace with the program and ; variables. ;;;$08D2 ME_NEW_LP: LD A,(HL) ; fetch next byte from workspace. AND $C0 ; compare with $3F. JR NZ,ME_VAR_LP ; forward to ME_VAR_LP if a variable. ; continue when HL addresses a Basic line number. ;;;$08D7 ME_OLD_LP: LD A,(DE) ; fetch high byte from program area. INC DE ; bump prog address. CP (HL) ; compare with that in workspace. INC HL ; bump workspace address. JR NZ,ME_OLD_L1 ; forward to ME_OLD_L1 if high bytes don't match LD A,(DE) ; fetch the low byte of program line number. CP (HL) ; compare with that in workspace. ;;;$08DF ME_OLD_L1: DEC DE ; point to start of DEC HL ; respective lines again. JR NC,ME_NEW_L2 ; forward to ME_NEW_L2 if line number in ; workspace is less than or equal to current ; program line as has to be added to program. PUSH HL ; else save workspace pointer. EX DE,HL ; transfer prog pointer to HL CALL NEXT_ONE ; routine NEXT_ONE finds next line in DE. POP HL ; restore workspace pointer JR ME_OLD_LP ; back to ME_OLD_LP until destination position ; in program area found. ; the branch was here with an insertion or replacement point. ;;;$08EB: ME_NEW_L2: CALL ME_ENTER ; routine ME_ENTER enters the line JR ME_NEW_LP ; loop back to ME_NEW_LP. ; the branch was here when the location in workspace held a variable. ;;;$08F0 ME_VAR_LP: LD A,(HL) ; fetch first byte of workspace variable. LD C,A ; copy to C also. CP $80 ; is it the end-marker ? RET Z ; return if so as complete. >>>>> PUSH HL ; save workspace area pointer. LD HL,(VARS) ; load HL with VARS - start of variables area. ;;;$08F9 ME_OLD_VP: LD A,(HL) ; fetch first byte. CP $80 ; is it the end-marker ? JR Z,ME_VAR_L2 ; forward if so to ME_VAR_L2 to add ; variable at end of variables area. CP C ; compare with variable in workspace area. JR Z,ME_OLD_V2 ; forward to ME_OLD_V2 if a match to replace. ; else entire variables area has to be searched. ;;;$0901 ME_OLD_V1: PUSH BC ; save character in C. CALL NEXT_ONE ; routine NEXT_ONE gets following variable address in DE. POP BC ; restore character in C EX DE,HL ; transfer next address to HL. JR ME_OLD_VP ; loop back to ME_OLD_VP ; the branch was here when first characters of name matched. ;;;$0909 ME_OLD_V2: AND $E0 ; keep bits 11100000 CP $A0 ; compare 10100000 - a long-named variable. JR NZ,ME_VAR_L1 ; forward to ME_VAR_L1 if just one-character. ; but long-named variables have to be matched character by character. POP DE ; fetch workspace 1st character pointer PUSH DE ; and save it on the stack again. PUSH HL ; save variables area pointer on stack. ;;;$0912 ME_OLD_V3: INC HL ; address next character in vars area. INC DE ; address next character in workspace area. LD A,(DE) ; fetch workspace character. CP (HL) ; compare to variables character. JR NZ,ME_OLD_V4 ; forward to ME_OLD_V4 with a mismatch. RLA ; test if the terminal inverted character. JR NC,ME_OLD_V3 ; loop back to ME_OLD_V3 if more to test. ; otherwise the long name matches in it's entirety. POP HL ; restore pointer to first character of variable JR ME_VAR_L1 ; forward to ME_VAR_L1 ; the branch is here when two characters don't match ;;;$091E ME_OLD_V4: POP HL ; restore the prog/vars pointer. JR ME_OLD_V1 ; back to ME_OLD_V1 to resume search. ; branch here when variable is to replace an existing one ;;;$0921 ME_VAR_L1: LD A,$FF ; indicate a replacement. ; this entry point is when A holds $80 indicating a new variable. ;;;$0923 ME_VAR_L2: POP DE ; pop workspace pointer. EX DE,HL ; now make HL workspace pointer, DE vars pointer INC A ; zero flag set if replacement. SCF ; set carry flag indicating a variable not a program line. CALL ME_ENTER ; routine ME_ENTER copies variable in. JR ME_VAR_LP ; loop back to ME_VAR_LP ;------------------------- ; Merge a Line or Variable ;------------------------- ; A Basic line or variable is inserted at the current point. If the line numbers ; or variable names match (zero flag set) then a replacement takes place. ;;;$092C ME_ENTER: JR NZ,ME_ENT_1 ; forward to ME_ENT_1 for insertion only. ; but the program line or variable matches so old one is reclaimed. EX AF,AF' ; save flag?? LD (X_PTR),HL ; preserve workspace pointer in dynamic X_PTR EX DE,HL ; transfer program dest pointer to HL. CALL NEXT_ONE ; routine NEXT_ONE finds following location ; in program or variables area. CALL RECLAIM_2 ; routine RECLAIM_2 reclaims the space between. EX DE,HL ; transfer program dest pointer back to DE. LD HL,(X_PTR) ; fetch adjusted workspace pointer from X_PTR EX AF,AF' ; restore flags. ; now the new line or variable is entered. ;;;$093E ME_ENT_1: EX AF,AF' ; save or re-save flags. PUSH DE ; save dest pointer in prog/vars area. CALL NEXT_ONE ; routine NEXT_ONE finds next in workspace. ; gets next in DE, difference in BC. ; prev addr in HL LD (X_PTR),HL ; store pointer in X_PTR LD HL,(PROG) ; load HL from system variable PROG EX (SP),HL ; swap with prog/vars pointer on stack. PUSH BC ; ** save length of new program line/variable. EX AF,AF' ; fetch flags back. JR C,ME_ENT_2 ; skip to ME_ENT_2 if variable DEC HL ; address location before pointer CALL MAKE_ROOM ; routine MAKE_ROOM creates room for basic line INC HL ; address next. JR ME_ENT_3 ; forward to ME_ENT_3 ;;;$0955 ME_ENT_2: CALL MAKE_ROOM ; routine MAKE_ROOM creates room for variable. ;;;$0958 ME_ENT_3: INC HL ; address next? POP BC ; ** pop length POP DE ; * pop value for PROG which may have been ; altered by POINTERS if first line. LD (PROG),DE ; set PROG to original value. LD DE,(X_PTR) ; fetch adjusted workspace pointer from X_PTR PUSH BC ; save length PUSH DE ; and workspace pointer EX DE,HL ; make workspace pointer source, prog/vars ; pointer the destination LDIR ; copy bytes of line or variable into new area. POP HL ; restore workspace pointer. POP BC ; restore length. PUSH DE ; save new prog/vars pointer. CALL RECLAIM_2 ; routine RECLAIM_2 reclaims the space used ; by the line or variable in workspace block ; as no longer required and space could be ; useful for adding more lines. POP DE ; restore the prog/vars pointer RET ; return. ;-------------------- ; Handle SAVE control ;-------------------- ; A branch from the main SAVE_ETC routine at SAVE-ALL. ; First the header data is saved. Then after a wait of 1 second ; the data itself is saved. ; HL points to start of data. ; IX points to start of descriptor. ;;;$0970 SA_CONTRL: PUSH HL ; save start of data LD A,$FD ; select system channel 'S' CALL CHAN_OPEN ; routine CHAN_OPEN XOR A ; clear to address table directly LD DE,TAPE_MSGS ; address: TAPE_MSGS CALL PO_MSG ; routine PO_MSG - ; 'Start tape then press any key.' SET 5,(IY+$02) ; TV_FLAG - Signal lower screen requires clearing CALL WAIT_KEY ; routine WAIT_KEY PUSH IX ; save pointer to descriptor. LD DE,$0011 ; there are seventeen bytes. XOR A ; signal a header. CALL SA_BYTES ; routine SA_BYTES POP IX ; restore descriptor pointer. LD B,$32 ; wait for a second - 50 interrupts. ;;;$0991 SA_1_SEC: HALT ; wait for interrupt DJNZ SA_1_SEC ; back to SA_1_SEC until pause complete. LD E,(IX+$0B) ; fetch length of bytes from the LD D,(IX+$0C) ; descriptor. LD A,$FF ; signal data bytes. POP IX ; retrieve pointer to start JP SA_BYTES ; jump back to SA_BYTES ; Arrangement of two headers in workspace. ; Originally IX addresses first location and only one header is required ; when saving. ; ; OLD NEW PROG DATA DATA CODE ; HEADER HEADER num chr NOTES. ; ------ ------ ---- ---- ---- ---- ----------------------------- ; IX-$11 IX+$00 0 1 2 3 Type. ; IX-$10 IX+$01 x x x x F ($FF if filename is null). ; IX-$0F IX+$02 x x x x i ; IX-$0E IX+$03 x x x x l ; IX-$0D IX+$04 x x x x e ; IX-$0C IX+$05 x x x x n ; IX-$0B IX+$06 x x x x a ; IX-$0A IX+$07 x x x x m ; IX-$09 IX+$08 x x x x e ; IX-$08 IX+$09 x x x x . ; IX-$07 IX+$0A x x x x (terminal spaces). ; IX-$06 IX+$0B lo lo lo lo Total ; IX-$05 IX+$0C hi hi hi hi Length of datablock. ; IX-$04 IX+$0D Auto - - Start Various ; IX-$03 IX+$0E Start a-z a-z addr ($80 if no autostart). ; IX-$02 IX+$0F lo - - - Length of Program ; IX-$01 IX+$10 hi - - - only i.e. without variables. ;------------------------- ; Canned cassette messages ;------------------------- ; The last-character-inverted Cassette messages. ; Starts with normal initial step-over byte. ;;;$09A1 TAPE_MSGS: DEFB $80 DEFB "Start tape, then press any key" TAPE_MSGS2: DEFB '.'+$80 DEFB $0D DEFB "Program:",' '+$80 DEFB $0D DEFB "Number array:",' '+$80 DEFB $0D DEFB "Character array:",' '+$80 DEFB $0D DEFB "Bytes:",' '+$80 ;************************************************** ;** Part 5. SCREEN AND PRINTER HANDLING ROUTINES ** ;************************************************** ;---------------------- ; General PRINT routine ;---------------------- ; This is the routine most often used by the RST 10 restart although the ; subroutine is on two occasions called directly when it is known that ; output will definitely be to the lower screen. ;;;$09F4 PRINT_OUT: CALL PO_FETCH ; routine PO_FETCH fetches print position ; to HL register pair. CP $20 ; is character a space or higher ? JP NC,PO_ABLE ; jump forward to PO_ABLE if so. CP $06 ; is character in range 00-05 ? JR C,PO_QUEST ; to PO_QUEST to print '?' if so. CP $18 ; is character in range 24d - 31d ? JR NC,PO_QUEST ; to PO_QUEST to also print '?' if so. LD HL,CTLCHRTAB - 6; address $0A0B - the base address of control ; character table - where zero would be. LD E,A ; control character 06 - 23d LD D,$00 ; is transferred to DE. ADD HL,DE ; index into table. LD E,(HL) ; fetch the offset to routine. ADD HL,DE ; add to make HL the address. PUSH HL ; push the address. JP PO_FETCH ; to PO_FETCH, as the screen/printer position ; has been disturbed, and indirectly to ; routine on stack. ;------------------------ ; Control character table ;------------------------ ; For control characters in the range 6 - 23d the following table ; is indexed to provide an offset to the handling routine that ; follows the table. ;;;$0A11 CTLCHRTAB: DEFB PO_COMMA - $ ; 06d offset $4E to Address: PO_COMMA DEFB PO_QUEST - $ ; 07d offset $57 to Address: PO_QUEST DEFB PO_BACK_1 - $ ; 08d offset $10 to Address: PO_BACK_1 DEFB PO_RIGHT - $ ; 09d offset $29 to Address: PO_RIGHT DEFB PO_QUEST - $ ; 10d offset $54 to Address: PO_QUEST DEFB PO_QUEST - $ ; 11d offset $53 to Address: PO_QUEST DEFB PO_QUEST - $ ; 12d offset $52 to Address: PO_QUEST DEFB PO_ENTER - $ ; 13d offset $37 to Address: PO_ENTER DEFB PO_QUEST - $ ; 14d offset $50 to Address: PO_QUEST DEFB PO_QUEST - $ ; 15d offset $4F to Address: PO_QUEST DEFB PO_1_OPER - $ ; 16d offset $5F to Address: PO_1_OPER DEFB PO_1_OPER - $ ; 17d offset $5E to Address: PO_1_OPER DEFB PO_1_OPER - $ ; 18d offset $5D to Address: PO_1_OPER DEFB PO_1_OPER - $ ; 19d offset $5C to Address: PO_1_OPER DEFB PO_1_OPER - $ ; 20d offset $5B to Address: PO_1_OPER DEFB PO_1_OPER - $ ; 21d offset $5A to Address: PO_1_OPER DEFB PO_2_OPER - $ ; 22d offset $54 to Address: PO_2_OPER DEFB PO_2_OPER - $ ; 23d offset $53 to Address: PO_2_OPER ;-------------------- ; Cursor left routine ;-------------------- ; Backspace and up a line if that action is from the left of screen. ; For ZX printer backspace up to first column but not beyond. ;;;$0A23 PO_BACK_1: INC C ; move left one column. LD A,$22 ; value $21 is leftmost column. CP C ; have we passed ? JR NZ,PO_BACK_3 ; to PO_BACK_3 if not and store new position. BIT 1,(IY+$01) ; test FLAGS - is printer in use ? JR NZ,PO_BACK_2 ; to PO_BACK_2 if so, as we are unable to ; backspace from the leftmost position. INC B ; move up one screen line LD C,$02 ; the rightmost column position. LD A,$18 ; Note. This should be $19 ; credit. Dr. Frank O'Hara, 1982 CP B ; has position moved past top of screen ? JR NZ,PO_BACK_3 ; to PO_BACK_3 if not and store new position. DEC B ; else back to $18. ;;;$0A38 PO_BACK_2: LD C,$21 ; the leftmost column position. ;;;$0A3A PO_BACK_3: JP CL_SET ; to CL_SET and PO_STORE to save new ; position in system variables. ;--------------------- ; Cursor right routine ;--------------------- ; This moves the print position to the right leaving a trail in the ; current background colour. ; "However the programmer has failed to store the new print position ; so CHR$ 9 will only work if the next print position is at a newly ; defined place. ; e.g. PRINT PAPER 2; CHR$ 9; AT 4,0; ; does work but is not very helpful" ; - Dr. Ian Logan, Understanding Your Spectrum, 1982. ;;;$0A3D PO_RIGHT: LD A,(P_FLAG) ; fetch P_FLAG value PUSH AF ; and save it on stack. LD (IY+$57),$01 ; temporarily set P_FLAG 'OVER 1'. LD A,$20 ; prepare a space. CALL PO_CHAR ; routine PO_CHAR to print it. ; Note. could be PO_ABLE which would update ; the column position. POP AF ; restore the permanent flag. LD (P_FLAG),A ; and restore system variable P_FLAG RET ; return without updating column position ;------------------------ ; Perform carriage return ;------------------------ ; A carriage return is 'printed' to screen or printer buffer. ;;;$0A4F PO_ENTER: BIT 1,(IY+$01) ; test FLAGS - is printer in use ? JP NZ,COPY_BUFF ; to COPY_BUFF if so, to flush buffer and reset ; the print position. LD C,$21 ; the leftmost column position. CALL PO_SCR ; routine PO_SCR handles any scrolling required. DEC B ; to next screen line. JP CL_SET ; jump forward to CL_SET to store new position. ;------------ ; Print comma ;------------ ; The comma control character. The 32 column screen has two 16 character ; tabstops. The routine is only reached via the control character table. ;;;$0A5F PO_COMMA: CALL PO_FETCH ; routine PO_FETCH - seems unnecessary. LD A,C ; the column position. $21-$01 DEC A ; move right. $20-$00 DEC A ; and again $1F-$00 or $FF if trailing AND $10 ; will be $00 or $10. JR PO_FILL ; forward to PO_FILL ;-------------------- ; Print question mark ;-------------------- ; This routine prints a question mark which is commonly ; used to print an unassigned control character in range 0-31d. ; there are a surprising number yet to be assigned. ;;;$0A69 PO_QUEST: LD A,$3F ; prepare the character '?'. JR PO_ABLE ; forward to PO_ABLE. ;--------------------------------- ; Control characters with operands ;--------------------------------- ; Certain control characters are followed by 1 or 2 operands. ; The entry points from control character table are PO_2_OPER and PO_1_OPER. ; The routines alter the output address of the current channel so that ; subsequent RST $10 instructions take the appropriate action ; before finally resetting the output address back to PRINT_OUT. ;;;$0A6D PO_TV_2: LD DE,PO_CONT ; address: PO_CONT will be next output routine LD (TVDATA_HI),A ; store first operand in TVDATA_HI JR PO_CHANGE ; forward to PO_CHANGE >> ; -> This initial entry point deals with two operands - AT or TAB. ;;;$0A75 PO_2_OPER: LD DE,PO_TV_2 ; address: PO_TV_2 will be next output routine JR PO_TV_1 ; forward to PO_TV_1 ; -> This initial entry point deals with one operand INK to OVER. ;;;$0A7A PO_1_OPER: LD DE,PO_CONT ; address: PO_CONT will be next output routine ;;;$0A7D PO_TV_1: LD (TVDATA_LO),A ; store control code in TVDATA_LO ;;;$0A80 PO_CHANGE: LD HL,(CURCHL) ; use CURCHL to find current output channel. LD (HL),E ; make it INC HL ; the supplied LD (HL),D ; address from DE. RET ; Note. should clear carry before returning ;;;$0A87 PO_CONT: LD DE,PRINT_OUT ; Address: PRINT_OUT CALL PO_CHANGE ; routine PO_CHANGE to restore normal channel. LD HL,(TVDATA_LO) ; TVDATA gives control code and possible ; subsequent character LD D,A ; save current character LD A,L ; the stored control code CP $16 ; was it INK to OVER (1 operand) ? JP C,CO_TEMP_5 ; to CO_TEMP_5 JR NZ,PO_TAB ; to PO_TAB if not 22d i.e. 23d TAB. ; else must have been 22d AT. LD B,H ; line to H (0-23d) LD C,D ; column to C (0-31d) LD A,$1F ; the value 31d SUB C ; reverse the column number. JR C,PO_AT_ERR ; to PO_AT_ERR if C was greater than 31d. ADD A,$02 ; transform to system range $02-$21 LD C,A ; and place in column register. BIT 1,(IY+$01) ; test FLAGS - is printer in use ? JR NZ,PO_AT_SET ; to PO_AT_SET as line can be ignored. LD A,$16 ; 22 decimal SUB B ; subtract line number to reverse ; 0 - 22 becomes 22 - 0. ;;;$0AAC PO_AT_ERR: JP C,REPORT_BB ; to REPORT_BB if higher than 22 decimal ; Integer out of range. INC A ; adjust for system range $01-$17 LD B,A ; place in line register INC B ; adjust to system range $02-$18 BIT 0,(IY+$02) ; TV_FLAG - Lower screen in use ? JP NZ,PO_SCR ; exit to PO_SCR to test for scrolling CP (IY+$31) ; Compare against DF_SZ JP C,REPORT_5 ; to REPORT_5 if too low ; Out of screen. ;;;$0ABF PO_AT_SET: JP CL_SET ; print position is valid so exit via CL_SET ; Continue here when dealing with TAB. ; Note. In basic TAB is followed by a 16-bit number and was initially ; designed to work with any output device. ;;;$0AC2 PO_TAB: LD A,H ; transfer parameter to A ; Losing current character - ; High byte of TAB parameter. ;;;$0AC3 PO_FILL: CALL PO_FETCH ; routine PO_FETCH, HL-addr, BC=line/column. ; column 1 (right), $21 (left) ADD A,C ; add operand to current column DEC A ; range 0 - 31+ AND $1F ; make range 0 - 31d RET Z ; return if result zero LD D,A ; Counter to D SET 0,(IY+$01) ; update FLAGS - signal suppress leading space. ;;;$0AD0 PO_SPACE: LD A,$20 ; space character. CALL PO_SAVE ; routine PO_SAVE prints the character ; using alternate set (normal output routine) DEC D ; decrement counter. JR NZ,PO_SPACE ; to PO_SPACE until done RET ; return ;----------------------- ; Printable character(s) ;----------------------- ; This routine prints printable characters and continues into ; the position store routine ;;;$0AD9 PO_ABLE: CALL PO_ANY ; routine PO_ANY ; and continue into position store routine. ;-------------------------------------- ; Store line, column, and pixel address ;-------------------------------------- ; This routine updates the system variables associated with ; The main screen, lower screen/input buffer or ZX printer. ;;;$0ADC PO_STORE: BIT 1,(IY+$01) ; test FLAGS - Is printer in use ? JR NZ,PO_ST_PR ; to PO_ST_PR if so BIT 0,(IY+$02) ; TV_FLAG - Lower screen in use ? JR NZ,PO_ST_E ; to PO_ST_E if so LD (S_POSN),BC ; S_POSN line/column upper screen LD (DF_CC),HL ; DF_CC display file address RET ;;;$0AF0: PO_ST_E: LD (SPOSNL),BC ; SPOSNL line/column lower screen LD (ECHO_E),BC ; ECHO_E line/column input buffer LD (DFCCL),HL ; DFCCL lower screen memory address RET ;;;$0AFC PO_ST_PR: LD (IY+$45),C ; P_POSN column position printer LD (PR_CC),HL ; PR_CC full printer buffer memory address RET ;-------------------------- ; Fetch position parameters ;-------------------------- ; This routine fetches the line/column and display file address ; of the upper and lower screen or, if the printer is in use, ; the column position and absolute memory address. ; Note. that PR-CC-hi (23681) is used by this routine and the one above ; and if, in accordance with the manual (that says this is unused), the ; location has been used for other purposes, then subsequent output ; to the printer buffer could corrupt a 256-byte section of memory. ;;;$0B03 PO_FETCH: BIT 1,(IY+$01) ; test FLAGS - Is printer in use JR NZ,PO_F_PR ; to PO_F_PR if so ; assume upper screen LD BC,(S_POSN) ; S_POSN LD HL,(DF_CC) ; DF_CC display file address BIT 0,(IY+$02) ; TV_FLAG - Lower screen in use ? RET Z ; return if upper screen ; ah well, was lower screen LD BC,(SPOSNL) ; SPOSNL LD HL,(DFCCL) ; DFCCL RET ; return ;;;$0B1D PO_F_PR: LD C,(IY+$45) ; P_POSN column only LD HL,(PR_CC) ; PR_CC printer buffer address RET ; return ;-------------------- ; Print any character ;-------------------- ; This routine is used to print any character in range 32d - 255d ; It is only called from PO_ABLE and continues into PO_STORE ;;;$0B24 PO_ANY: CP $80 ; ascii ? JR C,PO_CHAR ; to PO_CHAR is so. CP $90 ; test if a block graphic character. JR NC,PO_T_UDG ; to PO_T_UDG to print tokens and udg's ; The 16 2*2 mosaic characters 128-143 decimal are formed from ; bits 0-3 of the character. LD B,A ; save character CALL PO_GR_1 ; routine PO_GR_1 to construct top half then bottom half. CALL PO_FETCH ; routine PO_FETCH fetches print position. LD DE,MEM_0 ; MEM_0 is location of 8 bytes of character JR PR_ALL ; to PR_ALL to print to screen or printer ;;;$0B38 PO_GR_1: LD HL,MEM_0 ; address MEM_0 - a temporary buffer in ; systems variables which is normally used by the calculator. CALL PO_GR_2 ; routine PO_GR_2 to construct top half ; and continue into routine to construct bottom half. ;;;$0B3E PO_GR_2: RR B ; rotate bit 0/2 to carry SBC A,A ; result $00 or $FF AND $0F ; mask off right hand side LD C,A ; store part in C RR B ; rotate bit 1/3 of original chr to carry SBC A,A ; result $00 or $FF AND $F0 ; mask off left hand side OR C ; combine with stored pattern LD C,$04 ; four bytes for top/bottom half ;;;$0B4C PO_GR_3: LD (HL),A ; store bit patterns in temporary buffer INC HL ; next address DEC C ; jump back to JR NZ,PO_GR_3 ; to PO_GR_3 until byte is stored 4 times RET ; return ; Tokens and User defined graphics are now separated. ;;;$0B52 PO_T_UDG: SUB $A5 ; the 'RND' character JR NC,PO_T ; to PO_T to print tokens ADD A,$15 ; add 21d to restore to 0 - 20 PUSH BC ; save current print position LD BC,(UDG) ; fetch UDG to address bit patterns JR PO_CHAR_2 ; to PO_CHAR_2 - common code to lay down ; a bit patterned character ;;;$0B5F PO_T: CALL PO_TOKENS ; routine PO_TOKENS prints tokens JP PO_FETCH ; exit via PO_FETCH as this routine must continue into PO_STORE ; This point is used to print ascii characters 32d - 127d. ;;;$0B65 PO_CHAR: PUSH BC ; save print position LD BC,(CHARS) ; address CHARS ; This common code is used to transfer the character bytes to memory. ;;;$0B6A PO_CHAR_2: EX DE,HL ; transfer destination address to DE LD HL,FLAGS ; point to FLAGS RES 0,(HL) ; allow for leading space CP $20 ; is it a space ? JR NZ,PO_CHAR_3 ; to PO_CHAR_3 if not SET 0,(HL) ; signal no leading space to FLAGS ;;;$0B76 PO_CHAR_3: LD H,$00 ; set high byte to 0 LD L,A ; character to A ; 0-21 UDG or 32-127 ascii. ADD HL,HL ; multiply ADD HL,HL ; by ADD HL,HL ; eight ADD HL,BC ; HL now points to first byte of character POP BC ; the source address CHARS or UDG EX DE,HL ; character address to DE ;--------------------- ; Print all characters ;--------------------- ; This entry point entered from above to print ascii and UDGs ; but also from earlier to print mosaic characters. ; HL=destination ; DE=character source ; BC=line/column ;;;$0B7F PR_ALL: LD A,C ; column to A DEC A ; move right LD A,$21 ; pre-load with leftmost position JR NZ,PR_ALL_1 ; but if not zero to PR_ALL_1 DEC B ; down one line LD C,A ; load C with $21 BIT 1,(IY+$01) ; test FLAGS - Is printer in use JR Z,PR_ALL_1 ; to PR_ALL_1 if not PUSH DE ; save source address CALL COPY_BUFF ; routine COPY_BUFF outputs line to printer POP DE ; restore character source address LD A,C ; the new column number ($21) to C ;;;$0B93 PR_ALL_1: CP C ; this test is really for screen - new line ? PUSH DE ; save source CALL Z,PO_SCR ; routine PO_SCR considers scrolling POP DE ; restore source PUSH BC ; save line/column PUSH HL ; and destination LD A,(P_FLAG) ; fetch P_FLAG to accumulator LD B,$FF ; prepare OVER mask in B. RRA ; bit 0 set if OVER 1 JR C,PR_ALL_2 ; to PR_ALL_2 INC B ; set OVER mask to 0 ;;;$0BA4 PR_ALL_2: RRA ; skip bit 1 of P_FLAG RRA ; bit 2 is INVERSE SBC A,A ; will be FF for INVERSE 1 else zero LD C,A ; transfer INVERSE mask to C LD A,$08 ; prepare to count 8 bytes AND A ; clear carry to signal screen BIT 1,(IY+$01) ; test FLAGS - Is printer in use ? JR Z,PR_ALL_3 ; to PR_ALL_3 if screen SET 1,(IY+$30) ; update FLAGS2 - Signal printer buffer has been used. SCF ; set carry flag to signal printer. ;;;$0BB6 PR_ALL_3: EX DE,HL ; now HL=source, DE=destination ;;;$0BB7 PR_ALL_4: EX AF,AF' ; save printer/screen flag LD A,(DE) ; fetch existing destination byte AND B ; consider OVER XOR (HL) ; now XOR with source XOR C ; now with INVERSE MASK LD (DE),A ; update screen/printer EX AF,AF' ; restore flag JR C,PR_ALL_6 ; to PR_ALL_6 - printer address update INC D ; gives next pixel line down screen ;;;$0BC1 PR_ALL_5: INC HL ; address next character byte DEC A ; the byte count is decremented JR NZ,PR_ALL_4 ; back to PR_ALL_4 for all 8 bytes EX DE,HL ; destination to HL DEC H ; bring back to last updated screen position BIT 1,(IY+$01) ; test FLAGS - is printer in use ? CALL Z,PO_ATTR ; if not, call routine PO_ATTR to update corresponding colour attribute. POP HL ; restore original screen/printer position POP BC ; and line column DEC C ; move column to right INC HL ; increase screen/printer position RET ; return and continue into PO_STORE within PO_ABLE ; This branch is used to update the printer position by 32 places ; Note. The high byte of the address D remains constant (which it should). ;;;$0BD3 PR_ALL_6: EX AF,AF' ; save the flag LD A,$20 ; load A with 32 decimal ADD A,E ; add this to E LD E,A ; and store result in E EX AF,AF' ; fetch the flag JR PR_ALL_5 ; back to PR_ALL_5 ;-------------- ; Set attribute ;-------------- ; This routine is entered with the HL register holding the last screen ; address to be updated by PRINT or PLOT. ; The Spectrum screen arrangement leads to the L register holding ; the correct value for the attribute file and it is only necessary ; to manipulate H to form the correct colour attribute address. ;;;$0BDB PO_ATTR: LD A,H ; fetch high byte $40 - $57 RRCA ; shift RRCA ; bits 3 and 4 RRCA ; to right. AND $03 ; range is now 0 - 2 OR $58 ; form correct high byte for third of screen LD H,A ; HL is now correct LD DE,(ATTRT_MASKT); make D hold ATTR_T, E hold MASK-T LD A,(HL) ; fetch existing attribute XOR E ; apply masks AND D XOR E BIT 6,(IY+$57) ; test P_FLAG - is this PAPER 9 ?? JR Z,PO_ATTR_1 ; skip to PO_ATTR_1 if not. AND $C7 ; set paper BIT 2,A ; to contrast with ink JR NZ,PO_ATTR_1 ; skip to PO_ATTR_1 XOR $38 ;;;$0BFA PO_ATTR_1: BIT 4,(IY+$57) ; test P_FLAG - Is this INK 9 ?? JR Z,PO_ATTR_2 ; skip to PO_ATTR_2 if not AND $F8 ; make ink BIT 5,A ; contrast with paper. JR NZ,PO_ATTR_2 ; to PO_ATTR_2 XOR $07 ;;;$0C08 PO_ATTR_2: LD (HL),A ; save the new attribute. RET ; return. ;----------------- ; Message printing ;----------------- ; This entry point is used to print tape, boot-up, scroll? and error messages ; On entry the DE register points to an initial step-over byte or ; the inverted end-marker of the previous entry in the table. ; A contains the message number, often zero to print first message. ; (HL has nothing important usually P_FLAG) ;;;$0C0A PO_MSG: PUSH HL ; put hi-byte zero on stack to suppress LD H,$00 ; trailing spaces EX (SP),HL ; ld h,0; push hl would have done ?. JR PO_TABLE ; forward to PO_TABLE. ; This entry point prints the basic keywords, '<>' etc. from alt set ;;;$0C10 PO_TOKENS: LD DE,TKN_TABLE ; address: TKN_TABLE PUSH AF ; save the token number to control ; trailing spaces - see later * ;;;$0C14 PO_TABLE: CALL PO_SEARCH ; routine PO_SEARCH will set carry for ; all messages and function words. JR C,PO_EACH ; forward to PO_EACH if not a command, ; '<>' etc. LD A,$20 ; prepare leading space BIT 0,(IY+$01) ; test FLAGS - leading space if not set CALL Z,PO_SAVE ; routine PO_SAVE to print a space ; without disturbing registers ;;;$0C22 PO_EACH: LD A,(DE) ; fetch character AND $7F ; remove any inverted bit CALL PO_SAVE ; routine PO_SAVE to print using alternate set of registers. LD A,(DE) ; re-fetch character. INC DE ; address next ADD A,A ; was character inverted? (this also doubles character) JR NC,PO_EACH ; back to PO_EACH if not POP DE ; * re-fetch trailing space flag to D (was A) CP $48 ; was last character '$' ($24*2) JR Z,PO_TR_SP ; forward to PO_TR_SP to consider trailing space if so. CP $82 ; was it < 'A' i.e. '#','>','=' from tokens ; or ' ','.' (from tape) or '?' from scroll RET C ; no trailing space ;;;$0C35 PO_TR_SP: LD A,D ; the trailing space flag (zero if an error msg) CP $03 ; test against RND, INKEY$ and PI ; which have no parameters and RET C ; therefore no trailing space so return. LD A,$20 ; else continue and print a trailing space. ;-------------------------- ; Handle recursive printing ;-------------------------- ; This routine which is part of PRINT_OUT allows RST $10 to be ; used recursively to print tokens and the spaces associated with them. ;;;$0C3B PO_SAVE: PUSH DE ; save DE as CALL_SUB doesn't. EXX ; switch in main set RST 10H ; PRINT_A prints using this alternate set. EXX ; back to this alternate set. POP DE ; restore initial DE. RET ; return. ;------------- ; Table search ;------------- ; This subroutine searches a message or the token table for the ; message number held in A. DE holds the address of the table. ;;;$0C41 PO_SEARCH: PUSH AF ; save the message/token number EX DE,HL ; transfer DE to HL INC A ; adjust for initial step-over byte ;;;$0C44 PO_STEP: BIT 7,(HL) ; is character inverted ? INC HL ; address next JR Z,PO_STEP ; back to PO-STEP if not inverted. DEC A ; decrease counter JR NZ,PO_STEP ; back to PO-STEP if not zero EX DE,HL ; transfer address to DE POP AF ; restore message/token number CP $20 ; return with carry set RET C ; for all messages and function tokens LD A,(DE) ; test first character of token SUB $41 ; and return with carry set RET ; if it is less that 'A' ; i.e. '<>', '<=', '>=' ;---------------- ; Test for scroll ;---------------- ; This test routine is called when printing carriage return, when considering ; PRINT AT and from the general PRINT ALL characters routine to test if ; scrolling is required, prompting the user if necessary. ; This is therefore using the alternate set. ; The B register holds the current line. ;;;$0C55 PO_SCR: BIT 1,(IY+$01) ; test FLAGS - is printer in use ? RET NZ ; return immediately if so. LD DE,CL_SET ; set DE to address: CL_SET PUSH DE ; and push for return address. LD A,B ; transfer the line to A. BIT 0,(IY+$02) ; test TV_FLAG - Lower screen in use ? JP NZ,PO_SCR_4 ; jump forward to PO_SCR_4 if so. CP (IY+$31) ; greater than DF_SZ display file size ? JR C,REPORT_5 ; forward to REPORT_5 if less. ; 'Out of screen' RET NZ ; return (via CL_SET) if greater BIT 4,(IY+$02) ; test TV_FLAG - Automatic listing ? JR Z,PO_SCR_2 ; forward to PO_SCR_2 if not. LD E,(IY+$2D) ; fetch BREG - the count of scroll lines to E. DEC E ; decrease and jump JR Z,PO_SCR_3 ; to PO_SCR_3 if zero and scrolling required. LD A,$00 ; explicit - select channel zero. CALL CHAN_OPEN ; routine CHAN_OPEN opens it. LD SP,(LIST_SP) ; set stack pointer to LIST_SP RES 4,(IY+$02) ; reset TV_FLAG - signal auto listing finished. RET ; return ignoring pushed value, CL_SET ; to MAIN or EDITOR without updating ; print position -> ;;;$0C86 REPORT_5: RST 08H ; ERROR_1 DEFB $04 ; Error Report: Out of screen ; continue here if not an automatic listing. ;;;$0C88 PO_SCR_2: DEC (IY+$52) ; decrease SCR_CT JR NZ,PO_SCR_3 ; forward to PO_SCR_3 to scroll display if ; result not zero. ; now produce prompt. LD A,$18 ; reset SUB B ; the LD (SCR_CT),A ; SCR_CT scroll count LD HL,(ATTRT_MASKT); L=ATTR_T, H=MASK_T PUSH HL ; save on stack LD A,(P_FLAG) ; P_FLAG PUSH AF ; save on stack to prevent lower screen ; attributes (BORDCR etc.) being applied. LD A,$FD ; select system channel 'K' CALL CHAN_OPEN ; routine CHAN_OPEN opens it XOR A ; clear to address message directly LD DE,SCRL_MSSG ; make DE address: SCRL_MSSG CALL PO_MSG ; routine PO_MSG prints to lower screen SET 5,(IY+$02) ; set TV_FLAG - signal lower screen requires clearing LD HL,FLAGS ; make HL address FLAGS SET 3,(HL) ; signal 'L' mode. RES 5,(HL) ; signal 'no new key'. EXX ; switch to main set. ; as calling chr input from alternative set. CALL WAIT_KEY ; routine WAIT_KEY waits for new key ; Note. this is the right routine but the ; stream in use is unsatisfactory. From the ; choices available, it is however the best. EXX ; switch back to alternate set. CP $20 ; space is considered as BREAK JR Z,REPORT_D ; forward to REPORT_D if so ; 'BREAK - CONT repeats' CP $E2 ; is character 'STOP' ? JR Z,REPORT_D ; forward to REPORT_D if so OR $20 ; convert to lower-case CP $6E ; is character 'n' ? JR Z,REPORT_D ; forward to REPORT_D if so else scroll. LD A,$FE ; select system channel 'S' CALL CHAN_OPEN ; routine CHAN_OPEN POP AF ; restore original P_FLAG LD (P_FLAG),A ; and save in P_FLAG. POP HL ; restore original ATTR_T, MASK_T LD (ATTRT_MASKT),HL; and reset ATTR_T, MASK-T as 'scroll?' has been printed. ;;;$0CD2 PO_SCR_3: CALL CL_SC_ALL ; routine CL_SC_ALL to scroll whole display LD B,(IY+$31) ; fetch DF_SZ to B INC B ; increase to address last line of display LD C,$21 ; set C to $21 (was $21 from above routine) PUSH BC ; save the line and column in BC. CALL CL_ADDR ; routine CL_ADDR finds display address. LD A,H ; now find the corresponding attribute byte RRCA ; (this code sequence is used twice RRCA ; elsewhere and is a candidate for RRCA ; a subroutine.) AND $03 OR $58 LD H,A LD DE,$5AE0 ; start of last 'line' of attribute area LD A,(DE) ; get attribute for last line LD C,(HL) ; transfer to base line of upper part LD B,$20 ; there are thirty two bytes EX DE,HL ; swap the pointers. ;;;$0CF0 PO_SCR_3A: LD (DE),A ; transfer LD (HL),C ; attributes. INC DE ; address next. INC HL ; address next. DJNZ PO_SCR_3A ; loop back to PO_SCR_3A for all adjacent ; attribute lines. POP BC ; restore the line/column. RET ; return via CL_SET (was pushed on stack). ; The message 'scroll?' appears here with last byte inverted. ;;;$0CF8 SCRL_MSSG: DEFB $80 ; initial step-over byte. DEFB "scroll",'?'+$80 ;;;$0D00 REPORT_D: RST 08H ; ERROR_1 DEFB $0C ; Error Report: BREAK - CONT repeats ; continue here if using lower display - A holds line number. ;;;$0D02 PO_SCR_4: CP $02 ; is line number less than 2 ? JR C,REPORT_5 ; to REPORT_5 if so ; 'Out of Screen'. ADD A,(IY+$31) ; add DF_SZ SUB $19 RET NC ; return if scrolling unnecessary NEG ; Negate to give number of scrolls required. PUSH BC ; save line/column LD B,A ; count to B LD HL,(ATTRT_MASKT); fetch current ATTR_T, MASK_T to HL. PUSH HL ; and save LD HL,(P_FLAG) ; fetch P_FLAG PUSH HL ; and save. ; to prevent corruption by input AT CALL TEMPS ; routine TEMPS sets to BORDCR etc LD A,B ; transfer scroll number to A. ;;;$0D1C PO_SCR_4A: PUSH AF ; save scroll number. LD HL,DF_SZ ; address DF_SZ LD B,(HL) ; fetch old value LD A,B ; transfer to A INC A ; and increment LD (HL),A ; then put back. LD HL,S_POSN_HI ; address S_POSN_HI - line CP (HL) ; compare JR C,PO_SCR_4B ; forward to PO_SCR_4B if scrolling required INC (HL) ; else increment S_POSN_HI LD B,$18 ; set count to whole display ?? ; Note. should be $17 and the top line ; will be scrolled into the ROM which ; is harmless on the standard set up. ;;;$0D2D PO_SCR_4B: CALL CL_SCROLL ; routine CL_SCROLL scrolls B lines POP AF ; restore scroll counter. DEC A ; decrease JR NZ,PO_SCR_4A ; back to to PO_SCR_4A until done POP HL ; restore original P_FLAG. LD (IY+$57),L ; and overwrite system variable P_FLAG. POP HL ; restore original ATTR_T/MASK_T. LD (ATTRT_MASKT),HL; and update system variables. LD BC,(S_POSN) ; fetch S_POSN to BC. RES 0,(IY+$02) ; signal to TV_FLAG - main screen in use. CALL CL_SET ; call routine CL_SET for upper display. SET 0,(IY+$02) ; signal to TV_FLAG - lower screen in use. POP BC ; restore line/column RET ; return via CL_SET for lower display. ;----------------------- ; Temporary colour items ;----------------------- ; This subroutine is called 11 times to copy the permanent colour items ; to the temporary ones. ;;;$0D4D TEMPS: XOR A ; clear the accumulator LD HL,(ATTRP_MASKP); fetch L=ATTR_P and H=MASK_P BIT 0,(IY+$02) ; test TV_FLAG - is lower screen in use ? JR Z,TEMPS_1 ; skip to TEMPS_1 if not LD H,A ; set H, MASK P, to 00000000. LD L,(IY+$0E) ; fetch BORDCR to L which is used for lower screen. ;;;$0D5B TEMPS_1: LD (ATTRT_MASKT),HL; transfer values to ATTR_T and MASK_T ; for the print flag the permanent values are odd bits, temporary even bits. LD HL,P_FLAG ; address P_FLAG. JR NZ,TEMPS_2 ; skip to TEMPS_2 if lower screen using A=0. LD A,(HL) ; else pick up flag bits. RRCA ; rotate permanent bits to temporary bits. ;;;$0D65 TEMPS_2: XOR (HL) AND $55 ; BIN 01010101 XOR (HL) ; permanent now as original LD (HL),A ; apply permanent bits to temporary bits. RET ; and return. ;------------------- ; Handle CLS command ;------------------- ; clears the display. ; if it's difficult to write it should be difficult to read. ;;;$0D6B CLS: CALL CL_ALL ; routine CL_ALL clears display and ; resets attributes to permanent. ; re-attaches it to this computer. ; this routine called from input, ** ;;;$0D6E CLS_LOWER: LD HL,TV_FLAG ; address TV_FLAG RES 5,(HL) ; TV_FLAG - signal do not clear lower screen. SET 0,(HL) ; TV_FLAG - signal lower screen in use. CALL TEMPS ; routine TEMPS picks up temporary colours. LD B,(IY+$31) ; fetch lower screen DF_SZ CALL CL_LINE ; routine CL_LINE clears lower part ; and sets permanent attributes. LD HL,$5AC0 ; fetch attribute address leftmost cell, second line up. LD A,(ATTRP_MASKP) ; fetch permanent attribute from ATTR_P. DEC B ; decrement lower screen display file size JR CLS_3 ; forward to CLS_3 -> ;;;$0D87 CLS_1: LD C,$20 ; set counter to 32 characters per line ;;;$0D89 CLS_2: DEC HL ; decrease attribute address. LD (HL),A ; and place attributes in next line up. DEC C ; decrease 32 counter. JR NZ,CLS_2 ; loop back to CLS_2 until all 32 done. ;;;$0D8E CLS_3: DJNZ CLS_1 ; decrease B counter and back to CLS_1 ; if not zero. LD (IY+$31),$02 ; set DF_SZ lower screen to 2 ; This entry point is called from CL_ALL below to ; reset the system channel input and output addresses to normal. ;;;$0D94 CL_CHAN: LD A,$FD ; select system channel 'K' CALL CHAN_OPEN ; routine CHAN_OPEN opens it. LD HL,(CURCHL) ; fetch CURCHL to HL to address current channel LD DE,PRINT_OUT ; set address to PRINT_OUT for first pass. AND A ; clear carry for first pass. ;;;$0DA0 CL_CHAN_A: LD (HL),E ; insert output address first pass. INC HL ; or input address on second pass. LD (HL),D INC HL LD DE,KEY_INPUT ; fetch address KEY_INPUT for second pass CCF ; complement carry flag - will set on pass 1. JR C,CL_CHAN_A ; back to CL_CHAN_A if first pass else done. LD BC,$1721 ; line 23 for lower screen JR CL_SET ; exit via CL_SET to set column ; for lower display ;---------------------------- ; Clearing whole display area ;---------------------------- ; This subroutine called from CLS, AUTO_LIST and MAIN_3 ; clears 24 lines of the display and resets the relevant system variables ; and system channels. ;;;$0DAF CL_ALL: LD HL,$0000 ; initialize plot coordinates. LD (COORDS),HL ; set COORDS to 0,0. RES 0,(IY+$30) ; update FLAGS2 - signal main screen is clear. CALL CL_CHAN ; routine CL_CHAN makes channel 'K' 'normal'. LD A,$FE ; select system channel 'S' CALL CHAN_OPEN ; routine CHAN_OPEN opens it CALL TEMPS ; routine TEMPS picks up permanent values. LD B,$18 ; There are 24 lines. CALL CL_LINE ; routine CL_LINE clears 24 text lines ; (and sets BC to $1821) LD HL,(CURCHL) ; fetch CURCHL make HL address current channel 'S' LD DE,PRINT_OUT ; address: PRINT_OUT LD (HL),E ; is made INC HL ; the normal LD (HL),D ; output address. LD (IY+$52),$01 ; set SCR_CT - scroll count is set to default. ; Note. BC already contains $1821. LD BC,$1821 ; reset column and line to 0,0 ; and continue into CL_SET, below, exiting ; via PO_STORE (for upper screen). ;---------------------------- ; Set line and column numbers ;---------------------------- ; This important subroutine is used to calculate the character output ; address for screens or printer based on the line/column for screens ; or the column for printer. ;;;$0DD9 CL_SET: LD HL,$5B00 ; the base address of printer buffer BIT 1,(IY+$01) ; test FLAGS - is printer in use ? JR NZ,CL_SET_2 ; forward to CL_SET_2 if so. LD A,B ; transfer line to A. BIT 0,(IY+$02) ; test TV_FLAG - lower screen in use ? JR Z,CL_SET_1 ; skip to CL_SET_1 if handling upper part ADD A,(IY+$31) ; add DF_SZ for lower screen SUB $18 ; and adjust. ;;;$0DEE CL_SET_1: PUSH BC ; save the line/column. LD B,A ; transfer line to B ; (adjusted if lower screen) CALL CL_ADDR ; routine CL_ADDR calculates address at left of screen. POP BC ; restore the line/column. ;;;$0DF4 CL_SET_2: LD A,$21 ; the column $1-$21 is reversed SUB C ; to range $00 - $20 LD E,A ; now transfer to DE LD D,$00 ; prepare for addition ADD HL,DE ; and add to base address JP PO_STORE ; exit via PO_STORE to update relevant ; system variables. ;----------------- ; Handle scrolling ;----------------- ; The routine CL_SC_ALL is called once from PO to scroll all the display ; and from the routine CL_SCROLL, once, to scroll part of the display. ;;;$0DFE CL_SC_ALL: LD B,$17 ; scroll 23 lines, after 'scroll?'. ;;;$0E00 CL_SCROLL: CALL CL_ADDR ; routine CL_ADDR gets screen address in HL. LD C,$08 ; there are 8 pixel lines to scroll. ;;;$0E05 CL_SCR_1: PUSH BC ; save counters. PUSH HL ; and initial address. LD A,B ; get line count. AND $07 ; will set zero if all third to be scrolled. LD A,B ; re-fetch the line count. JR NZ,CL_SCR_3 ; forward to CL_SCR_3 if partial scroll. ; HL points to top line of third and must be copied to bottom of previous 3rd. ; ( so HL = $4800 or $5000 ) ( but also sometimes $4000 ) ;;;$0E0D CL_SCR_2: EX DE,HL ; copy HL to DE. LD HL,$F8E0 ; subtract $08 from H and add $E0 to L - ADD HL,DE ; to make destination bottom line of previous third. EX DE,HL ; restore the source and destination. LD BC,$0020 ; thirty-two bytes are to be copied. DEC A ; decrement the line count. LDIR ; copy a pixel line to previous third. ;;;$0E19 CL_SCR_3: EX DE,HL ; save source in DE. LD HL,$FFE0 ; load the value -32. ADD HL,DE ; add to form destination in HL. EX DE,HL ; switch source and destination LD B,A ; save the count in B. AND $07 ; mask to find count applicable to current RRCA ; third and RRCA ; multiply by RRCA ; thirty two (same as 5 RLCAs) LD C,A ; transfer byte count to C ($E0 at most) LD A,B ; store line count to A LD B,$00 ; make B zero LDIR ; copy bytes (BC=0, H incremented, L=0) LD B,$07 ; set B to 7, C is zero. ADD HL,BC ; add 7 to H to address next third. AND $F8 ; has last third been done ? JR NZ,CL_SCR_2 ; back to CL_SCR_2 if not POP HL ; restore topmost address. INC H ; next pixel line down. POP BC ; restore counts. DEC C ; reduce pixel line count. JR NZ,CL_SCR_1 ; back to CL_SCR_1 if all eight not done. CALL CL_ATTR ; routine CL_ATTR gets address in attributes ; from current 'ninth line', count in BC. LD HL,$FFE0 ; set HL to the 16-bit value -32. ADD HL,DE ; and add to form destination address. EX DE,HL ; swap source and destination addresses. LDIR ; copy bytes scrolling the linear attributes. LD B,$01 ; continue to clear the bottom line. ;---------------------------- ; Clear text lines of display ;---------------------------- ; This subroutine, called from CL_ALL, CLS_LOWER and AUTO_LIST and above, ; clears text lines at bottom of display. ; The B register holds on entry the number of lines to be cleared 1-24. ;;;$0E44 CL_LINE: PUSH BC ; save line count CALL CL_ADDR ; routine CL_ADDR gets top address LD C,$08 ; there are eight screen lines to a text line. ;;;$0E4A CL_LINE_1: PUSH BC ; save pixel line count PUSH HL ; and save the address LD A,B ; transfer the line to A (1-24). ;;;$0E4D CL_LINE_2: AND $07 ; mask 0-7 to consider thirds at a time RRCA ; multiply RRCA ; by 32 (same as five RLCA instructions) RRCA ; now 32 - 256(0) LD C,A ; store result in C LD A,B ; save line in A (1-24) LD B,$00 ; set high byte to 0, prepare for ldir. DEC C ; decrement count 31-255. LD D,H ; copy HL LD E,L ; to DE. LD (HL),$00 ; blank the first byte. INC DE ; make DE point to next byte. LDIR ; ldir will clear lines. LD DE,$0701 ; now address next third adjusting ADD HL,DE ; register E to address left hand side DEC A ; decrease the line count. AND $F8 ; will be 16, 8 or 0 (AND $18 will do). LD B,A ; transfer count to B. JR NZ,CL_LINE_2 ; back to CL_LINE_2 if 16 or 8 to do ; the next third. POP HL ; restore start address. INC H ; address next line down. POP BC ; fetch counts. DEC C ; decrement pixel line count JR NZ,CL_LINE_1 ; back to CL_LINE_1 till all done. CALL CL_ATTR ; routine CL_ATTR gets attribute address ; in DE and B * 32 in BC. LD H,D ; transfer the address LD L,E ; to HL. INC DE ; make DE point to next location. LD A,(ATTRP_MASKP) ; fetch ATTR_P - permanent attributes BIT 0,(IY+$02) ; test TV_FLAG - lower screen in use ? JR Z,CL_LINE_3 ; skip to CL_LINE_3 if not. LD A,(BORDCR) ; else lower screen uses BORDCR as attribute. ;;;$0E80 CL_LINE_3: LD (HL),A ; put attribute in first byte. DEC BC ; decrement the counter. LDIR ; copy bytes to set all attributes. POP BC ; restore the line $01-$24. LD C,$21 ; make column $21. (No use is made of this) RET ; return to the calling routine. ;------------------- ; Attribute handling ;------------------- ; This subroutine is called from CL_LINE or CL_SCROLL with the HL register ; pointing to the 'ninth' line and H needs to be decremented before or after ; the division. Had it been done first then either present code or that used ; at the start of PO_ATTR could have been used. ; The Spectrum screen arrangement leads to the L register holding already ; the correct value for the attribute file and it is only necessary ; to manipulate H to form the correct colour attribute address. ;;;$0E88 CL_ATTR: LD A,H ; fetch H to A - $48, $50, or $58. RRCA ; divide by RRCA ; eight. RRCA ; $09, $0A or $0B. DEC A ; $08, $09 or $0A. OR $50 ; $58, $59 or $5A. LD H,A ; save high byte of attributes. EX DE,HL ; transfer attribute address to DE LD H,C ; set H to zero - from last LDIR. LD L,B ; load L with the line from B. ADD HL,HL ; multiply ADD HL,HL ; by ADD HL,HL ; thirty two ADD HL,HL ; to give count of attribute ADD HL,HL ; cells to end of display. LD B,H ; transfer result LD C,L ; to register BC. RET ; and return. ;-------------------------------- ; Handle display with line number ;-------------------------------- ; This subroutine is called from four places to calculate the address ; of the start of a screen character line which is supplied in B. ;;;$0E9B CL_ADDR: LD A,$18 ; reverse the line number SUB B ; to range $00 - $17. LD D,A ; save line in D for later. RRCA ; multiply RRCA ; by RRCA ; thirty-two. AND $E0 ; mask off low bits to make LD L,A ; L a multiple of 32. LD A,D ; bring back the line to A. AND $18 ; now $00, $08 or $10. OR $40 ; add the base address of screen. LD H,A ; HL now has the correct address. RET ; return. ;-------------------- ; Handle COPY command ;-------------------- ; This command copies the top 176 lines to the ZX Printer ; It is popular to call this from machine code at point ; L0EAF with B holding 192 (and interrupts disabled) for a full-screen ; copy. This particularly applies to 16K Spectrums as time-critical ; machine code routines cannot be written in the first 16K of RAM as ; it is shared with the ULA which has precedence over the Z80 chip. ;;;$0EAC COPY: DI ; disable interrupts as this is time-critical. LD B,$B0 ; top 176 lines. L0EAF: LD HL,$4000 ; address start of the display file. ; now enter a loop to handle each pixel line. ;;;$0EB2 COPY_1: PUSH HL ; save the screen address. PUSH BC ; and the line counter. CALL COPY_LINE ; routine COPY_LINE outputs one line. POP BC ; restore the line counter. POP HL ; and display address. INC H ; next line down screen within 'thirds'. LD A,H ; high byte to A. AND $07 ; result will be zero if we have left third. JR NZ,COPY_2 ; forward to COPY_2 if not to continue loop. LD A,L ; consider low byte first. ADD A,$20 ; increase by 32 - sets carry if back to zero. LD L,A ; will be next group of 8. CCF ; complement - carry set if more lines in the previous third. SBC A,A ; will be FF, if more, else 00. AND $F8 ; will be F8 (-8) or 00. ADD A,H ; that is subtract 8, if more to do in third. LD H,A ; and reset address. ;;;$0EC9 COPY_2: DJNZ COPY_1 ; back to COPY_1 for all lines. JR COPY_END ; forward to COPY_END to switch off the printer ; motor and enable interrupts. ; Note. Nothing else required. ;------------------------------- ; Pass printer buffer to printer ;------------------------------- ; This routine is used to copy 8 text lines from the printer buffer ; to the ZX Printer. These text lines are mapped linearly so HL does ; not need to be adjusted at the end of each line. ;;;$0ECD COPY_BUFF: DI ; disable interrupts LD HL,$5B00 ; the base address of the Printer Buffer. LD B,$08 ; set count to 8 lines of 32 bytes. ;;;$0ED3 COPY_3: PUSH BC ; save counter. CALL COPY_LINE ; routine COPY_LINE outputs 32 bytes POP BC ; restore counter. DJNZ COPY_3 ; loop back to COPY_3 for all 8 lines. ; then stop motor and clear buffer. ; Note. the COPY command rejoins here, essentially to execute the next ; three instructions. ;;;$0EDA COPY_END: LD A,$04 ; output value 4 to port OUT ($FB),A ; to stop the slowed printer motor. EI ; enable interrupts. ;--------------------- ; Clear Printer Buffer ;--------------------- ; This routine clears an arbitrary 256 bytes of memory. ; Note. The routine seems designed to clear a buffer that follows the ; system variables. ; The routine should check a flag or HL address and simply return if COPY ; is in use. ; (T-ADDR-lo would work for the system but not if COPY called externally.) ; As a consequence of this omission the buffer will needlessly ; be cleared when COPY is used and the screen/printer position may be set to ; the start of the buffer and the line number to 0 (B) ; giving an 'Out of Screen' error. ; There seems to have been an unsuccessful attempt to circumvent the use ; of PR_CC_hi. ;;;$0EDF CLEAR_PRB: LD HL,$5B00 ; the location of the buffer. LD (IY+$46),L ; update PR_CC_lo - set to zero - superfluous. XOR A ; clear the accumulator. LD B,A ; set count to 256 bytes. ;;;$0EE7 PRB_BYTES: LD (HL),A ; set addressed location to zero. INC HL ; address next byte - Note. not INC L. DJNZ PRB_BYTES ; back to PRB_BYTES. repeat for 256 bytes. RES 1,(IY+$30) ; set FLAGS2 - signal printer buffer is clear. LD C,$21 ; set the column position . JP CL_SET ; exit via CL_SET and then PO_STORE. ;------------------ ; Copy line routine ;------------------ ; This routine is called from COPY and COPY_BUFF to output a line of ; 32 bytes to the ZX Printer. ; Output to port $FB - ; bit 7 set - activate stylus. ; bit 7 low - deactivate stylus. ; bit 2 set - stops printer. ; bit 2 reset - starts printer ; bit 1 set - slows printer. ; bit 1 reset - normal speed. ;;;$0EF4 COPY_LINE: LD A,B ; fetch the counter 1-8 or 1-176 CP $03 ; is it 01 or 02 ?. SBC A,A ; result is $FF if so else $00. AND $02 ; result is 02 now else 00. ; bit 1 set slows the printer. OUT ($FB),A ; slow the printer for the ; last two lines. LD D,A ; save the mask to control the printer later. ;;;$0EFD COPY_L_1: CALL BREAK_KEY ; call BREAK_KEY to read keyboard immediately. JR C,COPY_L_2 ; forward to COPY_L_2 if 'break' not pressed. LD A,$04 ; else stop the OUT ($FB),A ; printer motor. EI ; enable interrupts. CALL CLEAR_PRB ; call routine CLEAR_PRB. ; Note. should not be cleared if COPY in use. ;;;$0F0A REPORT_DC: RST 08H ; ERROR_1 DEFB $0C ; Error Report: BREAK - CONT repeats ;;;$0F0C COPY_L_2: IN A,($FB) ; test now to see if ADD A,A ; a printer is attached. RET M ; return if not - but continue with parent ; command. JR NC,COPY_L_1 ; back to COPY_L_1 if stylus of printer not ; in position. LD C,$20 ; set count to 32 bytes. ;;;$0F14 COPY_L_3: LD E,(HL) ; fetch a byte from line. INC HL ; address next location. Note. not INC L. LD B,$08 ; count the bits. ;;;$0F18 COPY_L_4: RL D ; prepare mask to receive bit. RL E ; rotate leftmost print bit to carry RR D ; and back to bit 7 of D restoring bit 1 ;;;$0F1E COPY_L_5: IN A,($FB) ; read the port. RRA ; bit 0 to carry. JR NC,COPY_L_5 ; back to COPY_L_5 if stylus not in position. LD A,D ; transfer command bits to A. OUT ($FB),A ; and output to port. DJNZ COPY_L_4 ; loop back to COPY_L_4 for all 8 bits. DEC C ; decrease the byte count. JR NZ,COPY_L_3 ; back to COPY_L_3 until 256 bits done. RET ; return to calling routine COPY/COPY_BUFF. ;----------------------------------- ; Editor routine for BASIC and INPUT ;----------------------------------- ; The editor is called to prepare or edit a basic line. ; It is also called from INPUT to input a numeric or string expression. ; The behaviour and options are quite different in the various modes ; and distinguished by bit 5 of FLAGX. ; ; This is a compact and highly versatile routine. ;;;$0F2C EDITOR: LD HL,(ERR_SP) ; fetch ERR_SP PUSH HL ; save on stack ;;;$0F30 ED_AGAIN: LD HL,ED_ERROR ; address: ED_ERROR PUSH HL ; save address on stack and LD (ERR_SP),SP ; make ERR_SP point to it. ; Note. While in editing/input mode should an error occur then RST 08 will ; update X_PTR to the location reached by CH_ADD and jump to ED_ERROR ; where the error will be cancelled and the loop begin again from ED_AGAIN ; above. The position of the error will be apparent when the lower screen is ; reprinted. If no error then the re-iteration is to ED_LOOP below when ; input is arriving from the keyboard. ;;;$0F38 ED_LOOP: CALL WAIT_KEY ; routine WAIT_KEY gets key possibly changing the mode. PUSH AF ; save key. LD D,$00 ; and give a short click based LD E,(IY-$01) ; on PIP value for duration. LD HL,$00C8 ; and pitch. CALL BEEPER ; routine BEEPER gives click - effective with rubber keyboard. POP AF ; get saved key value. LD HL,ED_LOOP ; address: ED_LOOP is loaded to HL. PUSH HL ; and pushed onto stack. ; At this point there is a looping return address on the stack, an error ; handler and an input stream set up to supply characters. ; The character that has been received can now be processed. CP $18 ; range 24 to 255 ? JR NC,ADD_CHAR ; forward to ADD_CHAR if so. CP $07 ; lower than 7 ? JR C,ADD_CHAR ; forward to ADD_CHAR also. ; Note. This is a 'bug' and CHR$ 6, the comma ; control character, should have had an ; entry in the ED_KEYS table. ; Steven Vickers, 1984, Pitman. CP $10 ; less than 16 ? JR C,ED_KEYS ; forward to ED_KEYS if editing control ; range 7 to 15 dealt with by a table LD BC,$0002 ; prepare for ink/paper etc. LD D,A ; save character in D CP $16 ; is it ink/paper/bright etc. ? JR C,ED_CONTR ; forward to ED_CONTR if so ; leaves 22d AT and 23d TAB ; which can't be entered via KEY_INPUT. ; so this code is never normally executed ; when the keyboard is used for input. INC BC ; if it was AT/TAB - 3 locations required BIT 7,(IY+$37) ; test FLAGX - Is this INPUT LINE ? JP Z,ED_IGNORE ; jump to ED_IGNORE if not, else CALL WAIT_KEY ; routine WAIT_KEY - input address is KEY_NEXT ; but is reset to KEY_INPUT LD E,A ; save first in E ;;;$0F6C ED_CONTR: CALL WAIT_KEY ; routine WAIT_KEY for control. ; input address will be KEY_NEXT. PUSH DE ; saved code/parameters LD HL,(K_CUR) ; fetch address of keyboard cursor from K_CUR RES 0,(IY+$07) ; set MODE to 'L' CALL MAKE_ROOM ; routine MAKE_ROOM makes 2/3 spaces at cursor POP BC ; restore code/parameters INC HL ; address first location LD (HL),B ; place code (ink etc.) INC HL ; address next LD (HL),C ; place possible parameter. If only one ; then DE points to this location also. JR ADD_CH_1 ; forward to ADD_CH_1 ;------------------------- ; Add code to current line ;------------------------- ; this is the branch used to add normal non-control characters ; with ED_LOOP as the stacked return address. ; it is also the OUTPUT service routine for system channel 'R'. ;;;$0F81 ADD_CHAR: RES 0,(IY+$07) ; set MODE to 'L' LD HL,(K_CUR) ; fetch address of keyboard cursor from K_CUR CALL ONE_SPACE ; routine ONE_SPACE creates one space. ; either a continuation of above or from ED_CONTR with ED_LOOP on stack. ;;;$0F8B ADD_CH_1: LD (DE),A ; load current character to last new location. INC DE ; address next LD (K_CUR),DE ; and update K_CUR system variable. RET ; return - either a simple return ; from ADD_CHAR or to ED_LOOP on stack. ; a branch of the editing loop to deal with control characters ; using a look-up table. ;;;$0F92 ED_KEYS: LD E,A ; character to E. LD D,$00 ; prepare to add. LD HL,ED_KEYS_T - 7; base address of editing keys table. $0F99 ADD HL,DE ; add E LD E,(HL) ; fetch offset to E ADD HL,DE ; add offset for address of handling routine. PUSH HL ; push the address on machine stack. LD HL,(K_CUR) ; load address of cursor from K_CUR. RET ; an make an indirect jump forward to routine. ;------------------- ; Editing keys table ;------------------- ; For each code in the range $07 to $0F this table contains a ; single offset byte to the routine that services that code. ; Note. for what was intended there should also have been an ; entry for CHR$ 6 with offset to ED_SYMBOL. ;;;$0FA0 ED_KEYS_T: DEFB ED_EDIT - $ ; 07d offset $09 to Address: ED_EDIT DEFB ED_LEFT - $ ; 08d offset $66 to Address: ED_LEFT DEFB ED_RIGHT - $ ; 09d offset $6A to Address: ED_RIGHT DEFB ED_DOWN - $ ; 10d offset $50 to Address: ED_DOWN DEFB ED_UP - $ ; 11d offset $B5 to Address: ED_UP DEFB ED_DELETE - $ ; 12d offset $70 to Address: ED_DELETE DEFB ED_ENTER - $ ; 13d offset $7E to Address: ED_ENTER DEFB ED_SYMBOL - $ ; 14d offset $CF to Address: ED-SYMBOL DEFB ED_GRAPH - $ ; 15d offset $D4 to Address: ED_GRAPH ;---------------- ; Handle EDIT key ;---------------- ; The user has pressed SHIFT 1 to bring edit line down to bottom of screen. ; Alternatively the user wishes to clear the input buffer and start again. ; Alternatively ... ;;;$0FA9 ED_EDIT: LD HL,(E_PPC) ; fetch E_PPC the last line number entered. ; Note. may not exist and may follow program. BIT 5,(IY+$37) ; test FLAGX - input mode ? JP NZ,CLEAR_SP ; jump forward to CLEAR_SP if not in editor. CALL LINE_ADDR ; routine LINE_ADDR to find address of line ; or following line if it doesn't exist. CALL LINE_NO ; routine LINE_NO will get line number from ; address or previous line if at end-marker. LD A,D ; if there is no program then DE will OR E ; contain zero so test for this. JP Z,CLEAR_SP ; jump to to CLEAR_SP if so. ; Note. at this point we have a validated line number, not just an ; approximation and it would be best to update E_PPC with the true ; cursor line value which would enable the line cursor to be suppressed ; in all situations - see shortly. PUSH HL ; save address of line. INC HL ; address low byte of length. LD C,(HL) ; transfer to C INC HL ; next to high byte LD B,(HL) ; transfer to B. LD HL,$000A ; an overhead of ten bytes ADD HL,BC ; is added to length. LD B,H ; transfer adjusted value LD C,L ; to BC register. CALL TEST_ROOM ; routine TEST_ROOM checks free memory. CALL CLEAR_SP ; routine CLEAR_SP clears editing area. LD HL,(CURCHL) ; address CURCHL EX (SP),HL ; swap with line address on stack PUSH HL ; save line address underneath LD A,$FF ; select system channel 'R' CALL CHAN_OPEN ; routine CHAN_OPEN opens it POP HL ; drop line address DEC HL ; make it point to first byte of line num. DEC (IY+$0F) ; decrease E_PPC_LO to suppress line cursor. ; Note. ineffective when E_PPC is one ; greater than last line of program perhaps ; as a result of a delete. ; credit. Paul Harrison 1982. CALL OUT_LINE ; routine OUT_LINE outputs the BASIC line ; to the editing area. INC (IY+$0F) ; restore E_PPC_LO to the previous value. LD HL,(E_LINE) ; address E_LINE in editing area. INC HL ; advance INC HL ; past space INC HL ; and digit characters INC HL ; of line number. LD (K_CUR),HL ; update K_CUR to address start of BASIC. POP HL ; restore the address of CURCHL. CALL CHAN_FLAG ; routine CHAN_FLAG sets flags for it. RET ; return to ED_LOOP. ;-------------------- ; Cursor down editing ;-------------------- ; The basic lines are displayed at the top of the screen and the user ; wishes to move the cursor down one line in edit mode. ; In input mode this key can be used as an alternative to entering STOP. ;;;$0FF3 ED_DOWN: BIT 5,(IY+$37) ; test FLAGX - Input Mode ? JR NZ,ED_STOP ; skip to ED_STOP if so LD HL,E_PPC ; address E_PPC - 'current line' CALL LN_FETCH ; routine LN_FETCH fetches number of next ; line or same if at end of program. JR ED_LIST ; forward to ED_LIST to produce an ; automatic listing. ;;;$1001 ED_STOP: LD (IY+$00),$10 ; set ERR_NR to 'STOP in INPUT' code JR ED_ENTER ; forward to ED_ENTER to produce error. ;-------------------- ; Cursor left editing ;-------------------- ; This acts on the cursor in the lower section of the screen in both ; editing and input mode. ;;;$1007 ED_LEFT: CALL ED_EDGE ; routine ED_EDGE moves left if possible JR ED_CUR ; forward to ED_CUR to update K-CUR ; and return to ED_LOOP. ;--------------------- ; Cursor right editing ;--------------------- ; This acts on the cursor in the lower screen in both editing and input ; mode and moves it to the right. ;;;$100C ED_RIGHT: LD A,(HL) ; fetch addressed character. CP $0D ; is it carriage return ? RET Z ; return if so to ED_LOOP INC HL ; address next character ;;;$1011 ED_CUR: LD (K_CUR),HL ; update K_CUR system variable RET ; return to ED_LOOP ;--------------- ; DELETE editing ;--------------- ; This acts on the lower screen and deletes the character to left of ; cursor. If control characters are present these are deleted first ; leaving the naked parameter (0-7) which appears as a '?' except in the ; case of CHR$ 6 which is the comma control character. It is not mandatory ; to delete these second characters. ;;;$1015 ED_DELETE: CALL ED_EDGE ; routine ED_EDGE moves cursor to left. LD BC,$0001 ; of character to be deleted. JP RECLAIM_2 ; to RECLAIM_2 reclaim the character. ;------------------------------------------- ; Ignore next 2 codes from KEY_INPUT routine ;------------------------------------------- ; Since AT and TAB cannot be entered this point is never reached ; from the keyboard. If inputting from a tape device or network then ; the control and two following characters are ignored and processing ; continues as if a carriage return had been received. ; Here, perhaps, another Spectrum has said print #15; AT 0,0; "This is yellow" ; and this one is interpreting input #15; a$. ;;;$101E ED_IGNORE: CALL WAIT_KEY ; routine WAIT_KEY to ignore keystroke. CALL WAIT_KEY ; routine WAIT_KEY to ignore next key. ;-------------- ; Enter/newline ;-------------- ; The enter key has been pressed to have basic line or input accepted. ;;;$1024 ED_ENTER: POP HL ; discard address ED_LOOP POP HL ; drop address ED_ERROR ;;;$1026 ED_END: POP HL ; the previous value of ERR_SP LD (ERR_SP),HL ; is restored to ERR_SP system variable BIT 7,(IY+$00) ; is ERR_NR $FF (= 'OK') ? RET NZ ; return if so LD SP,HL ; else put error routine on stack RET ; and make an indirect jump to it. ;------------------------------ ; Move cursor left when editing ;------------------------------ ; This routine moves the cursor left. The complication is that it must ; not position the cursor between control codes and their parameters. ; It is further complicated in that it deals with TAB and AT characters ; which are never present from the keyboard. ; The method is to advance from the beginning of the line each time, ; jumping one, two, or three characters as necessary saving the original ; position at each jump in DE. Once it arrives at the cursor then the next ; legitimate leftmost position is in DE. ;;;$1031 ED_EDGE: SCF ; carry flag must be set to call the nested CALL SET_DE ; subroutine SET_DE. ; if input then DE=WORKSP ; if editing then DE=E_LINE SBC HL,DE ; subtract address from start of line ADD HL,DE ; and add back. INC HL ; adjust for carry. POP BC ; drop return address RET C ; return to ED_LOOP if already at left of line. PUSH BC ; resave return address - ED_LOOP. LD B,H ; transfer HL - cursor address LD C,L ; to BC register pair. ; at this point DE addresses start of line. ;;;$103E ED_EDGE_1: LD H,D ; transfer DE - leftmost pointer LD L,E ; to HL INC HL ; address next leftmost character to advance position each time. LD A,(DE) ; pick up previous in A AND $F0 ; lose the low bits CP $10 ; is it INK to TAB $10-$1F ? ; that is, is it followed by a parameter ? JR NZ,ED_EDGE_2 ; to ED_EDGE_2 if not ; HL has been incremented once INC HL ; address next as at least one parameter. ; in fact since 'tab' and 'at' cannot be entered the next section seems ; superfluous. ; The test will always fail and the jump to ED_EDGE_2 will be taken. LD A,(DE) ; reload leftmost character SUB $17 ; decimal 23 ('tab') ADC A,$00 ; will be 0 for 'tab' and 'at'. JR NZ,ED_EDGE_2 ; forward to ED_EDGE_2 if not ; HL has been incremented twice INC HL ; increment a third time for 'at'/'tab' ;;;$1051 ED_EDGE_2: AND A ; prepare for true subtraction SBC HL,BC ; subtract cursor address from pointer ADD HL,BC ; and add back ; Note when HL matches the cursor position BC, ; there is no carry and the previous ; position is in DE. EX DE,HL ; transfer result to DE if looping again. ; transfer DE to HL to be used as K-CUR ; if exiting loop. JR C,ED_EDGE_1 ; back to ED_EDGE_1 if cursor not matched. RET ; return. ;------------------ ; Cursor up editing ;------------------ ; The main screen displays part of the BASIC program and the user wishes ; to move up one line scrolling if necessary. ; This has no alternative use in input mode. ;;;$1059 ED_UP: BIT 5,(IY+$37) ; test FLAGX - input mode ? RET NZ ; return if not in editor - to ED_LOOP. LD HL,(E_PPC) ; get current line from E_PPC CALL LINE_ADDR ; routine LINE_ADDR gets address EX DE,HL ; and previous in DE CALL LINE_NO ; routine LINE_NO gets prev line number LD HL,E_PPC_HI ; set HL to E_PPC_HI as next routine stores top first. CALL LN_STORE ; routine LN_STORE loads DE value to HL ; high byte first - E_PPC_LO takes E ; this branch is also taken from ED_DOWN. ;;;$106E ED_LIST: CALL AUTO_LIST ; routine AUTO_LIST lists to upper screen ; including adjusted current line. LD A,$00 ; select lower screen again JP CHAN_OPEN ; exit via CHAN_OPEN to ED_LOOP ;--------------------------------- ; Use of symbol and graphics codes ;--------------------------------- ; These will not be encountered with the keyboard but would be handled ; otherwise as follows. ; As noted earlier, Vickers says there should have been an entry in ; the KEYS table for CHR$ 6 which also pointed here. ; If, for simplicity, two Spectrums were both using #15 as a bi-directional ; channel connected to each other:- ; then when the other Spectrum has said PRINT #15; x, y ; input #15; i ; j would treat the comma control as a newline and the ; control would skip to input j. ; You can get round the missing CHR$ 6 handler by sending multiple print ; items separated by a newline '. ; CHR$ 14 would have the same functionality. ; This is CHR$ 14. ;;;$1076 ED_SYMBOL: BIT 7,(IY+$37) ; test FLAGX - is this INPUT LINE ? JR Z,ED_ENTER ; back to ED_ENTER if not to treat as if ; enter had been pressed. ; else continue and add code to buffer. ; Next is CHR$ 15 ; Note that ADD_CHAR precedes the table so we can't offset to it directly. ;;;$107C ED_GRAPH: JP ADD_CHAR ; jump back to ADD_CHAR ;--------------------- ; Editor error routine ;--------------------- ; If an error occurs while editing, or inputting, then ERR_SP ; points to the stack location holding address ED_ERROR. ;;;$107F ED_ERROR: BIT 4,(IY+$30) ; test FLAGS2 - is K channel in use ? JR Z,ED_END ; back to ED_END if not. ; but as long as we're editing lines or inputting from the keyboard, then ; we've run out of memory so give a short rasp. LD (IY+$00),$FF ; reset ERR_NR to 'OK'. LD D,$00 ; prepare for beeper. LD E,(IY-$02) ; use RASP value. LD HL,$1A90 ; set a duration. CALL BEEPER ; routine BEEPER emits a warning rasp. JP ED_AGAIN ; to ED_AGAIN to re-stack address of ; this routine and make ERR_SP point to it. ;---------------------- ; Clear edit/work space ;---------------------- ; The editing area or workspace is cleared depending on context. ; This is called from ED_EDIT to clear workspace if edit key is ; used during input, to clear editing area if no program exists ; and to clear editing area prior to copying the edit line to it. ; It is also used by the error routine to clear the respective ; area depending on FLAGX. ;;;$1097 CLEAR_SP: PUSH HL ; preserve HL CALL SET_HL ; routine SET_HL ; if in edit HL = WORKSP-1, DE = E_LINE ; if in input HL = STKBOT, DE = WORKSP DEC HL ; adjust CALL RECLAIM_1 ; routine RECLAIM_1 reclaims space LD (K_CUR),HL ; set K_CUR to start of empty area LD (IY+$07),$00 ; set MODE to 'KLC' POP HL ; restore HL. RET ; return. ;---------------------- ; Handle keyboard input ;---------------------- ; This is the service routine for the input stream of the keyboard ; channel 'K'. ;;;$10A8 KEY_INPUT: BIT 3,(IY+$02) ; test TV_FLAG - has a key been pressed in editor ? CALL NZ,ED_COPY ; routine ED_COPY if so to reprint the lower ; screen at every keystroke. AND A ; clear carry - required exit condition. BIT 5,(IY+$01) ; test FLAGS - has a new key been pressed ? RET Z ; return if not. LD A,(LASTK) ; system variable LASTK will hold last key - ; from the interrupt routine. RES 5,(IY+$01) ; update FLAGS - reset the new key flag. PUSH AF ; save the input character. BIT 5,(IY+$02) ; test TV_FLAG - clear lower screen ? CALL NZ,CLS_LOWER ; routine CLS_LOWER if so. POP AF ; restore the character code. CP $20 ; if space or higher then JR NC,KEY_DONE2 ; forward to KEY_DONE2 and return with carry ; set to signal key-found. CP $10 ; with 16d INK and higher skip JR NC,KEY_CONTR ; forward to KEY_CONTR. CP $06 ; for 6 - 15d JR NC,KEY_M_CL ; skip forward to KEY_M_CL to handle Modes ; and CapsLock. ; that only leaves 0-5, the flash bright inverse switches. LD B,A ; save character in B AND $01 ; isolate the embedded parameter (0/1). LD C,A ; and store in C LD A,B ; re-fetch copy (0-5) RRA ; halve it 0, 1 or 2. ADD A,$12 ; add 18d gives 'flash', 'bright' and 'inverse'. JR KEY_DATA ; forward to KEY_DATA with the ; parameter (0/1) in C. ; Now separate capslock 06 from modes 7-15. ;;;$10DB KEY_M_CL: JR NZ,KEY_MODE ; forward to KEY_MODE if not 06 (capslock) LD HL,FLAGS2 ; point to FLAGS2 LD A,$08 ; value 00000100 XOR (HL) ; toggle BIT 2 of FLAGS2 the capslock bit LD (HL),A ; and store result in FLAGS2 again. JR KEY_FLAG ; forward to KEY_FLAG to signal no-key. ;;;$10E6 KEY_MODE: CP $0E ; compare with chr 14d RET C ; return with carry set "key found" for ; codes 7 - 13d leaving 14d and 15d ; which are converted to mode codes. SUB $0D ; subtract 13d leaving 1 and 2 ; 1 is 'E' mode, 2 is 'G' mode. LD HL,MODE ; address the MODE system variable. CP (HL) ; compare with existing value before LD (HL),A ; inserting the new value. JR NZ,KEY_FLAG ; forward to KEY_FLAG if it has changed. LD (HL),$00 ; else make MODE zero - KLC mode ; Note. while in Extended/Graphics mode, ; the Extended Mode/Graphics key is pressed ; again to get out. ;;;$10F4 KEY_FLAG: SET 3,(IY+$02) ; update TV_FLAG - show key state has changed CP A ; clear carry and reset zero flags - no actual key returned. RET ; make the return. ; now deal with colour controls - 16-23 ink, 24-31 paper ;;;$10FA KEY_CONTR: LD B,A ; make a copy of character. AND $07 ; mask to leave bits 0-7 LD C,A ; and store in C. LD A,$10 ; initialize to 16d - INK. BIT 3,B ; was it paper ? JR NZ,KEY_DATA ; forward to KEY_DATA with INK 16d and colour in C. INC A ; else change from INK to PAPER (17d) if so. ;;;$1105 KEY_DATA: LD (IY-$2D),C ; put the colour (0-7)/state(0/1) in KDATA LD DE,KEY_NEXT ; address: KEY_NEXT will be next input stream JR KEY_CHAN ; forward to KEY_CHAN to change it ... ; ... so that INPUT_AD directs control to here at next call to WAIT_KEY ;;;$110D KEY_NEXT: LD A,(KDATA) ; pick up the parameter stored in KDATA. LD DE,KEY_INPUT ; address: KEY_INPUT will be next input stream ; continue to restore default channel and ; make a return with the control code. ;;;$1113 KEY_CHAN: LD HL,(CHANS) ; address start of CHANNELS area using CHANS ; Note. One might have expected CURCHL to ; have been used. INC HL ; step over the INC HL ; output address LD (HL),E ; and update the input INC HL ; routine address for LD (HL),D ; the next call to WAIT_KEY. ;;;$111B KEY_DONE2: SCF ; set carry flag to show a key has been found RET ; and return. ;--------------------- ; Lower screen copying ;--------------------- ; This subroutine is called whenever the line in the editing area or ; input workspace is required to be printed to the lower screen. ; It is by calling this routine after any change that the cursor, for ; instance, appears to move to the left. ; Remember the edit line will contain characters and tokens ; e.g. "1000 LET a = 1" is 12 characters. ;;;$111D ED_COPY: CALL TEMPS ; routine TEMPS sets temporary attributes. RES 3,(IY+$02) ; update TV_FLAG - signal no change in mode RES 5,(IY+$02) ; update TV_FLAG - signal don't clear lower screen. LD HL,(SPOSNL) ; fetch SPOSNL PUSH HL ; and save on stack. LD HL,(ERR_SP) ; fetch ERR_SP PUSH HL ; and save also LD HL,ED_FULL ; address: ED_FULL PUSH HL ; is pushed as the error routine LD (ERR_SP),SP ; and ERR_SP made to point to it. LD HL,(ECHO_E) ; fetch ECHO_E PUSH HL ; and push also SCF ; set carry flag to control SET_DE CALL SET_DE ; call routine SET_DE ; if in input DE = WORKSP ; if in edit DE = E_LINE EX DE,HL ; start address to HL CALL OUT_LINE2 ; routine OUT_LINE2 outputs entire line up to ; carriage return including initial ; characterized line number when present. EX DE,HL ; transfer new address to DE CALL OUT_CURS ; routine OUT_CURS considers a terminating cursor. LD HL,(SPOSNL) ; fetch updated SPOSNL EX (SP),HL ; exchange with ECHO_E on stack EX DE,HL ; transfer ECHO_E to DE CALL TEMPS ; routine TEMPS to re-set attributes ; if altered. ; the lower screen was not cleared, at the outset, so if deleting then old ; text from a previous print may follow this line and requires blanking. ;;;$1150 ED_BLANK: LD A,(SPOSNL_HI) ; fetch SPOSNL_HI is current line SUB D ; compare with old JR C,ED_C_DONE ; forward to ED_C_DONE if no blanking JR NZ,ED_SPACES ; forward to ED_SPACES if line has changed LD A,E ; old column to A SUB (IY+$50) ; subtract new in SPOSNL_lo JR NC,ED_C_DONE ; forward to ED_C_DONE if no backfilling. ;;;$115E ED_SPACES: LD A,$20 ; prepare a space. PUSH DE ; save old line/column. CALL PRINT_OUT ; routine PRINT_OUT prints a space over ; any text from previous print. ; Note. Since the blanking only occurs when ; using $09F4 to print to the lower screen, ; there is no need to vector via a RST 10 ; and we can use this alternate set. POP DE ; restore the old line column. JR ED_BLANK ; back to ED_BLANK until all old text blanked. ;-------- ; ED_FULL ;-------- ; this is the error routine addressed by ERR_SP. This is not for the out of ; memory situation as we're just printing. The pitch and duration are exactly ; the same as used by ED_ERROR from which this has been augmented. The ; situation is that the lower screen is full and a rasp is given to suggest ; that this is perhaps not the best idea you've had that day. ;;;$1167 ED_FULL: LD D,$00 ; prepare to moan. LD E,(IY-$02) ; fetch RASP value. LD HL,$1A90 ; set duration. CALL BEEPER ; routine BEEPER. LD (IY+$00),$FF ; clear ERR_NR. LD DE,(SPOSNL) ; fetch SPOSNL. JR ED_C_END ; forward to ED_C_END ; the exit point from line printing continues here. ;;;$117C ED_C_DONE: POP DE ; fetch new line/column. POP HL ; fetch the error address. ; the error path rejoins here. ;;;$117E ED_C_END: POP HL ; restore the old value of ERR_SP. LD (ERR_SP),HL ; update the system variable ERR_SP POP BC ; old value of SPOSN_L PUSH DE ; save new value CALL CL_SET ; routine CL_SET and PO_STORE ; update ECHO_E and SPOSN_L from BC POP HL ; restore new value LD (ECHO_E),HL ; and update ECHO_E LD (IY+$26),$00 ; make error pointer X_PTR_HI out of bounds RET ; return ;------------------------------------------------ ; Point to first and last locations of work space ;------------------------------------------------ ; These two nested routines ensure that the appropriate pointers are ; selected for the editing area or workspace. The routines that call ; these routines are designed to work on either area. ; this routine is called once ;;;$1190 SET_HL: LD HL,(WORKSP) ; fetch WORKSP to HL. DEC HL ; point to last location of editing area. AND A ; clear carry to limit exit points to first or last. ; this routine is called with carry set and exits at a conditional return. ;;;$1195 SET_DE: LD DE,(E_LINE) ; fetch E_LINE to DE BIT 5,(IY+$37) ; test FLAGX - Input Mode ? RET Z ; return now if in editing mode LD DE,(WORKSP) ; fetch WORKSP to DE RET C ; return if carry set ( entry = SET_DE) LD HL,(STKBOT) ; fetch STKBOT to HL as well RET ; and return (entry = SET_HL (in input)) ;-------------------------------- ; Remove floating point from line ;-------------------------------- ; When a BASIC LINE or the INPUT BUFFER is parsed any numbers will have ; an invisible chr 14d inserted after them and the 5-byte integer or ; floating point form inserted after that. Similar invisible value holders ; are also created after the numeric and string variables in a DEF FN list. ; This routine removes these 'compiled' numbers from the edit line or ; input workspace. ;;;$11A7 REMOVE_FP: LD A,(HL) ; fetch character CP $0E ; is it the number marker ? LD BC,$0006 ; prepare for six bytes CALL Z,RECLAIM_2 ; routine RECLAIM_2 reclaims space if $0E LD A,(HL) ; reload next (or same) character INC HL ; and advance address CP $0D ; end of line or input buffer ? JR NZ,REMOVE_FP ; back to REMOVE_FP until entire line done. RET ; return ;********************************* ;** Part 6. EXECUTIVE ROUTINES ** ;********************************* ; The memory. ; ; +---------+-----------+------------+--------------+-------------+-- ; | BASIC | Display | Attributes | ZX Printer | System | ; | ROM | File | File | Buffer | Variables | ; +---------+-----------+------------+--------------+-------------+-- ; ^ ^ ^ ^ ^ ^ ; $0000 $4000 $5800 $5B00 $5C00 $5CB6 = CHANS ; ; ; --+----------+---+---------+-----------+---+------------+--+---+-- ; | Channel |$80| Basic | Variables |$80| Edit Line |NL|$80| ; | Info | | Program | Area | | or Command | | | ; --+----------+---+---------+-----------+---+------------+--+---+-- ; ^ ^ ^ ^ ^ ; CHANS PROG VARS E_LINE WORKSP ; ; ; ---5--> <---2--- <--3--- ; --+-------+--+------------+-------+-------+---------+-------+-+---+------+ ; | INPUT |NL| Temporary | Calc. | Spare | Machine | Gosub |?|$3E| UDGs | ; | data | | Work Space | Stack | | Stack | Stack | | | | ; --+-------+--+------------+-------+-------+---------+-------+-+---+------+ ; ^ ^ ^ ^ ^ ^ ^ ; WORKSP STKBOT STKEND sp RAMTOP UDG P_RAMT ; ;-------------------- ; Handle NEW command ;-------------------- ; The NEW command is about to set all RAM below RAMTOP to zero and ; then re-initialize the system. All RAM above RAMTOP should, and will be, ; preserved. ; There is nowhere to store values in RAM or on the stack which becomes ; inoperable. Similarly PUSH and CALL instructions cannot be used to ; store values or section common code. The alternate register set is the only ; place available to store 3 persistent 16-bit system variables. ;;;$11B7 NEW: DI ; disable interrupts - machine stack will be cleared. LD A,$FF ; flag coming from NEW. LD DE,(RAMTOP) ; fetch RAMTOP as top value. EXX ; switch in alternate set. LD BC,(P_RAMT) ; fetch P_RAMT differs on 16K/48K machines. LD DE,(RASP_PIP) ; fetch RASP/PIP. LD HL,(UDG) ; fetch UDG differs on 16K/48K machines. EXX ; switch back to main set and continue into... ;---------------------------- ; Main entry (initialization) ;---------------------------- ; This common code tests ram and sets it to zero re-initializing ; all the non-zero system variables and channel information. ; The A register tells if coming from START or NEW ;;;$11CB START_NEW: LD B,A ; save the flag for later branching. LD A,$07 ; select a white border OUT ($FE),A ; and set it now. LD A,$3F ; load accumulator with last page in ROM. LD I,A ; set the I register - this remains constant ; and can't be in range $40 - $7F as 'snow' ; appears on the screen. NOP ; these seem unnecessary. NOP NOP NOP NOP NOP ;------------- ; Check RAM ;------------- ; Typically a Spectrum will have 16K or 48K of Ram and this code will ; test it all till it finds an unpopulated location or, less likely, a ; faulty location. Usually it stops when it reaches the top $FFFF or ; in the case of NEW the supplied top value. The entire screen turns ; black with sometimes red stripes on black paper visible. ;;;$11DA RAM_CHECK: LD H,D ; transfer the top value to LD L,E ; the HL register pair. ;;;$11DC RAM_FILL: LD (HL),$02 ; load with 2 - red ink on black paper DEC HL ; next lower CP H ; have we reached ROM - $3F ? JR NZ,RAM_FILL ; back to RAM_FILL if not. ;;;$11E2 RAM_READ: AND A ; clear carry - prepare to subtract SBC HL,DE ; subtract and add back setting ADD HL,DE ; carry when back at start. INC HL ; and increment for next iteration. JR NC,RAM_DONE ; forward to RAM_DONE if we've got back to ; starting point with no errors. DEC (HL) ; decrement to 1. JR Z,RAM_DONE ; forward to RAM_DONE if faulty. DEC (HL) ; decrement to zero. JR Z,RAM_READ ; back to RAM_READ if zero flag was set. ;;;$11EF RAM_DONE: DEC HL ; step back to last valid location. EXX ; regardless of state, set up possibly ; stored system variables in case from NEW. LD (P_RAMT),BC ; insert P_RAMT. LD (RASP_PIP),DE ; insert RASP/PIP. LD (UDG),HL ; insert UDG. EXX ; switch in main set. INC B ; now test if we arrived here from NEW. JR Z,RAM_SET ; forward to RAM_SET if we did. ; this section applies to START only. LD (P_RAMT),HL ; set P_RAMT to the highest working RAM address. LD DE,$3EAF ; address of last byte of 'U' bitmap in ROM. LD BC,$00A8 ; there are 21 user defined graphics. EX DE,HL ; switch pointers and make the UDGs a LDDR ; copy of the standard characters A - U. EX DE,HL ; switch the pointer to HL. INC HL ; update to start of 'A' in RAM. LD (UDG),HL ; make UDG system variable address the first bitmap. DEC HL ; point at RAMTOP again. LD BC,$0040 ; set the values of LD (RASP_PIP),BC ; the PIP and RASP system variables. ; the NEW command path rejoins here. ;;;$1219 RAM_SET: LD (RAMTOP),HL ; set system variable RAMTOP to HL. LD HL,$3C00 ; a strange place to set the pointer to the LD (CHARS),HL ; character set, CHARS - as no printing yet. LD HL,(RAMTOP) ; fetch RAMTOP to HL again as we've lost it. LD (HL),$3E ; top of user ram holds GOSUB end marker ; an impossible line number - see RETURN. ; no significance in the number $3E. It has ; been traditional since the ZX80. DEC HL ; followed by empty byte (not important). LD SP,HL ; set up the machine stack pointer. DEC HL DEC HL LD (ERR_SP),HL ; ERR_SP is where the error pointer is ; at moment empty - will take address MAIN_4 ; at the call preceding that address, ; although interrupts and calls will make use ; of this location in meantime. IM 1 ; select interrupt mode 1. LD IY,ERR_NR ; set IY to ERR_NR. IY can reach all standard ; system variables but shadow ROM system ; variables will be mostly out of range. EI ; enable interrupts now that we have a stack. LD HL,$5CB6 ; the address of the channels - initially ; following system variables. LD (CHANS),HL ; set the CHANS system variable. LD DE,INIT_CHAN ; address: INIT_CHAN in ROM. LD BC,$0015 ; there are 21 bytes of initial data in ROM. EX DE,HL ; swap the pointers. LDIR ; copy the bytes to RAM. EX DE,HL ; swap pointers. HL points to program area. DEC HL ; decrement address. LD (DATADD),HL ; set DATADD to location before program area. INC HL ; increment again. LD (PROG),HL ; set PROG the location where BASIC starts. LD (VARS),HL ; set VARS to same location with a LD (HL),$80 ; variables end-marker. INC HL ; advance address. LD (E_LINE),HL ; set E_LINE, where the edit line ; will be created. ; Note. it is not strictly necessary to ; execute the next fifteen bytes of code ; as this will be done by the call to SET_MIN. LD (HL),$0D ; initially just has a carriage return INC HL ; followed by LD (HL),$80 ; an end-marker. INC HL ; address the next location. LD (WORKSP),HL ; set WORKSP - empty workspace. LD (STKBOT),HL ; set STKBOT - bottom of the empty stack. LD (STKEND),HL ; set STKEND to the end of the empty stack. LD A,$38 ; the colour system is set to white paper, ; black ink, no flash or bright. LD (ATTRP_MASKP),A ; set ATTR_P permanent colour attributes. LD (ATTRT_MASKT),A ; set ATTR_T temporary colour attributes. LD (BORDCR),A ; set BORDCR the border colour/lower screen ; attributes. LD HL,$0523 ; The keyboard repeat and delay values LD (REPDEL),HL ; are loaded to REPDEL and REPPER. DEC (IY-$3A) ; set KSTATE_0 to $FF. DEC (IY-$36) ; set KSTATE_4 to $FF. ; thereby marking both available. LD HL,INIT_STRM ; set source to ROM Address: INIT_STRM LD DE,STRMS_FD ; set destination to system variable STRMS_FD LD BC,$000E ; copy the 14 bytes of initial 7 streams data LDIR ; from ROM to RAM. SET 1,(IY+$01) ; update FLAGS - signal printer in use. CALL CLEAR_PRB ; call routine CLEAR_PRB to initialize system ; variables associated with printer. LD (IY+$31),$02 ; set DF_SZ the lower screen display size to ; two lines CALL CLS ; call routine CLS to set up system ; variables associated with screen and clear ; the screen and set attributes. XOR A ; clear accumulator so that we can address LD DE,COPYRIGHT - 1; the message table directly. CALL PO_MSG ; routine PO_MSG puts ; '(c) 1982 Sinclair Research Ltd' ; at bottom of display. SET 5,(IY+$02) ; update TV_FLAG - signal lower screen will ; require clearing. JR MAIN_1 ; forward to MAIN_1 ;-------------------- ; Main execution loop ;-------------------- ;;;$12A2 MAIN_EXEC: LD (IY+$31),$02 ; set DF_SZ lower screen display file size to 2 lines. CALL AUTO_LIST ; routine AUTO_LIST ;;;$12A9 MAIN_1: CALL SET_MIN ; routine SET_MIN clears work areas. ;;;$12AC MAIN_2: LD A,$00 ; select channel 'K' the keyboard CALL CHAN_OPEN ; routine CHAN_OPEN opens it CALL EDITOR ; routine EDITOR is called. ; Note the above routine is where the Spectrum ; waits for user-interaction. Perhaps the ; most common input at this stage is LOAD "". CALL LINE_SCAN ; routine LINE_SCAN scans the input. BIT 7,(IY+$00) ; test ERR_NR - will be $FF if syntax is correct. JR NZ,MAIN_3 ; forward, if correct, to MAIN_3. BIT 4,(IY+$30) ; test FLAGS2 - K channel in use ? JR Z,MAIN_4 ; forward to MAIN_4 if not. LD HL,(E_LINE) ; an editing error so address E_LINE. CALL REMOVE_FP ; routine REMOVE_FP removes the hidden floating-point forms. LD (IY+$00),$FF ; system variable ERR_NR is reset to 'OK'. JR MAIN_2 ; back to MAIN_2 to allow user to correct. ; the branch was here if syntax has passed test. ;;;$12CF MAIN_3: LD HL,(E_LINE) ; fetch the edit line address from E_LINE. LD (CH_ADD),HL ; system variable CH_ADD is set to first ; character of edit line. ; Note. the above two instructions are a little ; inadequate. ; They are repeated with a subtle difference ; at the start of the next subroutine and are ; therefore not required above. CALL E_LINE_NO ; routine E_LINE_NO will fetch any line ; number to BC if this is a program line. LD A,B ; test if the number of OR C ; the line is non-zero. JP NZ,MAIN_ADD ; jump forward to MAIN_ADD if so to add the ; line to the BASIC program. ; Has the user just pressed the ENTER key ? RST 18H ; GET_CHAR gets character addressed by CH_ADD. CP $0D ; is it a carriage return ? JR Z,MAIN_EXEC ; back to MAIN_EXEC if so for an automatic ; listing. ; this must be a direct command. BIT 0,(IY+$30) ; test FLAGS2 - clear the main screen ? CALL NZ,CL_ALL ; routine CL_ALL, if so, e.g. after listing. CALL CLS_LOWER ; routine CLS_LOWER anyway. LD A,$19 ; compute scroll count to 25 minus SUB (IY+$4F) ; value of S_POSN_HI. LD (SCR_CT),A ; update SCR_CT system variable. SET 7,(IY+$01) ; update FLAGS - signal running program. LD (IY+$00),$FF ; set ERR_NR to 'OK'. LD (IY+$0A),$01 ; set NSPPC to one for first statement. CALL LINE_RUN ; call routine LINE_RUN to run the line. ; sysvar ERR_SP therefore addresses MAIN_4 ; Examples of direct commands are RUN, CLS, LOAD "", PRINT USR 40000, ; LPRINT "A"; etc.. ; If a user written machine-code program disables interrupts then it ; must enable them to pass the next step. We also jumped to here if the ; keyboard was not being used. ;;;$1303 MAIN_4: HALT ; wait for interrupt. RES 5,(IY+$01) ; update FLAGS - signal no new key. BIT 1,(IY+$30) ; test FLAGS2 - is printer buffer clear ? CALL NZ,COPY_BUFF ; call routine COPY_BUFF if not. ; Note. the programmer has neglected ; to set bit 1 of FLAGS first. LD A,(ERR_NR) ; fetch ERR_NR INC A ; increment to give true code. ; Now deal with a runtime error as opposed to an editing error. ; However if the error code is now zero then the OK message will be printed. ;;;$1313 MAIN_G: PUSH AF ; save the error number. LD HL,$0000 ; prepare to clear some system variables. LD (IY+$37),H ; clear all the bits of FLAGX. LD (IY+$26),H ; blank X_PTR_HI to suppress error marker. LD (DEFADD),HL ; blank DEFADD to signal that no defined ; function is currently being evaluated. LD HL,$0001 ; explicit - inc hl would do. LD (STRMS_00),HL ; ensure STRMS_00 is keyboard. CALL SET_MIN ; routine SET_MIN clears workspace etc. RES 5,(IY+$37) ; update FLAGX - signal in EDIT not INPUT mode. ; Note. all the bits were reset earlier. CALL CLS_LOWER ; call routine CLS_LOWER. SET 5,(IY+$02) ; update TV_FLAG - signal lower screen ; requires clearing. POP AF ; bring back the error number LD B,A ; and make a copy in B. CP $0A ; is it a print-ready digit ? JR C,MAIN_5 ; forward to MAIN_5 if so. ADD A,$07 ; add ascii offset to letters. ;;;$133C MAIN_5: CALL OUT_CODE ; call routine OUT_CODE to print the code. LD A,$20 ; followed by a space. RST 10H ; PRINT_A LD A,B ; fetch stored report code. LD DE,RPT_MESGS ; address: RPT_MESGS. CALL PO_MSG ; call routine PO_MSG to print. XOR A ; clear to directly LD DE,COMMA_SP - 1 ; address comma and space message. CALL PO_MSG ; routine PO_MSG prints them although it would ; be more succinct to use RST $10. LD BC,(PPC) ; fetch PPC the current line number. CALL OUT_NUM_1 ; routine OUT_NUM_1 will print that LD A,$3A ; then a ':'. RST 10H ; PRINT_A LD C,(IY+$0D) ; then SUBPPC for statement LD B,$00 ; limited to 127 CALL OUT_NUM_1 ; routine OUT_NUM_1 CALL CLEAR_SP ; routine CLEAR_SP clears editing area. ; which probably contained 'RUN'. LD A,(ERR_NR) ; fetch ERR_NR again INC A ; test for no error originally $FF. JR Z,MAIN_9 ; forward to MAIN_9 if no error. CP $09 ; is code Report 9 STOP ? JR Z,MAIN_6 ; forward to MAIN_6 if so CP $15 ; is code Report L Break ? JR NZ,MAIN_7 ; forward to MAIN_7 if not ; Stop or Break was encountered so consider CONTINUE. ;;;$1373 MAIN_6: INC (IY+$0D) ; increment SUBPPC to next statement. ;;;$1376 MAIN_7: LD BC,$0003 ; prepare to copy 3 system variables to LD DE,OSPPC ; address OSPPC - statement for CONTINUE. ; also updating OLDPPC line number below. LD HL,NSPPC ; set source top to NSPPC next statement. BIT 7,(HL) ; did BREAK occur before the jump ? ; e.g. between GO TO and next statement. JR Z,MAIN_8 ; skip forward to MAIN_8, if not, as setup ; is correct. ADD HL,BC ; set source to SUBPPC number of current ; statement/line which will be repeated. ;;;$1384 MAIN_8: LDDR ; copy PPC to OLDPPC and SUBPPC to OSPCC ; or NSPPC to OLDPPC and NEWPPC to OSPCC ;;;$1386 MAIN_9: LD (IY+$0A),$FF ; update NSPPC - signal 'no jump'. RES 3,(IY+$01) ; update FLAGS - signal use 'K' mode for ; the first character in the editor and JP MAIN_2 ; jump back to MAIN_2. ;----------------------- ; Canned report messages ;----------------------- ; The Error reports with the last byte inverted. The first entry ; is a dummy entry. The last, which begins with $7F, the Spectrum ; character for copyright symbol, is placed here for convenience ; as is the preceding comma and space. ; The report line must accomodate a 4-digit line number and a 3-digit ; statement number which limits the length of the message text to twenty ; characters. ; e.g. "B Integer out of range, 1000:127" ;;;$1391 RPT_MESGS: DEFB $80 DEFB "O",'K'+$80 ; 0 DEFB "NEXT without FO",'R'+$80 ; 1 DEFB "Variable not foun",'d'+$80 ; 2 DEFB "Subscript wron",'g'+$80 ; 3 DEFB "Out of memor",'y'+$80 ; 4 DEFB "Out of scree",'n'+$80 ; 5 DEFB "Number too bi",'g'+$80 ; 6 DEFB "RETURN without GOSU",'B'+$80 ; 7 DEFB "End of fil",'e'+$80 ; 8 DEFB "STOP statemen",'t'+$80 ; 9 DEFB "Invalid argumen",'t'+$80 ; A DEFB "Integer out of rang",'e'+$80 ; B DEFB "Nonsense in BASI",'C'+$80 ; C DEFB "BREAK - CONT repeat",'s'+$80 ; D DEFB "Out of DAT",'A'+$80 ; E DEFB "Invalid file nam",'e'+$80 ; F DEFB "No room for lin",'e'+$80 ; G DEFB "STOP in INPU",'T'+$80 ; H DEFB "FOR without NEX",'T'+$80 ; I DEFB "Invalid I/O devic",'e'+$80 ; J DEFB "Invalid colou",'r'+$80 ; K DEFB "BREAK into progra",'m'+$80 ; L DEFB "RAMTOP no goo",'d'+$80 ; M DEFB "Statement los",'t'+$80 ; N DEFB "Invalid strea",'m'+$80 ; O DEFB "FN without DE",'F'+$80 ; P DEFB "Parameter erro",'r'+$80 ; Q DEFB "Tape loading erro",'r'+$80 ; R ;;;$1537 COMMA_SP: DEFB ",",' '+$80 ; used in report line. ;;;$1539 COPYRIGHT: DEFB $7F ; copyright DEFB " 1982 Sinclair Research Lt",'d'+$80 ;--------- ; REPORT_G ;--------- ; Note ERR_SP points here during line entry which allows the ; normal 'Out of Memory' report to be augmented to the more ; precise 'No Room for line' report. ;;;$1555 ; No Room for line REPORT_G: LD A,$10 ; i.e. 'G' -$30 -$07 LD BC,$0000 ; this seems unnecessary. JP MAIN_G ; jump back to MAIN_G ;------------------------------ ; Handle addition of BASIC line ;------------------------------ ; Note this is not a subroutine but a branch of the main execution loop. ; System variable ERR_SP still points to editing error handler. ; A new line is added to the Basic program at the appropriate place. ; An existing line with same number is deleted first. ; Entering an existing line number deletes that line. ; Entering a non-existent line allows the subsequent line to be edited next. ;;;$155D MAIN_ADD: LD (E_PPC),BC ; set E_PPC to extracted line number. LD HL,(CH_ADD) ; fetch CH_ADD - points to location after the ; initial digits (set in E_LINE_NO). EX DE,HL ; save start of BASIC in DE. LD HL,REPORT_G ; Address: REPORT_G PUSH HL ; is pushed on stack and addressed by ERR_SP. ; the only error that can occur is ; 'Out of memory'. LD HL,(WORKSP) ; fetch WORKSP - end of line. SCF ; prepare for true subtraction. SBC HL,DE ; find length of BASIC and PUSH HL ; save it on stack. LD H,B ; transfer line number LD L,C ; to HL register. CALL LINE_ADDR ; routine LINE_ADDR will see if ; a line with the same number exists. JR NZ,MAIN_ADD1 ; forward if no existing line to MAIN_ADD1. CALL NEXT_ONE ; routine NEXT_ONE finds the existing line. CALL RECLAIM_2 ; routine RECLAIM_2 reclaims it. ;;;$157D MAIN_ADD1: POP BC ; retrieve the length of the new line. LD A,C ; and test if carriage return only DEC A ; i.e. one byte long. OR B ; result would be zero. JR Z,MAIN_ADD2 ; forward to MAIN_ADD2 is so. PUSH BC ; save the length again. INC BC ; adjust for inclusion INC BC ; of line number (two bytes) INC BC ; and line length INC BC ; (two bytes). DEC HL ; HL points to location before the destination LD DE,(PROG) ; fetch the address of PROG PUSH DE ; and save it on the stack CALL MAKE_ROOM ; routine MAKE_ROOM creates BC spaces in ; program area and updates pointers. POP HL ; restore old program pointer. LD (PROG),HL ; and put back in PROG as it may have been ; altered by the POINTERS routine. POP BC ; retrieve BASIC length PUSH BC ; and save again. INC DE ; points to end of new area. LD HL,(WORKSP) ; set HL to WORKSP - location after edit line. DEC HL ; decrement to address end marker. DEC HL ; decrement to address carriage return. LDDR ; copy the Basic line back to initial command. LD HL,(E_PPC) ; fetch E_PPC - line number. EX DE,HL ; swap it to DE, HL points to last of four locations. POP BC ; retrieve length of line. LD (HL),B ; high byte last. DEC HL LD (HL),C ; then low byte of length. DEC HL LD (HL),E ; then low byte of line number. DEC HL LD (HL),D ; then high byte range $0 - $27 (1-9999). ;;;$15AB MAIN_ADD2: POP AF ; drop the address of Report G JP MAIN_EXEC ; and back to MAIN_EXEC producing a listing ; and to reset ERR_SP in EDITOR. ;---------------------------- ; Initial channel information ;---------------------------- ; This initial channel information is copied from ROM to RAM, ; during initialization. It's new location is after the system ; variables and is addressed by the system variable CHANS ; which means that it can slide up and down in memory. ; The table is never searched and the last character which could be anything ; other than a comma provides a convenient resting place for DATADD. ;;;$15AF INIT_CHAN: DEFW PRINT_OUT ; PRINT_OUT DEFW KEY_INPUT ; KEY_INPUT DEFB $4B ; 'K' DEFW PRINT_OUT ; PRINT_OUT DEFW REPORT_J ; REPORT_J DEFB $53 ; 'S' DEFW ADD_CHAR ; ADD_CHAR DEFW REPORT_J ; REPORT_J DEFB $52 ; 'R' DEFW PRINT_OUT ; PRINT_OUT DEFW REPORT_J ; REPORT_J DEFB $50 ; 'P' DEFB $80 ; End Marker ;;;$15C4 REPORT_J: RST 08H ; ERROR_1 DEFB $12 ; Error Report: Invalid I/O device ;-------------------- ; Initial stream data ;-------------------- ; This is the initial stream data for the seven streams $FD - $03 that is ; copied from ROM to the STRMS system variables area during initialization. ; There are reserved locations there for another 12 streams. ; Each location contains an offset to the second byte of a channel. ; The first byte of a channel can't be used as that would result in an ; offset of zero for some and zero is used to denote that a stream is closed. ;;;$15C6 INIT_STRM: DEFB $01, $00 ; stream $FD offset to channel 'K' DEFB $06, $00 ; stream $FE offset to channel 'S' DEFB $0B, $00 ; stream $FF offset to channel 'R' DEFB $01, $00 ; stream $00 offset to channel 'K' DEFB $01, $00 ; stream $01 offset to channel 'K' DEFB $06, $00 ; stream $02 offset to channel 'S' DEFB $10, $00 ; stream $03 offset to channel 'P' ;----------------------------- ; Control for input subroutine ;----------------------------- ;;;$15D4 WAIT_KEY: BIT 5,(IY+$02) ; test TV_FLAG - clear lower screen ? JR NZ,WAIT_KEY1 ; forward to WAIT_KEY1 if so. SET 3,(IY+$02) ; update TV_FLAG - signal reprint the edit ; line to the lower screen. ;;;$15DE WAIT_KEY1: CALL INPUT_AD ; routine INPUT_AD is called. RET C ; return with acceptable keys. JR Z,WAIT_KEY1 ; back to WAIT_KEY1 if no key is pressed ; or it has been handled within INPUT_AD. ; Note. When inputting from the keyboard all characters are returned with ; above conditions so this path is never taken. ;;;$15E4 REPORT_8: RST 08H ; ERROR_1 DEFB $07 ; Error Report: End of file ;------------------------------- ; Make HL point to input address ;------------------------------- ; This routine fetches the address of the input stream from the current ; channel area using system variable CURCHL. ;;;$15E6 INPUT_AD: EXX ; switch in alternate set. PUSH HL ; save HL register LD HL,(CURCHL) ; fetch address of CURCHL - current channel. INC HL ; step over output routine INC HL ; to point to low byte of input routine. JR CALL_SUB ; forward to CALL_SUB. ;-------------------- ; Main Output Routine ;-------------------- ; The entry point OUT_CODE is called on five occasions to print ; the ascii equivalent of a value 0-9. ; ; PRINT_A_2 is a continuation of the RST 10 to print any character. ; Both print to the current channel and the printing of control codes ; may alter that channel to divert subsequent RST 10 instructions ; to temporary routines. The normal channel is $09F4. ;;;$15EF OUT_CODE: LD E,$30 ; add 48 decimal to give ascii ADD A,E ; character '0' to '9'. ;;;$15F2 PRINT_A_2: EXX ; switch in alternate set PUSH HL ; save HL register LD HL,(CURCHL) ; fetch CURCHL the current channel. ; INPUT_AD rejoins here also. ;;;$15F7 CALL_SUB: LD E,(HL) ; put the low byte in E. INC HL ; advance address. LD D,(HL) ; put the high byte to D. EX DE,HL ; transfer the stream to HL. CALL CALL_JUMP ; use routine CALL_JUMP. ; in effect CALL (HL). POP HL ; restore saved HL register. EXX ; switch back to the main set and RET ; return. ;------------- ; Open channel ;------------- ; This subroutine is used by the ROM to open a channel 'K', 'S', 'R' or 'P'. ; This is either for it's own use or in response to a user's request, for ; example, when '#' is encountered with output - PRINT, LIST etc. ; or with input - INPUT, INKEY$ etc. ; it is entered with a system stream $FD - $FF, or a user stream $00 - $0F ; in the accumulator. ;;;$1601 CHAN_OPEN: ADD A,A ; double the stream ($FF will become $FE etc.) ADD A,$16 ; add the offset to stream 0 from $5C00 LD L,A ; result to L LD H,$5C ; now form the address in STRMS area. LD E,(HL) ; fetch low byte of CHANS offset INC HL ; address next LD D,(HL) ; fetch high byte of offset LD A,D ; test that the stream is open. OR E ; zero if closed. JR NZ,CHAN_OP_1 ; forward to CHAN_OP_1 if open. ;;;$160E REPORT_OA: RST 08H ; ERROR_1 DEFB $17 ; Error Report: Invalid stream ; continue here if stream was open. Note that the offset is from CHANS ; to the second byte of the channel. ;;;$1610 CHAN_OP_1: DEC DE ; reduce offset so it points to the channel. LD HL,(CHANS) ; Fetch CHANS the location of the base of ; the channel information area ADD HL,DE ; and add the offset to address the channel. ; and continue to set flags. ;------------------ ; Set channel flags ;------------------ ; This subroutine is used from ED_EDIT, STR$ and READ_IN to reset the ; current channel when it has been temporarily altered. ;;;$1615 CHAN_FLAG: LD (CURCHL),HL ; set CURCHL system variable to the address in HL RES 4,(IY+$30) ; update FLAGS2 - signal K channel not in use. ; Note. provide a default for channel 'R'. INC HL ; advance past INC HL ; output routine. INC HL ; advance past INC HL ; input routine. LD C,(HL) ; pick up the letter. LD HL,CHN_CD_LU ; address: CHN_CD_LU CALL INDEXER ; routine INDEXER finds offset to a ; flag-setting routine. RET NC ; but if the letter wasn't found in the ; table just return now. - channel 'R'. LD D,$00 ; prepare to add LD E,(HL) ; offset to E ADD HL,DE ; add offset to location of offset to form ; address of routine ;;;$L162C CALL_JUMP: JP (HL) ; jump to the routine ; Footnote. calling any location that holds JP (HL) is the equivalent to ; a pseudo Z80 instruction CALL (HL). The ROM uses the instruction above. ;--------------------------- ; Channel code look-up table ;--------------------------- ; This table is used by the routine above to find one of the three ; flag setting routines below it. ; A zero end-marker is required as channel 'R' is not present. ;;;$162D CHN_CD_LU: DEFB 'K', CHAN_K-$-1 ; offset $06 to CHAN_K DEFB 'S', CHAN_S-$-1 ; offset $12 to CHAN_S DEFB 'P', CHAN_P-$-1 ; offset $1B to CHAN_P DEFB $00 ; end marker. ;--------------- ; Channel K flag ;--------------- ; routine to set flags for lower screen/keyboard channel. ;;;$1634 CHAN_K: SET 0,(IY+$02) ; update TV_FLAG - signal lower screen in use RES 5,(IY+$01) ; update FLAGS - signal no new key SET 4,(IY+$30) ; update FLAGS2 - signal K channel in use JR CHAN_S_1 ; forward to CHAN_S_1 for indirect exit ;--------------- ; Channel S flag ;--------------- ; routine to set flags for upper screen channel. ;;;$1642 CHAN_S: RES 0,(IY+$02) ; TV_FLAG - signal main screen in use ;;;$1646 CHAN_S_1: RES 1,(IY+$01) ; update FLAGS - signal printer not in use JP TEMPS ; jump back to TEMPS and exit via that ; routine after setting temporary attributes. ;--------------- ; Channel P flag ;--------------- ; This routine sets a flag so that subsequent print related commands ; print to printer or update the relevant system variables. ; This status remains in force until reset by the routine above. ;;;$164D CHAN_P: SET 1,(IY+$01) ; update FLAGS - signal printer in use RET ; return ;------------------------ ; Just one space required ;------------------------ ; This routine is called once only to create a single space ; in workspace by ADD_CHAR. It is slightly quicker than using a RST $30. ; There are several instances in the calculator where the sequence ; ld bc, 1; rst $30 could be replaced by a call to this routine but it ; only gives a saving of one byte each time. ;;;$1652 ONE_SPACE: LD BC,$0001 ; create space for a single character. ;---------- ; Make Room ;---------- ; This entry point is used to create BC spaces in various areas such as ; program area, variables area, workspace etc.. ; The entire free RAM is available to each BASIC statement. ; On entry, HL addresses where the first location is to be created. ; Afterwards, HL will point to the location before this. ;;;$1655 MAKE_ROOM: PUSH HL ; save the address pointer. CALL TEST_ROOM ; routine TEST_ROOM checks if room ; exists and generates an error if not. POP HL ; restore the address pointer. CALL POINTERS ; routine POINTERS updates the ; dynamic memory location pointers. ; DE now holds the old value of STKEND. LD HL,(STKEND) ; fetch new STKEND the top destination. EX DE,HL ; HL now addresses the top of the area to ; be moved up - old STKEND. LDDR ; the program, variables, etc are moved up. RET ; return with new area ready to be populated. ; HL points to location before new area, ; and DE to last of new locations. ;------------------------------------------------ ; Adjust pointers before making or reclaiming room ;------------------------------------------------ ; This routine is called by MAKE_ROOM to adjust upwards and by RECLAIM to ; adjust downwards the pointers within dynamic memory. ; The fourteen pointers to dynamic memory, starting with VARS and ending ; with STKEND, are updated adding BC if they are higher than the position ; in HL. ; The system variables are in no particular order except that STKEND, the first ; free location after dynamic memory must be the last encountered. ;;;$1664 POINTERS: PUSH AF ; preserve accumulator. PUSH HL ; put pos pointer on stack. LD HL,VARS ; address VARS the first of the LD A,$0E ; fourteen variables to consider. ;;;$166B PTR_NEXT: LD E,(HL) ; fetch the low byte of the system variable. INC HL ; advance address. LD D,(HL) ; fetch high byte of the system variable. EX (SP),HL ; swap pointer on stack with the variable pointer. AND A ; prepare to subtract. SBC HL,DE ; subtract variable address ADD HL,DE ; and add back EX (SP),HL ; swap pos with system variable pointer JR NC,PTR_DONE ; forward to PTR_DONE if var before pos PUSH DE ; save system variable address. EX DE,HL ; transfer to HL ADD HL,BC ; add the offset EX DE,HL ; back to DE LD (HL),D ; load high byte DEC HL ; move back LD (HL),E ; load low byte INC HL ; advance to high byte POP DE ; restore old system variable address. ;;;$167F PTR_DONE: INC HL ; address next system variable. DEC A ; decrease counter. JR NZ,PTR_NEXT ; back to PTR_NEXT if more. EX DE,HL ; transfer old value of STKEND to HL. ; Note. this has always been updated. POP DE ; pop the address of the position. POP AF ; pop preserved accumulator. AND A ; clear carry flag preparing to subtract. SBC HL,DE ; subtract position from old stkend LD B,H ; to give number of data bytes LD C,L ; to be moved. INC BC ; increment as we also copy byte at old STKEND. ADD HL,DE ; recompute old stkend. EX DE,HL ; transfer to DE. RET ; return. ;-------------------- ; Collect line number ;-------------------- ; This routine extracts a line number, at an address that has previously ; been found using LINE_ADDR, and it is entered at LINE_NO. If it encounters ; the program 'end-marker' then the previous line is used and if that ; should also be unacceptable then zero is used as it must be a direct ; command. The program end-marker is the variables end-marker $80, or ; if variables exist, then the first character of any variable name. ;;;$168F LINE_ZERO: DEFB $00, $00 ; dummy line number used for direct commands ;;;$1691 LINE_NO_A: EX DE,HL ; fetch the previous line to HL and set LD DE,LINE_ZERO ; DE to LINE_ZERO should HL also fail. ; -> The Entry Point. ;;;$1695 LINE_NO: LD A,(HL) ; fetch the high byte - max $2F AND $C0 ; mask off the invalid bits. JR NZ,LINE_NO_A ; to LINE_NO_A if an end-marker. LD D,(HL) ; reload the high byte. INC HL ; advance address. LD E,(HL) ; pick up the low byte. RET ; return from here. ;-------------------- ; Handle reserve room ;-------------------- ; This is a continuation of the restart BC_SPACES ;;;$169E RESERVE: LD HL,(STKBOT) ; STKBOT first location of calculator stack DEC HL ; make one less than new location CALL MAKE_ROOM ; routine MAKE_ROOM creates the room. INC HL ; address the first new location INC HL ; advance to second POP BC ; restore old WORKSP LD (WORKSP),BC ; system variable WORKSP was perhaps ; changed by POINTERS routine. POP BC ; restore count for return value. EX DE,HL ; switch. DE = location after first new space INC HL ; HL now location after new space RET ; return. ;---------------------------- ; Clear various editing areas ;---------------------------- ; This routine sets the editing area, workspace and calculator stack ; to their minimum configurations as at initialization and indeed this ; routine could have been relied on to perform that task. ; This routine uses HL only and returns with that register holding ; WORKSP/STKBOT/STKEND though no use is made of this. The routines also ; reset MEM to it's usual place in the systems variable area should it ; have been relocated to a FOR-NEXT variable. The main entry point ; SET_MIN is called at the start of the MAIN_EXEC loop and prior to ; displaying an error. ;;;$16B0 SET_MIN: LD HL,(E_LINE) ; fetch E_LINE LD (HL),$0D ; insert carriage return LD (K_CUR),HL ; make K_CUR keyboard cursor point there. INC HL ; next location LD (HL),$80 ; holds end-marker $80 INC HL ; next location becomes LD (WORKSP),HL ; start of WORKSP ; This entry point is used prior to input and prior to the execution, ; or parsing, of each statement. ;;;$16BF SET_WORK: LD HL,(WORKSP) ; fetch WORKSP value LD (STKBOT),HL ; and place in STKBOT ; This entry point is used to move the stack back to it's normal place ; after temporary relocation during line entry and also from ERROR_3 ;;;$16C5 SET_STK: LD HL,(STKBOT) ; fetch STKBOT value LD (STKEND),HL ; and place in STKEND. PUSH HL ; perhaps an obsolete entry point. LD HL,MEM_0 ; normal location of MEM_0 LD (MEM),HL ; is restored to system variable MEM. POP HL ; saved value not required. RET ; return. ;------------------- ; Reclaim edit-line? ;------------------- ; This seems to be legacy code from the ZX80/ZX81 as it is ; not used in this ROM. ; That task, in fact, is performed here by the dual-area routine CLEAR_SP. ; This routine is designed to deal with something that is known to be in the ; edit buffer and not workspace. ; On entry, HL must point to the end of the something to be deleted. ;;;$16D4 REC_EDIT: LD DE,(E_LINE) ; fetch start of edit line from E_LINE. JP RECLAIM_1 ; jump forward to RECLAIM_1. ;--------------------------- ; The Table INDEXING routine ;--------------------------- ; This routine is used to search two-byte hash tables for a character ; held in C, returning the address of the following offset byte. ; if it is known that the character is in the table e.g. for priorities, ; then the table requires no zero end-marker. If this is not known at the ; outset then a zero end-marker is required and carry is set to signal ; success. ;;;$16DB INDEXER_1: INC HL ; address the next pair of values. ; -> The Entry Point. ;;;$16DC INDEXER: LD A,(HL) ; fetch the first byte of pair AND A ; is it the end-marker ? RET Z ; return with carry reset if so. CP C ; is it the required character ? INC HL ; address next location. JR NZ,INDEXER_1 ; back to INDEXER_1 if no match. SCF ; else set the carry flag. RET ; return with carry set ;--------------------------------- ; The Channel and Streams Routines ;--------------------------------- ; A channel is is an input/output route to a hardware device ; and is identified to the system by a single letter e.g. 'K' for ; the keyboard. A channel can have an input and output route ; associated with it in which case it is bi-directional like ; the keyboard. Others like the upper screen 'S' are output ; only and the input routine usually points to a report message. ; Channels 'K' and 'S' are system channels and it would be inappropriate ; to close the associated streams so a mechanism is provided to ; re-attach them. When the re-attachment is no longer required, then ; closing these streams resets them as at initialization. ; The same also would have applied to channel 'R', the RS232 channel ; as that is used by the system. It's input stream seems to have been ; removed and it is not available to the user. However the channel could ; not be removed entirely as its output routine was used by the system. ; As a result of removing this channel, channel 'P', the printer is ; erroneously treated as a system channel. ; Ironically the tape streamer is not accessed through streams and ; channels. ; Early demonstrations of the Spectrum showed a single microdrive being ; controlled by this ROM. Adverts also said that the network and RS232 ; were in this ROM. Channels 'M' and 'N' are user channels and have been ; removed successfully if, as seems possible, they existed. ;---------------------- ; Handle CLOSE# command ;---------------------- ; This command allows streams to be closed after use. ; Any temporary memory areas used by the stream would be reclaimed and ; finally flags set or reset if necessary. ;;;$16E5 CLOSE: CALL STR_DATA ; routine STR_DATA fetches parameter ; from calculator stack and gets the ; existing STRMS data pointer address in HL ; and stream offset from CHANS in BC. ; Note. this offset could be zero if the ; stream is already closed. A check for this ; should occur now and an error should be ; generated, for example, ; Report S 'Stream already closed'. CALL CLOSE_2 ; routine CLOSE_2 would perform any actions ; peculiar to that stream without disturbing ; data pointer to STRMS entry in HL. LD BC,$0000 ; the stream is to be blanked. LD DE,$A3E2 ; the number of bytes from stream 4, $5C1E, to $10000 EX DE,HL ; transfer offset to HL, STRMS data pointer to DE. ADD HL,DE ; add the offset to the data pointer. JR C,CLOSE_1 ; forward to CLOSE_1 if a non-system stream. ; i.e. higher than 3. ; proceed with a negative result. LD BC,INIT_STRM+14 ; prepare the address of the byte after ; the initial stream data in ROM. ($15D4) ADD HL,BC ; index into the data table with negative value. LD C,(HL) ; low byte to C INC HL ; address next. LD B,(HL) ; high byte to B. ; and for streams 0 - 3 just enter the initial data back into the STRMS entry ; streams 0 - 2 can't be closed as they are shared by the operating system. ; -> for streams 4 - 15 then blank the entry. ;;;$16FC CLOSE_1: EX DE,HL ; address of stream to HL. LD (HL),C ; place zero (or low byte). INC HL ; next address. LD (HL),B ; place zero (or high byte). RET ; return. ;------------------- ; CLOSE_2 Subroutine ;------------------- ; There is not much point in coming here. ; The purpose was once to find the offset to a special closing routine, ; in this ROM and within 256 bytes of the close stream look up table that ; would reclaim any buffers associated with a stream. At least one has been ; removed. ;;;$1701 CLOSE_2: PUSH HL ; * save address of stream data pointer ; in STRMS on the machine stack. LD HL,(CHANS) ; fetch CHANS address to HL ADD HL,BC ; add the offset to address the second ; byte of the output routine hopefully. INC HL ; step past INC HL ; the input routine. INC HL ; to address channel's letter LD C,(HL) ; pick it up in C. ; Note. but if stream is already closed we ; get the value $10 (the byte preceding 'K'). EX DE,HL ; save the pointer to the letter in DE. LD HL,CL_STR_LU ; address: CL_STR_LU in ROM. CALL INDEXER ; routine INDEXER uses the code to get ; the 8-bit offset from the current point to ; the address of the closing routine in ROM. ; Note. it won't find $10 there! LD C,(HL) ; transfer the offset to C. LD B,$00 ; prepare to add. ADD HL,BC ; add offset to point to the address of the ; routine that closes the stream. ; (and presumably removes any buffers that ; are associated with it.) JP (HL) ; jump to that routine. ;--------------------------- ; CLOSE stream look-up table ;--------------------------- ; This table contains an entry for a letter found in the CHANS area. ; followed by an 8-bit displacement, from that byte's address in the ; table to the routine that performs any ancillary actions associated ; with closing the stream of that channel. ; The table doesn't require a zero end-marker as the letter has been ; picked up from a channel that has an open stream. ;;;$1716 CL_STR_LU: DEFB 'K', CLOSE_STR-$-1 ; offset 5 to CLOSE_STR DEFB 'S', CLOSE_STR-$-1 ; offset 3 to CLOSE_STR DEFB 'P', CLOSE_STR-$-1 ; offset 1 to CLOSE_STR ;------------------------- ; Close Stream Subroutines ;------------------------- ; The close stream routines in fact have no ancillary actions to perform ; which is not surprising with regard to 'K' and 'S'. ;;;$171C CLOSE_STR: POP HL ; * now just restore the stream data pointer RET ; in STRMS and return. ;------------ ; Stream data ;------------ ; This routine finds the data entry in the STRMS area for the specified ; stream which is passed on the calculator stack. It returns with HL ; pointing to this system variable and BC holding a displacement from ; the CHANS area to the second byte of the stream's channel. If BC holds ; zero, then that signifies that the stream is closed. ;;;$171E STR_DATA: CALL FIND_INT1 ; routine FIND_INT1 fetches parameter to A CP $10 ; is it less than 16d ? JR C,STR_DATA1 ; skip forward to STR_DATA1 if so. ;;;$1725 REPORT_OB: RST 08H ; ERROR_1 DEFB $17 ; Error Report: Invalid stream ;;;$1727 STR_DATA1: ADD A,$03 ; add the offset for 3 system streams. ; range 00 - 15d becomes 3 - 18d. RLCA ; double as there are two bytes per ; stream - now 06 - 36d LD HL,STRMS_FD ; address STRMS_FD - the start of the streams ; data area in system variables. LD C,A ; transfer the low byte to A. LD B,$00 ; prepare to add offset. ADD HL,BC ; add to address the data entry in STRMS_FD. ; the data entry itself contains an offset from CHANS to the address of the ; stream LD C,(HL) ; low byte of displacement to C. INC HL ; address next. LD B,(HL) ; high byte of displacement to B. DEC HL ; step back to leave HL pointing to STRMS_FD data entry. RET ; return with CHANS displacement in BC ; and address of stream data entry in HL. ;--------------------- ; Handle OPEN# command ;--------------------- ; Command syntax example: OPEN #5,"s" ; On entry the channel code entry is on the calculator stack with the next ; value containing the stream identifier. They have to swapped. ;;;$1736 OPEN: RST 28H ;; FP_CALC ;s,c. DEFB $01 ;;EXCHANGE ;c,s. DEFB $38 ;;END_CALC CALL STR_DATA ; routine STR_DATA fetches the stream off ; the stack and returns with the CHANS ; displacement in BC and HL addressing ; the STRMS_FD data entry. LD A,B ; test for zero which OR C ; indicates the stream is closed. JR Z,OPEN_1 ; skip forward to OPEN_1 if so. ; if it is a system channel then it can re-attached. EX DE,HL ; save STRMS_FD address in DE. LD HL,(CHANS) ; fetch CHANS. ADD HL,BC ; add the offset to address the second byte of the channel. INC HL ; skip over the INC HL ; input routine. INC HL ; and address the letter. LD A,(HL) ; pick up the letter. EX DE,HL ; save letter pointer and bring back the STRMS_FD pointer. CP $4B ; is it 'K' ? JR Z,OPEN_1 ; forward to OPEN_1 if so CP $53 ; is it 'S' ? JR Z,OPEN_1 ; forward to OPEN_1 if so CP $50 ; is it 'P' ? JR NZ,REPORT_OB ; back to REPORT_OB if not. ; to report 'Invalid stream'. ; continue if one of the upper-case letters was found. ; and rejoin here from above if stream was closed. ;;;$1756 OPEN_1: CALL OPEN_2 ; routine OPEN_2 opens the stream. ; it now remains to update the STRMS_FD variable. LD (HL),E ; insert or overwrite the low byte. INC HL ; address high byte in STRMS_FD. LD (HL),D ; insert or overwrite the high byte. RET ; return. ;------------------ ; OPEN_2 Subroutine ;------------------ ; There is some point in coming here as, as well as once creating buffers, ; this routine also sets flags. ;;;$175D OPEN_2: PUSH HL ; * save the STRMS_FD data entry pointer. CALL STK_FETCH ; routine STK_FETCH now fetches the ; parameters of the channel string. ; start in DE, length in BC. LD A,B ; test that it is not OR C ; the null string. JR NZ,OPEN_3 ; skip forward to OPEN_3 with 1 character ; or more! ;;;$1765 REPORT_F: RST 08H ; ERROR_1 DEFB $0E ; Error Report: Invalid file name ;;;$1767 OPEN_3: PUSH BC ; save the length of the string. LD A,(DE) ; pick up the first character. ; Note. if the second character is used to ; distinguish between a binary or text ; channel then it will be simply a matter ; of setting bit 7 of FLAGX. AND $DF ; make it upper-case. LD C,A ; place it in C. LD HL,OP_STR_LU ; address: OP_STR_LU is loaded. CALL INDEXER ; routine INDEXER will search for letter. JR NC,REPORT_F ; back to REPORT_F if not found ; 'Invalid filename' LD C,(HL) ; fetch the displacement to opening routine. LD B,$00 ; prepare to add. ADD HL,BC ; now form address of opening routine. POP BC ; restore the length of string. JP (HL) ; now jump forward to the relevant routine. ;-------------------------- ; OPEN stream look-up table ;-------------------------- ; The open stream look-up table consists of matched pairs. ; The channel letter is followed by an 8-bit displacement to the ; associated stream-opening routine in this ROM. ; The table requires a zero end-marker as the letter has been ; provided by the user and not the operating system. ;;;$177A OP_STR_LU: DEFB 'K', OPEN_K-$-1 ; $06 offset to OPEN_K DEFB 'S', OPEN_S-$-1 ; $08 offset to OPEN_S DEFB 'P', OPEN_P-$-1 ; $0A offset to OPEN_P DEFB $00 ; end-marker. ;----------------------------- ; The Stream Opening Routines. ;----------------------------- ; These routines would have opened any buffers associated with the stream ; before jumping forward to to OPEN_END with the displacement value in E ; and perhaps a modified value in BC. The strange pathing does seem to ; provide for flexibility in this respect. ; ; There is no need to open the printer buffer as it is there already ; even if you are still saving up for a ZX Printer or have moved onto ; something bigger. In any case it would have to be created after ; the system variables but apart from that it is a simple task ; and all but one of the ROM routines can handle a buffer in that position. ; (PR_ALL_6 would require an extra 3 bytes of code). ; However it wouldn't be wise to have two streams attached to the ZX Printer ; as you can now, so one assumes that if PR_CC_hi was non-zero then ; the OPEN_P routine would have refused to attach a stream if another ; stream was attached. ; Something of significance is being passed to these ghost routines in the ; second character. Strings 'RB', 'RT' perhaps or a drive/station number. ; The routine would have to deal with that and exit to OPEN_END with BC ; containing $0001 or more likely there would be an exit within the routine. ; Anyway doesn't matter, these routines are long gone. ;------------------ ; OPEN_K Subroutine ;------------------ ; Open Keyboard stream. ;;;$1781 OPEN_K: LD E,$01 ; 01 is offset to second byte of channel 'K'. JR OPEN_END ; forward to OPEN_END ;------------------ ; OPEN_S Subroutine ;------------------ ; Open Screen stream. ;;;$1785 OPEN_S: LD E,$06 ; 06 is offset to 2nd byte of channel 'S' JR OPEN_END ; to OPEN_END ;------------------ ; OPEN_P Subroutine ;------------------ ; Open Printer stream. ;;;$1789 OPEN_P: LD E,$10 ; 16d is offset to 2nd byte of channel 'P' ;;;$178B OPEN_END: DEC BC ; the stored length of 'K','S','P' or ; whatever is now tested. ?? LD A,B ; test now if initial or residual length OR C ; is one character. JR NZ,REPORT_F ; to REPORT_F 'Invalid file name' if not. LD D,A ; load D with zero to form the displacement ; in the DE register. POP HL ; * restore the saved STRMS_FD pointer. RET ; return to update STRMS_FD entry thereby ; signalling stream is open. ;----------------------------------------- ; Handle CAT, ERASE, FORMAT, MOVE commands ;----------------------------------------- ; These just generate an error report as the ROM is 'incomplete'. ; ; Luckily this provides a mechanism for extending these in a shadow ROM ; but without the powerful mechanisms set up in this ROM. ; An instruction fetch on $0008 may page in a peripheral ROM, ; e.g. the Sinclair Interface 1 ROM, to handle these commands. ; However that wasn't the plan. ; Development of this ROM continued for another three months until the cost ; of replacing it and the manual became unfeasible. ; The ultimate power of channels and streams died at birth. ;;;$1793 CAT_ETC: JR REPORT_OB ; to REPORT_OB ;------------------ ; Perform AUTO_LIST ;------------------ ; This produces an automatic listing in the upper screen. ;;;$1795 AUTO_LIST: LD (LIST_SP),SP ; save stack pointer in LIST_SP LD (IY+$02),$10 ; update TV_FLAG set bit 3 CALL CL_ALL ; routine CL_ALL. SET 0,(IY+$02) ; update TV_FLAG - signal lower screen in use LD B,(IY+$31) ; fetch DF_SZ to B. CALL CL_LINE ; routine CL_LINE clears lower display preserving B. RES 0,(IY+$02) ; update TV_FLAG - signal main screen in use SET 0,(IY+$30) ; update FLAGS2 - signal unnecessary to clear main screen. LD HL,(E_PPC) ; fetch E_PPC current edit line to HL. LD DE,(S_TOP) ; fetch S_TOP to DE, the current top line ; (initially zero) AND A ; prepare for true subtraction. SBC HL,DE ; subtract and ADD HL,DE ; add back. JR C,AUTO_L_2 ; to AUTO_L_2 if S_TOP higher than E_PPC ; to set S_TOP to E_PPC PUSH DE ; save the top line number. CALL LINE_ADDR ; routine LINE_ADDR gets address of E_PPC. LD DE,$02C0 ; prepare known number of characters in ; the default upper screen. EX DE,HL ; offset to HL, program address to DE. SBC HL,DE ; subtract high value from low to obtain ; negated result used in addition. EX (SP),HL ; swap result with top line number on stack. CALL LINE_ADDR ; routine LINE_ADDR gets address of that ; top line in HL and next line in DE. POP BC ; restore the result to balance stack. ;;;$17CE AUTO_L_1: PUSH BC ; save the result. CALL NEXT_ONE ; routine NEXT_ONE gets address in HL of ; line after auto-line (in DE). POP BC ; restore result. ADD HL,BC ; compute back. JR C,AUTO_L_3 ; to AUTO_L_3 if line 'should' appear EX DE,HL ; address of next line to HL. LD D,(HL) ; get line INC HL ; number LD E,(HL) ; in DE. DEC HL ; adjust back to start. LD (S_TOP),DE ; update S_TOP. JR AUTO_L_1 ; to AUTO_L_1 until estimate reached. ; the jump was to here if S_TOP was greater than E_PPC ;;;$17E1 AUTO_L_2: LD (S_TOP),HL ; make S_TOP the same as E_PPC. ; continue here with valid starting point from above or good estimate ; from computation ;;;$17E4 AUTO_L_3: LD HL,(S_TOP) ; fetch S_TOP line number to HL. CALL LINE_ADDR ; routine LINE_ADDR gets address in HL. ; address of next in DE. JR Z,AUTO_L_4 ; to AUTO_L_4 if line exists. EX DE,HL ; else use address of next line. ;;;$17ED AUTO_L_4: CALL LIST_ALL ; routine LIST_ALL >>> ; The return will be to here if no scrolling occurred RES 4,(IY+$02) ; update TV_FLAG - signal no auto listing. RET ; return. ;------------- ; Handle LLIST ;------------- ; A short form of LIST #3. The listing goes to stream 3 - default printer. ;;;$17F5 LLIST: LD A,$03 ; the usual stream for ZX Printer JR LIST_1 ; forward to LIST_1 ;------------ ; Handle LIST ;------------ ; List to any stream. ; Note. While a starting line can be specified it is ; not possible to specify an end line. ; Just listing a line makes it the current edit line. ;;;$17F9 LIST: LD A,$02 ; default is stream 2 - the upper screen. ;;;$17FB LIST_1: LD (IY+$02),$00 ; the TV_FLAG is initialized. CALL SYNTAX_Z ; routine SYNTAX_Z - checking syntax ? CALL NZ,CHAN_OPEN ; routine CHAN_OPEN if in run-time. RST 18H ; GET_CHAR CALL STR_ALTER ; routine STR_ALTER will alter if '#'. JR C,LIST_4 ; forward to LIST_4 not a '#' . RST 18H ; GET_CHAR CP $3B ; is it ';' ? JR Z,LIST_2 ; skip to LIST_2 if so. CP $2C ; is it ',' ? JR NZ,LIST_3 ; forward to LIST_3 if neither separator. ; we have, say, LIST #15, and a number must follow the separator. ;;;$1814 LIST_2: RST 20H ; NEXT_CHAR CALL EXPT_1NUM ; routine EXPT_1NUM JR LIST_5 ; forward to LIST_5 ; the branch was here with just LIST #3 etc. ;;;$181A LIST_3: CALL USE_ZERO ; routine USE_ZERO JR LIST_5 ; forward to LIST_5 ; the branch was here with LIST ;;;$181F LIST_4: CALL FETCH_NUM ; routine FETCH_NUM checks if a number ; follows else uses zero. ;;;$1822 LIST_5: CALL CHECK_END ; routine CHECK_END quits if syntax OK >>> CALL FIND_INT2 ; routine FIND_INT2 fetches the number ; from the calculator stack in run-time. LD A,B ; fetch high byte of line number and AND $3F ; make less than $40 so that NEXT_ONE ; (from LINE_ADDR) doesn't lose context. ; Note. this is not satisfactory and the typo ; LIST 20000 will list an entirely different ; section than LIST 2000. Such typos are not ; available for checking if they are direct ; commands. LD H,A ; transfer the modified LD L,C ; line number to HL. LD (E_PPC),HL ; update E_PPC to new line number. CALL LINE_ADDR ; routine LINE_ADDR gets the address of the line. ; This routine is called from AUTO_LIST ;;;$1833 LIST_ALL: LD E,$01 ; signal current line not yet printed ;;;$1835 LIST_ALL_2: CALL OUT_LINE ; routine OUT_LINE outputs a BASIC line ; using PRINT_OUT and makes an early return ; when no more lines to print. >>> RST 10H ; PRINT_A prints the carriage return (in A) BIT 4,(IY+$02) ; test TV_FLAG - automatic listing ? JR Z,LIST_ALL_2 ; back to LIST_ALL_2 if not ; (loop exit is via OUT_LINE) ; continue here if an automatic listing required. LD A,(DF_SZ) ; fetch DF_SZ lower display file size. SUB (IY+$4F) ; subtract S_POSN_HI ithe current line number. JR NZ,LIST_ALL_2 ; back to LIST_ALL_2 if upper screen not full. XOR E ; A contains zero, E contains one if the ; current edit line has not been printed ; or zero if it has (from OUT_LINE). RET Z ; return if the screen is full and the line ; has been printed. ; continue with automatic listings if the screen is full and the current ; edit line is missing. OUT_LINE will scroll automatically. PUSH HL ; save the pointer address. PUSH DE ; save the E flag. LD HL,S_TOP ; fetch S_TOP the rough estimate. CALL LN_FETCH ; routine LN_FETCH updates S_TOP with the number of the next line. POP DE ; restore the E flag. POP HL ; restore the address of the next line. JR LIST_ALL_2 ; back to LIST_ALL_2. ;------------------------- ; Print a whole BASIC line ;------------------------- ; This routine prints a whole basic line and it is called ; from LIST_ALL to output the line to current channel ; and from ED_EDIT to 'sprint' the line to the edit buffer. ;;;$1855 OUT_LINE: LD BC,(E_PPC) ; fetch E_PPC the current line which may be ; unchecked and not exist. CALL CP_LINES ; routine CP_LINES finds match or line after. LD D,$3E ; prepare cursor '>' in D. JR Z,OUT_LINE1 ; to OUT_LINE1 if matched or line after. LD DE,$0000 ; put zero in D, to suppress line cursor. RL E ; pick up carry in E if line before current ; leave E zero if same or after. ;;;$1865 OUT_LINE1: LD (IY+$2D),E ; save flag in BREG which is spare. LD A,(HL) ; get high byte of line number. CP $40 ; is it too high ($2F is maximum possible) ? POP BC ; drop the return address and RET NC ; make an early return if so >>> PUSH BC ; save return address CALL OUT_NUM_2 ; routine OUT_NUM_2 to print addressed number ; with leading space. INC HL ; skip low number byte. INC HL ; and the two INC HL ; length bytes. RES 0,(IY+$01) ; update FLAGS - signal leading space required. LD A,D ; fetch the cursor. AND A ; test for zero. JR Z,OUT_LINE3 ; to OUT_LINE3 if zero. RST 10H ; PRINT_A prints '>' the current line cursor. ; this entry point is called from ED_COPY ;;;$187D OUT_LINE2: SET 0,(IY+$01) ; update FLAGS - suppress leading space. ;;;$1881 OUT_LINE3: PUSH DE ; save flag E for a return value. EX DE,HL ; save HL address in DE. RES 2,(IY+$30) ; update FLAGS2 - signal NOT in QUOTES. LD HL,FLAGS ; point to FLAGS. RES 2,(HL) ; signal 'K' mode. (starts before keyword) BIT 5,(IY+$37) ; test FLAGX - input mode ? JR Z,OUT_LINE4 ; forward to OUT_LINE4 if not. SET 2,(HL) ; signal 'L' mode. (used for input) ;;;$1894 OUT_LINE4: LD HL,(X_PTR) ; fetch X_PTR - possibly the error pointer address. AND A ; clear the carry flag. SBC HL,DE ; test if an error address has been reached. JR NZ,OUT_LINE5 ; forward to OUT_LINE5 if not. LD A,$3F ; load A with '?' the error marker. CALL OUT_FLASH ; routine OUT_FLASH to print flashing marker. ;;;$18A1 OUT_LINE5: CALL OUT_CURS ; routine OUT_CURS will print the cursor if ; this is the right position. EX DE,HL ; restore address pointer to HL. LD A,(HL) ; fetch the addressed character. CALL NUMBER ; routine NUMBER skips a hidden floating ; point number if present. INC HL ; now increment the pointer. CP $0D ; is character end-of-line ? JR Z,OUT_LINE6 ; to OUT_LINE6, if so, as line is finished. EX DE,HL ; save the pointer in DE. CALL OUT_CHAR ; routine OUT_CHAR to output character/token. JR OUT_LINE4 ; back to OUT_LINE4 until entire line is done. ;;;$18B4 OUT_LINE6: POP DE ; bring back the flag E, zero if current ; line printed else 1 if still to print. RET ; return with A holding $0D ;-------------------------- ; Check for a number marker ;-------------------------- ; this subroutine is called from two processes. while outputting basic lines ; and while searching statements within a basic line. ; during both, this routine will pass over an invisible number indicator ; and the five bytes floating-point number that follows it. ; Note that this causes floating point numbers to be stripped from ; the basic line when it is fetched to the edit buffer by OUT_LINE. ; the number marker also appears after the arguments of a DEF FN statement ; and may mask old 5-byte string parameters. ;;;$18B6 NUMBER: CP $0E ; character fourteen ? RET NZ ; return if not. INC HL ; skip the character INC HL ; and five bytes INC HL ; following. INC HL INC HL INC HL LD A,(HL) ; fetch the following character RET ; for return value. ;--------------------------- ; Print a flashing character ;--------------------------- ; This subroutine is called from OUT_LINE to print a flashing error ; marker '?' or from the next routine to print a flashing cursor e.g. 'L'. ; However, this only gets called from OUT_LINE when printing the edit line ; or the input buffer to the lower screen so a direct call to 09F4 can ; be used, even though out-line outputs to other streams. ; In fact the alternate set is used for the whole routine. ;;;$18C1 OUT_FLASH: EXX ; switch in alternate set LD HL,(ATTRT_MASKT); fetch L = ATTR_T, H = MASK-T PUSH HL ; save masks. RES 7,H ; reset flash mask bit so active. SET 7,L ; make attribute FLASH. LD (ATTRT_MASKT),HL; resave ATTR_T and MASK-T LD HL,P_FLAG ; address P_FLAG LD D,(HL) ; fetch to D PUSH DE ; and save. LD (HL),$00 ; clear inverse, over, ink/paper 9 CALL PRINT_OUT ; routine PRINT_OUT outputs character ; without the need to vector via RST 10. POP HL ; pop P_FLAG to H. LD (IY+$57),H ; and restore system variable P_FLAG. POP HL ; restore temporary masks LD (ATTRT_MASKT),HL; and restore system variables ATTR_T/MASK_T EXX ; switch back to main set RET ; return ;----------------- ; Print the cursor ;----------------- ; This routine is called before any character is output while outputting ; a basic line or the input buffer. This includes listing to a printer ; or screen, copying a basic line to the edit buffer and printing the ; input buffer or edit buffer to the lower screen. It is only in the ; latter two cases that it has any relevance and in the last case it ; performs another very important function also. ;;;$18E1 OUT_CURS: LD HL,(K_CUR) ; fetch K_CUR the current cursor address AND A ; prepare for true subtraction. SBC HL,DE ; test against pointer address in DE and RET NZ ; return if not at exact position. ; the value of MODE, maintained by KEY_INPUT, is tested and if non-zero ; then this value 'E' or 'G' will take precedence. LD A,(MODE) ; fetch MODE 0='KLC', 1='E', 2='G'. RLC A ; double the value and set flags. JR Z,OUT_C_1 ; to OUT_C_1 if still zero ('KLC'). ADD A,$43 ; add 'C' - will become 'E' if originally 1 ; or 'G' if originally 2. JR OUT_C_2 ; forward to OUT_C_2 to print. ; If mode was zero then, while printing a basic line, bit 2 of flags has been ; set if 'THEN' or ':' was encountered as a main character and reset otherwise. ; This is now used to determine if the 'K' cursor is to be printed but this ; transient state is also now transferred permanently to bit 3 of FLAGS ; to let the interrupt routine know how to decode the next key. ;;;$18F3 OUT_C_1: LD HL,FLAGS ; Address FLAGS RES 3,(HL) ; signal 'K' mode initially. LD A,$4B ; prepare letter 'K'. BIT 2,(HL) ; test FLAGS - was the ; previous main character ':' or 'THEN' ? JR Z,OUT_C_2 ; forward to OUT_C_2 if so to print. SET 3,(HL) ; signal 'L' mode to interrupt routine. ; Note. transient bit has been made permanent. INC A ; augment from 'K' to 'L'. BIT 3,(IY+$30) ; test FLAGS2 - consider caps lock ? ; which is maintained by KEY_INPUT. JR Z,OUT_C_2 ; forward to OUT_C_2 if not set to print. LD A,$43 ; alter 'L' to 'C'. ;;;$1909 OUT_C_2: PUSH DE ; save address pointer but OK as OUT_FLASH ; uses alternate set without RST 10. CALL OUT_FLASH ; routine OUT_FLASH to print. POP DE ; restore and RET ; return. ;----------------------------- ; Get line number of next line ;----------------------------- ; These two subroutines are called while editing. ; This entry point is from ED_DOWN with HL addressing E_PPC ; to fetch the next line number. ; Also from AUTO_LIST with HL addressing S_TOP just to update S_TOP ; with the value of the next line number. It gets fetched but is discarded. ; These routines never get called while the editor is being used for input. ;;;$190F LN_FETCH: LD E,(HL) ; fetch low byte INC HL ; address next LD D,(HL) ; fetch high byte. PUSH HL ; save system variable hi pointer. EX DE,HL ; line number to HL, INC HL ; increment as a starting point. CALL LINE_ADDR ; routine LINE_ADDR gets address in HL. CALL LINE_NO ; routine LINE_NO gets line number in DE. POP HL ; restore system variable hi pointer. ; This entry point is from the ED_UP with HL addressing E_PPC_HI ;;;$191C LN_STORE: BIT 5,(IY+$37) ; test FLAGX - input mode ? RET NZ ; return if so. ; Note. above already checked by ED_UP/ED_DOWN. LD (HL),D ; save high byte of line number. DEC HL ; address lower LD (HL),E ; save low byte of line number. RET ; return. ;------------------------------------------ ; Outputting numbers at start of BASIC line ;------------------------------------------ ; This routine entered at OUT_SP_NO is used to compute then output the first ; three digits of a 4-digit basic line printing a space if necessary. ; The line number, or residual part, is held in HL and the BC register ; holds a subtraction value -1000, -100 or -10. ; Note. for example line number 200 - ; space(out_char), 2(out_code), 0(out_char) final number always out-code. ;;;$1925 OUT_SP_2: LD A,E ; will be space if OUT_CODE not yet called. ; or $FF if spaces are suppressed. ; else $30 ('0'). ; (from the first instruction at OUT_CODE) ; this guy is just too clever. AND A ; test bit 7 of A. RET M ; return if $FF, as leading spaces not ; required. This is set when printing line ; number and statement in MAIN_5. JR OUT_CHAR ; forward to exit via OUT_CHAR. ; -> the single entry point. ;;;$192A OUT_SP_NO: XOR A ; initialize digit to 0 ;;;$192B OUT_SP_1: ADD HL,BC ; add negative number to HL. INC A ; increment digit JR C,OUT_SP_1 ; back to OUT_SP_1 until no carry from ; the addition. SBC HL,BC ; cancel the last addition DEC A ; and decrement the digit. JR Z,OUT_SP_2 ; back to OUT_SP_2 if it is zero. JP OUT_CODE ; jump back to exit via OUT_CODE. -> ;-------------------------------------- ; Outputting characters in a BASIC line ;-------------------------------------- ; This subroutine ... ;;;$1937 OUT_CHAR: CALL NUMERIC ; routine NUMERIC tests if it is a digit ? JR NC,OUT_CH_3 ; to OUT_CH_3 to print digit without ; changing mode. Will be 'K' mode if digits ; are at beginning of edit line. CP $21 ; less than quote character ? JR C,OUT_CH_3 ; to OUT_CH_3 to output controls and space. RES 2,(IY+$01) ; initialize FLAGS to 'K' mode and leave ; unchanged if this character would precede a keyword. CP $CB ; is character 'THEN' token ? JR Z,OUT_CH_3 ; to OUT_CH_3 to output if so. CP $3A ; is it ':' ? JR NZ,OUT_CH_1 ; to OUT_CH_1 if not statement separator ; to change mode back to 'L'. BIT 5,(IY+$37) ; FLAGX - Input Mode ?? JR NZ,OUT_CH_2 ; to OUT_CH_2 if in input as no statements. ; Note. this check should seemingly be at ; the start. Commands seem inappropriate in ; INPUT mode and are rejected by the syntax checker anyway. ; unless INPUT LINE is being used. BIT 2,(IY+$30) ; test FLAGS2 - is the ':' within quotes ? JR Z,OUT_CH_3 ; to OUT_CH_3 if ':' is outside quoted text. JR OUT_CH_2 ; to OUT_CH_2 as ':' is within quotes ;;;$195A OUT_CH_1: CP $22 ; is it quote character '"' ? JR NZ,OUT_CH_2 ; to OUT_CH_2 with others to set 'L' mode. PUSH AF ; save character. LD A,(FLAGS2) ; fetch FLAGS2. XOR $04 ; toggle the quotes flag. LD (FLAGS2),A ; update FLAGS2 POP AF ; and restore character. ;;;$1968 OUT_CH_2: SET 2,(IY+$01) ; update FLAGS - signal L mode if the cursor ; is next. ;;;$196C OUT_CH_3: RST 10H ; PRINT_A vectors the character to ; channel 'S', 'K', 'R' or 'P'. RET ; return. ;-------------------------------------------- ; Get starting address of line, or line after ;-------------------------------------------- ; This routine is used often to get the address, in HL, of a basic line ; number supplied in HL, or failing that the address of the following line ; and the address of the previous line in DE. ;;;$196E LINE_ADDR: PUSH HL ; save line number in HL register LD HL,(PROG) ; fetch start of program from PROG LD D,H ; transfer address to LD E,L ; the DE register pair. ;;;$1974 LINE_AD_1: POP BC ; restore the line number to BC CALL CP_LINES ; routine CP_LINES compares with that addressed by HL RET NC ; return if line has been passed or matched. ; if NZ, address of previous is in DE PUSH BC ; save the current line number CALL NEXT_ONE ; routine NEXT_ONE finds address of next line number in DE, previous in HL. EX DE,HL ; switch so next in HL JR LINE_AD_1 ; back to LINE_AD_1 for another comparison ;--------------------- ; Compare line numbers ;--------------------- ; This routine compares a line number supplied in BC with an addressed ; line number pointed to by HL. ;;;$1980 CP_LINES: LD A,(HL) ; Load the high byte of line number and CP B ; compare with that of supplied line number. RET NZ ; return if yet to match (carry will be set). INC HL ; address low byte of LD A,(HL) ; number and pick up in A. DEC HL ; step back to first position. CP C ; now compare. RET ; zero set if exact match. ; carry set if yet to match. ; no carry indicates a match or ; next available basic line or ; program end marker. ;-------------------- ; Find each statement ;-------------------- ; The single entry point EACH_STMT is used to ; 1) To find the D'th statement in a line. ; 2) To find a token in held E. ;;;$1988 NOT_USED: INC HL INC HL INC HL ; -> entry point. ;;;$198B EACH_STMT: LD (CH_ADD),HL ; save HL in CH_ADD LD C,$00 ; initialize quotes flag ;;;$1990 EACH_S_1: DEC D ; decrease statement count RET Z ; return if zero RST 20H ; NEXT_CHAR CP E ; is it the search token ? JR NZ,EACH_S_3 ; forward to EACH_S_3 if not AND A ; clear carry RET ; return signalling success. ;;;$1998 EACH_S_2: INC HL ; next address LD A,(HL) ; next character ;;;$199A EACH_S_3: CALL NUMBER ; routine NUMBER skips if number marker LD (CH_ADD),HL ; save in CH_ADD CP $22 ; is it quotes '"' ? JR NZ,EACH_S_4 ; to EACH_S_4 if not DEC C ; toggle bit 0 of C ;;;$19A5 EACH_S_4: CP $3A ; is it ':' JR Z,EACH_S_5 ; to EACH_S_5 CP $CB ; 'THEN' JR NZ,EACH_S_6 ; to EACH_S_6 ;;;$19AD EACH_S_5: BIT 0,C ; is it in quotes JR Z,EACH_S_1 ; to EACH_S_1 if not ;;;$19B1 EACH_S_6: CP $0D ; end of line ? JR NZ,EACH_S_2 ; to EACH_S_2 DEC D ; decrease the statement counter ; which should be zero else ; 'Statement Lost'. SCF ; set carry flag - not found RET ; return ;------------------------------------------------------------------------ ; Storage of variables. For full details - see chapter 24. ; ZX Spectrum BASIC Programming by Steven Vickers 1982. ; It is bits 7-5 of the first character of a variable that allow ; the six types to be distinguished. Bits 4-0 are the reduced letter. ; So any variable name is higher that $3F and can be distinguished ; also from the variables area end-marker $80. ; ; 76543210 meaning brief outline of format. ; -------- ------------------------ ----------------------- ; 010 string variable. 2 byte length + contents. ; 110 string array. 2 byte length + contents. ; 100 array of numbers. 2 byte length + contents. ; 011 simple numeric variable. 5 bytes. ; 101 variable length named numeric. 5 bytes. ; 111 for-next loop variable. 18 bytes. ; 10000000 the variables area end-marker. ; ; Note. any of the above seven will serve as a program end-marker. ; ; ----------------------------------------------------------------------- ;------------- ; Get next one ;------------- ; This versatile routine is used to find the address of the next line ; in the program area or the next variable in the variables area. ; The reason one routine is made to handle two apparently unrelated tasks ; is that it can be called indiscriminately when merging a line or a ; variable. ;;;$19B8 NEXT_ONE: PUSH HL ; save the pointer address. LD A,(HL) ; get first byte. CP $40 ; compare with upper limit for line numbers. JR C,NEXT_O_3 ; forward to NEXT_O_3 if within basic area. ; the continuation here is for the next variable unless the supplied ; line number was erroneously over 16383. see RESTORE command. BIT 5,A ; is it a string or an array variable ? JR Z,NEXT_O_4 ; forward to NEXT_O_4 to compute length. ADD A,A ; test bit 6 for single-character variables. JP M,NEXT_O_1 ; forward to NEXT_O_1 if so CCF ; clear the carry for long-named variables. ; it remains set for for-next loop variables. ;;;$19C7 NEXT_O_1: LD BC,$0005 ; set BC to 5 for floating point number JR NC,NEXT_O_2 ; forward to NEXT_O_2 if not a for/next ; variable. LD C,$12 ; set BC to eighteen locations. ; value, limit, step, line and statement. ; now deal with long-named variables ;;;$19CE NEXT_O_2: RLA ; test if character inverted. carry will also ; be set for single character variables INC HL ; address next location. LD A,(HL) ; and load character. JR NC,NEXT_O_2 ; back to NEXT_O_2 if not inverted bit. ; forward immediately with single character ; variable names. JR NEXT_O_5 ; forward to NEXT_O_5 to add length of ; floating point number(s etc.). ; this branch is for line numbers. ;;;$19D5 NEXT_O_3: INC HL ; increment pointer to low byte of line no. ; strings and arrays rejoin here ;;;$19D6 NEXT_O_4: INC HL ; increment to address the length low byte. LD C,(HL) ; transfer to C and INC HL ; point to high byte of length. LD B,(HL) ; transfer that to B INC HL ; point to start of basic/variable contents. ; the three types of numeric variables rejoin here ;;;$19DB NEXT_O_5: ADD HL,BC ; add the length to give address of next line/variable in HL. POP DE ; restore previous address to DE. ;------------------- ; Difference routine ;------------------- ; This routine terminates the above routine and is also called from the ; start of the next routine to calculate the length to reclaim. ;;;$19DD DIFFER: AND A ; prepare for true subtraction. SBC HL,DE ; subtract the two pointers. LD B,H ; transfer result LD C,L ; to BC register pair. ADD HL,DE ; add back EX DE,HL ; and switch pointers RET ; return values are the length of area in BC, ; low pointer (previous) in HL, ; high pointer (next) in DE. ;------------------------ ; Handle reclaiming space ;------------------------ ; ;;;$19E5 RECLAIM_1: CALL DIFFER ; routine DIFFER immediately above ;;;$19E8 RECLAIM_2: PUSH BC LD A,B CPL LD B,A LD A,C CPL LD C,A INC BC CALL POINTERS ; routine POINTERS EX DE,HL POP HL ADD HL,DE PUSH DE LDIR ; copy bytes POP HL RET ;----------------------------------------- ; Read line number of line in editing area ;----------------------------------------- ; This routine reads a line number in the editing area returning the number ; in the BC register or zero if no digits exist before commands. ; It is called from LINE_SCAN to check the syntax of the digits. ; It is called from MAIN_3 to extract the line number in preparation for ; inclusion of the line in the BASIC program area. ; ; Interestingly the calculator stack is moved from it's normal place at the ; end of dynamic memory to an adequate area within the system variables area. ; This ensures that in a low memory situation, that valid line numbers can ; be extracted without raising an error and that memory can be reclaimed ; by deleting lines. If the stack was in it's normal place then a situation ; arises whereby the Spectrum becomes locked with no means of reclaiming space. ;;;$19FB E_LINE_NO: LD HL,(E_LINE) ; load HL from system variable E_LINE. DEC HL ; decrease so that NEXT_CHAR can be used ; without skipping the first digit. LD (CH_ADD),HL ; store in the system variable CH_ADD. RST 20H ; NEXT_CHAR skips any noise and white-space ; to point exactly at the first digit. LD HL,MEM_0 ; use MEM_0 as a temporary calculator stack ; an overhead of three locations are needed. LD (STKEND),HL ; set new STKEND. CALL INT_TO_FP ; routine INT_TO_FP will read digits till ; a non-digit found. CALL FP_TO_BC ; routine FP_TO_BC will retrieve number from stack at membot. JR C,E_L_1 ; forward to E_L_1 if overflow i.e. > 65535. ; 'Nonsense in basic' LD HL,$D8F0 ; load HL with value -9999 ADD HL,BC ; add to line number in BC ;;;$1A15 E_L_1: JP C,REPORT_C ; to REPORT_C 'Nonsense in Basic' if over. ; Note. As ERR_SP points to ED_ERROR ; the report is never produced although ; the RST $08 will update X_PTR leading to ; the error marker being displayed when ; the ED_LOOP is reiterated. ; in fact, since it is immediately ; cancelled, any report will do. ; a line in the range 0 - 9999 has been entered. JP SET_STK ; jump back to SET_STK to set the calculator ; stack back to it's normal place and exit ; from there. ;---------------------------------- ; Report and line number outputting ;---------------------------------- ; Entry point OUT_NUM_1 is used by the Error Reporting code to print ; the line number and later the statement number held in BC. ; If the statement was part of a direct command then -2 is used as a ; dummy line number so that zero will be printed in the report. ; This routine is also used to print the exponent of E-format numbers. ; ; Entry point OUT_NUM_2 is used from OUT_LINE to output the line number ; addressed by HL with leading spaces if necessary. ;;;$1A1B OUT_NUM_1: PUSH DE ; save the PUSH HL ; registers. XOR A ; set A to zero. BIT 7,B ; is the line number minus two ? JR NZ,OUT_NUM_4 ; forward to OUT_NUM_4 if so to print zero ; for a direct command. LD H,B ; transfer the LD L,C ; number to HL. LD E,$FF ; signal 'no leading zeros'. JR OUT_NUM_3 ; forward to continue at OUT_NUM_3 ; from OUT_LINE - HL addresses line number. ;;;$1A28 OUT_NUM_2: PUSH DE ; save flags LD D,(HL) ; high byte to D INC HL ; address next LD E,(HL) ; low byte to E PUSH HL ; save pointer EX DE,HL ; transfer number to HL LD E,$20 ; signal 'output leading spaces' ;;;$1A30 OUT_NUM_3: LD BC,$FC18 ; value -1000 CALL OUT_SP_NO ; routine OUT_SP_NO outputs space or number LD BC,$FF9C ; value -100 CALL OUT_SP_NO ; routine OUT_SP_NO LD C,$F6 ; value -10 ( B is still $FF ) CALL OUT_SP_NO ; routine OUT_SP_NO LD A,L ; remainder to A. ;;;$1A42 OUT_NUM_4: CALL OUT_CODE ; routine OUT_CODE for final digit. ; else report code zero wouldn't get printed. POP HL ; restore the POP DE ; registers and RET ; return. ;*************************************************** ;** Part 7. BASIC LINE AND COMMAND INTERPRETATION ** ;*************************************************** ;----------------- ; The offset table ;----------------- ; The BASIC interpreter has found a command code $CE - $FF ; which is then reduced to range $00 - $31 and added to the base address ; of this table to give the address of an offset which, when added to ; the offset therein, gives the location in the following parameter table ; where a list of class codes, separators and addresses relevant to the ; command exists. ;;;$1A48 OFFST_TBL: DEFB P_DEF_FN - $ ; B1 offset to Address: P_DEF_FN DEFB P_CAT - $ ; CB offset to Address: P_CAT DEFB P_FORMAT - $ ; BC offset to Address: P_FORMAT DEFB P_MOVE - $ ; BF offset to Address: P_MOVE DEFB P_ERASE - $ ; C4 offset to Address: P_ERASE DEFB P_OPEN - $ ; AF offset to Address: P_OPEN DEFB P_CLOSE - $ ; B4 offset to Address: P_CLOSE DEFB P_MERGE - $ ; 93 offset to Address: P_MERGE DEFB P_VERIFY - $ ; 91 offset to Address: P_VERIFY DEFB P_BEEP - $ ; 92 offset to Address: P_BEEP DEFB P_CIRCLE - $ ; 95 offset to Address: P_CIRCLE DEFB P_INK - $ ; 98 offset to Address: P_INK DEFB P_PAPER - $ ; 98 offset to Address: P_PAPER DEFB P_FLASH - $ ; 98 offset to Address: P_FLASH DEFB P_BRIGHT - $ ; 98 offset to Address: P_BRIGHT DEFB P_INVERSE - $ ; 98 offset to Address: P_INVERSE DEFB P_OVER - $ ; 98 offset to Address: P_OVER DEFB P_OUT - $ ; 98 offset to Address: P_OUT DEFB P_LPRINT - $ ; 7F offset to Address: P_LPRINT DEFB P_LLIST - $ ; 81 offset to Address: P_LLIST DEFB P_STOP - $ ; 2E offset to Address: P_STOP DEFB P_READ - $ ; 6C offset to Address: P_READ DEFB P_DATA - $ ; 6E offset to Address: P_DATA DEFB P_RESTORE - $ ; 70 offset to Address: P_RESTORE DEFB P_NEW - $ ; 48 offset to Address: P_NEW DEFB P_BORDER - $ ; 94 offset to Address: P_BORDER DEFB P_CONT - $ ; 56 offset to Address: P_CONT DEFB P_DIM - $ ; 3F offset to Address: P_DIM DEFB P_REM - $ ; 41 offset to Address: P_REM DEFB P_FOR - $ ; 2B offset to Address: P_FOR DEFB P_GO_TO - $ ; 17 offset to Address: P_GO_TO DEFB P_GO_SUB - $ ; 1F offset to Address: P_GO_SUB DEFB P_INPUT - $ ; 37 offset to Address: P_INPUT DEFB P_LOAD - $ ; 77 offset to Address: P_LOAD DEFB P_LIST - $ ; 44 offset to Address: P_LIST DEFB P_LET - $ ; 0F offset to Address: P_LET DEFB P_PAUSE - $ ; 59 offset to Address: P_PAUSE DEFB P_NEXT - $ ; 2B offset to Address: P_NEXT DEFB P_POKE - $ ; 43 offset to Address: P_POKE DEFB P_PRINT - $ ; 2D offset to Address: P_PRINT DEFB P_PLOT - $ ; 51 offset to Address: P_PLOT DEFB P_RUN - $ ; 3A offset to Address: P_RUN DEFB P_SAVE - $ ; 6D offset to Address: P_SAVE DEFB P_RANDOM - $ ; 42 offset to Address: P_RANDOM DEFB P_IF - $ ; 0D offset to Address: P_IF DEFB P_CLS - $ ; 49 offset to Address: P_CLS DEFB P_DRAW - $ ; 5C offset to Address: P_DRAW DEFB P_CLEAR - $ ; 44 offset to Address: P_CLEAR DEFB P_RETURN - $ ; 15 offset to Address: P_RETURN DEFB P_COPY - $ ; 5D offset to Address: P_COPY ;-------------------------------- ; The parameter or "Syntax" table ;-------------------------------- ; For each command there exists a variable list of parameters. ; If the character is greater than a space it is a required separator. ; If less, then it is a command class in the range 00 - 0B. ; Note that classes 00, 03 and 05 will fetch the addresses from this table. ; Some classes e.g. 07 and 0B have the same address in all invocations ; and the command is re-computed from the low-byte of the parameter address. ; Some e.g. 02 are only called once so a call to the command is made from ; within the class routine rather than holding the address within the table. ; Some class routines check syntax entirely and some leave this task for the ; command itself. ; Others for example CIRCLE (x,y,z) check the first part (x,y) using the ; class routine and the final part (,z) within the command. ; The last few commands appear to have been added in a rush but their syntax ; is rather simple e.g. MOVE "M1","M2" ;;;$1A7A P_LET: DEFB $01 ; CLASS_01 - A variable is required. DEFB $3D ; Separator: '=' DEFB $02 ; CLASS_02 - An expression, numeric or string, must follow. ;;;$1A7D P_GO_TO: DEFB $06 ; CLASS_06 - A numeric expression must follow. DEFB $00 ; CLASS_00 - No further operands. DEFW GO_TO ; Address: $1E67; Address: GO_TO ;;;$1A81 P_IF: DEFB $06 ; CLASS_06 - A numeric expression must follow. DEFB $CB ; Separator: 'THEN' DEFB $05 ; CLASS_05 - Variable syntax checked by routine. DEFW IF_CMD ; Address: $1CF0; Address: IF ;;;$1A86 P_GO_SUB: DEFB $06 ; CLASS_06 - A numeric expression must follow. DEFB $00 ; CLASS_00 - No further operands. DEFW GO_SUB ; Address: $1EED; Address: GO_SUB ;;;$1A8A P_STOP: DEFB $00 ; CLASS_00 - No further operands. DEFW STOP ; Address: $1CEE; Address: STOP ;;;$1A8D P_RETURN: DEFB $00 ; CLASS_00 - No further operands. DEFW RETURN ; Address: $1F23; Address: RETURN ;;;$1A90 P_FOR: DEFB $04 ; CLASS_04 - A single character variable must follow. DEFB $3D ; Separator: '=' DEFB $06 ; CLASS_06 - A numeric expression must follow. DEFB $CC ; Separator: 'TO' DEFB $06 ; CLASS_06 - A numeric expression must follow. DEFB $05 ; CLASS_05 - Variable syntax checked by routine. DEFW FOR ; Address: $1D03; Address: FOR ;;;$1A98 P_NEXT: DEFB $04 ; CLASS_04 - A single character variable must follow. DEFB $00 ; CLASS_00 - No further operands. DEFW NEXT ; Address: $1DAB; Address: NEXT ;;;$1A9C P_PRINT: DEFB $05 ; CLASS_05 - Variable syntax checked entirely by routine. DEFW PRINT ; Address: $1FCD; Address: PRINT ;;;$1A9F P_INPUT: DEFB $05 ; CLASS_05 - Variable syntax checked entirely by routine. DEFW INPUT ; Address: $2089; Address: INPUT ;;;$1AA2 P_DIM: DEFB $05 ; CLASS_05 - Variable syntax checked entirely by routine. DEFW DIM ; Address: $2C02; Address: DIM ;;;$1AA5 P_REM: DEFB $05 ; CLASS_05 - Variable syntax checked entirely by routine. DEFW REM ; Address: $1BB2; Address: REM ;;;$1AA8 P_NEW: DEFB $00 ; CLASS_00 - No further operands. DEFW NEW ; Address: $11B7; Address: NEW ;;;$1AAB P_RUN: DEFB $03 ; CLASS_03 - A numeric expression may follow else default to zero. DEFW RUN ; Address: $1EA1; Address: RUN ;;;$1AAE P_LIST: DEFB $05 ; CLASS_05 - Variable syntax checked entirely by routine. DEFW LIST ; Address: $17F9; Address: LIST ;;;$1AB1 P_POKE: DEFB $08 ; CLASS_08 - Two comma-separated numeric expressions required. DEFB $00 ; CLASS_00 - No further operands. DEFW POKE ; Address: $1E80; Address: POKE ;;;$1AB5 P_RANDOM: DEFB $03 ; CLASS_03 - A numeric expression may follow else default to zero. DEFW RANDOMIZE ; Address: $1E4F; Address: RANDOMIZE ;;;$1AB8 P_CONT: DEFB $00 ; CLASS_00 - No further operands. DEFW CONTINUE ; Address: $1E5F; Address: CONTINUE ;;;$1ABB P_CLEAR: DEFB $03 ; CLASS_03 - A numeric expression may follow else default to zero. DEFW CLEAR ; Address: $1EAC; Address: CLEAR ;;;$1ABE P_CLS: DEFB $00 ; CLASS_00 - No further operands. DEFW CLS ; Address: $0D6B; Address: CLS ;;;$1AC1 P_PLOT: DEFB $09 ; CLASS_09 - Two comma-separated numeric expressions required with optional colour items. DEFB $00 ; CLASS_00 - No further operands. DEFW PLOT ; Address: $22DC; Address: PLOT ;;;$1AC5 P_PAUSE: DEFB $06 ; CLASS_06 - A numeric expression must follow. DEFB $00 ; CLASS_00 - No further operands. DEFW PAUSE ; Address: $1F3A; Address: PAUSE ;;;$1AC9 P_READ: DEFB $05 ; CLASS_05 - Variable syntax checked entirely by routine. DEFW READ ; Address: $1DED; Address: READ ;;;$1ACC P_DATA: DEFB $05 ; CLASS_05 - Variable syntax checked entirely by routine. DEFW DATA ; Address: $1E27; Address: DATA ;;;$1ACF P_RESTORE: DEFB $03 ; CLASS_03 - A numeric expression may follow else default to zero. DEFW RESTORE ; Address: $1E42; Address: RESTORE ;;;$1AD2 P_DRAW: DEFB $09 ; CLASS_09 - Two comma-separated numeric expressions required with optional colour items. DEFB $05 ; CLASS_05 - Variable syntax checked by routine. DEFW DRAW ; Address: $2382; Address: DRAW ;;;$1AD6 P_COPY: DEFB $00 ; CLASS_00 - No further operands. DEFW COPY ; Address: $0EAC; Address: COPY ;;;$1AD9 P_LPRINT: DEFB $05 ; CLASS_05 - Variable syntax checked entirely by routine. DEFW LPRINT ; Address: $1FC9; Address: LPRINT ;;;$1ADC P_LLIST: DEFB $05 ; CLASS_05 - Variable syntax checked entirely by routine. DEFW LLIST ; Address: $17F5; Address: LLIST ;;;$1ADF P_SAVE: DEFB $0B ; CLASS_0B - Offset address converted to tape command. ;;;$L1AE0 P_LOAD: DEFB $0B ; CLASS_0B - Offset address converted to tape command. ;;;$1AE1 P_VERIFY: DEFB $0B ; CLASS_0B - Offset address converted to tape command. ;;;$1AE2 P_MERGE: DEFB $0B ; CLASS_0B - Offset address converted to tape command. ;;;$1AE3 P_BEEP: DEFB $08 ; CLASS_08 - Two comma-separated numeric expressions required. DEFB $00 ; CLASS_00 - No further operands. DEFW BEEP ; Address: $03F8; Address: BEEP ;;;$1AE7 P_CIRCLE: DEFB $09 ; CLASS_09 - Two comma-separated numeric expressions required with optional colour items. DEFB $05 ; CLASS_05 - Variable syntax checked by routine. DEFW CIRCLE ; Address: $2320; Address: CIRCLE ;;;$1AEB P_INK: DEFB $07 ; CLASS_07 - Offset address is converted to colour code. ; ;;;$1AEC P_PAPER: DEFB $07 ; CLASS_07 - Offset address is converted to colour code. ;;;$1AED P_FLASH: DEFB $07 ; CLASS_07 - Offset address is converted to colour code. ;;;$1AEE P_BRIGHT: DEFB $07 ; CLASS_07 - Offset address is converted to colour code. ;;;$1AEF P_INVERSE: DEFB $07 ; CLASS_07 - Offset address is converted to colour code. ;;;$1AF0 P_OVER: DEFB $07 ; CLASS_07 - Offset address is converted to colour code. ;;;$1AF1 P_OUT: DEFB $08 ; CLASS_08 - Two comma-separated numeric expressions required. DEFB $00 ; CLASS_00 - No further operands. DEFW OUT_CMD ; Address: $1E7A; Address: OUT ;;;$1AF5 P_BORDER: DEFB $06 ; CLASS_06 - A numeric expression must follow. DEFB $00 ; CLASS_00 - No further operands. DEFW BORDER ; Address: $2294; Address: BORDER ;;;$1AF9 P_DEF_FN: DEFB $05 ; CLASS_05 - Variable syntax checked entirely by routine. DEFW DEF_FN ; Address: $1F60; Address: DEF_FN ;;;$1AFC P_OPEN: DEFB $06 ; CLASS_06 - A numeric expression must follow. DEFB $2C ; Separator: ',' see Footnote * DEFB $0A ; CLASS_0A - A string expression must follow. DEFB $00 ; CLASS_00 - No further operands. DEFW OPEN ; Address: $1736; Address: OPEN ;;;$1B02 P_CLOSE: DEFB $06 ; CLASS_06 - A numeric expression must follow. DEFB $00 ; CLASS_00 - No further operands. DEFW CLOSE ; Address: $16E5; Address: CLOSE ;;;$1B06 P_FORMAT: DEFB $0A ; CLASS_0A - A string expression must follow. DEFB $00 ; CLASS_00 - No further operands. DEFW CAT_ETC ; Address: $1793; Address: CAT_ETC ;;;$1B0A P_MOVE: DEFB $0A ; CLASS_0A - A string expression must follow. DEFB $2C ; Separator: ',' DEFB $0A ; CLASS_0A - A string expression must follow. DEFB $00 ; CLASS_00 - No further operands. DEFW CAT_ETC ; Address: $1793; Address: CAT_ETC ;;;$1B10 P_ERASE: DEFB $0A ; CLASS_0A - A string expression must follow. DEFB $00 ; CLASS_00 - No further operands. DEFW CAT_ETC ; Address: $1793; Address: CAT_ETC ;;;$1B14 P_CAT: DEFB $00 ; CLASS_00 - No further operands. DEFW CAT_ETC ; Address: $1793; Address: CAT_ETC ; * Note that a comma is required as a separator with the OPEN command ; but the Interface 1 programmers relaxed this allowing ';' as an ; alternative for their channels creating a confusing mixture of ; allowable syntax as it is this ROM which opens or re-opens the ; normal channels. ;-------------------------------- ; Main parser (BASIC interpreter) ;-------------------------------- ; This routine is called once from MAIN_2 when the Basic line is to ; be entered or re-entered into the Program area and the syntax ; requires checking. ;;;$1B17 LINE_SCAN: RES 7,(IY+$01) ; update FLAGS - signal checking syntax CALL E_LINE_NO ; routine E_LINE_NO >> ; fetches the line number if in range. XOR A ; clear the accumulator. LD (SUBPPC),A ; set statement number SUBPPC to zero. DEC A ; set accumulator to $FF. LD (ERR_NR),A ; set ERR_NR to 'OK' - 1. JR STMT_L_1 ; forward to continue at STMT_L_1. ;--------------- ; Statement loop ;--------------- ;;;$1B28 STMT_LOOP: RST 20H ; NEXT_CHAR ; -> the entry point from above or LINE_RUN ;;;$1B29 STMT_L_1: CALL SET_WORK ; routine SET_WORK clears workspace etc. INC (IY+$0D) ; increment statement number SUBPPC JP M,REPORT_C ; to REPORT_C to raise ; 'Nonsense in basic' if over 127. RST 18H ; GET_CHAR LD B,$00 ; set B to zero for later indexing. ; early so any other reason ??? CP $0D ; is character carriage return ? ; i.e. an empty statement. JR Z,LINE_END ; forward to LINE_END if so. CP $3A ; is it statement end marker ':' ? ; i.e. another type of empty statement. JR Z,STMT_LOOP ; back to STMT_LOOP if so. LD HL,STMT_RET ; address: STMT_RET PUSH HL ; is now pushed as a return address LD C,A ; transfer the current character to C. ; advance CH_ADD to a position after command and test if it is a command. RST 20H ; NEXT_CHAR to advance pointer LD A,C ; restore current character SUB $CE ; subtract 'DEF FN' - first command JP C,REPORT_C ; jump to REPORT_C if less than a command raising ; 'Nonsense in basic' LD C,A ; put the valid command code back in C. ; register B is zero. LD HL,OFFST_TBL ; address: OFFST_TBL ADD HL,BC ; index into table with one of 50 commands. LD C,(HL) ; pick up displacement to syntax table entry. ADD HL,BC ; add to address the relevant entry. JR GET_PARAM ; forward to continue at GET_PARAM ;----------------------- ; The main scanning loop ;----------------------- ; not documented properly ;;;$1B52 SCAN_LOOP: LD HL,(T_ADDR) ; fetch temporary address from T_ADDR ; during subsequent loops. ; -> the initial entry point with HL addressing start of syntax table entry. ;;;$1B55 GET_PARAM: LD A,(HL) ; pick up the parameter. INC HL ; address next one. LD (T_ADDR),HL ; save pointer in system variable T_ADDR LD BC,SCAN_LOOP ; address: SCAN_LOOP PUSH BC ; is now pushed on stack as looping address. LD C,A ; store parameter in C. CP $20 ; is it greater than ' ' ? JR NC,SEPARATOR ; forward to SEPARATOR to check that correct ; separator appears in statement if so. LD HL,CLASS_TBL ; address: CLASS_TBL. LD B,$00 ; prepare to index into the class table. ADD HL,BC ; index to find displacement to routine. LD C,(HL) ; displacement to BC ADD HL,BC ; add to address the CLASS routine. PUSH HL ; push the address on the stack. RST 18H ; GET_CHAR - HL points to place in statement. DEC B ; reset the zero flag - the initial state ; for all class routines. RET ; and make an indirect jump to routine ; and then SCAN_LOOP (also on stack). ; Note. one of the class routines will eventually drop the return address ; off the stack breaking out of the above seemingly endless loop. ;----------------- ; Verify separator ;----------------- ; This routine is called once to verify that the mandatory separator ; present in the parameter table is also present in the correct ; location following the command. For example, the 'THEN' token after ; the 'IF' token and expression. ;;;$1B6F SEPARATOR: RST 18H ; GET_CHAR CP C ; does it match the character in C ? JP NZ,REPORT_C ; jump forward to REPORT_C if not ; 'Nonsense in basic'. RST 20H ; NEXT_CHAR advance to next character RET ; return. ;------------------------------- ; Come here after interpretation ;------------------------------- ;;;$1B76 STMT_RET: CALL BREAK_KEY ; routine BREAK_KEY is tested after every statement. JR C,STMT_R_1 ; step forward to STMT_R_1 if not pressed. ;;;$1B7B REPORT_L: RST 08H ; ERROR_1 DEFB $14 ; Error Report: BREAK into program ;;;$1B7D STMT_R_1: BIT 7,(IY+$0A) ; test NSPPC - will be set if $FF - no jump to be made. JR NZ,STMT_NEXT ; forward to STMT_NEXT if a program line. LD HL,(NEWPPC) ; fetch line number from NEWPPC BIT 7,H ; will be set if minus two - direct command(s) JR Z,LINE_NEW ; forward to LINE_NEW if a jump is to be ; made to a new program line/statement. ;--------------------- ; Run a direct command ;--------------------- ; A direct command is to be run or, if continuing from above, ; the next statement of a direct command is to be considered. ;;;$1B8A LINE_RUN: LD HL,$FFFE ; The dummy value minus two LD (PPC),HL ; is set/reset as line number in PPC. LD HL,(WORKSP) ; point to end of line + 1 - WORKSP. DEC HL ; now point to $80 end-marker. LD DE,(E_LINE) ; address the start of line E_LINE. DEC DE ; now location before - for GET_CHAR. LD A,(NSPPC) ; load statement to A from NSPPC. JR NEXT_LINE ; forward to NEXT_LINE. ;------------------------------- ; Find start address of new line ;------------------------------- ; The branch was to here if a jump is to made to a new line number ; and statement. ; That is the previous statement was a GO TO, GO SUB, RUN, RETURN, NEXT etc.. ;;;$1B9E LINE_NEW: CALL LINE_ADDR ; routine LINE_ADDR gets address of line ; returning zero flag set if line found. LD A,(NSPPC) ; fetch new statement from NSPPC JR Z,LINE_USE ; forward to LINE_USE if line matched. ; continue as must be a direct command. AND A ; test statement which should be zero JR NZ,REPORT_N ; forward to REPORT_N if not. ; 'Statement lost' LD B,A ; save statement in B. ? LD A,(HL) ; fetch high byte of line number. AND $C0 ; test if using direct command ; a program line is less than $3F LD A,B ; retrieve statement. ; (we can assume it is zero). JR Z,LINE_USE ; forward to LINE_USE if was a program line ; Alternatively a direct statement has finished correctly. ;;;$1BB0 REPORT_0: RST 08H ; ERROR_1 DEFB $FF ; Error Report: OK ;------------------- ; Handle REM command ;------------------- ; The REM command routine. ; The return address STMT_RET is dropped and the rest of line ignored. ;;;$1BB2 REM: POP BC ; drop return address STMT_RET and ; continue ignoring rest of line. ;------------- ; End of line? ;------------- ;;;$1BB3 LINE_END: CALL SYNTAX_Z ; routine SYNTAX_Z (UNSTACK_Z?) RET Z ; return if checking syntax. LD HL,(NXTLIN) ; fetch NXTLIN to HL. LD A,$C0 ; test against the AND (HL) ; system limit $3F. RET NZ ; return if more as must be end of program. ; (or direct command) XOR A ; set statement to zero. ; and continue to set up the next following line and then consider this new one. ;---------------------- ; General line checking ;---------------------- ; The branch was here from LINE_NEW if Basic is branching. ; or a continuation from above if dealing with a new sequential line. ; First make statement zero number one leaving others unaffected. ;;;$1BBF LINE_USE: CP $01 ; will set carry if zero. ADC A,$00 ; add in any carry. LD D,(HL) ; high byte of line number to D. INC HL ; advance pointer. LD E,(HL) ; low byte of line number to E. LD (PPC),DE ; set system variable PPC. INC HL ; advance pointer. LD E,(HL) ; low byte of line length to E. INC HL ; advance pointer. LD D,(HL) ; high byte of line length to D. EX DE,HL ; swap pointer to DE before ADD HL,DE ; adding to address the end of line. INC HL ; advance to start of next line. ;------------------------------ ; Update NEXT LINE but consider ; previous line or edit line. ;------------------------------ ; The pointer will be the next line if continuing from above or to ; edit line end-marker ($80) if from LINE_RUN. ;;;$1BD1 NEXT_LINE: LD (NXTLIN),HL ; store pointer in system variable NXTLIN EX DE,HL ; bring back pointer to previous or edit line LD (CH_ADD),HL ; and update CH_ADD with character address. LD D,A ; store statement in D. LD E,$00 ; set E to zero to suppress token searching if EACH_STMT is to be called. LD (IY+$0A),$FF ; set statement NSPPC to $FF signalling no jump to be made. DEC D ; decrement and test statement LD (IY+$0D),D ; set SUBPPC to decremented statement number. JP Z,STMT_LOOP ; to STMT_LOOP if result zero as statement is ; at start of line and address is known. INC D ; else restore statement. CALL EACH_STMT ; routine EACH_STMT finds the D'th statement address as E does not contain a token. JR Z,STMT_NEXT ; forward to STMT_NEXT if address found. ;;;$1BEC REPORT_N: RST 08H ; ERROR_1 DEFB $16 ; Error Report: Statement lost ;------------------ ; End of statement? ;------------------ ; This combination of routines is called from 20 places when ; the end of a statement should have been reached and all preceding ; syntax is in order. ;;;$1BEE CHECK_END: CALL SYNTAX_Z ; routine SYNTAX_Z RET NZ ; return immediately in runtime POP BC ; drop address of calling routine. POP BC ; drop address STMT_RET. ; and continue to find next statement. ;--------------------- ; Go to next statement ;--------------------- ; Acceptable characters at this point are carriage return and ':'. ; If so go to next statement which in the first case will be on next line. ;;;$1BF4 STMT_NEXT: RST 18H ; GET_CHAR - ignoring white space etc. CP $0D ; is it carriage return ? JR Z,LINE_END ; back to LINE_END if so. CP $3A ; is it ':' ? JP Z,STMT_LOOP ; jump back to STMT_LOOP to consider ; further statements JP REPORT_C ; jump to REPORT_C with any other character ; 'Nonsense in BASIC'. ; Note. the two-byte sequence 'rst 08; defb $0b' could replace the above jp. ;-------------------- ; Command class table ;-------------------- ;;;$1C01 CLASS_TBL: DEFB CLASS_00 - $ ; 0F offset to Address: CLASS_00 DEFB CLASS_01 - $ ; 1D offset to Address: CLASS_01 DEFB CLASS_02 - $ ; 4B offset to Address: CLASS_02 DEFB CLASS_03 - $ ; 09 offset to Address: CLASS_03 DEFB CLASS_04 - $ ; 67 offset to Address: CLASS_04 DEFB CLASS_05 - $ ; 0B offset to Address: CLASS_05 DEFB CLASS_06 - $ ; 7B offset to Address: CLASS_06 DEFB CLASS_07 - $ ; 8E offset to Address: CLASS_07 DEFB CLASS_08 - $ ; 71 offset to Address: CLASS_08 DEFB CLASS_09 - $ ; B4 offset to Address: CLASS_09 DEFB CLASS_0A - $ ; 81 offset to Address: CLASS_0A DEFB CLASS_0B - $ ; CF offset to Address: CLASS_0B ;------------------------------- ; Command classes 00, 03, and 05 ;------------------------------- ; CLASS_03 e.g RUN or RUN 200 ; optional operand ; CLASS_00 e.g CONTINUE ; no operand ; CLASS_05 e.g PRINT ; variable syntax checked by routine ;;;$1C0D CLASS_03: CALL FETCH_NUM ; routine FETCH_NUM ;;;$1C10 CLASS_00: CP A ; reset zero flag. ; if entering here then all class routines are entered with zero reset. ;;;$1C11 CLASS_05: POP BC ; drop address SCAN_LOOP. CALL Z,CHECK_END ; if zero set then call routine CHECK_END >>> ; as should be no further characters. EX DE,HL ; save HL to DE. LD HL,(T_ADDR) ; fetch T_ADDR LD C,(HL) ; fetch low byte of routine INC HL ; address next. LD B,(HL) ; fetch high byte of routine. EX DE,HL ; restore HL from DE PUSH BC ; push the address RET ; and make an indirect jump to the command. ;------------------------------- ; Command classes 01, 02, and 04 ;------------------------------- ; CLASS_01 e.g LET A = 2*3 ; a variable is reqd ; This class routine is also called from INPUT and READ to find the ; destination variable for an assignment. ;;;$1C1F CLASS_01: CALL LOOK_VARS ; routine LOOK_VARS returns carry set if not ; found in runtime. ;----------------------- ; Variable in assignment ;----------------------- ;;;$1C22 VAR_A_1: LD (IY+$37),$00 ; set FLAGX to zero JR NC,VAR_A_2 ; forward to VAR_A_2 if found or checking syntax. SET 1,(IY+$37) ; FLAGX - Signal a new variable JR NZ,VAR_A_3 ; to VAR_A_3 if not assigning to an array ; e.g. LET a$(3,3) = "X" ;;;$1C2E REPORT_2: RST 08H ; ERROR_1 DEFB $01 ; Error Report: Variable not found ;;;$1C30 VAR_A_2: CALL Z,STK_VAR ; routine STK_VAR considers a subscript/slice BIT 6,(IY+$01) ; test FLAGS - Numeric or string result ? JR NZ,VAR_A_3 ; to VAR_A_3 if numeric XOR A ; default to array/slice - to be retained. CALL SYNTAX_Z ; routine SYNTAX_Z CALL NZ,STK_FETCH ; routine STK_FETCH is called in runtime ; may overwrite A with 1. LD HL,FLAGX ; address system variable FLAGX OR (HL) ; set bit 0 if simple variable to be reclaimed LD (HL),A ; update FLAGX EX DE,HL ; start of string/subscript to DE ;;;$1C46 VAR_A_3: LD (STRLEN),BC ; update STRLEN LD (DEST),HL ; and DEST of assigned string. RET ; return. ; --------------------------- ; CLASS_02 e.g. LET a = 1 + 1 ; an expression must follow ;;;$1C4E CLASS_02: POP BC ; drop return address SCAN_LOOP CALL VAL_FET_1 ; routine VAL_FET_1 is called to check ; expression and assign result in runtime CALL CHECK_END ; routine CHECK_END checks nothing else ; is present in statement. RET ; return ;-------------- ; Fetch a value ;-------------- ;;;$1C56 VAL_FET_1: LD A,(FLAGS) ; initial FLAGS to A ;;;$LC59 VAL_FET_2: PUSH AF ; save A briefly CALL SCANNING ; routine SCANNING evaluates expression. POP AF ; restore A LD D,(IY+$01) ; post-SCANNING FLAGS to D XOR D ; xor the two sets of flags AND $40 ; pick up bit 6 of xored FLAGS should be zero JR NZ,REPORT_C ; forward to REPORT_C if not zero ; 'Nonsense in Basic' - results don't agree. BIT 7,D ; test FLAGS - is syntax being checked ? JP NZ,LET ; jump forward to LET to make the assignment ; in runtime. RET ; but return from here if checking syntax. ;------------------- ; Command CLASS_--04 ;------------------- ; CLASS_04 e.g. FOR i ; a single character variable must follow ;;;$1C6C CLASS_04: CALL LOOK_VARS ; routine LOOK_VARS PUSH AF ; preserve flags. LD A,C ; fetch type - should be 011xxxxx OR $9F ; combine with 10011111. INC A ; test if now $FF by incrementing. JR NZ,REPORT_C ; forward to REPORT_C if result not zero. POP AF ; else restore flags. JR VAR_A_1 ; back to VAR_A_1 ;--------------------------------- ; Expect numeric/string expression ;--------------------------------- ; This routine is used to get the two coordinates of STRING$, ATTR and POINT. ; It is also called from PRINT_ITEM to get the two numeric expressions that ; follow the AT ( in PRINT AT, INPUT AT). ;;;$1C79 NEXT_2NUM: RST 20H ; NEXT_CHAR advance past 'AT' or '('. ; ------------------------- ; CLASS_08 e.g POKE 65535,2 ; two numeric expressions separated by comma ;;;$1C7A CLASS_08: EXPT_2NUM: CALL EXPT_1NUM ; routine EXPT_1NUM is called for first ; numeric expression CP $2C ; is character ',' ? JR NZ,REPORT_C ; to REPORT_C if not required separator. ; 'Nonsense in basic'. RST 20H ; NEXT_CHAR ; --------------------------- ; CLASS_06 e.g. GOTO a*1000 ; a numeric expression must follow ;;;$1C82 CLASS_06: EXPT_1NUM: CALL SCANNING ; routine SCANNING BIT 6,(IY+$01) ; test FLAGS - Numeric or string result ? RET NZ ; return if result is numeric. ;;;$1C8A REPORT_C: RST 08H ; ERROR_1 DEFB $0B ; Error Report: Nonsense in BASIC ; -------------------------- ; CLASS_0A e.g. ERASE "????" ; a string expression must follow. ; ; these only occur in unimplemented commands ; ; although the routine EXPT_EXP is called ; ; from SAVE_ETC ;;;$1C8C CLASS_0A: EXPT_EXP: CALL SCANNING ; routine SCANNING BIT 6,(IY+$01) ; test FLAGS - Numeric or string result ? RET Z ; return if string result. JR REPORT_C ; back to REPORT_C if numeric. ;---------------------- ; Set permanent colours ; class 07 ;---------------------- ; CLASS_07 e.g PAPER 6 ; a single class for a collection of ; ; similar commands. Clever. ; ; Note. these commands should ensure that current channel is 'S' ;;;$1C96 CLASS_07: BIT 7,(IY+$01) ; test FLAGS - checking syntax only ? RES 0,(IY+$02) ; TV_FLAG - signal main screen in use CALL NZ,TEMPS ; routine TEMPS is called in runtime. POP AF ; drop return address SCAN_LOOP LD A,(T_ADDR) ; T_ADDR_lo to accumulator. ; points to '$07' entry + 1 ; e.g. for INK points to $EC now ; Note if you move alter the syntax table next line may have to be altered. SUB $13 ; convert $EB to $D8 ('INK') etc. ; ( is SUB $13 in standard ROM ) CALL CO_TEMP_4 ; routine CO_TEMP_4 CALL CHECK_END ; routine CHECK_END check that nothing else in statement. ; return here in runtime. LD HL,(ATTRT_MASKT); pick up ATTR_T and MASK_T LD (ATTRP_MASKP),HL; and store in ATTR_P and MASK_P LD HL,P_FLAG ; point to P_FLAG. LD A,(HL) ; pick up in A RLCA ; rotate to left XOR (HL) ; combine with HL AND $AA ; 10101010 XOR (HL) ; only permanent bits affected LD (HL),A ; reload into P_FLAG. RET ; return. ;----------------- ; Command CLASS 09 ;----------------- ; e.g. PLOT PAPER 0; 128,88 ; two coordinates preceded by optional ; ; embedded colour items. ; ; Note. this command should ensure that current channel is 'S'. ;;;$1CBE CLASS_09: CALL SYNTAX_Z ; routine SYNTAX_Z JR Z,CL_09_1 ; forward to CL_09_1 if checking syntax. RES 0,(IY+$02) ; update TV_FLAG - signal main screen in use CALL TEMPS ; routine TEMPS is called. LD HL,MASK_T ; point to MASK_T LD A,(HL) ; fetch mask to accumulator. OR $F8 ; or with 11111000 paper/bright/flash 8 LD (HL),A ; mask back to MASK_T system variable. RES 6,(IY+$57) ; reset P_FLAG - signal NOT PAPER 9 ? RST 18H ; GET_CHAR ;;;$1CD6 CL_09_1: CALL CO_TEMP_2 ; routine CO_TEMP_2 deals with embedded colour items. JR EXPT_2NUM ; exit via EXPT_2NUM to check for x,y. ;----------------- ; Command CLASS 0B ;----------------- ; Again a single class for four commands. ; This command just jumps back to SAVE_ETC to handle the four tape commands. ; The routine itself works out which command has called it by examining the ; address in T_ADDR_lo. Note therefore that the syntax table has to be ; located where these and other sequential command addresses are not split ; over a page boundary. ;;;$1CDB CLASS_0B: JP SAVE_ETC ; jump way back to SAVE_ETC ;--------------- ; Fetch a number ;--------------- ; This routine is called from CLASS_03 when a command may be followed by ; an optional numeric expression e.g. RUN. If the end of statement has ; been reached then zero is used as the default. ; Also called from LIST_4. ;;;$1CDE FETCH_NUM: CP $0D ; is character a carriage return ? JR Z,USE_ZERO ; forward to USE_ZERO if so CP $3A ; is it ':' ? JR NZ,EXPT_1NUM ; forward to EXPT_1NUM if not. ; else continue and use zero. ;----------------- ; Use zero routine ;----------------- ; This routine is called four times to place the value zero on the ; calculator stack as a default value in runtime. ;;;$1CE6 USE_ZERO: CALL SYNTAX_Z ; routine SYNTAX_Z (UNSTACK_Z?) RET Z ; RST 28H ;; FP_CALC DEFB $A0 ;;STK_ZERO ;0. DEFB $38 ;;END_CALC RET ; return. ;-------------------- ; Handle STOP command ;-------------------- ; Command Syntax: STOP ; One of the shortest and least used commands. As with 'OK' not an error. ;;;$1CEE STOP: RST 08H ; ERROR_1 DEFB $08 ; Error Report: STOP statement ;------------------ ; Handle IF command ;------------------ ; e.g. IF score>100 THEN PRINT "You Win" ; The parser has already checked the expression the result of which is on ; the calculator stack. The presence of the 'THEN' separator has also been ; checked and CH-ADD points to the command after THEN. ;;;$1CF0 IF_CMD: POP BC ; drop return address - STMT_RET CALL SYNTAX_Z ; routine SYNTAX_Z JR Z,IF_1 ; forward to IF_1 if checking syntax ; to check syntax of PRINT "You Win" RST 28H ;; FP_CALC score>100 (1=TRUE 0=FALSE) DEFB $02 ;;DELETE DEFB $38 ;;END_CALC EX DE,HL ; make HL point to deleted value CALL TEST_ZERO ; routine TEST_ZERO JP C,LINE_END ; jump to LINE_END if FALSE (0) ;;;$1D00 IF_1: JP STMT_L_1 ; to STMT_L_1, if true (1) to execute command ; after 'THEN' token. ;------------------- ; Handle FOR command ;------------------- ; e.g. FOR i = 0 TO 1 STEP 0.1 ; Using the syntax tables, the parser has already checked for a start and ; limit value and also for the intervening separator. ; the two values v,l are on the calculator stack. ; CLASS_04 has also checked the variable and the name is in STRLEN_lo. ; The routine begins by checking for an optional STEP. ;;;$1D03 FOR: CP $CD ; is there a 'STEP' ? JR NZ,F_USE_1 ; to F_USE_1 if not to use 1 as default. RST 20H ; NEXT_CHAR CALL EXPT_1NUM ; routine EXPT_1NUM CALL CHECK_END ; routine CHECK_END JR F_REORDER ; to F_REORDER ;;;$1D10 F_USE_1: CALL CHECK_END ; routine CHECK_END RST 28H ;; FP_CALC v,l. DEFB $A1 ;;STK_ONE v,l,1=s. DEFB $38 ;;END_CALC ;;;$1D16 F_REORDER: RST 28H ;; FP_CALC v,l,s. DEFB $C0 ;;st-mem-0 v,l,s. DEFB $02 ;;DELETE v,l. DEFB $01 ;;EXCHANGE l,v. DEFB $E0 ;;get-mem-0 l,v,s. DEFB $01 ;;EXCHANGE l,s,v. DEFB $38 ;;END_CALC CALL LET ; routine LET assigns the initial value v to ; the variable altering type if necessary. LD (MEM),HL ; The system variable MEM is made to point to ; the variable instead of it's normal location MEMBOT DEC HL ; point to single-character name LD A,(HL) ; fetch name SET 7,(HL) ; set bit 7 at location LD BC,$0006 ; add six to HL ADD HL,BC ; to address where limit should be. RLCA ; test bit 7 of original name. JR C,F_L_S ; forward to F_L_S if already a FOR/NEXT ; variable LD C,$0D ; otherwise an additional 13 bytes are needed. ; 5 for each value, two for line number and ; 1 byte for looping statement. CALL MAKE_ROOM ; routine MAKE_ROOM creates them. INC HL ; make HL address limit. ;;;$1D34 F_L_S: PUSH HL ; save position. RST 28H ;; FP_CALC l,s. DEFB $02 ;;DELETE l. DEFB $02 ;;DELETE . DEFB $38 ;;END_CALC ; DE points to STKEND, l. POP HL ; restore variable position EX DE,HL ; swap pointers LD C,$0A ; ten bytes to move LDIR ; Copy 'deleted' values to variable. LD HL,(PPC) ; Load with current line number from PPC EX DE,HL ; exchange pointers. LD (HL),E ; save the looping line INC HL ; in the next LD (HL),D ; two locations. LD D,(IY+$0D) ; fetch statement from SUBPPC system variable. INC D ; increment statement. INC HL ; and pointer LD (HL),D ; and store the looping statement. ; CALL NEXT_LOOP ; routine NEXT_LOOP considers an initial RET NC ; iteration. Return to STMT_RET if a loop is ; possible to execute next statement. ; no loop is possible so execution continues after the matching 'NEXT' LD B,(IY+$38) ; get single-character name from STRLEN_lo LD HL,(PPC) ; get the current line from PPC LD (NEWPPC),HL ; and store it in NEWPPC LD A,(SUBPPC) ; fetch current statement from SUBPPC NEG ; Negate as counter decrements from zero ; initially and we are in the middle of a line. LD D,A ; Store result in D. LD HL,(CH_ADD) ; get current address from CH_ADD LD E,$F3 ; search will be for token 'NEXT' ;;;$1D64 F_LOOP: PUSH BC ; save variable name. LD BC,(NXTLIN) ; fetch NXTLIN CALL LOOK_PROG ; routine LOOK_PROG searches for 'NEXT' token. LD (NXTLIN),BC ; update NXTLIN POP BC ; and fetch the letter JR C,REPORT_I ; forward to REPORT_I if the end of program ; was reached by LOOK_PROG. ; 'FOR without NEXT' RST 20H ; NEXT_CHAR fetches character after NEXT OR $20 ; ensure it is upper-case. CP B ; compare with FOR variable name JR Z,F_FOUND ; forward to F_FOUND if it matches. ; but if no match i.e. nested FOR/NEXT loops then continue search. RST 20H ; NEXT_CHAR JR F_LOOP ; back to F_LOOP ;;;$1D7C F_FOUND: RST 20H ; NEXT_CHAR LD A,$01 ; subtract the negated counter from 1 SUB D ; to give the statement after the NEXT LD (NSPPC),A ; set system variable NSPPC RET ; return to STMT_RET to branch to new ; line and statement. -> ;;;$1D84 REPORT_I: RST 08H ; ERROR_1 DEFB $11 ; Error Report: FOR without NEXT ;---------- ; LOOK_PROG ;---------- ; Find DATA, DEF FN or NEXT. ; This routine searches the program area for one of the above three keywords. ; On entry, HL points to start of search area. ; The token is in E, and D holds a statement count, decremented from zero. ;;;$1D86 LOOK_PROG: LD A,(HL) ; fetch current character CP $3A ; is it ':' a statement separator ? JR Z,LOOK_P_2 ; forward to LOOK_P_2 if so. ; The starting point was PROG - 1 or the end of a line. ;;;$1D8B LOOK_P_1: INC HL ; increment pointer to address LD A,(HL) ; the high byte of line number AND $C0 ; test for program end marker $80 or a variable SCF ; Set Carry Flag RET NZ ; return with carry set if at end ; of program. -> LD B,(HL) ; high byte of line number to B INC HL LD C,(HL) ; low byte to C. LD (NEWPPC),BC ; set system variable NEWPPC. INC HL LD C,(HL) ; low byte of line length to C. INC HL LD B,(HL) ; high byte to B. PUSH HL ; save address ADD HL,BC ; add length to position. LD B,H ; and save result LD C,L ; in BC. POP HL ; restore address. LD D,$00 ; initialize statement counter to zero. ;;;$1DA3 LOOK_P_2: PUSH BC ; save address of next line CALL EACH_STMT ; routine EACH_STMT searches current line. POP BC ; restore address. RET NC ; return if match was found. -> JR LOOK_P_1 ; back to LOOK_P_1 for next line. ;-------------------- ; Handle NEXT command ;-------------------- ; e.g. NEXT i ; The parameter tables have already evaluated the presence of a variable ;;;$1DAB NEXT: BIT 1,(IY+$37) ; test FLAGX - handling a new variable ? JP NZ,REPORT_2 ; jump back to REPORT_2 if so ; 'Variable not found' ; now test if found variable is a simple variable uninitialized by a FOR. LD HL,(DEST) ; load address of variable from DEST BIT 7,(HL) ; is it correct type ? JR Z,REPORT_1 ; forward to REPORT_1 if not ; 'NEXT without FOR' INC HL ; step past variable name LD (MEM),HL ; and set MEM to point to three 5-byte values ; value, limit, step. RST 28H ;; FP_CALC add step and re-store DEFB $E0 ;;get-mem-0 v. DEFB $E2 ;;get-mem-2 v,s. DEFB $0F ;;ADDITION v+s. DEFB $C0 ;;st-mem-0 v+s. DEFB $02 ;;DELETE . DEFB $38 ;;END_CALC CALL NEXT_LOOP ; routine NEXT_LOOP tests against limit. RET C ; return if no more iterations possible. LD HL,(MEM) ; find start of variable contents from MEM. LD DE,$000F ; add 3*5 to ADD HL,DE ; address the looping line number LD E,(HL) ; low byte to E INC HL LD D,(HL) ; high byte to D INC HL ; address looping statement LD H,(HL) ; and store in H EX DE,HL ; swap registers JP GO_TO_2 ; exit via GO_TO_2 to execute another loop. ;;;$1DD8 REPORT_1: RST 08H ; ERROR_1 DEFB $00 ; Error Report: NEXT without FOR ;------------------ ; Perform NEXT loop ;------------------ ; This routine is called from the FOR command to test for an initial ; iteration and from the NEXT command to test for all subsequent iterations. ; the system variable MEM addresses the variable's contents which, in the ; latter case, have had the step, possibly negative, added to the value. ;;;$1DDA NEXT_LOOP: RST 28H ;; FP_CALC DEFB $E1 ;;get-mem-1 l. DEFB $E0 ;;get-mem-0 l,v. DEFB $E2 ;;get-mem-2 l,v,s. DEFB $36 ;;LESS_0 l,v,(1/0) negative step ? DEFB $00 ;;JUMP_TRUE l,v.(1/0) DEFB $02 ;;to NEXT_1 if step negative DEFB $01 ;;EXCHANGE v,l. ;;;$1DE2 NEXT_1: DEFB $03 ;;SUBTRACT l-v OR v-l. DEFB $37 ;;GREATER_0 (1/0) DEFB $00 ;;JUMP_TRUE . DEFB $04 ;;to NEXT_2 if no more iterations. DEFB $38 ;;END_CALC . AND A ; clear carry flag signalling another loop. RET ; return ;;;$1DE9 NEXT_2: DEFB $38 ;;END_CALC . SCF ; set carry flag signalling looping exhausted. RET ; return ;-------------------- ; Handle READ command ;-------------------- ; e.g. READ a, b$, c$(1000 TO 3000) ; A list of comma-separated variables is assigned from a list of ; comma-separated expressions. ; As it moves along the first list, the character address CH_ADD is stored ; in X_PTR while CH_ADD is used to read the second list. ;;;$1DEC READ_3: RST 20H ; NEXT_CHAR ; -> Entry point. ;;;$1DED READ: CALL CLASS_01 ; routine CLASS_01 checks variable. CALL SYNTAX_Z ; routine SYNTAX_Z JR Z,READ_2 ; forward to READ_2 if checking syntax RST 18H ; GET_CHAR LD (X_PTR),HL ; save character position in X_PTR. LD HL,(DATADD) ; load HL with Data Address DATADD, which is ; the start of the program or the address ; after the last expression that was read or ; the address of the line number of the ; last RESTORE command. LD A,(HL) ; fetch character CP $2C ; is it a comma ? JR Z,READ_1 ; forward to READ_1 if so. ; else all data in this statement has been read so look for next DATA token LD E,$E4 ; token 'DATA' CALL LOOK_PROG ; routine LOOK_PROG JR NC,READ_1 ; forward to READ_1 if DATA found ; else report the error. ;;;$1E08 REPORT_E: RST 08H ; ERROR_1 DEFB $0D ; Error Report: Out of DATA ;;;$1E0A READ_1: CALL TEMP_PTR1 ; routine TEMP_PTR1 advances updating CH_ADD with new DATADD position. CALL VAL_FET_1 ; routine VAL_FET_1 assigns value to variable ; checking type match and adjusting CH_ADD. RST 18H ; GET_CHAR fetches adjusted character position LD (DATADD),HL ; store back in DATADD LD HL,(X_PTR) ; fetch X_PTR the original READ CH_ADD LD (IY+$26),$00 ; now nullify X_PTR_HI CALL TEMP_PTR2 ; routine TEMP_PTR2 restores READ CH_ADD ;;;$1E1E READ_2: RST 18H ; GET_CHAR CP $2C ; is it ',' indicating more variables to read ? JR Z,READ_3 ; back to READ_3 if so CALL CHECK_END ; routine CHECK_END RET ; return from here in runtime to STMT_RET. ;-------------------- ; Handle DATA command ;-------------------- ; In runtime this 'command' is passed by but the syntax is checked when such ; a statement is found while parsing a line. ; e.g. DATA 1, 2, "text", score-1, a$(location, room, object), FN r(49), ; wages - tax, TRUE, The meaning of life ;;;$1E27 DATA: CALL SYNTAX_Z ; routine SYNTAX_Z to check status JR NZ,DATA_2 ; forward to DATA_2 if in runtime ;;;$1E2C DATA_1: CALL SCANNING ; routine SCANNING to check syntax of expression CP $2C ; is it a comma ? CALL NZ,CHECK_END ; routine CHECK_END checks that statement ; is complete. Will make an early exit if ; so. >>> RST 20H ; NEXT_CHAR JR DATA_1 ; back to DATA_1 ;;;$1E37 DATA_2: LD A,$E4 ; set token to 'DATA' and continue into ; the the PASS_BY routine. ;----------------------------------- ; Check statement for DATA or DEF FN ;----------------------------------- ; This routine is used to backtrack to a command token and then ; forward to the next statement in runtime. ;;;$1E39 PASS_BY: LD B,A ; Give BC enough space to find token. CPDR ; Compare decrement and repeat. (Only use). ; Work backwards till keyword is found which ; is start of statement before any quotes. ; HL points to location before keyword. LD DE,$0200 ; count 1+1 statements, dummy value in E to ; inhibit searching for a token. JP EACH_STMT ; to EACH_STMT to find next statement ;------------------------------------------------------------------------ ; A General Note on Invalid Line Numbers. ; ======================================= ; One of the revolutionary concepts of Sinclair Basic was that it supported ; virtual line numbers. That is the destination of a GO TO, RESTORE etc. need ; not exist. It could be a point before or after an actual line number. ; Zero suffices for a before but the after should logically be infinity. ; Since the maximum actual line limit is 9999 then the system limit, 16383 ; when variables kick in, would serve fine as a virtual end point. ; However, ironically, only the LOAD command gets it right. It will not ; autostart a program that has been saved with a line higher than 16383. ; All the other commands deal with the limit unsatisfactorily. ; LIST, RUN, GO TO, GO SUB and RESTORE have problems and the latter may ; crash the machine when supplied with an inappropriate virtual line number. ; This is puzzling as very careful consideration must have been given to ; this point when the new variable types were allocated their masks and also ; when the routine NEXT-ONE was successfully re-written to reflect this. ; An enigma. ;-------------------------------------------------------------------------- ;----------------------- ; Handle RESTORE command ;----------------------- ; The restore command sets the system variable for the data address to ; point to the location before the supplied line number or first line ; thereafter. ; This alters the position where subsequent READ commands look for data. ; Note. If supplied with inappropriate high numbers the system may crash ; in the LINE-ADDR routine as it will pass the program/variables end-marker ; and then lose control of what it is looking for - variable or line number. ; - observation, Steven Vickers, 1984, Pitman. ;;;$1E42 RESTORE: CALL FIND_INT2 ; routine FIND_INT2 puts integer in BC. ; Note. B should be checked against limit $3F ; and an error generated if higher. ; this entry point is used from RUN command with BC holding zero ;;;$1E45 REST_RUN: LD H,B ; transfer the line LD L,C ; number to the HL register. CALL LINE_ADDR ; routine LINE_ADDR to fetch the address. DEC HL ; point to the location before the line. LD (DATADD),HL ; update system variable DATADD. RET ; return to STMT_RET (or RUN) ;------------------------- ; Handle RANDOMIZE command ;------------------------- ; This command sets the SEED for the RND function to a fixed value. ; With the parameter zero, a random start point is used depending on ; how long the computer has been switched on. ;;;$1E4F RANDOMIZE: CALL FIND_INT2 ; routine FIND_INT2 puts parameter in BC. LD A,B ; test this OR C ; for zero. JR NZ,RAND_1 ; forward to RAND_1 if not zero. LD BC,(FRAMES1) ; use the lower two bytes at FRAMES1. ;;;$1E5A RAND_1: LD (SEED),BC ; place in SEED system variable. RET ; return to STMT_RET ;------------------------ ; Handle CONTINUE command ;------------------------ ; The CONTINUE command transfers the OLD (but incremented) values of ; line number and statement to the equivalent "NEW VALUE" system variables ; by using the last part of GO TO and exits indirectly to STMT_RET. ;;;$1E5F CONTINUE: LD HL,(OLDPPC) ; fetch OLDPPC line number. LD D,(IY+$36) ; fetch OSPPC statement. JR GO_TO_2 ; forward to GO_TO_2 ;--------------------- ; Handle GO TO command ;--------------------- ; The GO TO command routine is also called by GO SUB and RUN routines ; to evaluate the parameters of both commands. ; It updates the system variables used to fetch the next line/statement. ; It is at STMT_RET that the actual change in control takes place. ; Unlike some BASICs the line number need not exist. ; Note. the high byte of the line number is incorrectly compared with $F0 ; instead of $3F. This leads to commands with operands greater than 32767 ; being considered as having been run from the editing area and the ; error report 'Statement Lost' is given instead of 'OK'. ; - Steven Vickers, 1984. ;;;$1E67 GO_TO: CALL FIND_INT2 ; routine FIND_INT2 puts operand in BC LD H,B ; transfer line LD L,C ; number to HL. LD D,$00 ; set statement to 0 - first. LD A,H ; compare high byte only CP $F0 ; to $F0 i.e. 61439 in full. JR NC,REPORT_BB ; forward to REPORT_BB if above. ; This call entry point is used to update the system variables e.g. by RETURN. ;;;$1E73 GO_TO_2: LD (NEWPPC),HL ; save line number in NEWPPC LD (IY+$0A),D ; and statement in NSPPC RET ; to STMT_RET (or GO_SUB command) ;------------------- ; Handle OUT command ;------------------- ; Syntax has been checked and the two comma-separated values are on the ; calculator stack. ;;;$1E7A OUT_CMD: CALL TWO_PARAM ; routine TWO_PARAM fetches values to BC and A. OUT (C),A ; perform the operation. RET ; return to STMT_RET. ;-------------------- ; Handle POKE command ;-------------------- ; This routine alters a single byte in the 64K address space. ; Happily no check is made as to whether ROM or RAM is addressed. ; Sinclair Basic requires no poking of system variables. ;;;$1E80 POKE: CALL TWO_PARAM ; routine TWO_PARAM fetches values to BC and A. LD (BC),A ; load memory location with A. RET ; return to STMT_RET. ;-------------------------------------------- ; Fetch two parameters from calculator stack ;-------------------------------------------- ; This routine fetches a byte and word from the calculator stack ; producing an error if either is out of range. ;;;$1E85 TWO_PARAM: CALL FP_TO_A ; routine FP_TO_A JR C,REPORT_BB ; forward to REPORT_BB if overflow occurred JR Z,TWO_P_1 ; forward to TWO_P_1 if positive NEG ; negative numbers are made positive ;;;$1E8E TWO_P_1: PUSH AF ; save the value CALL FIND_INT2 ; routine FIND_INT2 gets integer to BC POP AF ; restore the value RET ; return ;-------------- ; Find integers ;-------------- ; The first of these routines fetches a 8-bit integer (range 0-255) from the ; calculator stack to the accumulator and is used for colours, streams, ; durations and coordinates. ; The second routine fetches 16-bit integers to the BC register pair ; and is used to fetch command and function arguments involving line numbers ; or memory addresses and also array subscripts and tab arguments. ; -> ;;;$1E94 FIND_INT1: CALL FP_TO_A ; routine FP_TO_A JR FIND_I_1 ; forward to FIND_I_1 for common exit routine. ; -> ;;;$1E99 FIND_INT2: CALL FP_TO_BC ; routine FP_TO_BC ;;;$1E9C FIND_I_1: JR C,REPORT_BB ; to REPORT_BB with overflow. RET Z ; return if positive. ;;;$1E9F REPORT_BB: RST 08H ; ERROR_1 DEFB $0A ; Error Report: Integer out of range ;------------------- ; Handle RUN command ;------------------- ; This command runs a program starting at an optional line. ; It performs a 'RESTORE 0' then CLEAR ;;;$1EA1 RUN: CALL GO_TO ; routine GO_TO puts line number in system variables. LD BC,$0000 ; prepare to set DATADD to first line. CALL REST_RUN ; routine REST_RUN does the 'restore'. ; Note BC still holds zero. JR CLEAR_RUN ; forward to CLEAR_RUN to clear variables ; without disturbing RAMTOP and ; exit indirectly to STMT_RET ;--------------------- ; Handle CLEAR command ;--------------------- ; This command reclaims the space used by the variables. ; It also clears the screen and the GO SUB stack. ; With an integer expression, it sets the uppermost memory ; address within the BASIC system. ; "Contrary to the manual, CLEAR doesn't execute a RESTORE" - ; Steven Vickers, Pitman Pocket Guide to the Spectrum, 1984. ;;;$1EAC CLEAR: CALL FIND_INT2 ; routine FIND_INT2 fetches to BC. ;;;$1EAF CLEAR_RUN: LD A,B ; test for OR C ; zero. JR NZ,CLEAR_1 ; skip to CLEAR_1 if not zero. LD BC,(RAMTOP) ; use the existing value of RAMTOP if zero. ;;;$1EB7 CLEAR_1: PUSH BC ; save ramtop value. LD DE,(VARS) ; fetch VARS LD HL,(E_LINE) ; fetch E_LINE DEC HL ; adjust to point at variables end-marker. CALL RECLAIM_1 ; routine RECLAIM_1 reclaims the space used by the variables. CALL CLS ; routine CLS to clear screen. LD HL,(STKEND) ; fetch STKEND the start of free memory. LD DE,$0032 ; allow for another 50 bytes. ADD HL,DE ; add the overhead to HL. POP DE ; restore the ramtop value. SBC HL,DE ; if HL is greater than the value then jump JR NC,REPORT_M ; forward to REPORT_M ; 'RAMTOP no good' LD HL,(P_RAMT) ; now P_RAMT ($7FFF on 16K RAM machine) AND A ; exact this time. SBC HL,DE ; new ramtop must be lower or the same. JR NC,CLEAR_2 ; skip to CLEAR_2 if in actual RAM. ;;;$1EDA REPORT_M: RST 08H ; ERROR_1 DEFB $15 ; Error Report: RAMTOP no good ;;;$1EDC CLEAR_2: EX DE,HL ; transfer ramtop value to HL. LD (RAMTOP),HL ; update system variable RAMTOP. POP DE ; pop the return address STMT_RET. POP BC ; pop the Error Address. LD (HL),$3E ; now put the GO SUB end-marker at RAMTOP. DEC HL ; leave a location beneath it. LD SP,HL ; initialize the machine stack pointer. PUSH BC ; push the error address. LD (ERR_SP),SP ; make ERR_SP point to location. EX DE,HL ; put STMT_RET in HL. JP (HL) ; and go there directly. ;---------------------- ; Handle GO SUB command ;---------------------- ; The GO SUB command diverts Basic control to a new line number ; in a very similar manner to GO TO but ; the current line number and current statement + 1 ; are placed on the GO SUB stack as a RETURN point. ;;;$1EED GO_SUB: POP DE ; drop the address STMT_RET LD H,(IY+$0D) ; fetch statement from SUBPPC and INC H ; increment it EX (SP),HL ; swap - error address to HL, ; H (statement) at top of stack, ; L (unimportant) beneath. INC SP ; adjust to overwrite unimportant byte LD BC,(PPC) ; fetch the current line number from PPC PUSH BC ; and PUSH onto GO SUB stack. ; the empty machine-stack can be rebuilt PUSH HL ; push the error address. LD (ERR_SP),SP ; make system variable ERR_SP point to it. PUSH DE ; push the address STMT_RET. CALL GO_TO ; call routine GO_TO to update the system ; variables NEWPPC and NSPPC. ; then make an indirect exit to STMT_RET via LD BC,$0014 ; a 20-byte overhead memory check. ;----------------------- ; Check available memory ;----------------------- ; This routine is used on many occasions when extending a dynamic area ; upwards or the GO SUB stack downwards. ;;;$1F05 TEST_ROOM: LD HL,(STKEND) ; fetch STKEND ADD HL,BC ; add the supplied test value JR C,REPORT_4 ; forward to REPORT_4 if over $FFFF EX DE,HL ; was less so transfer to DE LD HL,$0050 ; test against another 80 bytes ADD HL,DE ; anyway JR C,REPORT_4 ; forward to REPORT_4 if this passes $FFFF SBC HL,SP ; if less than the machine stack pointer RET C ; then return - OK. ;;;$1F15 REPORT_4: LD L,$03 ; prepare 'Out of Memory' JP ERROR_3 ; jump back to ERROR_3 at $0055 ; Note. this error can't be trapped at $0008 ;------------ ; Free memory ;------------ ; This routine is not used by the ROM but allows users to evaluate ; approximate free memory with PRINT 65536 - USR 7962. ;;$1F1A FREE_MEM: LD BC,$0000 ; allow no overhead. CALL TEST_ROOM ; routine TEST_ROOM. LD B,H ; transfer the result LD C,L ; to BC register. RET ; USR function returns value of BC. ;---------------------- ; Handle RETURN command ;---------------------- ; As with any command, there are two values on the ; machine stack at the time it is invoked. ; The machine stack is below the GOSUB stack ; Both grow downwards, the machine stack by two bytes, ; the gosub stack by 3 bytes. Highest is statement byte ; then a two-byte line number. ;;;$1F23 RETURN: POP BC ; drop the address STMT_RET. POP HL ; now the error address. POP DE ; now a possible basic return line. LD A,D ; the high byte $00 - $27 is CP $3E ; compared with the traditional end-marker $3E. JR Z,REPORT_7 ; forward to REPORT_7 with a match. ; 'RETURN without GOSUB' ; It was not the end-marker so a single statement byte remains at the base of ; the calculator stack. It can't be popped off. DEC SP ; adjust stack pointer to create room for two bytes. EX (SP),HL ; statement to H, error address to base of ; new machine stack. EX DE,HL ; statement to D, basic line number to HL. LD (ERR_SP),SP ; adjust ERR_SP to point to new stack pointer PUSH BC ; now re-stack the address STMT_RET JP GO_TO_2 ; to GO_TO_2 to update statement and line ; system variables and exit indirectly to the ; address just pushed on stack. ;;;$1F36 REPORT_7: PUSH DE ; replace the end-marker. PUSH HL ; now restore the error address ; as required in a few clock cycles. RST 08H ; ERROR_1 DEFB $06 ; Error Report: RETURN without GOSUB ;--------------------- ; Handle PAUSE command ;--------------------- ; The pause command takes as it's parameter the number of interrupts ; for which to wait. PAUSE 50 pauses for about a second. ; PAUSE 0 pauses indefinitely. ; Both forms can be finished by pressing a key. ;;;$1F3A PAUSE: CALL FIND_INT2 ; routine FIND_INT2 puts value in BC ;;;$1F3D PAUSE_1: HALT ; wait for interrupt. DEC BC ; decrease counter. LD A,B ; test if OR C ; result is zero. JR Z,PAUSE_END ; forward to PAUSE_END if so. LD A,B ; test if AND C ; now $FFFF INC A ; that is, initially zero. JR NZ,PAUSE_2 ; skip forward to PAUSE_2 if not. INC BC ; restore counter to zero. ;;;$1F49 PAUSE_2: BIT 5,(IY+$01) ; test FLAGS - has a new key been pressed ? JR Z,PAUSE_1 ; back to PAUSE_1 if not. ;;;$1F4F PAUSE_END: RES 5,(IY+$01) ; update FLAGS - signal no new key RET ; and return. ;-------------------- ; Check for BREAK key ;-------------------- ; This routine is called from COPY_LINE, when interrupts are disabled, ; to test if BREAK (SHIFT - SPACE) is being pressed. ; It is also called at STMT_RET after every statement. ;;;$1F54 BREAK_KEY: LD A,$7F ; Input address: $7FFE IN A,($FE) ; read lower right keys RRA ; rotate bit 0 - SPACE RET C ; return if not reset LD A,$FE ; Input address: $FEFE IN A,($FE) ; read lower left keys RRA ; rotate bit 0 - SHIFT RET ; carry will be set if not pressed. ; return with no carry if both keys pressed. ;---------------------- ; Handle DEF FN command ;---------------------- ; e.g DEF FN r$(a$,a) = a$(a TO ) ; this 'command' is ignored in runtime but has it's syntax checked ; during line-entry. ;;;$1F60 DEF_FN: CALL SYNTAX_Z ; routine SYNTAX_Z JR Z,DEF_FN_1 ; forward to DEF_FN_1 if parsing LD A,$CE ; else load A with 'DEF FN' and JP PASS_BY ; jump back to PASS_BY ; continue here if checking syntax. ;;;$1F6A DEF_FN_1: SET 6,(IY+$01) ; set FLAGS - Assume numeric result CALL ALPHA ; call routine ALPHA JR NC,DEF_FN_4 ; if not then to DEF_FN_4 to jump to ; 'Nonsense in Basic' RST 20H ; NEXT_CHAR CP $24 ; is it '$' ? JR NZ,DEF_FN_2 ; to DEF_FN_2 if not as numeric. RES 6,(IY+$01) ; set FLAGS - Signal string result RST 20H ; get NEXT_CHAR ;;;$1F7D DEF_FN_2: CP $28 ; is it '(' ? JR NZ,DEF_FN_7 ; to DEF_FN_7 'Nonsense in Basic' RST 20H ; NEXT_CHAR CP $29 ; is it ')' ? JR Z,DEF_FN_6 ; to DEF_FN_6 if null argument ;;;$1F86 DEF_FN_3: CALL ALPHA ; routine ALPHA checks that it is the expected alphabetic character. ;;;$1F89 DEF_FN_4: JP NC,REPORT_C ; to REPORT_C if not ; 'Nonsense in Basic'. EX DE,HL ; save pointer in DE RST 20H ; NEXT_CHAR re-initializes HL from CH_ADD and advances. CP $24 ; '$' ? is it a string argument. JR NZ,DEF_FN_5 ; forward to DEF_FN_5 if not. EX DE,HL ; save pointer to '$' in DE RST 20H ; NEXT_CHAR re-initializes HL and advances ;;;$1F94 DEF_FN_5: EX DE,HL ; bring back pointer. LD BC,$0006 ; the function requires six hidden bytes for ; each parameter passed. ; The first byte will be $0E ; then 5-byte numeric value ; or 5-byte string pointer. CALL MAKE_ROOM ; routine MAKE_ROOM creates space in program area. INC HL ; adjust HL (set by LDDR) INC HL ; to point to first location. LD (HL),$0E ; insert the 'hidden' marker. ; Note. these invisible storage locations hold nothing meaningful for the ; moment. They will be used every time the corresponding function is ; evaluated in runtime. ; Now consider the following character fetched earlier. CP $2C ; is it ',' ? (more than one parameter) JR NZ,DEF_FN_6 ; to DEF_FN_6 if not RST 20H ; else NEXT_CHAR JR DEF_FN_3 ; and back to DEF_FN_3 ;;;$1FA6 DEF_FN_6: CP $29 ; should close with a ')' JR NZ,DEF_FN_7 ; to DEF_FN_7 if not ; 'Nonsense in Basic' RST 20H ; get NEXT_CHAR CP $3D ; is it '=' ? JR NZ,DEF_FN_7 ; to DEF_FN_7 if not 'Nonsense...' RST 20H ; address NEXT_CHAR LD A,(FLAGS) ; get FLAGS which has been set above PUSH AF ; and save while CALL SCANNING ; routine SCANNING checks syntax of expression and sets flags also POP AF ; restore previous flags XOR (IY+$01) ; xor with FLAGS - bit 6 should be same, therefore will be reset. AND $40 ; isolate bit 6. ;;;$1FBD DEF_FN_7: JP NZ,REPORT_C ; jump back to REPORT_C if the expected result is not the same. ; 'Nonsense in Basic' CALL CHECK_END ; routine CHECK_END will return early if ; at end of statement and move onto next ; else produce error report. >>> ; There will be no return to here. ;-------------------------------- ; Returning early from subroutine ;-------------------------------- ; All routines are capable of being run in two modes - syntax checking mode ; and runtime mode. ; This routine is called often to allow a routine to return early ; if checking syntax. ;;;$1FC3 UNSTACK_Z: CALL SYNTAX_Z ; routine SYNTAX_Z sets zero flag if syntax is being checked. POP HL ; drop the return address. RET Z ; return to previous call in chain if checking syntax. JP (HL) ; jump to return address as Basic program is ; actually running. ;---------------------- ; Handle LPRINT command ;---------------------- ; A simple form of 'PRINT #3' although it can output to 16 streams. ; Probably for compatibility with other basics particularly ZX81 Basic. ; An extra UDG might have been better. ;;;$1FC9 LPRINT: LD A,$03 ; the printer channel JR PRINT_1 ; forward to PRINT_1 ;---------------------- ; Handle PRINT commands ;---------------------- ; The Spectrum's main stream output command. ; The default stream is stream 2 which is normally the upper screen ; of the computer. However the stream can be altered in range 0 - 15. ;;;$1FCD PRINT: LD A,$02 ; the stream for the upper screen. ; The LPRINT command joins here. ;;;$1FCF PRINT_1: CALL SYNTAX_Z ; routine SYNTAX_Z checks if program running CALL NZ,CHAN_OPEN ; routine CHAN_OPEN if so CALL TEMPS ; routine TEMPS sets temporary colours. CALL PRINT_2 ; routine PRINT_2 - the actual item CALL CHECK_END ; routine CHECK_END gives error if not at end of statement RET ; and return >>> ; this subroutine is called from above ; and also from INPUT. ;;;$1FDF PRINT_2: RST 18H ; GET_CHAR gets printable character CALL PR_END_Z ; routine PR_END_Z checks if more printing JR Z,PRINT_4 ; to PRINT_4 if not e.g. just 'PRINT :' ; This tight loop deals with combinations of positional controls and ; print items. An early return can be made from within the loop ; if the end of a print sequence is reached. ;;;$1FE5 PRINT_3: CALL PR_POSN_1 ; routine PR_POSN_1 returns zero if more ; but returns early at this point if ; at end of statement! JR Z,PRINT_3 ; to PRINT_3 if consecutive positioners CALL PR_ITEM_1 ; routine PR_ITEM_1 deals with strings etc. CALL PR_POSN_1 ; routine PR_POSN_1 for more position codes JR Z,PRINT_3 ; loop back to PRINT_3 if so ;;;$1FF2 PRINT_4: CP $29 ; return now if this is ')' from input-item. ; (see INPUT.) RET Z ; or continue and print carriage return in ; runtime ;---------------------- ; Print carriage return ;---------------------- ; This routine which continues from above prints a carriage return ; in run-time. It is also called once from PRINT_POSN. ;;;$1FF5 PRINT_CR: CALL UNSTACK_Z ; routine UNSTACK_Z LD A,$0D ; prepare a carriage return RST 10H ; PRINT_A RET ; return ;------------ ; Print items ;------------ ; This routine deals with print items as in ; PRINT AT 10,0;"The value of A is ";a ; It returns once a single item has been dealt with as it is part ; of a tight loop that considers sequences of positional and print items ;;;$1FFC PR_ITEM_1: RST 18H ; GET_CHAR CP $AC ; is character 'AT' ? JR NZ,PR_ITEM_2 ; forward to PR_ITEM_2 if not. CALL NEXT_2NUM ; routine NEXT_2NUM check for two comma ; separated numbers placing them on the ; calculator stack in runtime. CALL UNSTACK_Z ; routine UNSTACK_Z quits if checking syntax. CALL STK_TO_BC ; routine STK_TO_BC get the numbers in B and C. LD A,$16 ; prepare the 'at' control. JR PR_AT_TAB ; forward to PR_AT_TAB to print the sequence. ;;;$200E PR_ITEM_2: CP $AD ; is character 'TAB' ? JR NZ,PR_ITEM_3 ; to PR_ITEM_3 if not RST 20H ; NEXT_CHAR to address next character CALL EXPT_1NUM ; routine EXPT_1NUM CALL UNSTACK_Z ; routine UNSTACK_Z quits if checking syntax. CALL FIND_INT2 ; routine FIND_INT2 puts integer in BC. LD A,$17 ; prepare the 'tab' control. ;;;$201E PR_AT_TAB: RST 10H ; PRINT_A outputs the control LD A,C ; first value to A RST 10H ; PRINT_A outputs it. LD A,B ; second value RST 10H ; PRINT_A RET ; return - item finished >>> ; Now consider paper 2; #2; a$ ;;;$2024 PR_ITEM_3: CALL CO_TEMP_3 ; routine CO_TEMP_3 will print any colour RET NC ; items - return if success. CALL STR_ALTER ; routine STR_ALTER considers new stream RET NC ; return if altered. CALL SCANNING ; routine SCANNING now to evaluate expression CALL UNSTACK_Z ; routine UNSTACK_Z if not runtime. BIT 6,(IY+$01) ; test FLAGS - Numeric or string result ? CALL Z,STK_FETCH ; routine STK_FETCH if string. ; note no flags affected. JP NZ,PRINT_FP ; to PRINT_FP to print if numeric >>> ; It was a string expression - start in DE, length in BC ; Now enter a loop to print it ;;;$203C PR_STRING: LD A,B ; this tests if the OR C ; length is zero and sets flag accordingly. DEC BC ; this doesn't but decrements counter. RET Z ; return if zero. LD A,(DE) ; fetch character. INC DE ; address next location. RST 10H ; PRINT_A. JR PR_STRING ; loop back to PR_STRING. ;---------------- ; End of printing ;---------------- ; This subroutine returns zero if no further printing is required ; in the current statement. ; The first terminator is found in escaped input items only, ; the others in print_items. ;;;$2045 PR_END_Z: CP $29 ; is character a ')' ? RET Z ; return if so - e.g. INPUT (p$); a$ ;;;$2048 PR_ST_END: CP $0D ; is it a carriage return ? RET Z ; return also - e.g. PRINT a CP $3A ; is character a ':' ? RET ; return - zero flag will be set if so. ; e.g. PRINT a : ;--------------- ; Print position ;--------------- ; This routine considers a single positional character ';', ',', ''' ;;;$204E PR_POSN_1: RST 18H ; GET_CHAR CP $3B ; is it ';' ? ; i.e. print from last position. JR Z,PR_POSN_3 ; forward to PR_POSN_3 if so. ; i.e. do nothing. CP $2C ; is it ',' ? ; i.e. print at next tabstop. JR NZ,PR_POSN_2 ; forward to PR_POSN_2 if anything else. CALL SYNTAX_Z ; routine SYNTAX_Z JR Z,PR_POSN_3 ; forward to PR_POSN_3 if checking syntax. LD A,$06 ; prepare the 'comma' control character. RST 10H ; PRINT_A outputs to current channel in run-time. JR PR_POSN_3 ; skip to PR_POSN_3. ; check for newline. ;;;$2061 PR_POSN_2: CP $27 ; is character a "'" ? (newline) RET NZ ; return if no match >>> CALL PRINT_CR ; routine PRINT_CR outputs a carriage return in runtime only. ;;;$2067 PR_POSN_3: RST 20H ; NEXT_CHAR to A. CALL PR_END_Z ; routine PR_END_Z checks if at end. JR NZ,PR_POSN_4 ; to PR_POSN_4 if not. POP BC ; drop return address if at end. ;;;$206E PR_POSN_4: CP A ; reset the zero flag. RET ; and return to loop or quit. ;------------- ; Alter stream ;------------- ; This routine is called from PRINT ITEMS above, and also LIST as in ; LIST #15 ;;;$2070 STR_ALTER: CP $23 ; is character '#' ? SCF ; set carry flag. RET NZ ; return if no match. RST 20H ; NEXT_CHAR CALL EXPT_1NUM ; routine EXPT_1NUM gets stream number AND A ; prepare to exit early with carry reset CALL UNSTACK_Z ; routine UNSTACK_Z exits early if parsing CALL FIND_INT1 ; routine FIND_INT1 gets number off stack CP $10 ; must be range 0 - 15 decimal. JP NC,REPORT_OA ; jump back to REPORT_OA if not ; 'Invalid stream'. CALL CHAN_OPEN ; routine CHAN_OPEN AND A ; clear carry - signal item dealt with. RET ; return ;--------------------- ; Handle INPUT command ;--------------------- ; This command ; ;;;$2089 INPUT: CALL SYNTAX_Z ; routine SYNTAX_Z to check if in runtime. JR Z,INPUT_1 ; forward to INPUT_1 if checking syntax. LD A,$01 ; select channel 'K' the keyboard for input. CALL CHAN_OPEN ; routine CHAN_OPEN opens it. CALL CLS_LOWER ; routine CLS_LOWER clears the lower screen. ;;;$2096 INPUT_1: LD (IY+$02),$01 ; set TV_FLAG - signal lower screen in use and clear the other bits. CALL IN_ITEM_1 ; routine IN_ITEM_1 to handle the input. CALL CHECK_END ; routine CHECK_END will make an early exit if checking syntax. >>> ; keyboard input has been made and it remains to adjust the upper ; screen in case the lower two lines have been extended upwards. LD BC,(S_POSN) ; fetch S_POSN current line/column of the upper screen. LD A,(DF_SZ) ; fetch DF_SZ the display file size of the lower screen. CP B ; test that lower screen does not overlap JR C,INPUT_2 ; forward to INPUT_2 if not. ; the two screens overlap so adjust upper screen. LD C,$21 ; set column of upper screen to leftmost. LD B,A ; and line to one above lower screen. ; continue forward to update upper screen ; print position. ;;;$20AD INPUT_2: LD (S_POSN),BC ; set S_POSN update upper screen line/column. LD A,$19 ; subtract from twenty five SUB B ; the new line number. LD (SCR_CT),A ; and place result in SCR_CT - scroll count. RES 0,(IY+$02) ; update TV_FLAG - signal main screen in use. CALL CL_SET ; routine CL_SET sets the print position ; system variables for the upper screen. JP CLS_LOWER ; jump back to CLS_LOWER and make ; an indirect exit >>. ;---------------------- ; INPUT ITEM subroutine ;---------------------- ; This subroutine deals with the input items and print items. ; from the current input channel. ; It is only called from the above INPUT routine but was obviously ; once called from somewhere else in another context. ;;;$20C1 IN_ITEM_1: CALL PR_POSN_1 ; routine PR_POSN_1 deals with a single ; position item at each call. JR Z,IN_ITEM_1 ; back to IN_ITEM_1 until no more in a sequence. CP $28 ; is character '(' ? JR NZ,IN_ITEM_2 ; forward to IN_ITEM_2 if not. ; any variables within braces will be treated as part, or all, of the prompt ; instead of being used as destination variables. RST 20H ; NEXT_CHAR CALL PRINT_2 ; routine PRINT_2 to output the dynamic prompt. RST 18H ; GET_CHAR CP $29 ; is character a matching ')' ? JP NZ,REPORT_C ; jump back to REPORT_C if not. ; 'Nonsense in basic'. RST 20H ; NEXT_CHAR JP IN_NEXT_2 ; forward to IN_NEXT_2 ;;;$20D8 IN_ITEM_2: CP $CA ; is the character the token 'LINE' ? JR NZ,IN_ITEM_3 ; forward to IN_ITEM_3 if not. RST 20H ; NEXT_CHAR - variable must come next. CALL CLASS_01 ; routine CLASS_01 returns destination ; address of variable to be assigned. ; or generates an error if no variable ; at this position. SET 7,(IY+$37) ; update FLAGX - signal handling INPUT LINE BIT 6,(IY+$01) ; test FLAGS - numeric or string result ? JP NZ,REPORT_C ; jump back to REPORT_C if not string ; 'Nonsense in basic'. JR IN_PROMPT ; forward to IN_PROMPT to set up workspace. ; the jump was here for other variables. ;;;$20ED IN_ITEM_3: CALL ALPHA ; routine ALPHA checks if character is ; a suitable variable name. JP NC,IN_NEXT_1 ; forward to IN_NEXT_1 if not CALL CLASS_01 ; routine CLASS_01 returns destination ; address of variable to be assigned. RES 7,(IY+$37) ; update FLAGX - signal not INPUT LINE. ;;;$20FA IN_PROMPT: CALL SYNTAX_Z ; routine SYNTAX_Z JP Z,IN_NEXT_2 ; forward to IN_NEXT_2 if checking syntax. CALL SET_WORK ; routine SET_WORK clears workspace. LD HL,FLAGX ; point to system variable FLAGX RES 6,(HL) ; signal string result. SET 5,(HL) ; signal in Input Mode for editor. LD BC,$0001 ; initialize space required to one for ; the carriage return. BIT 7,(HL) ; test FLAGX - INPUT LINE in use ? JR NZ,IN_PR_2 ; forward to IN_PR_2 if so as that is all the space that is required. LD A,(FLAGS) ; load accumulator from FLAGS AND $40 ; mask to test BIT 6 of FLAGS and clear the other bits in A. ; numeric result expected ? JR NZ,IN_PR_1 ; forward to IN_PR_1 if so LD C,$03 ; increase space to three bytes for the pair of surrounding quotes. ;;;$211A IN_PR_1: OR (HL) ; if numeric result, set bit 6 of FLAGX. LD (HL),A ; and update system variable ;;;$211C IN_PR_2: RST 30H ; BC_SPACES opens 1 or 3 bytes in workspace LD (HL),$0D ; insert carriage return at last new location. LD A,C ; fetch the length, one or three. RRCA ; lose bit 0. RRCA ; test if quotes required. JR NC,IN_PR_3 ; forward to IN_PR_3 if not. LD A,$22 ; load the '"' character LD (DE),A ; place quote in first new location at DE. DEC HL ; decrease HL - from carriage return. LD (HL),A ; and place a quote in second location. ;;;$2129 IN_PR_3: LD (K_CUR),HL ; set keyboard cursor K_CUR to HL BIT 7,(IY+$37) ; test FLAGX - is this INPUT LINE ?? JR NZ,IN_VAR_3 ; forward to IN_VAR_3 if so as input will ; be accepted without checking it's syntax. LD HL,(CH_ADD) ; fetch CH_ADD PUSH HL ; and save on stack. LD HL,(ERR_SP) ; fetch ERR_SP PUSH HL ; and save on stack ;;;$213A IN_VAR_1: LD HL,IN_VAR_1 ; address: IN_VAR_1 - this address PUSH HL ; is saved on stack to handle errors. BIT 4,(IY+$30) ; test FLAGS2 - is K channel in use ? JR Z,IN_VAR_2 ; forward to IN_VAR_2 if not using the keyboard for input. (??) LD (ERR_SP),SP ; set ERR_SP to point to IN_VAR_1 on stack. ;;;$2148 IN_VAR_2: LD HL,(WORKSP) ; set HL to WORKSP - start of workspace. CALL REMOVE_FP ; routine REMOVE_FP removes floating point ; forms when looping in error condition. LD (IY+$00),$FF ; set ERR_NR to 'OK' cancelling the error. ; but X_PTR causes flashing error marker ; to be displayed at each call to the editor. CALL EDITOR ; routine EDITOR allows input to be entered ; or corrected if this is second time around. ; if we pass to next then there are no system errors RES 7,(IY+$01) ; update FLAGS - signal checking syntax CALL IN_ASSIGN ; routine IN_ASSIGN checks syntax using ; the VAL_FET_2 and powerful SCANNING routines. ; any syntax error and it's back to IN_VAR_1. ; but with the flashing error marker showing ; where the error is. ; Note. the syntax of string input has to be ; checked as the user may have removed the ; bounding quotes or escaped them as with ; "hat" + "stand" for example. ; proceed if syntax passed. JR IN_VAR_4 ; jump forward to IN_VAR_4 ; the jump was to here when using INPUT LINE. ;;;$215E IN_VAR_3: CALL EDITOR ; routine EDITOR is called for input ; when ENTER received rejoin other route but with no syntax check. ; INPUT and INPUT LINE converge here. ;;;$2161 IN_VAR_4: LD (IY+$22),$00 ; set K_CUR_hi to a low value so that the cursor ; no longer appears in the input line. CALL IN_CHAN_K ; routine IN_CHAN_K tests if the keyboard ; is being used for input. JR NZ,IN_VAR_5 ; forward to IN_VAR_5 if using another input channel. ; continue here if using the keyboard. CALL ED_COPY ; routine ED_COPY overprints the edit line ; to the lower screen. The only visible ; affect is that the cursor disappears. ; if you're inputting more than one item in ; a statement then that becomes apparent. LD BC,(ECHO_E) ; fetch line and column from ECHO_E CALL CL_SET ; routine CL_SET sets S-POSNL to those values. ; if using another input channel rejoin here. ;;;$2174 IN_VAR_5: LD HL,FLAGX ; point HL to FLAGX RES 5,(HL) ; signal not in input mode BIT 7,(HL) ; is this INPUT LINE ? RES 7,(HL) ; cancel the bit anyway. JR NZ,IN_VAR_6 ; forward to IN_VAR_6 if INPUT LINE. POP HL ; drop the looping address POP HL ; drop the the address of previous error handler. LD (ERR_SP),HL ; set ERR_SP to point to it. POP HL ; drop original CH_ADD which points to INPUT command in BASIC line. LD (X_PTR),HL ; save in X_PTR while input is assigned. SET 7,(IY+$01) ; update FLAGS - Signal running program CALL IN_ASSIGN ; routine IN_ASSIGN is called again ; this time the variable will be assigned ; the input value without error. ; Note. the previous example now ; becomes "hatstand" LD HL,(X_PTR) ; fetch stored CH_ADD value from X_PTR. LD (IY+$26),$00 ; set X_PTR_HI so that no longer relevant. LD (CH_ADD),HL ; put restored value back in CH_ADD JR IN_NEXT_2 ; forward to IN_NEXT_2 to see if anything ; more in the INPUT list. ; the jump was to here with INPUT LINE only ;;;$219B IN_VAR_6: LD HL,(STKBOT) ; STKBOT points to the end of the input. LD DE,(WORKSP) ; WORKSP points to the beginning. SCF ; prepare for true subtraction. SBC HL,DE ; subtract to get length LD B,H ; transfer it to LD C,L ; the BC register pair. CALL STK_STO_D ; routine STK_STO_D stores parameters on ; the calculator stack. CALL LET ; routine LET assigns it to destination. JR IN_NEXT_2 ; forward to IN_NEXT_2 as print items ; not allowed with INPUT LINE. ; Note. that "hat" + "stand" will, for ; example, be unchanged as also would ; 'PRINT "Iris was here"'. ; the jump was to here when ALPHA found more items while looking for ; a variable name. ;;;$21AF IN_NEXT_1: CALL PR_ITEM_1 ; routine PR_ITEM_1 considers further items. ;;;$21B2 IN_NEXT_2: CALL PR_POSN_1 ; routine PR_POSN_1 handles a position item. JP Z,IN_ITEM_1 ; jump back to IN_ITEM_1 if the zero flag ; indicates more items are present. RET ; return. ;---------------------------- ; INPUT ASSIGNMENT Subroutine ;---------------------------- ; This subroutine is called twice from the INPUT command when normal ; keyboard input is assigned. On the first occasion syntax is checked ; using SCANNING. The final call with the syntax flag reset is to make ; the assignment. ;;;$21B9 IN_ASSIGN: LD HL,(WORKSP) ; fetch WORKSP start of input LD (CH_ADD),HL ; set CH_ADD to first character RST 18H ; GET_CHAR ignoring leading white-space. CP $E2 ; is it 'STOP' JR Z,IN_STOP ; forward to IN_STOP if so. LD A,(FLAGX) ; load accumulator from FLAGX CALL VAL_FET_2 ; routine VAL_FET_2 makes assignment ; or goes through the motions if checking ; syntax. SCANNING is used. RST 18H ; GET_CHAR CP $0D ; is it carriage return ? RET Z ; return if so ; either syntax is OK ; or assignment has been made. ; if another character was found then raise an error. ; User doesn't see report but the flashing error marker ; appears in the lower screen. ;;;$21CE REPORT_CB: RST 08H ; ERROR_1 DEFB $0B ; Error Report: Nonsense in BASIC ;;;$21D0 IN_STOP: CALL SYNTAX_Z ; routine SYNTAX_Z (UNSTACK_Z?) RET Z ; return if checking syntax ; as user wouldn't see error report. ; but generate visible error report ; on second invocation. ;;;$21D4 REPORT_H: RST 08H ; ERROR_1 DEFB $10 ; Error Report: STOP in INPUT ;------------------- ; Test for channel K ;------------------- ; This subroutine is called once from the keyboard ; INPUT command to check if the input routine in ; use is the one for the keyboard. ;;;$21D6 IN_CHAN_K: LD HL,(CURCHL) ; fetch address of current channel CURCHL INC HL INC HL ; advance past INC HL ; input and INC HL ; output streams LD A,(HL) ; fetch the channel identifier. CP $4B ; test for 'K' RET ; return with zero set if keyboard is use. ;--------------------- ; Colour Item Routines ;--------------------- ; ; These routines have 3 entry points - ; 1) CO_TEMP_2 to handle a series of embedded Graphic colour items. ; 2) CO_TEMP_3 to handle a single embedded print colour item. ; 3) CO_TEMP_4 to handle a colour command such as FLASH 1 ; ; "Due to a bug, if you bring in a peripheral channel and later use a colour ; statement, colour controls will be sent to it by mistake." - Steven Vickers ; Pitman Pocket Guide, 1984. ; ; To be fair, this only applies if the last channel was other than 'K', 'S' ; or 'P', which are all that are supported by this ROM, but if that last ; channel was a microdrive file, network channel etc. then ; PAPER 6; CLS will not turn the screen yellow and ; CIRCLE INK 2; 128,88,50 will not draw a red circle. ; ; This bug does not apply to embedded PRINT items as it is quite permissible ; to mix stream altering commands and colour items. ; The fix therefore would be to ensure that CLASS_07 and CLASS_09 make ; PRINT_OUT the current channel when not checking syntax. ; ----------------------------------------------------------------- ;;;$21E1 CO_TEMP_1: RST 20H ; NEXT_CHAR ; -> Entry point from CLASS_09. Embedded Graphic colour items. ; e.g. PLOT INK 2; PAPER 8; 128,88 ; Loops till all colour items output, finally addressing the coordinates. ;;;$21E2 CO_TEMP_2: CALL CO_TEMP_3 ; routine CO_TEMP_3 to output colour control. RET C ; return if nothing more to output. -> RST 18H ; GET_CHAR CP $2C ; is it ',' separator ? JR Z,CO_TEMP_1 ; back if so to CO_TEMP_1 CP $3B ; is it ';' separator ? JR Z,CO_TEMP_1 ; back to CO_TEMP_1 for more. JP REPORT_C ; to REPORT_C (REPORT_CB is within range) ; 'Nonsense in Basic' ; ------------------- ; CO_TEMP_3 ; ------------------- ; -> this routine evaluates and outputs a colour control and parameter. ; It is called from above and also from PR_ITEM_3 to handle a single embedded ; print item e.g. PRINT PAPER 6; "Hi". In the latter case, the looping for ; multiple items is within the PR-ITEM routine. ; It is quite permissible to send these to any stream. ;;;$21F2 CO_TEMP_3: CP $D9 ; is it 'INK' ? RET C ; return if less. CP $DF ; compare with 'OUT' CCF ; Complement Carry Flag RET C ; return if greater than 'OVER', $DE. PUSH AF ; save the colour token. RST 20H ; address NEXT_CHAR POP AF ; restore token and continue. ; -> this entry point used by CLASS_07. e.g. the command PAPER 6. ;;;$21FC CO_TEMP_4: SUB $C9 ; reduce to control character $10 (INK) thru $15 (OVER). PUSH AF ; save control. CALL EXPT_1NUM ; routine EXPT_1NUM stacks addressed ; parameter on calculator stack. POP AF ; restore control. AND A ; clear carry CALL UNSTACK_Z ; routine UNSTACK_Z returns if checking syntax. PUSH AF ; save again CALL FIND_INT1 ; routine FIND_INT1 fetches parameter to A. LD D,A ; transfer now to D POP AF ; restore control. RST 10H ; PRINT_A outputs the control to current channel. LD A,D ; transfer parameter to A. RST 10H ; PRINT_A outputs parameter. RET ; return. -> ; ------------------------------------------------------------------------- ; ; {fl}{br}{ paper }{ ink } The temporary colour attributes ; ___ ___ ___ ___ ___ ___ ___ ___ system variable. ; ATTR_T | | | | | | | | | ; | | | | | | | | | ; 23695 |___|___|___|___|___|___|___|___| ; 7 6 5 4 3 2 1 0 ; ; ; {fl}{br}{ paper }{ ink } The temporary mask used for ; ___ ___ ___ ___ ___ ___ ___ ___ transparent colours. Any bit ; MASK_T | | | | | | | | | that is 1 shows that the ; | | | | | | | | | corresponding attribute is ; 23696 |___|___|___|___|___|___|___|___| taken not from ATTR-T but from ; 7 6 5 4 3 2 1 0 what is already on the screen. ; ; ; {paper9 }{ ink9 }{ inv1 }{ over1} The print flags. Even bits are ; ___ ___ ___ ___ ___ ___ ___ ___ temporary flags. The odd bits ; P_FLAG | | | | | | | | | are the permanent flags. ; | p | t | p | t | p | t | p | t | ; 23697 |___|___|___|___|___|___|___|___| ; 7 6 5 4 3 2 1 0 ; ; ----------------------------------------------------------------------- ; ------------------------------------ ; The colour system variable handler. ; ------------------------------------ ; This is an exit branch from PO_1_OPER, PO_2_OPER ; A holds control $10 (INK) to $15 (OVER) ; D holds parameter 0-9 for ink/paper 0,1 or 8 for bright/flash, ; 0 or 1 for over/inverse. ;;;$2211 CO_TEMP_5: SUB $11 ; reduce range $FF-$04 ADC A,$00 ; add in carry if INK JR Z,CO_TEMP_7 ; forward to CO_TEMP_7 with INK and PAPER. SUB $02 ; reduce range $FF-$02 ADC A,$00 ; add carry if FLASH JR Z,CO_TEMP_C ; forward to CO_TEMP_C with FLASH and BRIGHT. CP $01 ; is it 'INVERSE' ? LD A,D ; fetch parameter for INVERSE/OVER LD B,$01 ; prepare OVER mask setting bit 0. JR NZ,CO_TEMP_6 ; forward to CO_TEMP_6 if OVER RLCA ; shift bit 0 RLCA ; to bit 2 LD B,$04 ; set bit 2 of mask for inverse. ;;;$2228 CO_TEMP_6: LD C,A ; save the A LD A,D ; re-fetch parameter CP $02 ; is it less than 2 JR NC,REPORT_K ; to REPORT_K if not 0 or 1. ; 'Invalid colour'. LD A,C ; restore A LD HL,P_FLAG ; address system variable P_FLAG JR CO_CHANGE ; forward to exit via routine CO_CHANGE ; the branch was here with INK/PAPER and carry set for INK. ;;;$2234 CO_TEMP_7: LD A,D ; fetch parameter LD B,$07 ; set ink mask 00000111 JR C,CO_TEMP_8 ; forward to CO_TEMP_8 with INK RLCA ; shift bits 0-2 RLCA ; to RLCA ; bits 3-5 LD B,$38 ; set paper mask 00111000 ; both paper and ink rejoin here ;;;$223E CO_TEMP_8: LD C,A ; value to C LD A,D ; fetch parameter CP $0A ; is it less than 10d ? JR C,CO_TEMP_9 ; forward to CO_TEMP_9 if so. ; ink 10 etc. is not allowed. ;;;$2244 REPORT_K: RST 08H ; ERROR_1 DEFB $13 ; Error Report: Invalid colour ;;;$2246 CO_TEMP_9: LD HL,ATTRT_MASKT ; address system variable ATTR_T initially. CP $08 ; compare with 8 JR C,CO_TEMP_B ; forward to CO_TEMP_B with 0-7. LD A,(HL) ; fetch temporary attribute as no change. JR Z,CO_TEMP_A ; forward to CO_TEMP_A with INK/PAPER 8 ; it is either ink 9 or paper 9 (contrasting) OR B ; or with mask to make white CPL ; make black and change other to dark AND $24 ; 00100100 JR Z,CO_TEMP_A ; forward to CO_TEMP_A if black and ; originally light. LD A,B ; else just use the mask (white) ;;;$2257 CO_TEMP_A: LD C,A ; save A in C ;;;$2258 CO_TEMP_B: LD A,C ; load colour to A CALL CO_CHANGE ; routine CO_CHANGE addressing ATTR-T LD A,$07 ; put 7 in accumulator CP D ; compare with parameter SBC A,A ; $00 if 0-7, $FF if 8 CALL CO_CHANGE ; routine CO_CHANGE addressing MASK-T ; mask returned in A. ; now consider P-FLAG. RLCA ; 01110000 or 00001110 RLCA ; 11100000 or 00011100 AND $50 ; 01000000 or 00010000 (AND 01010000) LD B,A ; transfer to mask LD A,$08 ; load A with 8 CP D ; compare with parameter SBC A,A ; $FF if was 9, $00 if 0-8 ; continue while addressing P-FLAG ; setting bit 4 if ink 9 ; setting bit 6 if paper 9 ;------------------------ ; Handle change of colour ;------------------------ ; This routine addresses a system variable ATTR_T, MASK_T or P-FLAG in HL. ; colour value in A, mask in B. ;;;$226C CO_CHANGE: XOR (HL) ; impress bits specified AND B ; by mask XOR (HL) ; on system variable. LD (HL),A ; update system variable. INC HL ; address next location. LD A,B ; put current value of mask in A RET ; return. ; the branch was here with flash and bright ;;;$2273 CO_TEMP_C: SBC A,A ; set zero flag for bright. LD A,D ; fetch original parameter 0,1 or 8 RRCA ; rotate bit 0 to bit 7 LD B,$80 ; mask for flash 10000000 JR NZ,CO_TEMP_D ; forward to CO_TEMP_D if flash RRCA ; rotate bit 7 to bit 6 LD B,$40 ; mask for bright 01000000 ;;;$227D CO_TEMP_D: LD C,A ; store value in C LD A,D ; fetch parameter CP $08 ; compare with 8 JR Z,CO_TEMP_E ; forward to CO_TEMP_E if 8 CP $02 ; test if 0 or 1 JR NC,REPORT_K ; back to REPORT_K if not ; 'Invalid colour' ;;;$2287 CO_TEMP_E: LD A,C ; value to A LD HL,ATTRT_MASKT ; address ATTR_T CALL CO_CHANGE ; routine CO_CHANGE addressing ATTR_T LD A,C ; fetch value RRCA ; for flash8/bright8 complete RRCA ; rotations to put set bit in RRCA ; bit 7 (flash) bit 6 (bright) JR CO_CHANGE ; back to CO_CHANGE addressing MASK_T ; and indirect return. ;---------------------- ; Handle BORDER command ;---------------------- ; Command syntax example: BORDER 7 ; This command routine sets the border to one of the eight colours. ; The colours used for the lower screen are based on this. ;;;$2294 BORDER: CALL FIND_INT1 ; routine FIND_INT1 CP $08 ; must be in range 0 (black) to 7 (white) JR NC,REPORT_K ; back to REPORT_K if not ; 'Invalid colour'. OUT ($FE),A ; outputting to port effects an immediate ; change. RLCA ; shift the colour to RLCA ; the paper bits setting the RLCA ; ink colour black. BIT 5,A ; is the number light coloured ? ; i.e. in the range green to white. JR NZ,BORDER_1 ; skip to BORDER_1 if so XOR $07 ; make the ink white. ;;;$22A6 BORDER_1: LD (BORDCR),A ; update BORDCR with new paper/ink RET ; return. ;------------------ ; Get pixel address ;------------------ ;;;$22AA PIXEL_ADD: LD A,$AF ; load with 175 decimal. SUB B ; subtract the y value. JP C,REPORT_BC ; jump forward to REPORT_BC if greater. ; 'Integer out of range' ; the high byte is derived from Y only. ; the first 3 bits are always 010 ; the next 2 bits denote in which third of the screen the byte is. ; the last 3 bits denote in which of the 8 scan lines within a third ; the byte is located. There are 24 discrete values. LD B,A ; the line number from top of screen to B. AND A ; clear carry (already clear) RRA ; 0xxxxxxx SCF ; set carry flag RRA ; 10xxxxxx AND A ; clear carry flag RRA ; 010xxxxx XOR B AND $F8 ; keep the top 5 bits 11111000 XOR B ; 010xxbbb LD H,A ; transfer high byte to H. ; the low byte is derived from both X and Y. LD A,C ; the x value 0-255. RLCA RLCA RLCA XOR B ; the y value AND $C7 ; apply mask 11000111 XOR B ; restore unmasked bits xxyyyxxx RLCA ; rotate to xyyyxxxx RLCA ; required position. yyyxxxxx LD L,A ; low byte to L. ; finally form the pixel position in A. LD A,C ; x value to A AND $07 ; mod 8 RET ; return ;----------------- ; Point Subroutine ;----------------- ; The point subroutine is called from S_POINT via the scanning functions ; table. ;;;$22CB POINT_SUB: CALL STK_TO_BC ; routine STK_TO_BC CALL PIXEL_ADD ; routine PIXEL_ADD finds address of pixel. LD B,A ; pixel position to B, 0-7. INC B ; increment to give rotation count 1-8. LD A,(HL) ; fetch byte from screen. ;;;$22D4 POINT_LP: RLCA ; rotate and loop back DJNZ POINT_LP ; to POINT_LP until pixel at right. AND $01 ; test to give zero or one. JP STACK_A ; jump forward to STACK_A to save result. ;-------------------- ; Handle PLOT command ;-------------------- ; Command Syntax example: PLOT 128,88 ;;;$22DC PLOT: CALL STK_TO_BC ; routine STK_TO_BC CALL PLOT_SUB ; routine PLOT_SUB JP TEMPS ; to TEMPS ; ------------------- ; The Plot subroutine ; ------------------- ; A screen byte holds 8 pixels so it is necessary to rotate a mask ; into the correct position to leave the other 7 pixels unaffected. ; However all 64 pixels in the character cell take any embedded colour items. ; A pixel can be reset (inverse 1), toggled (over 1), or set ( with inverse ; and over switches off). With both switches on, the byte is simply put ; back on the screen though the colours may change. ;;;$22E5 PLOT_SUB: LD (COORDS),BC ; store new x/y values in COORDS CALL PIXEL_ADD ; routine PIXEL_ADD gets address in HL, ; count from left 0-7 in B. LD B,A ; transfer count to B. INC B ; increase 1-8. LD A,$FE ; 11111110 in A. ;;;$22F0 PLOT_LOOP: RRCA ; rotate mask. DJNZ PLOT_LOOP ; to PLOT_LOOP until B circular rotations. LD B,A ; load mask to B LD A,(HL) ; fetch screen byte to A LD C,(IY+$57) ; P_FLAG to C BIT 0,C ; is it to be OVER 1 ? JR NZ,PL_TST_IN ; forward to PL_TST_IN if so. ; was over 0 AND B ; combine with mask to blank pixel. ;;;$22FD PL_TST_IN: BIT 2,C ; is it inverse 1 ? JR NZ,PLOT_END ; to PLOT_END if so. XOR B ; switch the pixel CPL ; restore other 7 bits ;;;$2303 PLOT_END: LD (HL),A ; load byte to the screen. JP PO_ATTR ; exit to PO_ATTR to set colours for cell. ;------------------------------- ; Put two numbers in BC register ;------------------------------- ;;;$2307 STK_TO_BC: CALL STK_TO_A ; routine STK_TO_A LD B,A PUSH BC CALL STK_TO_A ; routine STK_TO_A LD E,C POP BC LD D,C LD C,A RET ;------------------------ ; Put stack in A register ;------------------------ ; This routine puts the last value on the calculator stack into the accumulator ; deleting the last value. ;;;$2314 STK_TO_A: CALL FP_TO_A ; routine FP_TO_A compresses last value into ; accumulator. e.g. PI would become 3. ; zero flag set if positive. JP C,REPORT_BC ; jump forward to REPORT_BC if >= 255.5. LD C,$01 ; prepare a positive sign byte. RET Z ; return if FP_TO_BC indicated positive. LD C,$FF ; prepare negative sign byte and RET ; return. ;---------------------- ; Handle CIRCLE command ;---------------------- ; ; syntax has been partly checked using the class for draw command. ;;;$2320 CIRCLE: RST 18H ; GET_CHAR CP $2C ; is it required comma ? JP NZ,REPORT_C ; jump to REPORT_C if not RST 20H ; NEXT_CHAR CALL EXPT_1NUM ; routine EXPT_1NUM fetches radius CALL CHECK_END ; routine CHECK_END will return here if ; nothing follows command. RST 28H ;; FP_CALC DEFB $2A ;;ABS ; make radius positive DEFB $3D ;;RE_STACK ; in full floating point form DEFB $38 ;;END_CALC LD A,(HL) ; fetch first floating point byte CP $81 ; compare to one JR NC,C_R_GRE_1 ; forward to C_R_GRE_1 if circle radius ; is greater than one. RST 28H ;; FP_CALC DEFB $02 ;;DELETE ; delete the radius from stack. DEFB $38 ;;END_CALC JR PLOT ; to PLOT to just plot x,y. ;;;$233B C_R_GRE_1: RST 28H ;; FP_CALC ; x, y, r DEFB $A3 ;;STK_PI_2 ; x, y, r, pi/2. DEFB $38 ;;END_CALC LD (HL),$83 ; x, y, r, 2*PI RST 28H ;; FP_CALC DEFB $C5 ;;st-mem-5 ; store 2*PI in mem-5 DEFB $02 ;;DELETE ; x, y, z. DEFB $38 ;;END_CALC CALL CD_PRMS1 ; routine CD_PRMS1 PUSH BC RST 28H ;; FP_CALC DEFB $31 ;;DUPLICATE DEFB $E1 ;;get-mem-1 DEFB $04 ;;MULTIPLY DEFB $38 ;;END_CALC LD A,(HL) CP $80 JR NC,C_ARC_GE1 ; to C_ARC_GE1 RST 28H ;; FP_CALC DEFB $02 ;;DELETE DEFB $02 ;;DELETE DEFB $38 ;;END_CALC POP BC JP PLOT ; to PLOT ;;;$235A C_ARC_GE1: RST 28H ;; FP_CALC DEFB $C2 ;;st-mem-2 DEFB $01 ;;EXCHANGE DEFB $C0 ;;st-mem-0 DEFB $02 ;;DELETE DEFB $03 ;;SUBTRACT DEFB $01 ;;EXCHANGE DEFB $E0 ;;get-mem-0 DEFB $0F ;;ADDITION DEFB $C0 ;;st-mem-0 DEFB $01 ;;EXCHANGE DEFB $31 ;;DUPLICATE DEFB $E0 ;;get-mem-0 DEFB $01 ;;EXCHANGE DEFB $31 ;;DUPLICATE DEFB $E0 ;;get-mem-0 DEFB $A0 ;;STK_ZERO DEFB $C1 ;;st-mem-1 DEFB $02 ;;DELETE DEFB $38 ;;END_CALC INC (IY+$62) ; MEM-2-1st CALL FIND_INT1 ; routine FIND_INT1 LD L,A PUSH HL CALL FIND_INT1 ; routine FIND_INT1 POP HL LD H,A LD (COORDS),HL ; COORDS POP BC JP DRW_STEPS ; to DRW_STEPS ;-------------------- ; Handle DRAW command ;-------------------- ;;;$2382 DRAW: RST 18H ; GET_CHAR CP $2C JR Z,DR_3_PRMS ; to DR_3_PRMS CALL CHECK_END ; routine CHECK_END JP LINE_DRAW ; to LINE_DRAW ;;;$238D DR_3_PRMS: RST 20H ; NEXT_CHAR CALL EXPT_1NUM ; routine EXPT_1NUM CALL CHECK_END ; routine CHECK_END RST 28H ;; FP_CALC DEFB $C5 ;;st-mem-5 DEFB $A2 ;;STK_HALF DEFB $04 ;;MULTIPLY DEFB $1F ;;SIN_ DEFB $31 ;;DUPLICATE DEFB $30 ;;NOT DEFB $30 ;;NOT DEFB $00 ;;JUMP_TRUE DEFB $06 ;;to DR_SIN_NZ DEFB $02 ;;DELETE DEFB $38 ;;END_CALC JP LINE_DRAW ; to LINE_DRAW ;;;$23A3 DR_SIN_NZ: DEFB $C0 ;;st-mem-0 DEFB $02 ;;DELETE DEFB $C1 ;;st-mem-1 DEFB $02 ;;DELETE DEFB $31 ;;DUPLICATE DEFB $2A ;;ABS DEFB $E1 ;;get-mem-1 DEFB $01 ;;EXCHANGE DEFB $E1 ;;get-mem-1 DEFB $2A ;;ABS DEFB $0F ;;ADDITION DEFB $E0 ;;get-mem-0 DEFB $05 ;;DIVISION DEFB $2A ;;ABS DEFB $E0 ;;get-mem-0 DEFB $01 ;;EXCHANGE DEFB $3D ;;RE_STACK DEFB $38 ;;END_CALC LD A,(HL) CP $81 JR NC,DR_PRMS ; to DR_PRMS RST 28H ;; FP_CALC DEFB $02 ;;DELETE DEFB $02 ;;DELETE DEFB $38 ;;END_CALC JP LINE_DRAW ; to LINE_DRAW ;;;$23C1 DR_PRMS: CALL CD_PRMS1 ; routine CD_PRMS1 PUSH BC ; RST 28H ;; FP_CALC DEFB $02 ;;DELETE DEFB $E1 ;;get-mem-1 DEFB $01 ;;EXCHANGE DEFB $05 ;;DIVISION DEFB $C1 ;;st-mem-1 DEFB $02 ;;DELETE DEFB $01 ;;EXCHANGE DEFB $31 ;;DUPLICATE DEFB $E1 ;;get-mem-1 DEFB $04 ;;MULTIPLY DEFB $C2 ;;st-mem-2 DEFB $02 ;;DELETE DEFB $01 ;;EXCHANGE DEFB $31 ;;DUPLICATE DEFB $E1 ;;get-mem-1 DEFB $04 ;;MULTIPLY DEFB $E2 ;;get-mem-2 DEFB $E5 ;;get-mem-5 DEFB $E0 ;;get-mem-0 DEFB $03 ;;SUBTRACT DEFB $A2 ;;STK_HALF DEFB $04 ;;MULTIPLY DEFB $31 ;;DUPLICATE DEFB $1F ;;SIN_ DEFB $C5 ;;st-mem-5 DEFB $02 ;;DELETE DEFB $20 ;;COS_ DEFB $C0 ;;st-mem-0 DEFB $02 ;;DELETE DEFB $C2 ;;st-mem-2 DEFB $02 ;;DELETE DEFB $C1 ;;st-mem-1 DEFB $E5 ;;get-mem-5 DEFB $04 ;;MULTIPLY DEFB $E0 ;;get-mem-0 DEFB $E2 ;;get-mem-2 DEFB $04 ;;MULTIPLY DEFB $0F ;;ADDITION DEFB $E1 ;;get-mem-1 DEFB $01 ;;EXCHANGE DEFB $C1 ;;st-mem-1 DEFB $02 ;;DELETE DEFB $E0 ;;get-mem-0 DEFB $04 ;;MULTIPLY DEFB $E2 ;;get-mem-2 DEFB $E5 ;;get-mem-5 DEFB $04 ;;MULTIPLY DEFB $03 ;;SUBTRACT DEFB $C2 ;;st-mem-2 DEFB $2A ;;ABS DEFB $E1 ;;get-mem-1 DEFB $2A ;;ABS DEFB $0F ;;ADDITION DEFB $02 ;;DELETE DEFB $38 ;;END_CALC LD A,(DE) CP $81 POP BC JP C,LINE_DRAW ; to LINE_DRAW PUSH BC RST 28H ;; FP_CALC DEFB $01 ;;EXCHANGE DEFB $38 ;;END_CALC LD A,(COORDS) ; COORDS-x CALL STACK_A ; routine STACK_A RST 28H ;; FP_CALC DEFB $C0 ;;st-mem-0 DEFB $0F ;;ADDITION DEFB $01 ;;EXCHANGE DEFB $38 ;;END_CALC LD A,(COORDS_Y) ; COORDS_Y CALL STACK_A ; routine STACK_A RST 28H ;; FP_CALC DEFB $C5 ;;st-mem-5 DEFB $0F ;;ADDITION DEFB $E0 ;;get-mem-0 DEFB $E5 ;;get-mem-5 DEFB $38 ;;END_CALC POP BC ;;;$2420 DRW_STEPS: DEC B JR Z,ARC_END ; to ARC_END JR ARC_START ; to ARC_START ;;;$2425 ARC_LOOP: RST 28H ;; FP_CALC DEFB $E1 ;;get-mem-1 DEFB $31 ;;DUPLICATE DEFB $E3 ;;get-mem-3 DEFB $04 ;;MULTIPLY DEFB $E2 ;;get-mem-2 DEFB $E4 ;;get-mem-4 DEFB $04 ;;MULTIPLY DEFB $03 ;;SUBTRACT DEFB $C1 ;;st-mem-1 DEFB $02 ;;DELETE DEFB $E4 ;;get-mem-4 DEFB $04 ;;MULTIPLY DEFB $E2 ;;get-mem-2 DEFB $E3 ;;get-mem-3 DEFB $04 ;;MULTIPLY DEFB $0F ;;ADDITION DEFB $C2 ;;st-mem-2 DEFB $02 ;;DELETE DEFB $38 ;;END_CALC ;;;$2439 ARC_START: PUSH BC RST 28H ;; FP_CALC DEFB $C0 ;;st-mem-0 DEFB $02 ;;DELETE DEFB $E1 ;;get-mem-1 DEFB $0F ;;ADDITION DEFB $31 ;;DUPLICATE DEFB $38 ;;END_CALC LD A,(COORDS) ; COORDS-x CALL STACK_A ; routine STACK_A RST 28H ;; FP_CALC DEFB $03 ;;SUBTRACT DEFB $E0 ;;get-mem-0 DEFB $E2 ;;get-mem-2 DEFB $0F ;;ADDITION DEFB $C0 ;;st-mem-0 DEFB $01 ;;EXCHANGE DEFB $E0 ;;get-mem-0 DEFB $38 ;;END_CALC LD A,(COORDS_Y) ; COORDS_Y CALL STACK_A ; routine STACK_A RST 28H ;; FP_CALC DEFB $03 ;;SUBTRACT DEFB $38 ;;END_CALC CALL DRAW_LINE ; routine DRAW_LINE POP BC DJNZ ARC_LOOP ; to ARC_LOOP ;;;$245F ARC_END: RST 28H ;; FP_CALC DEFB $02 ;;DELETE DEFB $02 ;;DELETE DEFB $01 ;;EXCHANGE DEFB $38 ;;END_CALC LD A,(COORDS) ; COORDS-x CALL STACK_A ; routine STACK_A RST 28H ;; FP_CALC DEFB $03 ;;SUBTRACT DEFB $01 ;;EXCHANGE DEFB $38 ;;END_CALC LD A,(COORDS_Y) ; COORDS_Y CALL STACK_A ; routine STACK_A RST 28H ;; FP_CALC DEFB $03 ;;SUBTRACT DEFB $38 ;;END_CALC ;;;$2477 LINE_DRAW: CALL DRAW_LINE ; routine DRAW_LINE JP TEMPS ; to TEMPS ;------------------- ; Initial parameters ;------------------- ;;;$247D CD_PRMS1: RST 28H ;; FP_CALC DEFB $31 ;;DUPLICATE DEFB $28 ;;SQR DEFB $34 ;;STK_DATA DEFB $32 ;;Exponent: $82, Bytes: 1 DEFB $00 ;;(+00,+00,+00) DEFB $01 ;;EXCHANGE DEFB $05 ;;DIVISION DEFB $E5 ;;get-mem-5 DEFB $01 ;;EXCHANGE DEFB $05 ;;DIVISION DEFB $2A ;;ABS DEFB $38 ;;END_CALC CALL FP_TO_A ; routine FP_TO_A JR C,USE_252 ; to USE_252 AND $FC ADD A,$04 JR NC,DRAW_SAVE ; to DRAW_SAVE ;;;$2495 USE_252: LD A,$FC ;;;$2497 DRAW_SAVE: PUSH AF CALL STACK_A ; routine STACK_A RST 28H ;; FP_CALC DEFB $E5 ;;get-mem-5 DEFB $01 ;;EXCHANGE DEFB $05 ;;DIVISION DEFB $31 ;;DUPLICATE DEFB $1F ;;SIN_ DEFB $C4 ;;st-mem-4 DEFB $02 ;;DELETE DEFB $31 ;;DUPLICATE DEFB $A2 ;;STK_HALF DEFB $04 ;;MULTIPLY DEFB $1F ;;SIN_ DEFB $C1 ;;st-mem-1 DEFB $01 ;;EXCHANGE DEFB $C0 ;;st-mem-0 DEFB $02 ;;DELETE DEFB $31 ;;DUPLICATE DEFB $04 ;;MULTIPLY DEFB $31 ;;DUPLICATE DEFB $0F ;;ADDITION DEFB $A1 ;;STK_ONE DEFB $03 ;;SUBTRACT DEFB $1B ;;NEGATE DEFB $C3 ;;st-mem-3 DEFB $02 ;;DELETE DEFB $38 ;;END_CALC POP BC RET ;------------- ; Line drawing ;------------- ;;;$24B7 DRAW_LINE: CALL STK_TO_BC ; routine STK_TO_BC LD A,C CP B JR NC,DL_X_GE_Y ; to DL_X_GE_Y LD L,C PUSH DE XOR A LD E,A JR DL_LARGER ; to DL_LARGER ;;;$24C4 DL_X_GE_Y: OR C RET Z LD L,B LD B,C PUSH DE LD D,$00 ;;;$24CB DL_LARGER: LD H,B LD A,B RRA ;;;$24CE D_L_LOOP: ADD A,L ; JR C,D_L_DIAG ; to D_L_DIAG CP H ; JR C,D_L_HR_VT ; to D_L_HR_VT ;;;$24D4 D_L_DIAG: SUB H LD C,A EXX POP BC PUSH BC JR D_L_STEP ; to D_L_STEP ;;;$24DB D_L_HR_VT: LD C,A PUSH DE EXX POP BC ;;;$24DF D_L_STEP: LD HL,(COORDS) LD A,B ADD A,H LD B,A LD A,C INC A ADD A,L JR C,D_L_RANGE ; to D_L_RANGE JR Z,REPORT_BC ; to REPORT_BC ;;;$24EC D_L_PLOT: DEC A LD C,A CALL PLOT_SUB ; routine PLOT_SUB EXX LD A,C DJNZ D_L_LOOP ; to D_L_LOOP POP DE RET ;;;$24F7 D_L_RANGE: JR Z,D_L_PLOT ; to D_L_PLOT ;;;$24F9 REPORT_BC: RST 08H ; ERROR_1 DEFB $0A ; Error Report: Integer out of range ;*********************************** ;** Part 8. EXPRESSION EVALUATION ** ;*********************************** ; ; It is a this stage of the ROM that the Spectrum ceases altogether to be ; just a colourful novelty. One remarkable feature is that in all previous ; commands when the Spectrum is expecting a number or a string then an ; expression of the same type can be substituted ad infinitum. ; This is the routine that evaluates that expression. ; This is what causes 2 + 2 to give the answer 4. ; That is quite easy to understand. However you don't have to make it much ; more complex to start a remarkable juggling act. ; e.g. PRINT 2 * (VAL "2+2" + TAN 3) ; In fact, provided there is enough free RAM, the Spectrum can evaluate ; an expression of unlimited complexity. ; Apart from a couple of minor glitches, which you can now correct, the ; system is remarkably robust. ;---------------------------------- ; Scan expression or sub-expression ;---------------------------------- ;;;$24FB SCANNING: RST 18H ; GET_CHAR LD B,$00 ; priority marker zero is pushed on stack ; to signify end of expression when it is popped off again. PUSH BC ; put in on stack. ; and proceed to consider the first character ; of the expression. ;;;$24FF S_LOOP_1: LD C,A ; store the character while a look up is done. LD HL,SCAN_FUNC ; Address: SCAN_FUNC CALL INDEXER ; routine INDEXER is called to see if it is ; part of a limited range '+', '(', 'ATTR' etc. LD A,C ; fetch the character back JP NC,S_ALPHNUM ; jump forward to S_ALPHNUM if not in primary ; operators and functions to consider in the ; first instance a digit or a variable and ; then anything else. >>> LD B,$00 ; but here if it was found in table so LD C,(HL) ; fetch offset from table and make B zero. ADD HL,BC ; add the offset to position found JP (HL) ; and jump to the routine e.g. S_BIN ; making an indirect exit from there. ;-------------------------------------------------------------------------- ; The four service subroutines for routines in the scannings function table ;-------------------------------------------------------------------------- ; PRINT """Hooray!"" he cried." ;;;$250F S_QUOTE_S: CALL CH_ADD_1 ; routine CH_ADD_1 points to next character ; and fetches that character. INC BC ; increase length counter. CP $0D ; is it carriage return ? ; inside a quote. JP Z,REPORT_C ; jump back to REPORT_C if so. ; 'Nonsense in basic'. CP $22 ; is it a quote '"' ? JR NZ,S_QUOTE_S ; back to S_QUOTE_S if not for more. CALL CH_ADD_1 ; routine CH_ADD_1 CP $22 ; compare with possible adjacent quote RET ; return. with zero set if two together. ; This subroutine is used to get two coordinate expressions for the three ; functions SCREEN$, ATTR and POINT that have two fixed parameters and ; therefore require surrounding braces. ;;;$2522 S_2_COORD: RST 20H ; NEXT_CHAR CP $28 ; is it the opening '(' ? JR NZ,S_RPORT_C ; forward to S_RPORT_C if not ; 'Nonsense in Basic'. CALL NEXT_2NUM ; routine NEXT_2NUM gets two comma-separated ; numeric expressions. Note. this could cause ; many more recursive calls to SCANNING but ; the parent function will be evaluated fully ; before rejoining the main juggling act. RST 18H ; GET_CHAR CP $29 ; is it the closing ')' ? ;; S_RPORT_C S_RPORT_C: JP NZ,REPORT_C ; jump back to REPORT_C if not. ; 'Nonsense in Basic'. ;------------- ; Check syntax ;------------- ; This routine is called on a number of occasions to check if syntax is being ; checked or if the program is being run. To test the flag inline would use ; four bytes of code, but a call instruction only uses 3 bytes of code. ;;;$2530 SYNTAX_Z: BIT 7,(IY+$01) ; test FLAGS - checking syntax only ? RET ; return. ;----------------- ; Scanning SCREEN$ ;----------------- ; This function returns the code of a bit-mapped character at screen ; position at line C, column B. It is unable to detect the mosaic characters ; which are not bit-mapped but detects the ascii 32 - 127 range. ; The bit-mapped UDGs are ignored which is curious as it requires only a ; few extra bytes of code. As usual, anything to do with CHARS is weird. ; If no match is found a null string is returned. ; No actual check on ranges is performed - that's up to the Basic programmer. ; No real harm can come from SCREEN$(255,255) although the Basic manual ; says that invalid values will be trapped. ; Interestingly, in the Pitman pocket guide, 1984, Vickers says that the ; range checking will be performed. ;;;$2535 S_SCRN_S: CALL STK_TO_BC ; routine STK_TO_BC. LD HL,(CHARS) ; fetch address of CHARS. LD DE,$0100 ; fetch offset to CHR$ 32 ADD HL,DE ; and find start of bitmaps. ; Note. not inc h. ?? LD A,C ; transfer line to A. RRCA ; multiply RRCA ; by RRCA ; thirty-two. AND $E0 ; and with 11100000 XOR B ; combine with column $00 - $1F LD E,A ; to give the low byte of top line LD A,C ; column to A range 00000000 to 00011111 AND $18 ; and with 00011000 XOR $40 ; xor with 01000000 (high byte screen start) LD D,A ; register DE now holds start address of cell. LD B,$60 ; there are 96 characters in ascii set. ;;;$254F S_SCRN_LP: PUSH BC ; save count PUSH DE ; save screen start address PUSH HL ; save bitmap start LD A,(DE) ; first byte of screen to A XOR (HL) ; xor with corresponding character byte JR Z,S_SC_MTCH ; forward to S_SC_MTCH if they match ; if inverse result would be $FF ; if any other then mismatch INC A ; set to $00 if inverse JR NZ,S_SCR_NXT ; forward to S_SCR_NXT if a mismatch DEC A ; restore $FF ; a match has been found so seven more to test. ;;;$255A S_SC_MTCH: LD C,A ; load C with inverse mask $00 or $FF LD B,$07 ; count seven more bytes ;;;$255D S_SC_ROWS: INC D ; increment screen address. INC HL ; increment bitmap address. LD A,(DE) ; byte to A XOR (HL) ; will give $00 or $FF (inverse) XOR C ; xor with inverse mask JR NZ,S_SCR_NXT ; forward to S_SCR_NXT if no match. DJNZ S_SC_ROWS ; back to S_SC_ROWS until all eight matched. ; continue if a match of all eight bytes was found POP BC ; discard the POP BC ; saved POP BC ; pointers LD A,$80 ; the endpoint of character set SUB B ; subtract the counter ; to give the code 32-127 LD BC,$0001 ; make one space in workspace. RST 30H ; BC_SPACES creates the space sliding ; the calculator stack upwards. LD (DE),A ; start is addressed by DE, so insert code JR S_SCR_STO ; forward to S_SCR_STO ; the jump was here if no match and more bitmaps to test. ;;;$2573 S_SCR_NXT: POP HL ; restore the last bitmap start LD DE,$0008 ; and prepare to add 8. ADD HL,DE ; now addresses next character bitmap. POP DE ; restore screen address POP BC ; and character counter in B DJNZ S_SCRN_LP ; back to S_SCRN_LP if more characters. LD C,B ; B is now zero, so BC now zero. ;;;$257D S_SCR_STO: JP STK_STO_D ; to STK_STO_D to store the string in ; workspace or a string with zero length. ; (value of DE doesn't matter in last case) ; Note. this exit seems correct but the general-purpose routine S_STRING ; that calls this one will also stack any of it's string results so this ; leads to a double storing of the result in this case. ; The instruction at S_SCR_STO should just be a RET. ; credit Stephen Kelly and others, 1982. ;-------------- ; Scanning ATTR ;-------------- ; This function subroutine returns the attributes of a screen location - ; a numeric result. ; Again it's up to the Basic programmer to supply valid values of line/column. ;;;$2580 S_ATTR_S: CALL STK_TO_BC ; routine STK_TO_BC fetches line to C, and column to B. LD A,C ; line to A $00 - $17 (max 00010111) RRCA ; rotate RRCA ; bits RRCA ; left. LD C,A ; store in C as an intermediate value. AND $E0 ; pick up bits 11100000 ( was 00011100 ) XOR B ; combine with column $00 - $1F LD L,A ; low byte now correct. LD A,C ; bring back intermediate result from C AND $03 ; mask to give correct third of ; screen $00 - $02 XOR $58 ; combine with base address. LD H,A ; high byte correct. LD A,(HL) ; pick up the colour attribute. JP STACK_A ; forward to STACK_A to store result ; and make an indirect exit. ;------------------------ ; Scanning function table ;------------------------ ; This table is used by INDEXER routine to find the offsets to ; four operators and eight functions. e.g. $A8 is the token 'FN'. ; This table is used in the first instance for the first character of an ; expression or by a recursive call to SCANNING for the first character of ; any sub-expression. It eliminates functions that have no argument or ; functions that can have more than one argument and therefore require ; braces. By eliminating and dealing with these now it can later take a ; simplistic approach to all other functions and assume that they have ; one argument. ; Similarly by eliminating BIN and '.' now it is later able to assume that ; all numbers begin with a digit and that the presence of a number or ; variable can be detected by a call to ALPHANUM. ; By default all expressions are positive and the spurious '+' is eliminated ; now as in print +2. This should not be confused with the operator '+'. ; Note. this does allow a degree of nonsense to be accepted as in ; PRINT +"3 is the greatest.". ; An acquired programming skill is the ability to include brackets where ; they are not necessary. ; A bracket at the start of a sub-expression may be spurious or necessary ; to denote that the contained expression is to be evaluated as an entity. ; In either case this is dealt with by recursive calls to SCANNING. ; An expression that begins with a quote requires special treatment. ;;;$2596 SCAN_FUNC: DEFB $22, S_QUOTE-$-1 ; $1C offset to S_QUOTE DEFB '(', S_BRACKET-$-1 ; $4F offset to S_BRACKET DEFB '.', S_DECIMAL-$-1 ; $F2 offset to S_DECIMAL DEFB '+', S_U_PLUS-$-1 ; $12 offset to S_U_PLUS DEFB $A8, S_FN-$-1 ; $56 offset to S_FN DEFB $A5, S_RND-$-1 ; $57 offset to S_RND DEFB $A7, S_PI-$-1 ; $84 offset to S_PI DEFB $A6, S_INKEY-$-1 ; $8F offset to S_INKEY DEFB $C4, S_BIN-$-1 ; $E6 offset to S_BIN DEFB $AA, S_SCREEN-$-1 ; $BF offset to S_SCREEN DEFB $AB, S_ATTR-$-1 ; $C7 offset to S_ATTR DEFB $A9, S_POINT-$-1 ; $CE offset to S_POINT DEFB $00 ; zero end marker ;--------------------------- ; Scanning function routines ;--------------------------- ; These are the 11 subroutines accessed by the above table. ; S_BIN and S_DECIMAL are the same ; The 1-byte offset limits their location to within 255 bytes of their ; entry in the table. ; -> ;;;$25AF S_U_PLUS: RST 20H ; NEXT_CHAR just ignore JP S_LOOP_1 ; to S_LOOP_1 ; -> ;;;$25B3 S_QUOTE: RST 18H ; GET_CHAR INC HL ; address next character (first in quotes) PUSH HL ; save start of quoted text. LD BC,$0000 ; initialize length of string to zero. CALL S_QUOTE_S ; routine S_QUOTE_S JR NZ,S_Q_PRMS ; forward to S_Q_PRMS if ;;;$25BE S_Q_AGAIN: CALL S_QUOTE_S ; routine S_QUOTE_S copies string until a ; quote is encountered JR Z,S_Q_AGAIN ; back to S_Q_AGAIN if two quotes WERE ; together. ; but if just an isolated quote then that terminates the string. CALL SYNTAX_Z ; routine SYNTAX_Z JR Z,S_Q_PRMS ; forward to S_Q_PRMS if checking syntax. RST 30H ; BC_SPACES creates the space for true ; copy of string in workspace. POP HL ; re-fetch start of quoted text. PUSH DE ; save start in workspace. ;;;$25CB S_Q_COPY: LD A,(HL) ; fetch a character from source. INC HL ; advance source address. LD (DE),A ; place in destination. INC DE ; advance destination address. CP $22 ; was it a '"' just copied ? JR NZ,S_Q_COPY ; back to S_Q_COPY to copy more if not LD A,(HL) ; fetch adjacent character from source. INC HL ; advance source address. CP $22 ; is this '"' ? - i.e. two quotes together ? JR Z,S_Q_COPY ; to S_Q_COPY if so including just one of the ; pair of quotes. ; proceed when terminating quote encountered. ;;;$25D9 S_Q_PRMS: DEC BC ; decrease count by 1. POP DE ; restore start of string in workspace. ;;;$25DB S_STRING: LD HL,FLAGS ; Address FLAGS system variable. RES 6,(HL) ; signal string result. BIT 7,(HL) ; is syntax being checked. CALL NZ,STK_STO_D ; routine STK_STO_D is called in runtime. JP S_CONT_2 ; jump forward to S_CONT_2 ===> ; -> ;;;$25E8 S_BRACKET: RST 20H ; NEXT_CHAR CALL SCANNING ; routine SCANNING is called recursively. CP $29 ; is it the closing ')' ? JP NZ,REPORT_C ; jump back to REPORT_C if not ; 'Nonsense in basic' RST 20H ; NEXT_CHAR JP S_CONT_2 ; jump forward to S_CONT_2 ===> ; -> ;;$25F5 S_FN: JP S_FN_SBRN ; jump forward to S_FN_SBRN. ; -> ;;;$25F8 S_RND: CALL SYNTAX_Z ; routine SYNTAX_Z JR Z,S_RND_END ; forward to S_RND_END if checking syntax. LD BC,(SEED) ; fetch system variable SEED CALL STACK_BC ; routine STACK_BC places on calculator stack RST 28H ;; FP_CALC ;s. DEFB $A1 ;;STK_ONE ;s,1. DEFB $0F ;;ADDITION ;s+1. DEFB $34 ;;STK_DATA ; DEFB $37 ;;Exponent: $87, ;;Bytes: 1 DEFB $16 ;;(+00,+00,+00) ;s+1,75. DEFB $04 ;;MULTIPLY ;(s+1)*75 = v DEFB $34 ;;STK_DATA ;v. DEFB $80 ;;Bytes: 3 DEFB $41 ;;Exponent $91 DEFB $00,$00,$80 ;;(+00) ;v,65537. DEFB $32 ;;N_MOD_M ;remainder,result. DEFB $02 ;;DELETE ;remainder. DEFB $A1 ;;STK_ONE ;remainder,1. DEFB $03 ;;SUBTRACT ;remainder - 1. = rnd DEFB $31 ;;DUPLICATE ;rnd,rnd. DEFB $38 ;;END_CALC CALL FP_TO_BC ; routine FP_TO_BC LD (SEED),BC ; store in SEED for next starting point. LD A,(HL) ; fetch exponent AND A ; is it zero ? JR Z,S_RND_END ; forward if so to S_RND_END SUB $10 ; reduce exponent by 2^16 LD (HL),A ; place back ;;;$2625 S_RND_END: JR S_PI_END ; forward to S_PI_END ; the number PI 3.14159... ; -> ;;;$2627 S_PI: CALL SYNTAX_Z ; routine SYNTAX_Z JR Z,S_PI_END ; to S_PI_END if checking syntax. RST 28H ;; FP_CALC DEFB $A3 ;;STK_PI_2 pi/2. DEFB $38 ;;END_CALC INC (HL) ; increment the exponent leaving pi ; on the calculator stack. ;;;$2630 S_PI_END: RST 20H ; NEXT_CHAR JP S_NUMERIC ; jump forward to S_NUMERIC ; -> ;;;$2634 S_INKEY: LD BC,$105A ; priority $10, operation code $1A ('READ_IN') ; +$40 for string result, numeric operand. ; set this up now in case we need to use the calculator. RST 20H ; NEXT_CHAR CP $23 ; '#' ? JP Z,S_PUSH_PO ; to S_PUSH_PO if so to use the calculator ; single operation ; to read from network/RS232 etc. . ; else read a key from the keyboard. LD HL,FLAGS ; fetch FLAGS RES 6,(HL) ; signal string result. BIT 7,(HL) ; checking syntax ? JR Z,S_INK_EN ; forward to S_INK_EN if so CALL KEY_SCAN ; routine KEY_SCAN key in E, shift in D. LD C,$00 ; the length of an empty string JR NZ,S_IK_STK ; to S_IK_STK to store empty string if no key returned. CALL K_TEST ; routine K_TEST get main code in A JR NC,S_IK_STK ; to S_IK_STK to stack null string if invalid DEC D ; D is expected to be FLAGS so set bit 3 $FF ; 'L' Mode so no keywords. LD E,A ; main key to A ; C is MODE 0 'KLC' from above still. CALL K_DECODE ; routine K_DECODE PUSH AF ; save the code LD BC,$0001 ; make room for one character RST 30H ; BC_SPACES POP AF ; bring the code back LD (DE),A ; put the key in workspace LD C,$01 ; set C length to one ;;;$2660 S_IK_STK: LD B,$00 ; set high byte of length to zero CALL STK_STO_D ; routine STK_STO_D ;;;$2665 S_INK_EN: JP S_CONT_2 ; to S_CONT_2 ===> ; -> ;;;$2668 S_SCREEN: CALL S_2_COORD ; routine S_2_COORD CALL NZ,S_SCRN_S ; routine S_SCRN_S RST 20H ; NEXT_CHAR JP S_STRING ; forward to S_STRING to stack result ; -> ;;;$2672 S_ATTR: CALL S_2_COORD ; routine S_2_COORD CALL NZ,S_ATTR_S ; routine S_ATTR_S RST 20H ; NEXT_CHAR JR S_NUMERIC ; forward to S_NUMERIC ; -> ;;;$267B S_POINT: CALL S_2_COORD ; routine S_2_COORD CALL NZ,POINT_SUB ; routine POINT_SUB RST 20H ; NEXT_CHAR JR S_NUMERIC ; forward to S_NUMERIC ; ==> The branch was here if not in table. ;;;$2684 S_ALPHNUM: CALL ALPHANUM ; routine ALPHANUM checks if variable or ; a digit. JR NC,S_NEGATE ; forward to S_NEGATE if not to consider ; a '-' character then functions. CP $41 ; compare 'A' JR NC,S_LETTER ; forward to S_LETTER if alpha -> ; else must have been numeric so continue ; into that routine. ; This important routine is called during runtime and from LINE_SCAN ; when a BASIC line is checked for syntax. It is this routine that ; inserts, during syntax checking, the invisible floating point numbers ; after the numeric expression. During runtime it just picks these ; numbers up. It also handles BIN format numbers. ; -> ;;;$268D S_DECIMAL: S_BIN: CALL SYNTAX_Z ; routine SYNTAX_Z JR NZ,S_STK_DEC ; to S_STK_DEC in runtime ; this route is taken when checking syntax. CALL DEC_TO_FP ; routine DEC_TO_FP to evaluate number RST 18H ; GET_CHAR to fetch HL LD BC,$0006 ; six locations required CALL MAKE_ROOM ; routine MAKE_ROOM INC HL ; to first new location LD (HL),$0E ; insert number marker INC HL ; address next EX DE,HL ; make DE destination. LD HL,(STKEND) ; STKEND points to end of stack. LD C,$05 ; result is five locations lower AND A ; prepare for true subtraction SBC HL,BC ; point to start of value. LD (STKEND),HL ; update STKEND as we are taking number. LDIR ; Copy five bytes to program location EX DE,HL ; transfer pointer to HL DEC HL ; adjust CALL TEMP_PTR1 ; routine TEMP_PTR1 sets CH-ADD JR S_NUMERIC ; to S_NUMERIC to record nature of result ; branch here in runtime. ;;;$26B5 S_STK_DEC: RST 18H ; GET_CHAR positions HL at digit. ;;;$26B6 S_SD_SKIP: INC HL ; advance pointer LD A,(HL) ; until we find CP $0E ; chr 14d - the number indicator JR NZ,S_SD_SKIP ; to S_SD_SKIP until a match it has to be here. INC HL ; point to first byte of number CALL STACK_NUM ; routine STACK_NUM stacks it LD (CH_ADD),HL ; update system variable CH_ADD ;;;$26C3 S_NUMERIC: SET 6,(IY+$01) ; update FLAGS - Signal numeric result JR S_CONT_1 ; forward to S_CONT_1 ===> ; actually S_CONT_2 is destination but why ; waste a byte on a jump when a JR will do. ; actually a JR S_CONT_2 can be used. Rats. ; end of functions accessed from scanning functions table. ;--------------------------- ; Scanning variable routines ;--------------------------- ;;;$26C9 S_LETTER: CALL LOOK_VARS ; routine LOOK_VARS JP C,REPORT_2 ; jump back to REPORT_2 if not found ; 'Variable not found' ; but a variable is always 'found' if syntax ; is being checked. CALL Z,STK_VAR ; routine STK_VAR considers a subscript/slice LD A,(FLAGS) ; fetch FLAGS value CP $C0 ; compare 11000000 JR C,S_CONT_1 ; step forward to S_CONT_1 if string ===> INC HL ; advance pointer CALL STACK_NUM ; routine STACK_NUM ;;;$26DD S_CONT_1: JR S_CONT_2 ; forward to S_CONT_2 ===> ;----------------------------------------- ; -> the scanning branch was here if not alphanumeric. ; All the remaining functions will be evaluated by a single call to the ; calculator. The correct priority for the operation has to be placed in ; the B register and the operation code, calculator literal in the C register. ; the operation code has bit 7 set if result is numeric and bit 6 is ; set if operand is numeric. so ; $C0 = numeric result, numeric operand. e.g. 'SIN' ; $80 = numeric result, string operand. e.g. 'CODE' ; $40 = string result, numeric operand. e.g. 'STR$' ; $00 = string result, string operand. e.g. 'VAL$' ;;;$26DF S_NEGATE: LD BC,$09DB ; prepare priority 09, operation code $C0 + ; 'NEGATE' ($1B) - bits 6 and 7 set for numeric ; result and numeric operand. CP $2D ; is it '-' ? JR Z,S_PUSH_PO ; forward if so to S_PUSH_PO LD BC,$1018 ; prepare priority $10, operation code 'VAL$' - ; bits 6 and 7 reset for string result and string operand. CP $AE ; is it 'VAL$' ? JR Z,S_PUSH_PO ; forward if so to S_PUSH_PO SUB $AF ; subtract token 'CODE' value to reduce ; functions 'CODE' to 'NOT' although the ; upper range is, as yet, unchecked. ; valid range would be $00 - $14. JP C,REPORT_C ; jump back to REPORT_C with anything else ; 'Nonsense in Basic' LD BC,$04F0 ; prepare priority $04, operation $C0 + ; 'not' ($30) CP $14 ; is it 'NOT' JR Z,S_PUSH_PO ; forward to S_PUSH_PO if so JP NC,REPORT_C ; to REPORT_C if higher ; 'Nonsense in Basic' LD B,$10 ; priority $10 for all the rest ADD A,$DC ; make range $DC - $EF ; $C0 + 'CODE'($1C) thru 'CHR$' ($2F) LD C,A ; transfer 'function' to C CP $DF ; is it 'SIN' ? JR NC,S_NO_TO ; forward to S_NO_TO with 'SIN' through ; 'CHR$' as operand is numeric. ; all the rest 'COS' through 'CHR$' give a numeric result except 'STR$' ; and 'CHR$'. RES 6,C ; signal string operand for 'CODE', 'VAL' and ; 'LEN'. ;;;$2707 S_NO_TO: CP $EE ; compare 'STR$' JR C,S_PUSH_PO ; forward to S_PUSH_PO if lower as result ; is numeric. RES 7,C ; reset bit 7 of op code for 'STR$', 'CHR$' ; as result is string. ; >> This is where they were all headed for. ;;;$270D S_PUSH_PO: PUSH BC ; push the priority and calculator operation code. RST 20H ; NEXT_CHAR JP S_LOOP_1 ; jump back to S_LOOP_1 to go round the loop ; again with the next character. ; ===> there were many branches forward to here ;;;$2712 S_CONT_2: RST 18H ; GET_CHAR ;;;$2713 S_CONT_3: CP $28 ; is it '(' ? JR NZ,S_OPERTR ; forward to S_OPERTR if not > BIT 6,(IY+$01) ; test FLAGS - numeric or string result ? JR NZ,S_LOOP ; forward to S_LOOP if numeric to evaluate > ; if a string preceded '(' then slice it. CALL SLICING ; routine SLICING RST 20H ; NEXT_CHAR JR S_CONT_3 ; back to S_CONT_3 ; the branch was here when possibility of an operator '(' has been excluded. ;;;$2723 S_OPERTR: LD B,$00 ; prepare to add LD C,A ; possible operator to C LD HL,TBL_OF_OPS ; Address: TBL_OF_OPS CALL INDEXER ; routine INDEXER JR NC,S_LOOP ; forward to S_LOOP if not in table ; but if found in table the priority has to be looked up. LD C,(HL) ; operation code to C ( B is still zero ) LD HL,TBL_PRIORS-$C3 ; $26ED is base of table ADD HL,BC ; index into table. LD B,(HL) ; priority to B. ;------------------- ; Scanning main loop ;------------------- ; the juggling act ;;;$2734 S_LOOP: POP DE ; fetch last priority and operation LD A,D ; priority to A CP B ; compare with this one JR C,S_TIGHTER ; forward to S_TIGHTER to execute the ; last operation before this one as it has ; higher priority. ; the last priority was greater or equal this one. AND A ; if it is zero then so is this JP Z,GET_CHAR ; jump to exit via GET_CHAR pointing at ; next character. ; This may be the character after the ; expression or, if exiting a recursive call, ; the next part of the expression to be ; evaluated. PUSH BC ; save current priority/operation ; as it has lower precedence than the one ; now in DE. ; the 'USR' function is special in that it is overloaded to give two types ; of result. LD HL,FLAGS ; address FLAGS LD A,E ; new operation to A register CP $ED ; is it $C0 + 'USR_NO' ($2D) ? JR NZ,S_STK_LST ; forward to S_STK_LST if not BIT 6,(HL) ; string result expected ? ; (from the lower priority operand we've ; just pushed on stack ) JR NZ,S_STK_LST ; forward to S_STK_LST if numeric ; as operand bits match. LD E,$99 ; reset bit 6 and substitute $19 'USR-$' ; for string operand. ;;;$274C S_STK_LST: PUSH DE ; now stack this priority/operation CALL SYNTAX_Z ; routine SYNTAX_Z JR Z,S_SYNTEST ; forward to S_SYNTEST if checking syntax. LD A,E ; fetch the operation code AND $3F ; mask off the result/operand bits to leave a calculator literal. LD B,A ; transfer to B register ; now use the calculator to perform the single operation - operand is on ; the calculator stack. ; Note. although the calculator is performing a single operation most ; functions e.g. TAN are written using other functions and literals and ; these in turn are written using further strings of calculator literals so ; another level of magical recursion joins the juggling act for a while ; as the calculator too is calling itself. RST 28H ;; FP_CALC DEFB $3B ;;FP_CALC_2 ;;;$2758 DEFB $38 ;;END_CALC JR S_RUNTEST ; forward to S_RUNTEST ; the branch was here if checking syntax only. ;;;$275B S_SYNTEST: LD A,E ; fetch the operation code to accumulator XOR (IY+$01) ; compare with bits of FLAGS AND $40 ; bit 6 will be zero now if operand ; matched expected result. ;;;$2761 S_RPORT_C2: JP NZ,REPORT_C ; to REPORT_C if mismatch ; 'Nonsense in Basic' ; else continue to set flags for next ; the branch is to here in runtime after a successful operation. ;;;$2764 S_RUNTEST: POP DE ; fetch the last operation from stack LD HL,FLAGS ; address FLAGS SET 6,(HL) ; set default to numeric result in FLAGS BIT 7,E ; test the operational result JR NZ,S_LOOPEND ; forward to S_LOOPEND if numeric RES 6,(HL) ; reset bit 6 of FLAGS to show string result. ;;;$2770 S_LOOPEND: POP BC ; fetch the previous priority/operation JR S_LOOP ; back to S_LOOP to perform these ; the branch was here when a stacked priority/operator had higher priority ; than the current one. ;;;$2773 S_TIGHTER: PUSH DE ; save high priority op on stack again LD A,C ; fetch lower priority operation code BIT 6,(IY+$01) ; test FLAGS - Numeric or string result ? JR NZ,S_NEXT ; forward to S_NEXT if numeric result ; if this is lower priority yet has string then must be a comparison. ; Since these can only be evaluated in context and were defaulted to ; numeric in operator look up they must be changed to string equivalents. AND $3F ; mask to give true calculator literal ADD A,$08 ; augment numeric literals to string ; equivalents. ; 'NO_AND_NO' => 'STR_AND_NO' ; 'NO_L_EQL' => 'STR_L_EQL' ; 'NO_GR_EQL' => 'STR_GR_EQL' ; 'NOS_NEQL' => 'STRS_NEQL' ; 'NO_GRTR' => 'STR_GRTR' ; 'NO_LESS' => 'STR_LESS' ; 'NOS_EQL' => 'STRS_EQL' ; 'ADDITION' => 'STRS_ADD' LD C,A ; put modified comparison operator back CP $10 ; is it now 'STR_AND_NO' ? JR NZ,S_NOT_AND ; forward to S_NOT_AND if not. SET 6,C ; set numeric operand bit JR S_NEXT ; forward to S_NEXT ;;;$2788 S_NOT_AND: JR C,S_RPORT_C2 ; back to S_RPORT_C2 if less ; 'Nonsense in basic'. ; e.g. a$ * b$ CP $17 ; is it 'STRS_ADD' ? JR Z,S_NEXT ; forward to to S_NEXT if so ; (bit 6 and 7 are reset) SET 7,C ; set numeric (Boolean) result for all others ;;;$2790 S_NEXT: PUSH BC ; now save this priority/operation on stack RST 20H ; NEXT_CHAR JP S_LOOP_1 ; jump back to S_LOOP_1 ;------------------- ; Table of operators ;------------------- ; This table is used to look up the calculator literals associated with ; the operator character. The thirteen calculator operations $03 - $0F ; have bits 6 and 7 set to signify a numeric result. ; Some of these codes and bits may be altered later if the context suggests ; a string comparison or operation. ; that is '+', '=', '>', '<', '<=', '>=' or '<>'. ;;;$2795 TBL_OF_OPS: DEFB '+', $CF ; $C0 + 'ADDITION' DEFB '-', $C3 ; $C0 + 'SUBTRACT' DEFB '*', $C4 ; $C0 + 'MULTIPLY' DEFB '/', $C5 ; $C0 + 'DIVISION' DEFB '^', $C6 ; $C0 + 'TO_POWER' DEFB '=', $CE ; $C0 + 'NOS_EQL' DEFB '>', $CC ; $C0 + 'NO_GRTR' DEFB '<', $CD ; $C0 + 'NO_LESS' DEFB $C7, $C9 ; '<=' $C0 + 'NO_L_EQL' DEFB $C8, $CA ; '>=' $C0 + 'NO_GR_EQL' DEFB $C9, $CB ; '<>' $C0 + 'NOS_NEQL' DEFB $C5, $C7 ; 'OR' $C0 + 'OR' DEFB $C6, $C8 ; 'AND' $C0 + 'NO_AND_NO' DEFB $00 ; zero end-marker. ;-------------------- ; Table of priorities ;-------------------- ; This table is indexed with the operation code obtained from the above ; table $C3 - $CF to obtain the priority for the respective operation. ;;;$27B0 TBL_PRIORS: DEFB $06 ; '-' opcode $C3 DEFB $08 ; '*' opcode $C4 DEFB $08 ; '/' opcode $C5 DEFB $0A ; '^' opcode $C6 DEFB $02 ; 'OR' opcode $C7 DEFB $03 ; 'AND' opcode $C8 DEFB $05 ; '<=' opcode $C9 DEFB $05 ; '>=' opcode $CA DEFB $05 ; '<>' opcode $CB DEFB $05 ; '>' opcode $CC DEFB $05 ; '<' opcode $CD DEFB $05 ; '=' opcode $CE DEFB $06 ; '+' opcode $CF ;----------------------- ; Scanning function (FN) ;----------------------- ; This routine deals with user-defined functions. ; The definition can be anywhere in the program area but these are best ; placed near the start of the program as we shall see. ; The evaluation process is quite complex as the Spectrum has to parse two ; statements at the same time. Syntax of both has been checked previously ; and hidden locations have been created immediately after each argument ; of the DEF FN statement. Each of the arguments of the FN function is ; evaluated by SCANNING and placed in the hidden locations. Then the ; expression to the right of the DEF FN '=' is evaluated by SCANNING and for ; any variables encountered, a search is made in the DEF FN variable list ; in the program area before searching in the normal variables area. ; ; Recursion is not allowed: i.e. the definition of a function should not use ; the same function, either directly or indirectly ( through another function). ; You'll normally get error 4, ('Out of memory'), although sometimes the sytem ; will crash. - Vickers, Pitman 1984. ; ; As the definition is just an expression, there would seem to be no means ; of breaking out of such recursion. ; However, by the clever use of string expressions and VAL, such recursion is ; possible. ; e.g. DEF FN a(n) = VAL "n+FN a(n-1)+0" ((n<1) * 10 + 1 TO ) ; will evaluate the full 11-character expression for all values where n is ; greater than zero but just the 11th character, "0", when n drops to zero ; thereby ending the recursion producing the correct result. ; Recursive string functions are possible using VAL$ instead of VAL and the ; null string as the final addend. ; - from a turn of the century newsgroup discussion initiated by Mike Wynne. ;;;$27BD S_FN_SBRN: CALL SYNTAX_Z ; routine SYNTAX_Z JR NZ,SF_RUN ; forward to SF_RUN in runtime RST 20H ; NEXT_CHAR CALL ALPHA ; routine ALPHA check for letters A-Z a-z JP NC,REPORT_C ; jump back to REPORT_C if not ; 'Nonsense in Basic' RST 20H ; NEXT_CHAR CP $24 ; is it '$' ? PUSH AF ; save character and flags JR NZ,SF_BRKT_1 ; forward to SF_BRKT_1 with numeric function RST 20H ; NEXT_CHAR ;;;$27D0 SF_BRKT_1: CP $28 ; is '(' ? JR NZ,SF_RPRT_C ; forward to SF_RPRT_C if not ; 'Nonsense in Basic' RST 20H ; NEXT_CHAR CP $29 ; is it ')' ? JR Z,SF_FLAG_6 ; forward to SF_FLAG_6 if no arguments. ;;;$27D9 SF_ARGMTS: CALL SCANNING ; routine SCANNING checks each argument ; which may be an expression. RST 18H ; GET_CHAR CP $2C ; is it a ',' ? JR NZ,SF_BRKT_2 ; forward if not to SF_BRKT_2 to test bracket RST 20H ; NEXT_CHAR if a comma was found JR SF_ARGMTS ; back to SF_ARGMTS to parse all arguments. ;;;$27E4 SF_BRKT_2: CP $29 ; is character the closing ')' ? ;;;$27E6 SF_RPRT_C: JP NZ,REPORT_C ; jump to REPORT_C ; 'Nonsense in Basic' ; at this point any optional arguments have had their syntax checked. ;;;$27E9 SF_FLAG_6: RST 20H ; NEXT_CHAR LD HL,FLAGS ; address system variable FLAGS RES 6,(HL) ; signal string result POP AF ; restore test against '$'. JR Z,SF_SYN_EN ; forward to SF_SYN_EN if string function. SET 6,(HL) ; signal numeric result ;;;$27F4 SF_SYN_EN: JP S_CONT_2 ; jump back to S_CONT_2 to continue scanning. ; the branch was here in runtime. ;;;$27F7 SF_RUN: RST 20H ; NEXT_CHAR fetches name AND $DF ; AND 11101111 - reset bit 5 - upper-case. LD B,A ; save in B RST 20H ; NEXT_CHAR SUB $24 ; subtract '$' LD C,A ; save result in C JR NZ,SF_ARGMT1 ; forward if not '$' to SF_ARGMT1 RST 20H ; NEXT_CHAR advances to bracket ;;;$2802 SF_ARGMT1: RST 20H ; NEXT_CHAR advances to start of argument PUSH HL ; save address LD HL,(PROG) ; fetch start of program area from PROG DEC HL ; the search starting point is the previous ; location. ;;;$2808 SF_FND_DF: LD DE,$00CE ; search is for token 'DEF FN' in E, statement count in D. PUSH BC ; save C the string test, and B the letter. CALL LOOK_PROG ; routine LOOK_PROG will search for token. POP BC ; restore BC. JR NC,SF_CP_DEF ; forward to SF_CP_DEF if a match was found. ;;;$2812 REPORT_P: RST 08H ; ERROR_1 DEFB $18 ; Error Report: FN without DEF ;;;$2814 SF_CP_DEF: PUSH HL ; save address of DEF FN CALL FN_SKPOVR ; routine FN_SKPOVR skips over white-space etc. ; without disturbing CH-ADD. AND $DF ; make fetched character upper-case. CP B ; compare with FN name JR NZ,SF_NOT_FD ; forward to SF_NOT_FD if no match. ; the letters match so test the type. CALL FN_SKPOVR ; routine FN_SKPOVR skips white-space SUB $24 ; subtract '$' from fetched character CP C ; compare with saved result of same operation on FN name. JR Z,SF_VALUES ; forward to SF_VALUES with a match. ; the letters matched but one was string and the other numeric. ;;;$2825 SF_NOT_FD: POP HL ; restore search point. DEC HL ; make location before LD DE,$0200 ; the search is to be for the end of the ; current definition - 2 statements forward. PUSH BC ; save the letter/type CALL EACH_STMT ; routine EACH_STMT steps past rejected definition. POP BC ; restore letter/type JR SF_FND_DF ; back to SF_FND_DF to continue search ; Success! ; the branch was here with matching letter and numeric/string type. ;;;$2831 SF_VALUES: AND A ; test A ( will be zero if string '$' - '$' ) CALL Z,FN_SKPOVR ; routine FN_SKPOVR advances HL past '$'. POP DE ; discard pointer to 'DEF FN'. POP DE ; restore pointer to first FN argument. LD (CH_ADD),DE ; save in CH_ADD CALL FN_SKPOVR ; routine FN_SKPOVR advances HL past '(' PUSH HL ; save start address in DEF FN *** CP $29 ; is character a ')' ? JR Z,SF_R_BR_2 ; forward to SF_R_BR_2 if no arguments. ;;;$2843 SF_ARG_LP: INC HL ; point to next character. LD A,(HL) ; fetch it. CP $0E ; is it the number marker LD D,$40 ; signal numeric in D. JR Z,SF_ARG_VL ; forward to SF_ARG_VL if numeric. DEC HL ; back to letter CALL FN_SKPOVR ; routine FN_SKPOVR skips any white-space INC HL ; advance past the expected '$' to the 'hidden' marker. LD D,$00 ; signal string. ;;;$2852 SF_ARG_VL: INC HL ; now address first of 5-byte location. PUSH HL ; save address in DEF FN statement PUSH DE ; save D - result type CALL SCANNING ; routine SCANNING evaluates expression in ; the FN statement setting FLAGS and leaving ; result as last value on calculator stack. POP AF ; restore saved result type to A XOR (IY+$01) ; xor with FLAGS AND $40 ; and with 01000000 to test bit 6 JR NZ,REPORT_Q ; forward to REPORT_Q if type mismatch. ; 'Parameter error' POP HL ; pop the start address in DEF FN statement EX DE,HL ; transfer to DE ?? pop straight into de ? LD HL,(STKEND) ; set HL to STKEND location after value LD BC,$0005 ; five bytes to move SBC HL,BC ; decrease HL by 5 to point to start. LD (STKEND),HL ; set STKEND 'removing' value from stack. LDIR ; copy value into DEF FN statement EX DE,HL ; set HL to location after value in DEF FN DEC HL ; step back one CALL FN_SKPOVR ; routine FN_SKPOVR gets next valid character CP $29 ; is it ')' end of arguments ? JR Z,SF_R_BR_2 ; forward to SF_R_BR_2 if so. ; a comma separator has been encountered in the DEF FN argument list. PUSH HL ; save position in DEF FN statement RST 18H ; GET_CHAR from FN statement CP $2C ; is it ',' ? JR NZ,REPORT_Q ; forward to REPORT_Q if not ; 'Parameter error' RST 20H ; NEXT_CHAR in FN statement advances to next ; argument. POP HL ; restore DEF FN pointer CALL FN_SKPOVR ; routine FN_SKPOVR advances to corresponding ; argument. JR SF_ARG_LP ; back to SF_ARG_LP looping until all ; arguments are passed into the DEF FN ; hidden locations. ; the branch was here when all arguments passed. ;;;$2885 SF_R_BR_2: PUSH HL ; save location of ')' in DEF FN RST 18H ; GET_CHAR gets next character in FN CP $29 ; is it a ')' also ? JR Z,SF_VALUE ; forward to SF_VALUE if so. ;;;$288B REPORT_Q: RST 08H ; ERROR_1 DEFB $19 ; Error Report: Parameter error ;;;$288D SF_VALUE: POP DE ; location of ')' in DEF FN to DE. EX DE,HL ; now to HL, FN ')' pointer to DE. LD (CH_ADD),HL ; initialize CH_ADD to this value. ; At this point the start of the DEF FN argument list is on the machine stack. ; We also have to consider that this defined function may form part of the ; definition of another defined function (though not itself). ; As this defined function may be part of a hierarchy of defined functions ; currently being evaluated by recursive calls to SCANNING, then we have to ; preserve the original value of DEFADD and not assume that it is zero. LD HL,(DEFADD) ; get original DEFADD address EX (SP),HL ; swap with DEF FN address on stack *** LD (DEFADD),HL ; set DEFADD to point to this argument list ; during scanning. PUSH DE ; save FN ')' pointer. RST 20H ; NEXT_CHAR advances past ')' in define RST 20H ; NEXT_CHAR advances past '=' to expression CALL SCANNING ; routine SCANNING evaluates but searches ; initially for variables at DEFADD POP HL ; pop the FN ')' pointer LD (CH_ADD),HL ; set CH_ADD to this POP HL ; pop the original DEFADD value LD (DEFADD),HL ; and re-insert into DEFADD system variable. RST 20H ; NEXT_CHAR advances to character after ')' JP S_CONT_2 ; to S_CONT_2 - to continue current ; invocation of scanning ;--------------------- ; Used to parse DEF FN ;--------------------- ; e.g. DEF FN s $ ( x ) = b $ ( TO x ) : REM exaggerated ; ; This routine is used 10 times to advance along a DEF FN statement ; skipping spaces and colour control codes. It is similar to NEXT-CHAR ; which is, at the same time, used to skip along the corresponding FN function ; except the latter has to deal with AT and TAB characters in string ; expressions. These cannot occur in a program area so this routine is ; simpler as both colour controls and their parameters are less than space. ;;;$28AB FN_SKPOVR: INC HL ; increase pointer LD A,(HL) ; fetch addressed character CP $21 ; compare with space + 1 JR C,FN_SKPOVR ; back to FN_SKPOVR if less RET ; return pointing to a valid character. ;---------- ; LOOK_VARS ;---------- ;;;$28B2 LOOK_VARS: SET 6,(IY+$01) ; update FLAGS - presume numeric result RST 18H ; GET_CHAR CALL ALPHA ; routine ALPHA tests for A-Za-z JP NC,REPORT_C ; jump to REPORT_C if not. ; 'Nonsense in basic' PUSH HL ; save pointer to first letter ^1 AND $1F ; mask lower bits, 1 - 26 decimal 000xxxxx LD C,A ; store in C. RST 20H ; NEXT_CHAR PUSH HL ; save pointer to second character ^2 CP $28 ; is it '(' - an array ? JR Z,V_RUN_SYN ; forward to V_RUN_SYN if so. SET 6,C ; set 6 signalling string if solitary 010 CP $24 ; is character a '$' ? JR Z,V_STR_VAR ; forward to V_STR_VAR SET 5,C ; signal numeric 011 CALL ALPHANUM ; routine ALPHANUM sets carry if second ; character is alphanumeric. JR NC,V_TEST_FN ; forward to V_TEST_FN if just one character ; it is more than one character but re-test current character so that 6 reset ; Note. this is a rare lack of elegance. Bit 6 could be reset once before ; entering the loop. Another puzzle is that this loop renders the similar ; loop at V_PASS redundant. ;;;$28D4 V_CHAR: CALL ALPHANUM ; routine ALPHANUM JR NC,V_RUN_SYN ; to V_RUN_SYN when no more RES 6,C ; make long named type 001 RST 20H ; NEXT_CHAR JR V_CHAR ; loop back to V_CHAR ;;;$28DE V_STR_VAR: RST 20H ; NEXT_CHAR advances past '$' RES 6,(IY+$01) ; update FLAGS - signal string result. ;;;$28E3 V_TEST_FN: LD A,($5C0C) ; load A with DEFADD_hi AND A ; and test for zero. JR Z,V_RUN_SYN ; forward to V_RUN_SYN if a defined function ; is not being evaluated. CALL SYNTAX_Z ; routine SYNTAX_Z JP NZ,STK_F_ARG ; branch to STK_F_ARG in runtime and then ; back to this point if no variable found. ;;;$28EF V_RUN_SYN: LD B,C ; save flags in B CALL SYNTAX_Z ; routine SYNTAX_Z JR NZ,V_RUN ; to V_RUN to look for the variable in runtime ; if checking syntax the letter is not returned LD A,C ; copy letter/flags to A AND $E0 ; and with 11100000 to get rid of the letter SET 7,A ; use spare bit to signal checking syntax. LD C,A ; and transfer to C. JR V_SYNTAX ; forward to V_SYNTAX ; but in runtime search for the variable. ;;;$28FD V_RUN: LD HL,(VARS) ; set HL to start of variables from VARS ;;;$2900 V_EACH: LD A,(HL) ; get first character AND $7F ; and with 01111111 ; ignoring bit 7 which distinguishes ; arrays or for/next variables. JR Z,V_80_BYTE ; to V_80_BYTE if zero as must be 10000000 ; the variables end-marker. CP C ; compare with supplied value. JR NZ,V_NEXT ; forward to V_NEXT if no match. RLA ; destructively test ADD A,A ; bits 5 and 6 of A ; jumping if bit 5 reset or 6 set JP P,V_FOUND_2 ; to V_FOUND_2 strings and arrays JR C,V_FOUND_2 ; to V_FOUND_2 simple and for next ; leaving long name variables. POP DE ; pop pointer to 2nd. char PUSH DE ; save it again PUSH HL ; save variable first character pointer ;;;$2912 V_MATCHES: INC HL ; address next character in vars area ;;;$2913 V_SPACES: LD A,(DE) ; pick up letter from prog area INC DE ; and advance address CP $20 ; is it a space JR Z,V_SPACES ; back to V_SPACES until non-space OR $20 ; convert to range 1 - 26. CP (HL) ; compare with addressed variables character JR Z,V_MATCHES ; loop back to V_MATCHES if a match on an ; intermediate letter. OR $80 ; now set bit 7 as last character of long ; names are inverted. CP (HL) ; compare again JR NZ,V_GET_PTR ; forward to V_GET_PTR if no match ; but if they match check that this is also last letter in prog area LD A,(DE) ; fetch next character CALL ALPHANUM ; routine ALPHANUM sets carry if not alphanum JR NC,V_FOUND_1 ; forward to V_FOUND_1 with a full match. ;;;$2929 V_GET_PTR: POP HL ; pop saved pointer to char 1 ;;;$292A V_NEXT: PUSH BC ; save flags CALL NEXT_ONE ; routine NEXT_ONE gets next variable in DE EX DE,HL ; transfer to HL. POP BC ; restore the flags JR V_EACH ; loop back to V_EACH ; to compare each variable ;;;$2932 V_80_BYTE: SET 7,B ; will signal not found ; the branch was here when checking syntax ;;;$2934 V_SYNTAX: POP DE ; discard the pointer to 2nd. character v2 ; in basic line/workspace. RST 18H ; GET_CHAR gets character after variable name. CP $28 ; is it '(' ? JR Z,V_PASS ; forward to V_PASS ; Note. could go straight to V_END ? SET 5,B ; signal not an array JR V_END ; forward to V_END ; the jump was here when a long name matched and HL pointing to last character ; in variables area. ;;;$293E V_FOUND_1: POP DE ; discard pointer to first var letter ; the jump was here with all other matches HL points to first var char. ;;;$293F V_FOUND_2: POP DE ; discard pointer to 2nd prog char v2 POP DE ; drop pointer to 1st prog char v1 PUSH HL ; save pointer to last char in vars RST 18H ; GET_CHAR ;;;$2943 V_PASS: CALL ALPHANUM ; routine ALPHANUM JR NC,V_END ; forward to V_END if not ; but it never will be as we advanced past long-named variables earlier. RST 20H ; NEXT_CHAR JR V_PASS ; back to V_PASS ;;;$294B V_END: POP HL ; pop the pointer to first character in basic line/workspace. RL B ; rotate the B register, left bit 7 to carry BIT 6,B ; test the array indicator bit. RET ; return ;------------------------ ; Stack function argument ;------------------------ ; This branch is taken from LOOK_VARS when a defined function is currently ; being evaluated. ; Scanning is evaluating the expression after the '=' and the variable ; found could be in the argument list to the left of the '=' or in the ; normal place after the program. Preference will be given to the former. ; The variable name to be matched is in C. ;;;$2951 STK_F_ARG: LD HL,(DEFADD) ; set HL to DEFADD LD A,(HL) ; load the first character CP $29 ; is it ')' ? JP Z,V_RUN_SYN ; back to V_RUN_SYN, if so, as no arguments. ; but proceed to search argument list of defined function first if not empty. ;;;$295A SFA_LOOP: LD A,(HL) ; fetch character again. OR $60 ; or with 01100000 presume a simple variable. LD B,A ; save result in B. INC HL ; address next location. LD A,(HL) ; pick up byte. CP $0E ; is it the number marker ? JR Z,SFA_CP_VR ; forward to SFA_CP_VR if so. ; it was a string. White-space may be present but syntax has been checked. DEC HL ; point back to letter. CALL FN_SKPOVR ; routine FN_SKPOVR skips to the '$' INC HL ; now address the hidden marker. RES 5,B ; signal a string variable. ;;;$296B SFA_CP_VR: LD A,B ; transfer found variable letter to A. CP C ; compare with expected. JR Z,SFA_MATCH ; forward to SFA_MATCH with a match. INC HL ; step INC HL ; past INC HL ; the INC HL ; five INC HL ; bytes. CALL FN_SKPOVR ; routine FN_SKPOVR skips to next character CP $29 ; is it ')' ? JP Z,V_RUN_SYN ; jump back if so to V_RUN_SYN to look in ; normal variables area. CALL FN_SKPOVR ; routine FN_SKPOVR skips past the ',' ; all syntax has been checked and these ; things can be taken as read. JR SFA_LOOP ; back to SFA_LOOP while there are more ; arguments. ;;;$2981 SFA_MATCH: BIT 5,C ; test if numeric JR NZ,SFA_END ; to SFA_END if so as will be stacked ; by scanning INC HL ; point to start of string descriptor LD DE,(STKEND) ; set DE to STKEND CALL MOVE_FP ; routine MOVE_FP puts parameters on stack. EX DE,HL ; new free location to HL. LD (STKEND),HL ; use it to set STKEND system variable. ;;;$2991 SFA_END: POP DE ; discard POP DE ; pointers. XOR A ; clear carry flag. INC A ; and zero flag. RET ; return. ;------------------------- ; Stack variable component ;------------------------- ; This is called to evaluate a complex structure that has been found, in ; runtime, by LOOK_VARS in the variables area. ; In this case HL points to the initial letter, bits 7-5 ; of which indicate the type of variable. ; 010 - simple string, 110 - string array, 100 - array of numbers. ; ; It is called from CLASS_01 when assigning to a string or array including ; a slice. ; It is called from SCANNING to isolate the required part of the structure. ; ; An important part of the runtime process is to check that the number of ; dimensions of the variable match the number of subscripts supplied in the ; basic line. ; ; If checking syntax, ; the B register, which counts dimensions is set to zero (256) to allow ; the loop to continue till all subscripts are checked. While doing this it ; is reading dimension sizes from some arbitrary area of memory. Although ; these are meaningless it is of no concern as the limit is never checked by ; int-exp during syntax checking. ; ; The routine is also called from the syntax path of DIM command to check the ; syntax of both string and numeric arrays definitions except that bit 6 of C ; is reset so both are checked as numeric arrays. This ruse avoids a terminal ; slice being accepted as part of the DIM command. ; All that is being checked is that there are a valid set of comma-separated ; expressions before a terminal ')', although, as above, it will still go ; through the motions of checking dummy dimension sizes. ;;;$2996 STK_VAR: XOR A ; clear A LD B,A ; and B, the syntax dimension counter (256) BIT 7,C ; checking syntax ? JR NZ,SV_COUNT ; forward to SV_COUNT if so. ; runtime evaluation. BIT 7,(HL) ; will be reset if a simple string. JR NZ,SV_ARRAYS ; forward to SV_ARRAYS otherwise INC A ; set A to 1, simple string. ;;;$29A1 SV_SIMPLE: INC HL ; address length low LD C,(HL) ; place in C INC HL ; address length high LD B,(HL) ; place in B INC HL ; address start of string EX DE,HL ; DE = start now. CALL STK_STO_D ; routine STK_STO_D stacks string parameters ; DE start in variables area, ; BC length, A=1 simple string ; the only thing now is to consider if a slice is required. RST 18H ; GET_CHAR puts character at CH_ADD in A JP SV_SLICE_EX ; jump forward to SV_SLICE_EX to test for '(' ; the branch was here with string and numeric arrays in runtime. ;;;$29AE SV_ARRAYS: INC HL ; step past INC HL ; the total length INC HL ; to address Number of dimensions. LD B,(HL) ; transfer to B overwriting zero. BIT 6,C ; a numeric array ? JR Z,SV_PTR ; forward to SV_PTR with numeric arrays DEC B ; ignore the final element of a string array ; the fixed string size. JR Z,SV_SIMPLE ; back to SV_SIMPLE if result is zero as has ; been created with DIM a$(10) for instance ; and can be treated as a simple string. ; proceed with multi-dimensioned string arrays in runtime. EX DE,HL ; save pointer to dimensions in DE RST 18H ; GET_CHAR looks at the Basic line CP $28 ; is character '(' ? JR NZ,REPORT_3 ; to REPORT_3 if not ; 'Subscript wrong' EX DE,HL ; dimensions pointer to HL to synchronize ; with next instruction. ; runtime numeric arrays path rejoins here. ;;;$29C0 SV_PTR: EX DE,HL ; save dimension pointer in DE JR SV_COUNT ; forward to SV_COUNT with true no of dims ; in B. As there is no initial comma the ; loop is entered at the midpoint. ; the dimension counting loop which is entered at mid-point. ;;;$29C3 SV_COMMA: PUSH HL ; save counter RST 18H ; GET_CHAR POP HL ; pop counter CP $2C ; is character ',' ? JR Z,SV_LOOP ; forward to SV_LOOP if so ; in runtime the variable definition indicates a comma should appear here BIT 7,C ; checking syntax ? JR Z,REPORT_3 ; forward to REPORT_3 if not ; 'Subscript error' ; proceed if checking syntax of an array? BIT 6,C ; array of strings JR NZ,SV_CLOSE ; forward to SV_CLOSE if so ; an array of numbers. CP $29 ; is character ')' ? JR NZ,SV_RPT_C ; forward to SV_RPT_C if not ; 'Nonsense in basic' RST 20H ; NEXT_CHAR moves CH-ADD past the statement RET ; return -> ; the branch was here with an array of strings. ;;;$29D8 SV_CLOSE: CP $29 ; as above ')' could follow the expression JR Z,SV_DIM ; forward to SV_DIM if so CP $CC ; is it 'TO' ? JR NZ,SV_RPT_C ; to SV_RPT_C with anything else ; 'Nonsense in basic' ; now backtrack CH_ADD to set up for slicing routine. ; Note. in a basic line we can safely backtrack to a colour parameter. ;;;$29E0 SV_CH_ADD: RST 18H ; GET_CHAR DEC HL ; backtrack HL LD (CH_ADD),HL ; to set CH_ADD up for slicing routine JR SV_SLICE ; forward to SV_SLICE and make a return ; when all slicing complete. ; -> the mid-point entry point of the loop ;;;$29E7 SV_COUNT: LD HL,$0000 ; initialize data pointer to zero. ;;;$29EA SV_LOOP: PUSH HL ; save the data pointer. RST 20H ; NEXT_CHAR in Basic area points to an expression. POP HL ; restore the data pointer. LD A,C ; transfer name/type to A. CP $C0 ; is it 11000000 ? ; Note. the letter component is absent if ; syntax checking. JR NZ,SV_MULT ; forward to SV_MULT if not an array of ; strings. ; proceed to check string arrays during syntax. RST 18H ; GET_CHAR CP $29 ; ')' end of subscripts ? JR Z,SV_DIM ; forward to SV_DIM to consider further slice CP $CC ; is it 'TO' ? JR Z,SV_CH_ADD ; back to SV_CH_ADD to consider a slice. ; (no need to repeat GET_CHAR at SV_CH_ADD) ; if neither, then an expression is required so rejoin runtime loop ?? ; registers HL and DE only point to somewhere meaningful in runtime so ; comments apply to that situation. ;;;$29FB SV_MULT: PUSH BC ; save dimension number. PUSH HL ; push data pointer/rubbish. ; DE points to current dimension. CALL DE_DE_1 ; routine DE_DE_1 gets next dimension in DE ; and HL points to it. EX (SP),HL ; dim pointer to stack, data pointer to HL (*) EX DE,HL ; data pointer to DE, dim size to HL. CALL INT_EXP1 ; routine INT_EXP1 checks integer expression ; and gets result in BC in runtime. JR C,REPORT_3 ; to REPORT_3 if > HL ; 'Subscript out of range' DEC BC ; adjust returned result from 1-x to 0-x CALL GET_HL_DE ; routine GET_HL_DE multiplies data pointer by dimension size. ADD HL,BC ; add the integer returned by expression. POP DE ; pop the dimension pointer. *** POP BC ; pop dimension counter. DJNZ SV_COMMA ; back to SV_COMMA if more dimensions ; Note. during syntax checking, unless there ; are more than 256 subscripts, the branch ; back to SV_COMMA is always taken. BIT 7,C ; are we checking syntax ? ; then we've got a joker here. ;;;$2A12 SV_RPT_C: JR NZ,SL_RPT_C ; forward to SL_RPT_C if so ; 'Nonsense in Basic' ; more than 256 subscripts in Basic line. ; but in runtime the number of subscripts are at least the same as dims PUSH HL ; save data pointer. BIT 6,C ; is it a string array ? JR NZ,SV_ELEM ; forward to SV_ELEM if so. ; a runtime numeric array subscript. LD B,D ; register DE has advanced past all dimensions LD C,E ; and points to start of data in variable. ; transfer it to BC. RST 18H ; GET_CHAR checks Basic line CP $29 ; must be a ')' ? JR Z,SV_NUMBER ; skip to SV_NUMBER if so ; else more subscripts in Basic line than the variable definition. ;;;$2A20 REPORT_3: RST 08H ; ERROR_1 DEFB $02 ; Error Report: Subscript wrong ; continue if subscripts matched the numeric array. ;;;$2A22 SV_NUMBER: RST 20H ; NEXT_CHAR moves CH_ADD to next statement - finished parsing. POP HL ; pop the data pointer. LD DE,$0005 ; each numeric element is 5 bytes. CALL GET_HL_DE ; routine GET_HL_DE multiplies. ADD HL,BC ; now add to start of data in the variable. RET ; return with HL pointing at the numeric ; array subscript. -> ; the branch was here for string subscripts when the number of subscripts ; in the basic line was one less than in variable definition. ;;;$2A2C SV_ELEM: CALL DE_DE_1 ; routine DE_DE_1 gets final dimension ; the length of strings in this array. EX (SP),HL ; start pointer to stack, data pointer to HL. CALL GET_HL_DE ; routine GET_HL_DE multiplies by element size. POP BC ; the start of data pointer is added ADD HL,BC ; in - now points to location before. INC HL ; point to start of required string. LD B,D ; transfer the length (final dimension size) LD C,E ; from DE to BC. EX DE,HL ; put start in DE. CALL STK_ST_0 ; routine STK_ST_0 stores the string parameters ; with A=0 - a slice or subscript. ; now check that there were no more subscripts in the Basic line. RST 18H ; GET_CHAR CP $29 ; is it ')' ? JR Z,SV_DIM ; forward to SV_DIM to consider a separate ; subscript or/and a slice. CP $2C ; a comma is allowed if the final subscript ; is to be sliced e.g a$(2,3,4 TO 6). JR NZ,REPORT_3 ; to REPORT_3 with anything else ; 'Subscript error' ;;;$2A45 SV_SLICE: CALL SLICING ; routine SLICING slices the string. ; but a slice of a simple string can itself be sliced. ;;;$2A48 SV_DIM: RST 20H ; NEXT_CHAR ;;;$2A49 SV_SLICE_EX: CP $28 ; is character '(' ? JR Z,SV_SLICE ; loop back if so to SV_SLICE RES 6,(IY+$01) ; update FLAGS - Signal string result RET ; and return. ; The above section deals with the flexible syntax allowed. ; DIM a$(3,3,10) can be considered as two dimensional array of ten-character ; strings or a 3-dimensional array of characters. ; a$(1,1) will return a 10-character string as will a$(1,1,1 TO 10) ; a$(1,1,1) will return a single character. ; a$(1,1) (1 TO 6) is the same as a$(1,1,1 TO 6) ; A slice can itself be sliced ad infinitum ; b$ () () () () () () (2 TO 10) (2 TO 9) (3) is the same as b$(5) ;-------------------------- ; Handle slicing of strings ;-------------------------- ; The syntax of string slicing is very natural and it is as well to reflect ; on the permutations possible. ; a$() and a$( TO ) indicate the entire string although just a$ would do ; and would avoid coming here. ; h$(16) indicates the single character at position 16. ; a$( TO 32) indicates the first 32 characters. ; a$(257 TO) indicates all except the first 256 characters. ; a$(19000 TO 19999) indicates the thousand characters at position 19000. ; Also a$(9 TO 5) returns a null string not an error. ; This enables a$(2 TO) to return a null string if the passed string is ; of length zero or 1. ; A string expression in brackets can be sliced. e.g. (STR$ PI) (3 TO ) ; We arrived here from SCANNING with CH-ADD pointing to the initial '(' ; or from above. ;;;$2A52 SLICING: CALL SYNTAX_Z ; routine SYNTAX_Z CALL NZ,STK_FETCH ; routine STK_FETCH fetches parameters of ; string at runtime, start in DE, length ; in BC. This could be an array subscript. RST 20H ; NEXT_CHAR CP $29 ; is it ')' ? e.g. a$() JR Z,SL_STORE ; forward to SL_STORE to store entire string. PUSH DE ; else save start address of string XOR A ; clear accumulator to use as a running flag. PUSH AF ; and save on stack before any branching. PUSH BC ; save length of string to be sliced. LD DE,$0001 ; default the start point to position 1. RST 18H ; GET_CHAR POP HL ; pop length to HL as default end point ; and limit. CP $CC ; is it 'TO' ? e.g. a$( TO 10000) JR Z,SL_SECOND ; to SL_SECOND to evaluate second parameter. POP AF ; pop the running flag. CALL INT_EXP2 ; routine INT_EXP2 fetches first parameter. PUSH AF ; save flag (will be $FF if parameter>limit) LD D,B ; transfer the start LD E,C ; to DE overwriting 0001. PUSH HL ; save original length. RST 18H ; GET_CHAR POP HL ; pop the limit length. CP $CC ; is it 'TO' after a start ? JR Z,SL_SECOND ; to SL_SECOND to evaluate second parameter CP $29 ; is it ')' ? e.g. a$(365) ;;;$2A7A SL_RPT_C: JP NZ,REPORT_C ; jump to REPORT_C with anything else ; 'Nonsense in basic' LD H,D ; copy start LD L,E ; to end - just a one character slice. JR SL_DEFINE ; forward to SL_DEFINE. ;;;$2A81 SL_SECOND: PUSH HL ; save limit length. RST 20H ; NEXT_CHAR POP HL ; pop the length. CP $29 ; is character ')' ? e.g a$(7 TO ) JR Z,SL_DEFINE ; to SL_DEFINE using length as end point. POP AF ; else restore flag. CALL INT_EXP2 ; routine INT_EXP2 gets second expression. PUSH AF ; save the running flag. RST 18H ; GET_CHAR LD H,B ; transfer second parameter LD L,C ; to HL. e.g. a$(42 to 99) CP $29 ; is character a ')' ? JR NZ,SL_RPT_C ; to SL_RPT_C if not ; 'Nonsense in basic' ; we now have start in DE and an end in HL. ;;;$2A94 SL_DEFINE: POP AF ; pop the running flag. EX (SP),HL ; put end point on stack, start address to HL ADD HL,DE ; add address of string to the start point. DEC HL ; point to first character of slice. EX (SP),HL ; start address to stack, end point to HL (*) AND A ; prepare to subtract. SBC HL,DE ; subtract start point from end point. LD BC,$0000 ; default the length result to zero. JR C,SL_OVER ; forward to SL_OVER if start > end. INC HL ; increment the length for inclusive byte. AND A ; now test the running flag. JP M,REPORT_3 ; jump back to REPORT_3 if $FF. ; 'Subscript out of range' LD B,H ; transfer the length LD C,L ; to BC. ;;;$2AA8 SL_OVER: POP DE ; restore start address from machine stack *** RES 6,(IY+$01) ; update FLAGS - signal string result for ; syntax. ;;;$2AAD SL_STORE: CALL SYNTAX_Z ; routine SYNTAX_Z (UNSTACK_Z?) RET Z ; return if checking syntax. ; but continue to store the string in runtime. ; ------------------------------------ ; other than from above, this routine is called from STK_VAR to stack ; a known string array element. ; ------------------------------------ ;;;$2AB1 STK_ST_0: XOR A ; clear to signal a sliced string or element. ; ------------------------- ; this routine is called from CHR$, scrn$ etc. to store a simple string result. ; -------------------------- ;;;$2AB2 STK_STO_D: RES 6,(IY+$01) ; update FLAGS - signal string result. ; and continue to store parameters of string. ;---------------------------------------- ; Pass five registers to calculator stack ;---------------------------------------- ; This subroutine puts five registers on the calculator stack. ;;;$2AB6 STK_STORE: PUSH BC ; save two registers CALL TEST_5_SP ; routine TEST_5_SP checks room and puts 5 in BC. POP BC ; fetch the saved registers. LD HL,(STKEND) ; make HL point to first empty location STKEND LD (HL),A ; place the 5 registers. INC HL LD (HL),E INC HL LD (HL),D INC HL LD (HL),C INC HL LD (HL),B INC HL LD (STKEND),HL ; update system variable STKEND. RET ; and return. ;-------------------------------------------- ; Return result of evaluating next expression ;-------------------------------------------- ; This clever routine is used to check and evaluate an integer expression ; which is returned in BC, setting A to $FF, if greater than a limit supplied ; in HL. It is used to check array subscripts, parameters of a string slice ; and the arguments of the DIM command. In the latter case, the limit check ; is not required and H is set to $FF. When checking optional string slice ; parameters, it is entered at the second entry point so as not to disturb ; the running flag A, which may be $00 or $FF from a previous invocation. ;;;$2ACC INT_EXP1: XOR A ; set result flag to zero. ; -> The entry point is here if A is used as a running flag. ;;;$2ACD INT_EXP2: PUSH DE ; preserve DE register throughout. PUSH HL ; save the supplied limit. PUSH AF ; save the flag. CALL EXPT_1NUM ; routine EXPT_1NUM evaluates expression ; at CH_ADD returning if numeric result, ; with value on calculator stack. POP AF ; pop the flag. CALL SYNTAX_Z ; routine SYNTAX_Z JR Z,I_RESTORE ; forward to I_RESTORE if checking syntax so ; avoiding a comparison with supplied limit. PUSH AF ; save the flag. CALL FIND_INT2 ; routine FIND_INT2 fetches value from ; calculator stack to BC producing an error if too high. POP DE ; pop the flag to D. LD A,B ; test value for zero and reject OR C ; as arrays and strings begin at 1. SCF ; set carry flag. JR Z,I_CARRY ; forward to I_CARRY if zero. POP HL ; restore the limit. PUSH HL ; and save. AND A ; prepare to subtract. SBC HL,BC ; subtract value from limit. ;;;$2AE8 I_CARRY: LD A,D ; move flag to accumulator $00 or $FF. SBC A,$00 ; will set to $FF if carry set. ;;;$2AEB I_RESTORE: POP HL ; restore the limit. POP DE ; and DE register. RET ; return. ;------------------------ ; LD DE,(DE+1) Subroutine ;------------------------ ; This routine just loads the DE register with the contents of the two ; locations following the location addressed by DE. ; It is used to step along the 16-bit dimension sizes in array definitions. ; Note. Such code is made into subroutines to make programs easier to ; write and it would use less space to include the five instructions in-line. ; However, there are so many exchanges going on at the places this is invoked ; that to implement it in-line would make the code hard to follow. ; It probably had a zipier label though as the intention is to simplify the ; program. ;;;$2AEE DE_DE_1: EX DE,HL INC HL LD E,(HL) INC HL LD D,(HL) RET ;-------------------- ; HL=HL*DE Subroutine ;-------------------- ; This routine calls the mathematical routine to multiply HL by DE in runtime. ; It is called from STK_VAR and from DIM. In the latter case syntax is not ; being checked so the entry point could have been at the second CALL ; instruction to save a few clock-cycles. ;;;$2AF4 GET_HL_DE: CALL SYNTAX_Z ; routine SYNTAX_Z. RET Z ; return if checking syntax. CALL HL_HL_DE ; routine HL_HL_DE. JP C,REPORT_4 ; jump back to REPORT_4 if over 65535. RET ; else return with 16-bit result in HL. ;------------------- ; Handle LET command ;------------------- ; Sinclair Basic adheres to the ANSI-79 standard and a LET is required in ; assignments e.g. LET a = 1 : LET h$ = "hat" ; Long names may contain spaces but not colour controls (when assigned). ; a substring can appear to the left of the equals sign. ; An earlier mathematician Lewis Carroll may have been pleased that ; 10 LET Babies cannot manage crocodiles = Babies are illogical AND ; Nobody is despised who can manage a crocodile AND Illogical persons ; are despised ; does not give the 'Nonsense..' error if the three variables exist. ; I digress. ;;;$2AFF LET: LD HL,(DEST) ; fetch system variable DEST to HL. BIT 1,(IY+$37) ; test FLAGX - handling a new variable ? JR Z,L_EXISTS ; forward to L_EXISTS if not. ; continue for a new variable. DEST points to start in Basic line. ; from the CLASS routines. LD BC,$0005 ; assume numeric and assign an initial 5 bytes ;;;$2B0B L_EACH_CH: INC BC ; increase byte count for each relevant ; character ;;;$2B0C L_NO_SP: INC HL ; increase pointer. LD A,(HL) ; fetch character. CP $20 ; is it a space ? JR Z,L_NO_SP ; back to L_NO_SP is so. JR NC,L_TEST_CH ; forward to L_TEST_CH if higher. CP $10 ; is it $00 - $0F ? JR C,L_SPACES ; forward to L_SPACES if so. CP $16 ; is it $16 - $1F ? JR NC,L_SPACES ; forward to L_SPACES if so. ; it was $10 - $15 so step over a colour code. INC HL ; increase pointer. JR L_NO_SP ; loop back to L_NO_SP. ; the branch was here if higher than space ;;;$2B1F L_TEST_CH: CALL ALPHANUM ; routine ALPHANUM sets carry if alphanumeric JR C,L_EACH_CH ; loop back to L_EACH_CH for more if so. CP $24 ; is it '$' ? JP Z,L_NEW ; jump forward if so, to L_NEW ; with a new string. ;;;$2B29 L_SPACES: LD A,C ; save length lo in A. LD HL,(E_LINE) ; fetch E_LINE to HL. DEC HL ; point to location before, the variables end-marker. CALL MAKE_ROOM ; routine MAKE_ROOM creates BC spaces ; for name and numeric value. INC HL ; advance to first new location. INC HL ; then to second. EX DE,HL ; set DE to second location. PUSH DE ; save this pointer. LD HL,(DEST) ; reload HL with DEST. DEC DE ; point to first. SUB $06 ; subtract six from length_lo. LD B,A ; save count in B. JR Z,L_SINGLE ; forward to L_SINGLE if it was just one character. ; HL points to start of variable name after 'LET' in Basic line. ;;;$2B3E L_CHAR: INC HL ; increase pointer. LD A,(HL) ; pick up character. CP $21 ; is it space or higher ? JR C,L_CHAR ; back to L_CHAR with space and less. OR $20 ; make variable lower-case. INC DE ; increase destination pointer. LD (DE),A ; and load to edit line. DJNZ L_CHAR ; loop back to L_CHAR until B is zero. OR $80 ; invert the last character. LD (DE),A ; and overwrite that in edit line. ; now consider first character which has bit 6 set LD A,$C0 ; set A 11000000 is xor mask for a long name. ; %101 is xor/or result ; single character numerics rejoin here with %00000000 in mask. ; %011 will be xor/or result ;;;$2B4F L_SINGLE: LD HL,(DEST) ; fetch DEST - HL addresses first character. XOR (HL) ; apply variable type indicator mask (above). OR $20 ; make lowercase - set bit 5. POP HL ; restore pointer to 2nd character. CALL L_FIRST ; routine L_FIRST puts A in first character. ; and returns with HL holding ; new E_LINE-1 the $80 vars end-marker. ;;;$2B59 L_NUMERIC: PUSH HL ; save the pointer. ; the value of variable is deleted but remains after calculator stack. RST 28H ;; FP_CALC DEFB $02 ;;DELETE ; delete variable value DEFB $38 ;;END_CALC ; DE (STKEND) points to start of value. POP HL ; restore the pointer. LD BC,$0005 ; start of number is five bytes before. AND A ; prepare for true subtraction. SBC HL,BC ; HL points to start of value. JR L_ENTER ; forward to L_ENTER ==> ; the jump was to here if the variable already existed. ;;;$2B66 L_EXISTS: BIT 6,(IY+$01) ; test FLAGS - numeric or string result ? JR Z,L_DELETE ; skip forward to L_DELETE -*-> ; if string result. ; A numeric variable could be simple or an array element. ; They are treated the same and the old value is overwritten. LD DE,$0006 ; six bytes forward points to loc past value. ADD HL,DE ; add to start of number. JR L_NUMERIC ; back to L_NUMERIC to overwrite value. ; -*-> the branch was here if a string existed. ;;;$2B72 L_DELETE: LD HL,(DEST) ; fetch DEST to HL. ; (still set from first instruction) LD BC,(STRLEN) ; fetch STRLEN to BC. BIT 0,(IY+$37) ; test FLAGX - handling a complete simple string ? JR NZ,L_ADD ; forward to L_ADD if so. ; must be a string array or a slice in workspace. ; Note. LET a$(3 TO 6) = h$ will assign "hat " if h$ = "hat" ; and "hats" if h$ = "hatstand". ; This is known as Procrustian lengthening and shortening after a ; character Procrustes in Greek legend who made travellers sleep in his bed, ; cutting off their feet or stretching them so they fitted the bed perfectly. ; The bloke was hatstand and slain by Theseus. LD A,B ; test if length OR C ; is zero and RET Z ; return if so. PUSH HL ; save pointer to start. RST 30H ; BC_SPACES creates room. PUSH DE ; save pointer to first new location. PUSH BC ; and length (*) LD D,H ; set DE to point to last location. LD E,L INC HL ; set HL to next location. LD (HL),$20 ; place a space there. LDDR ; copy bytes filling with spaces. PUSH HL ; save pointer to start. CALL STK_FETCH ; routine STK_FETCH start to DE, length to BC. POP HL ; restore the pointer. EX (SP),HL ; (*) length to HL, pointer to stack. AND A ; prepare for true subtraction. SBC HL,BC ; subtract old length from new. ADD HL,BC ; and add back. JR NC,L_LENGTH ; forward if it fits to L_LENGTH. LD B,H ; otherwise set LD C,L ; length to old length. ; "hatstand" becomes "hats" ;;;$2B9B L_LENGTH: EX (SP),HL ; (*) length to stack, pointer to HL. EX DE,HL ; pointer to DE, start of string to HL. LD A,B ; is the length zero ? OR C ; JR Z,L_IN_W_S ; forward to L_IN_W_S if so ; leaving prepared spaces. LDIR ; else copy bytes overwriting some spaces. ;;;$2BA3 L_IN_W_S: POP BC ; pop the new length. (*) POP DE ; pop pointer to new area. POP HL ; pop pointer to variable in assignment. ; and continue copying from workspace ; to variables area. ; ==> branch here from L_NUMERIC ;;;$2BA6 L_ENTER: EX DE,HL ; exchange pointers HL=STKEND DE=end of vars. LD A,B ; test the length OR C ; and make a RET Z ; return if zero (strings only). PUSH DE ; save start of destination. LDIR ; copy bytes. POP HL ; address the start. RET ; and return. ; the branch was here from L_DELETE if an existing simple string. ; register HL addresses start of string in variables area. ;;;$2BAF L_ADD: DEC HL ; point to high byte of length. DEC HL ; to low byte. DEC HL ; to letter. LD A,(HL) ; fetch masked letter to A. PUSH HL ; save the pointer on stack. PUSH BC ; save new length. CALL L_STRING ; routine L_STRING adds new string at end ; of variables area. ; if no room we still have old one. POP BC ; restore length. POP HL ; restore start. INC BC ; increase INC BC ; length by three INC BC ; to include character and length bytes. JP RECLAIM_2 ; jump to indirect exit via RECLAIM_2 ; deleting old version and adjusting pointers. ; the jump was here with a new string variable. ;;;$2BC0 L_NEW: LD A,$DF ; indicator mask %11011111 for ; %010xxxxx will be result LD HL,(DEST) ; address DEST first character. AND (HL) ; combine mask with character. ;;;$2BC6 L_STRING: PUSH AF ; save first character and mask. CALL STK_FETCH ; routine STK_FETCH fetches parameters of the string. EX DE,HL ; transfer start to HL. ADD HL,BC ; add to length. PUSH BC ; save the length. DEC HL ; point to end of string. LD (DEST),HL ; save pointer in DEST. ; (updated by POINTERS if in workspace) INC BC ; extra byte for letter. INC BC ; two bytes INC BC ; for the length of string. LD HL,(E_LINE) ; address E_LINE. DEC HL ; now end of VARS area. CALL MAKE_ROOM ; routine MAKE_ROOM makes room for string. ; updating pointers including DEST. LD HL,(DEST) ; pick up pointer to end of string from DEST. POP BC ; restore length from stack. PUSH BC ; and save again on stack. INC BC ; add a byte. LDDR ; copy bytes from end to start. EX DE,HL ; HL addresses length low INC HL ; increase to address high byte POP BC ; restore length to BC LD (HL),B ; insert high byte DEC HL ; address low byte location LD (HL),C ; insert that byte POP AF ; restore character and mask ;;;$2BEA L_FIRST: DEC HL ; address variable name LD (HL),A ; and insert character. LD HL,(E_LINE) ; load HL with E_LINE. DEC HL ; now end of VARS area. RET ; return ;------------------------------------- ; Get last value from calculator stack ;------------------------------------- ;;;$2BF1 STK_FETCH: LD HL,(STKEND) ; STKEND DEC HL LD B,(HL) DEC HL LD C,(HL) DEC HL LD D,(HL) DEC HL LD E,(HL) DEC HL LD A,(HL) LD (STKEND),HL ; STKEND RET ;------------------- ; Handle DIM command ;------------------- ; e.g. DIM a(2,3,4,7): DIM a$(32) : DIM b$(300,2,768) : DIM c$(20000) ; the only limit to dimensions is memory so, for example, ; DIM a(2,2,2,2,2,2,2,2,2,2,2,2,2) is possible and creates a multi- ; dimensional array of zeros. String arrays are initialized to spaces. ; It is not possible to erase an array, but it can be re-dimensioned to ; a minimal size of 1, after use, to free up memory. ;;;$2C02 DIM: CALL LOOK_VARS ; routine LOOK_VARS ;;;$2C05 D_RPORT_C: JP NZ,REPORT_C ; jump to REPORT_C if a long-name variable. ; DIM lottery numbers(49) doesn't work. CALL SYNTAX_Z ; routine SYNTAX_Z JR NZ,D_RUN ; forward to D_RUN in runtime. RES 6,C ; signal 'numeric' array even if string as ; this simplifies the syntax checking. CALL STK_VAR ; routine STK_VAR checks syntax. CALL CHECK_END ; routine CHECK_END performs early exit -> ; the branch was here in runtime. ;;;$2C15 D_RUN: JR C,D_LETTER ; skip to D_LETTER if variable did not exist. ; else reclaim the old one. PUSH BC ; save type in C. CALL NEXT_ONE ; routine NEXT_ONE find following variable ; or position of $80 end-marker. CALL RECLAIM_2 ; routine RECLAIM_2 reclaims the space between. POP BC ; pop the type. ;;;$2C1F D_LETTER: SET 7,C ; signal array. LD B,$00 ; initialize dimensions to zero and PUSH BC ; save with the type. LD HL,$0001 ; make elements one character presuming string BIT 6,C ; is it a string ? JR NZ,D_SIZE ; forward to D_SIZE if so. LD L,$05 ; make elements 5 bytes as is numeric. ;;;$2C2D D_SIZE: EX DE,HL ; save the element size in DE. ; now enter a loop to parse each of the integers in the list. ;;;$2C2E D_NO_LOOP: RST 20H ; NEXT_CHAR LD H,$FF ; disable limit check by setting HL high CALL INT_EXP1 ; routine INT_EXP1 JP C,REPORT_3 ; to REPORT_3 if > 65280 and then some ; 'Subscript out of range' POP HL ; pop dimension counter, array type PUSH BC ; save dimension size *** INC H ; increment the dimension counter PUSH HL ; save the dimension counter LD H,B ; transfer size LD L,C ; to HL CALL GET_HL_DE ; routine GET_HL_DE multiplies dimension by ; running total of size required initially ; 1 or 5. EX DE,HL ; save running total in DE RST 18H ; GET_CHAR CP $2C ; is it ',' ? JR Z,D_NO_LOOP ; loop back to D_NO_LOOP until all dimensions ; have been considered ; when loop complete continue. CP $29 ; is it ')' ? JR NZ,D_RPORT_C ; to D_RPORT_C with anything else ; 'Nonsense in basic' RST 20H ; NEXT_CHAR advances to next statement/CR POP BC ; pop dimension counter/type LD A,C ; type to A ; now calculate space required for array variable LD L,B ; dimensions to L since these require 16 bits ; then this value will be doubled LD H,$00 ; set high byte to zero ; another four bytes are required for letter(1), total length(2), number of ; dimensions(1) but since we have yet to double allow for two INC HL ; increment INC HL ; increment ADD HL,HL ; now double giving 4 + dimensions * 2 ADD HL,DE ; add to space required for array contents JP C,REPORT_4 ; to REPORT_4 if > 65535 ; 'Out of memory' PUSH DE ; save data space PUSH BC ; save dimensions/type PUSH HL ; save total space LD B,H ; total space LD C,L ; to BC LD HL,(E_LINE) ; address E_LINE - first location after variables area DEC HL ; point to location before - the $80 end-marker CALL MAKE_ROOM ; routine MAKE_ROOM creates the space if memory is available. INC HL ; point to first new location and LD (HL),A ; store letter/type POP BC ; pop total space DEC BC ; exclude name DEC BC ; exclude the 16-bit DEC BC ; counter itself INC HL ; point to next location the 16-bit counter LD (HL),C ; insert low byte INC HL ; address next LD (HL),B ; insert high byte POP BC ; pop the number of dimensions. LD A,B ; dimensions to A INC HL ; address next LD (HL),A ; and insert "No. of dims" LD H,D ; transfer DE space + 1 from MAKE_ROOM LD L,E ; to HL DEC DE ; set DE to next location down. LD (HL),$00 ; presume numeric and insert a zero BIT 6,C ; test bit 6 of C. numeric or string ? JR Z,DIM_CLEAR ; skip to DIM_CLEAR if numeric LD (HL),$20 ; place a space character in HL ;;;$2C7C DIM_CLEAR: POP BC ; pop the data length LDDR ; LDDR sets to zeros or spaces ; The number of dimensions is still in A. ; A loop is now entered to insert the size of each dimension that was pushed ; during the D_NO_LOOP working downwards from position before start of data. ;;;$2C7F DIM_SIZES: POP BC ; pop a dimension size *** LD (HL),B ; insert high byte at position DEC HL ; next location down LD (HL),C ; insert low byte DEC HL ; next location down DEC A ; decrement dimension counter JR NZ,DIM_SIZES ; back to DIM_SIZES until all done. RET ; return. ;------------------------------ ; Check whether digit or letter ;------------------------------ ; This routine checks that the character in A is alphanumeric ; returning with carry set if so. ;;;$2C88 ALPHANUM: CALL NUMERIC ; routine NUMERIC will reset carry if so. CCF ; Complement Carry Flag RET C ; Return if numeric else continue into next routine. ; This routine checks that the character in A is alphabetic ;;;$2C8D ALPHA: CP $41 ; less than 'A' ? CCF ; Complement Carry Flag RET NC ; return if so CP $5B ; less than 'Z'+1 ? RET C ; is within first range CP $61 ; less than 'a' ? CCF ; Complement Carry Flag RET NC ; return if so. CP $7B ; less than 'z'+1 ? RET ; carry set if within a-z. ;-------------------------- ; Decimal to floating point ;-------------------------- ; This routine finds the floating point number represented by an expression ; beginning with BIN, '.' or a digit. ; Note that BIN need not have any '0's or '1's after it. ; BIN is really just a notational symbol and not a function. ;;;$2C9B DEC_TO_FP: CP $C4 ; 'BIN' token ? JR NZ,NOT_BIN ; to NOT_BIN if not LD DE,$0000 ; initialize 16 bit buffer register. ;;;$2CA2 BIN_DIGIT: RST 20H ; NEXT_CHAR SUB $31 ; '1' ADC A,$00 ; will be zero if '1' or '0' ; carry will be set if was '0' JR NZ,BIN_END ; forward to BIN_END if result not zero EX DE,HL ; buffer to HL CCF ; Carry now set if originally '1' ADC HL,HL ; shift the carry into HL JP C,REPORT_6 ; to REPORT_6 if overflow - too many digits ; after first '1'. There can be an unlimited ; number of leading zeros. ; 'Number too big' - raise an error EX DE,HL ; save the buffer JR BIN_DIGIT ; back to BIN_DIGIT for more digits ;;;$2CB3 BIN_END: LD B,D ; transfer 16 bit buffer LD C,E ; to BC register pair. JP STACK_BC ; to STACK_BC to put on calculator stack ; continue here with .1, 42, 3.14, 5., 2.3 E -4 ;;;$2CB8 NOT_BIN: CP $2E ; '.' - leading decimal point ? JR Z,DECIMAL ; skip to DECIMAL if so. CALL INT_TO_FP ; routine INT_TO_FP to evaluate all digits ; This number 'x' is placed on stack. CP $2E ; '.' - mid decimal point ? JR NZ,E_FORMAT ; to E_FORMAT if not to consider that format RST 20H ; NEXT_CHAR CALL NUMERIC ; routine NUMERIC returns carry reset if 0-9 JR C,E_FORMAT ; to E_FORMAT if not a digit e.g. '1.' JR DEC_STO_1 ; to DEC_STO_1 to add the decimal part to 'x' ; a leading decimal point has been found in a number. ;;;$2CCB DECIMAL: RST 20H ; NEXT_CHAR CALL NUMERIC ; routine NUMERIC will reset carry if digit ;;;$2CCF DEC_RPT_C: JP C,REPORT_C ; to REPORT_C if just a '.' ; raise 'Nonsense in Basic' ; since there is no leading zero put one on the calculator stack. RST 28H ;; FP_CALC DEFB $A0 ;;STK_ZERO ; 0. DEFB $38 ;;END_CALC ; If rejoining from earlier there will be a value 'x' on stack. ; If continuing from above the value zero. ; Now store 1 in mem-0. ; Note. At each pass of the digit loop this will be divided by ten. ;;;$2CD5 DEC_STO_1: RST 28H ;; FP_CALC DEFB $A1 ;;STK_ONE ;x or 0,1. DEFB $C0 ;;st-mem-0 ;x or 0,1. DEFB $02 ;;DELETE ;x or 0. DEFB $38 ;;END_CALC ;;;$2CDA NXT_DGT_1: RST 18H ; GET_CHAR CALL STK_DIGIT ; routine STK_DIGIT stacks single digit 'd' JR C,E_FORMAT ; exit to E_FORMAT when digits exhausted > RST 28H ;; FP_CALC ;x or 0,d. first pass. DEFB $E0 ;;get-mem-0 ;x or 0,d,1. DEFB $A4 ;;STK_TEN ;x or 0,d,1,10. DEFB $05 ;;DIVISION ;x or 0,d,1/10. DEFB $C0 ;;st-mem-0 ;x or 0,d,1/10. DEFB $04 ;;MULTIPLY ;x or 0,d/10. DEFB $0F ;;ADDITION ;x or 0 + d/10. DEFB $38 ;;END_CALC last value. RST 20H ; NEXT_CHAR moves to next character JR NXT_DGT_1 ; back to NXT_DGT_1 ; although only the first pass is shown it can be seen that at each pass ; the new less significant digit is multiplied by an increasingly smaller ; factor (1/100, 1/1000, 1/10000 ... ) before being added to the previous ; last value to form a new last value. ; Finally see if an exponent has been input. ;;;$2CEB E_FORMAT: CP $45 ; is character 'E' ? JR Z,SIGN_FLAG ; to SIGN_FLAG if so CP $65 ; 'e' is acceptable as well. RET NZ ; return as no exponent. ;;;$2CF2 SIGN_FLAG: LD B,$FF ; initialize temporary sign byte to $FF RST 20H ; NEXT_CHAR CP $2B ; is character '+' ? JR Z,SIGN_DONE ; to SIGN_DONE CP $2D ; is character '-' ? JR NZ,ST_E_PART ; to ST_E_PART as no sign INC B ; set sign to zero ; now consider digits of exponent. ; Note. incidentally this is the only occasion in Spectrum Basic when an ; expression may not be used when a number is expected. ;;;$2CFE SIGN_DONE: RST 20H ; NEXT_CHAR ;;;$2CFF ST_E_PART: CALL NUMERIC ; routine NUMERIC JR C,DEC_RPT_C ; to DEC_RPT_C if not ; raise 'Nonsense in Basic'. PUSH BC ; save sign (in B) CALL INT_TO_FP ; routine INT_TO_FP places exponent on stack CALL FP_TO_A ; routine FP_TO_A transfers it to A POP BC ; restore sign JP C,REPORT_6 ; to REPORT_6 if overflow (over 255) ; raise 'Number too big'. AND A ; set flags JP M,REPORT_6 ; to REPORT_6 if over '127'. ; raise 'Number too big'. ; 127 is still way too high and it is ; impossible to enter an exponent greater ; than 39 from the keyboard. The error gets ; raised later in E_TO_FP so two different ; error messages depending how high A is. INC B ; $FF to $00 or $00 to $01 - expendable now. JR Z,E_FP_JUMP ; forward to E_FP_JUMP if exponent positive NEG ; Negate the exponent. ;;;$2D18 E_FP_JUMP: JP E_TO_FP ; jump forward to E_TO_FP to assign to ; last value x on stack x * 10 to power A ; a relative jump would have done. ;---------------------- ; Check for valid digit ;---------------------- ; This routine checks that the ascii character in A is numeric ; returning with carry reset if so. ;;;$2D1B NUMERIC: CP $30 ; '0' RET C ; return if less than zero character. CP $3A ; The upper test is '9' CCF ; Complement Carry Flag RET ; Return - carry clear if character '0' - '9' ;------------ ; Stack Digit ;------------ ; This subroutine is called from INT_TO_FP and DEC_TO_FP to stack a digit ; on the calculator stack. ;;;$2D22 STK_DIGIT: CALL NUMERIC ; routine NUMERIC RET C ; return if not numeric character SUB $30 ; convert from ascii to digit ;------------------ ; Stack accumulator ;------------------ ;;;$2D28 STACK_A: LD C,A ; transfer to C LD B,$00 ; and make B zero ;----------------------- ; Stack BC register pair ;----------------------- ;;;$2D2B STACK_BC: LD IY,ERR_NR ; re-initialize ERR_NR XOR A ; clear to signal small integer LD E,A ; place in E for sign LD D,C ; LSB to D LD C,B ; MSB to C LD B,A ; last byte not used CALL STK_STORE ; routine STK_STORE RST 28H ;; FP_CALC DEFB $38 ;;END_CALC make HL = STKEND-5 AND A ; clear carry RET ; before returning ;-------------------------- ; Integer to floating point ;-------------------------- ; This routine places one or more digits found in a basic line ; on the calculator stack multiplying the previous value by ten each time ; before adding in the new digit to form a last value on calculator stack. ;;;$2D3B INT_TO_FP: PUSH AF ; save first character RST 28H ;; FP_CALC DEFB $A0 ;;STK_ZERO ; v=0. initial value DEFB $38 ;;END_CALC POP AF ; fetch first character back. ;;;$2D40 NXT_DGT_2: CALL STK_DIGIT ; routine STK_DIGIT puts 0-9 on stack RET C ; will return when character is not numeric > RST 28H ;; FP_CALC ; v, d. DEFB $01 ;;EXCHANGE ; d, v. DEFB $A4 ;;STK_TEN ; d, v, 10. DEFB $04 ;;MULTIPLY ; d, v*10. DEFB $0F ;;ADDITION ; d + v*10 = newvalue DEFB $38 ;;END_CALC ; v. CALL CH_ADD_1 ; routine CH_ADD_1 get next character JR NXT_DGT_2 ; back to NXT_DGT_2 to process as a digit ;********************************* ;** Part 9. ARITHMETIC ROUTINES ** ;********************************* ;--------------------------- ; E-format to floating point ;--------------------------- ; This subroutine is used by the PRINT_FP routine and the decimal to FP ; routines to stack a number expressed in exponent format. ; Note. Though not used by the ROM as such, it has also been set up as ; a unary calculator literal but this will not work as the accumulator ; is not available from within the calculator. ; on entry there is a value x on the calculator stack and an exponent of ten ; in A. The required value is x + 10 ^ A ;;;$2D4F E_TO_FP: RLCA ; this will set the x. RRCA ; carry if bit 7 is set JR NC,E_SAVE ; to E_SAVE if positive. CPL ; make negative positive INC A ; without altering carry. ;;;$2D55 E_SAVE: PUSH AF ; save positive exp and sign in carry LD HL,MEM_0 ; address MEM_0 CALL FP_0_1 ; routine FP_0_1 ; places an integer zero, if no carry, ; else a one in mem-0 as a sign flag RST 28H ;; FP_CALC DEFB $A4 ;;STK_TEN x, 10. DEFB $38 ;;END_CALC POP AF ; pop the exponent. ; now enter a loop ;;;$2D60 E_LOOP: SRL A ; 0>76543210>C JR NC,E_TST_END ; forward to E_TST_END if no bit PUSH AF ; save shifted exponent. RST 28H ;; FP_CALC DEFB $C1 ;;st-mem-1 x, 10. DEFB $E0 ;;get-mem-0 x, 10, (0/1). DEFB $00 ;;JUMP_TRUE DEFB $04 ;;to E_DIVSN DEFB $04 ;;MULTIPLY x*10. DEFB $33 ;;jump DEFB $02 ;;to E_FETCH ;;;$2D6D E_DIVSN: DEFB $05 ;;DIVISION x/10. ;;;$2D6E E_FETCH: DEFB $E1 ;;get-mem-1 x/10 or x*10, 10. DEFB $38 ;;END_CALC new x, 10. POP AF ; restore shifted exponent ; the loop branched to here with no carry ;;;$2D71 E_TST_END: JR Z,E_END ; forward to E_END if A emptied of bits PUSH AF ; re-save shifted exponent RST 28H ;; FP_CALC DEFB $31 ;;DUPLICATE new x, 10, 10. DEFB $04 ;;MULTIPLY new x, 100. DEFB $38 ;;END_CALC POP AF ; restore shifted exponent JR E_LOOP ; back to E_LOOP until all bits done. ; although only the first pass is shown it can be seen that for each set bit ; representing a power of two, x is multiplied or divided by the ; corresponding power of ten. ;;;$2D7B E_END: RST 28H ;; FP_CALC final x, factor. DEFB $02 ;;DELETE final x. DEFB $38 ;;END_CALC x. RET ; return ;-------------- ; Fetch integer ;-------------- ; This routine is called by the mathematical routines - FP_TO_BC, PRINT_FP, ; MULTIPLY, RE_STACK and NEGATE to fetch an integer from address HL. ; HL points to the stack or a location in MEM and no deletion occurs. ; If the number is negative then a similar process to that used in INT_STORE ; is used to restore the twos complement number to normal in DE and a sign ; in C. ;;;$2D7F INT_FETCH: INC HL ; skip zero indicator. LD C,(HL) ; fetch sign to C INC HL ; address low byte LD A,(HL) ; fetch to A XOR C ; two's complement SUB C LD E,A ; place in E INC HL ; address high byte LD A,(HL) ; fetch to A ADC A,C ; two's complement XOR C LD D,A ; place in D RET ; return ;------------------------- ; Store a positive integer ;------------------------- ; This entry point is not used in this ROM but would ; store any integer as positive. ;;;$2D8C P_INT_STO: LD C,$00 ; make sign byte positive and continue ;-------------- ; Store integer ;-------------- ; this routine stores an integer in DE at address HL. ; It is called from MULTIPLY, TRUNCATE, NEGATE and SGN. ; The sign byte $00 +ve or $FF -ve is in C. ; If negative, the number is stored in 2's complement form so that it is ; ready to be added. ;;;$2D8E INT_STORE: PUSH HL ; preserve HL LD (HL),$00 ; first byte zero shows integer not exponent INC HL LD (HL),C ; then store the sign byte INC HL ; e.g. +1 -1 LD A,E ; fetch low byte 00000001 00000001 XOR C ; xor sign 00000000 or 11111111 ; gives 00000001 or 11111110 SUB C ; sub sign 00000000 or 11111111 ; gives 00000001>0 or 11111111>C LD (HL),A ; store 2's complement. INC HL LD A,D ; high byte 00000000 00000000 ADC A,C ; sign 00000000<0 11111111 65535, overflow PUSH AF ; save the value and flags DEC B ; and test that INC B ; the high byte is zero. JR Z,FP_A_END ; forward FP_A_END if zero ; else there has been 8-bit overflow POP AF ; retrieve the value SCF ; set carry flag to show overflow RET ; and return. ;;;$2DE1 FP_A_END: POP AF ; restore value and success flag and RET ; return. ;------------------------------ ; Print a floating point number ;------------------------------ ; Not a trivial task. ; Begin by considering whether to print a leading sign for negative numbers. ;;;$2DE3 PRINT_FP: RST 28H ;; FP_CALC DEFB $31 ;;DUPLICATE DEFB $36 ;;LESS_0 DEFB $00 ;;JUMP_TRUE DEFB $0B ;;to PF_NEGTVE DEFB $31 ;;DUPLICATE DEFB $37 ;;GREATER_0 DEFB $00 ;;JUMP_TRUE DEFB $0D ;;to PF_POSTVE ; must be zero itself DEFB $02 ;;DELETE DEFB $38 ;;END_CALC LD A,$30 ; prepare the character '0' RST 10H ; PRINT_A RET ; return. -> ;;;$2DF2 PF_NEGTVE: DEFB $2A ;;ABS DEFB $38 ;;END_CALC LD A,$2D ; the character '-' RST 10H ; PRINT_A ; and continue to print the now positive number. RST 28H ;; FP_CALC ;;;$2DF8 PF_POSTVE: DEFB $A0 ;;STK_ZERO x,0. begin by DEFB $C3 ;;st-mem-3 x,0. clearing a temporary DEFB $C4 ;;st-mem-4 x,0. output buffer to DEFB $C5 ;;st-mem-5 x,0. fifteen zeros. DEFB $02 ;;DELETE x. DEFB $38 ;;END_CALC x. EXX ; in case called from 'STR$' then save the PUSH HL ; pointer to whatever comes after EXX ; STR$ as H'L' will be used. ; now enter a loop? ;;;$2E01 PF_LOOP: RST 28H ;; FP_CALC DEFB $31 ;;DUPLICATE x,x. DEFB $27 ;;INT x,int x. DEFB $C2 ;;st-mem-2 x,int x. DEFB $03 ;;SUBTRACT x-int x. fractional part. DEFB $E2 ;;get-mem-2 x-int x, int x. DEFB $01 ;;EXCHANGE int x, x-int x. DEFB $C2 ;;st-mem-2 int x, x-int x. DEFB $02 ;;DELETE int x. DEFB $38 ;;END_CALC int x. ; ; mem-2 holds the fractional part. ; HL points to last value int x LD A,(HL) ; fetch exponent of int x. AND A ; test JR NZ,PF_LARGE ; forward to PF_LARGE if a large integer ; > 65535 ; continue with small positive integer components in range 0 - 65535 ; if original number was say .999 then this integer component is zero. CALL INT_FETCH ; routine INT_FETCH gets x in DE ; (but x is not deleted) LD B,$10 ; set B, bit counter, to 16d LD A,D ; test if AND A ; high byte is zero JR NZ,PF_SAVE ; forward to PF_SAVE if 16-bit integer. ; and continue with integer in range 0 - 255. OR E ; test the low byte for zero ; i.e. originally just point something or other. JR Z,PF_SMALL ; forward if so to PF_SMALL LD D,E ; transfer E to D LD B,$08 ; and reduce the bit counter to 8. ;;;$2E1E PF_SAVE: PUSH DE ; save the part before decimal point. EXX POP DE ; and pop in into D'E' EXX JR PF_BITS ; forward to PF_BITS ; the branch was here when 'int x' was found to be zero as in say 0.5. ; The zero has been fetched from the calculator stack but not deleted and ; this should occur now. This omission leaves the stack unbalanced and while ; that causes no problems with a simple PRINT statement, it will if STR$ is ; being used in an expression e.g. "2" + STR$ 0.5 gives the result "0.5" ; instead of the expected result "20.5". ; credit Tony Stratton, 1982. ; A DEFB 02 delete is required immediately on using the calculator. ;;;$2E24 PF_SMALL: RST 28H ;; FP_CALC int x = 0. L2E25: DEFB $E2 ;;get-mem-2 int x = 0, x-int x. DEFB $38 ;;END_CALC LD A,(HL) ; fetch exponent of positive fractional number SUB $7E ; subtract CALL LOG_2_A ; routine LOG_2_A calculates leading digits. LD D,A ; transfer count to D LD A,(MEM_5_1) ; fetch total digits - MEM_5 2nd byte SUB D LD (MEM_5_1),A ; store MEM_5 2nd byte LD A,D CALL E_TO_FP ; routine E_TO_FP RST 28H ;; FP_CALC DEFB $31 ;;DUPLICATE DEFB $27 ;;INT DEFB $C1 ;;st-mem-1 DEFB $03 ;;SUBTRACT DEFB $E1 ;;get-mem-1 DEFB $38 ;;END_CALC CALL FP_TO_A ; routine FP_TO_A PUSH HL ; save HL LD (MEM_3),A ; MEM_3 1st byte DEC A RLA SBC A,A INC A LD HL,MEM_5_0 ; address MEM_5 leading digit counter LD (HL),A ; store counter INC HL ; address MEM_5 2nd byte - total digits ADD A,(HL) ; add counter to contents LD (HL),A ; and store updated value POP HL ; restore HL JP PF_FRACTN ; jump forward to PF_FRACTN ; Note. while it would be pedantic to comment on every occasion a JP ; instruction could be replaced with a JR instruction, this applies to the ; above, which is useful if you wish to correct the unbalanced stack error ; by inserting a 'DEFB 02 delete' at L2E25, and maintain main addresses. ; the branch was here with a large positive integer > 65535 e.g. 123456789 ; the accumulator holds the exponent. ;;;$2E56 PF_LARGE: SUB $80 ; make exponent positive CP $1C ; compare to 28 JR C,PF_MEDIUM ; to PF_MEDIUM if integer <= 2^27 CALL LOG_2_A ; routine LOG_2_A SUB $07 LD B,A LD HL,MEM_5_1 ; address MEM_5_1 the leading digits counter. ADD A,(HL) ; add A to contents LD (HL),A ; store updated value. LD A,B NEG ; negate CALL E_TO_FP ; routine E_TO_FP JR PF_LOOP ; back to PF_LOOP ;;;$2E6F PF_MEDIUM: EX DE,HL CALL FETCH_TWO ; routine FETCH_TWO EXX SET 7,D LD A,L EXX SUB $80 LD B,A ; the branch was here to handle bits in DE with 8 or 16 in B if small int ; and integer in D'E', 6 nibbles will accommodate 065535 but routine does ; 32-bit numbers as well from above ;;;$2E7B PF_BITS: SLA E ; C ;;;$2F52 PF_OUT_LP: LD A,C ; fetch total digit count AND A ; test for zero JR Z,PF_OUT_DT ; forward to PF_OUT_DT if so LD A,(HL) ; fetch digit INC HL ; address next digit DEC C ; decrease total digit counter ;;;$2F59 PF_OUT_DT: CALL OUT_CODE ; routine OUT_CODE outputs it. DJNZ PF_OUT_LP ; loop back to PF_OUT_LP until B leading digits output. ;;;$2F5E PF_DC_OUT: LD A,C ; fetch total digits and AND A ; test if also zero RET Z ; return if so --> INC B ; increment B LD A,$2E ; prepare the character '.' ;;;$L2F64 PF_DEC_0: RST 10H ; PRINT_A outputs the character '.' or '0' LD A,$30 ; prepare the character '0' ; (for cases like .000012345678) DJNZ PF_DEC_0 ; loop back to PF_DEC_0 for B times. LD B,C ; load B with now trailing digit counter. JR PF_OUT_LP ; back to PF_OUT_LP ; the branch was here for E-format printing e.g 123456789 => 1.2345679e+8 ;;;$2F6C PF_E_FRMT: LD D,B ; counter to D DEC D ; decrement LD B,$01 ; load B with 1. CALL PF_E_SBRN ; routine PF_E_SBRN above LD A,$45 ; prepare character 'e' RST 10H ; PRINT_A LD C,D ; exponent to C LD A,C ; and to A AND A ; test exponent JP P,PF_E_POS ; to PF_E_POS if positive NEG ; negate LD C,A ; positive exponent to C LD A,$2D ; prepare character '-' JR PF_E_SIGN ; skip to PF_E_SIGN ;;;$2F83 PF_E_POS: LD A,$2B ; prepare character '+' ;;;$2F85 PF_E_SIGN: RST 10H ; PRINT_A outputs the sign LD B,$00 ; make the high byte zero. JP OUT_NUM_1 ; exit via OUT_NUM_1 to print exponent in BC ;------------------------------- ; Handle printing floating point ;------------------------------- ; This subroutine is called twice from above when printing floating-point ; numbers. It returns 10*A +C in registers C and A ;;;$2F8B ; CA-10*A+C CA_10_A_C: PUSH DE ; preserve DE. LD L,A ; transfer A to L LD H,$00 ; zero high byte. LD E,L ; copy HL LD D,H ; to DE. ADD HL,HL ; double (*2) ADD HL,HL ; double (*4) ADD HL,DE ; add DE (*5) ADD HL,HL ; double (*10) LD E,C ; copy C to E (D is 0) ADD HL,DE ; and add to give required result. LD C,H ; transfer to LD A,L ; destination registers. POP DE ; restore DE RET ; return with result. ;--------------- ; Prepare to add ;--------------- ; This routine is called twice by addition to prepare the two numbers. The ; exponent is picked up in A and the location made zero. Then the sign bit ; is tested before being set to the implied state. Negative numbers are twos ; complemented. ;;;$2F9B PREP_ADD: LD A,(HL) ; pick up exponent LD (HL),$00 ; make location zero AND A ; test if number is zero RET Z ; return if so INC HL ; address mantissa BIT 7,(HL) ; test the sign bit SET 7,(HL) ; set it to implied state DEC HL ; point to exponent RET Z ; return if positive number. PUSH BC ; preserve BC LD BC,$0005 ; length of number ADD HL,BC ; point HL past end LD B,C ; set B to 5 counter LD C,A ; store exponent in C SCF ; set carry flag ;;;$2FAF NEG_BYTE: DEC HL ; work from LSB to MSB LD A,(HL) ; fetch byte CPL ; complement ADC A,$00 ; add in initial carry or from prev operation LD (HL),A ; put back DJNZ NEG_BYTE ; loop to NEG_BYTE till all 5 done LD A,C ; stored exponent to A POP BC ; restore original BC RET ; return ;------------------ ; Fetch two numbers ;------------------ ; This routine is called twice when printing floating point numbers and also ; to fetch two numbers by the addition, multiply and division routines. ; HL addresses the first number, DE addresses the second number. ; For arithmetic only, A holds the sign of the result which is stored in ; the second location. ;;;$2FBA FETCH_TWO: PUSH HL ; save pointer to first number, result if math. PUSH AF ; save result sign. LD C,(HL) INC HL LD B,(HL) LD (HL),A ; store the sign at correct location in ; destination 5 bytes for arithmetic only. INC HL LD A,C LD C,(HL) PUSH BC INC HL LD C,(HL) INC HL LD B,(HL) EX DE,HL LD D,A LD E,(HL) PUSH DE INC HL LD D,(HL) INC HL LD E,(HL) PUSH DE EXX POP DE POP HL POP BC EXX INC HL LD D,(HL) INC HL LD E,(HL) POP AF ; restore possible result sign. POP HL ; and pointer to possible result. RET ; return. ;---------------------------------- ; Shift floating point number right ;---------------------------------- ;;;$2FDD SHIFT_FP: AND A RET Z CP $21 JR NC,ADDEND_0 ; to ADDEND_0 PUSH BC LD B,A ;;;$2FE5 ONE_SHIFT: EXX SRA L RR D RR E EXX RR D RR E DJNZ ONE_SHIFT ; to ONE_SHIFT POP BC RET NC CALL ADD_BACK ; routine ADD_BACK RET NZ ;;;$2FF9 ADDEND_0: EXX XOR A ;;;$2FFB ZEROS_4_5: LD L,$00 LD D,A LD E,L EXX LD DE,$0000 RET ;------------------- ; Add back any carry ;------------------- ;;;$3004 ADD_BACK: INC E RET NZ INC D RET NZ EXX INC E JR NZ,ALL_ADDED ; to ALL_ADDED INC D ;;;$300D ALL_ADDED: EXX RET ;------------------------- ; Handle subtraction ($03) ;------------------------- ; Subtraction is done by switching the sign byte/bit of the second number ; which may be integer of floating point and continuing into addition. ;;;$300F SUBTRACT: EX DE,HL ; address second number with HL CALL NEGATE ; routine NEGATE switches sign EX DE,HL ; address first number again ; and continue. ;---------------------- ; Handle addition ($0F) ;---------------------- ; HL points to first number, DE to second. ; If they are both integers, then go for the easy route. ;; ADDITION ADDITION: LD A,(DE) ; fetch first byte of second OR (HL) ; combine with first byte of first JR NZ,FULL_ADDN ; forward to FULL_ADDN if at least one was ; in floating point form. ; continue if both were small integers. PUSH DE ; save pointer to lowest number for result. INC HL ; address sign byte and PUSH HL ; push the pointer. INC HL ; address low byte LD E,(HL) ; to E INC HL ; address high byte LD D,(HL) ; to D INC HL ; address unused byte INC HL ; address known zero indicator of 1st number INC HL ; address sign byte LD A,(HL) ; sign to A, $00 or $FF INC HL ; address low byte LD C,(HL) ; to C INC HL ; address high byte LD B,(HL) ; to B POP HL ; pop result sign pointer EX DE,HL ; integer to HL ADD HL,BC ; add to the other one in BC ; setting carry if overflow. EX DE,HL ; save result in DE bringing back sign pointer ADC A,(HL) ; if pos/pos A=01 with overflow else 00 ; if neg/neg A=FF with overflow else FE ; if mixture A=00 with overflow else FF RRCA ; bit 0 to (C) ADC A,$00 ; both acceptable signs now zero JR NZ,ADDN_OFLW ; forward to ADDN_OFLW if not SBC A,A ; restore a negative result sign LD (HL),A INC HL LD (HL),E INC HL LD (HL),D DEC HL DEC HL DEC HL POP DE ; STKEND RET ;;;$303C ADDN_OFLW: DEC HL POP DE ;;;$303E FULL_ADDN: CALL RE_ST_TWO ; routine RE_ST_TWO EXX PUSH HL EXX PUSH DE PUSH HL CALL PREP_ADD ; routine PREP_ADD LD B,A EX DE,HL CALL PREP_ADD ; routine PREP_ADD LD C,A CP B JR NC,SHIFT_LEN ; to SHIFT_LEN LD A,B LD B,C EX DE,HL ;;;$3055 SHIFT_LEN: PUSH AF SUB B CALL FETCH_TWO ; routine FETCH_TWO CALL SHIFT_FP ; routine SHIFT_FP POP AF POP HL LD (HL),A PUSH HL LD L,B LD H,C ADD HL,DE EXX EX DE,HL ADC HL,BC EX DE,HL LD A,H ADC A,L LD L,A RRA XOR L EXX EX DE,HL POP HL RRA JR NC,TEST_NEG ; to TEST_NEG LD A,$01 CALL SHIFT_FP ; routine SHIFT_FP INC (HL) JR Z,ADD_REP_6 ; to ADD_REP_6 ;;;$307C TEST_NEG: EXX LD A,L AND $80 EXX INC HL LD (HL),A DEC HL JR Z,GO_NC_MLT ; to GO_NC_MLT LD A,E NEG ; Negate CCF ; Complement Carry Flag LD E,A LD A,D CPL ADC A,$00 LD D,A EXX LD A,E CPL ADC A,$00 LD E,A LD A,D CPL ADC A,$00 JR NC,END_COMPL ; to END_COMPL RRA EXX INC (HL) ;;;$309F ADD_REP_6: JP Z,REPORT_6 ; to REPORT_6 EXX ;;;$30A3 END_COMPL: LD D,A EXX ;;;$30A5 GO_NC_MLT: XOR A JP TEST_NORM ; to TEST_NORM ;------------------------------ ; Used in 16 bit multiplication ;------------------------------ ; This routine is used, in the first instance, by the multiply calculator ; literal to perform an integer multiplication in preference to ; 32-bit multiplication to which it will resort if this overflows. ; ; It is also used by STK_VAR to calculate array subscripts and by DIM to ; calculate the space required for multi-dimensional arrays. ;;;$30A9 ;; HL-HL*DE HL_HL_DE: PUSH BC ; preserve BC throughout LD B,$10 ; set B to 16 LD A,H ; save H in A high byte LD C,L ; save L in C low byte LD HL,$0000 ; initialize result to zero ; now enter a loop. ;;;$30B1 HL_LOOP: ADD HL,HL ; double result JR C,HL_END ; to HL_END if overflow RL C ; shift AC left into carry RLA ; JR NC,HL_AGAIN ; to HL_AGAIN to skip addition if no carry ADD HL,DE ; add in DE JR C,HL_END ; to HL_END if overflow ;;;$30BC HL_AGAIN: DJNZ HL_LOOP ; back to HL_LOOP for all 16 bits ;;;$30BE HL_END: POP BC ; restore preserved BC RET ; return with carry reset if successful ; and result in HL. ;------------------------------ ; Prepare to multiply or divide ;------------------------------ ; This routine is called in succession from multiply and divide to prepare ; two mantissas by setting the leftmost bit that is used for the sign. ; On the first call A holds zero and picks up the sign bit. On the second ; call the two bits are XORed to form the result sign - minus * minus giving ; plus etc. If either number is zero then this is flagged. ; HL addresses the exponent. ;;;$30C0 PREP_M_D: CALL TEST_ZERO ; routine TEST_ZERO preserves accumulator. RET C ; return carry set if zero INC HL ; address first byte of mantissa XOR (HL) ; pick up the first or xor with first. SET 7,(HL) ; now set to give true 32-bit mantissa DEC HL ; point to exponent RET ; return with carry reset ;---------------------------- ; Handle multiplication ($04) ;---------------------------- ;;;$30CA MULTIPLY: LD A,(DE) OR (HL) JR NZ,MULT_LONG ; to MULT_LONG PUSH DE PUSH HL PUSH DE CALL INT_FETCH ; routine INT_FETCH EX DE,HL EX (SP),HL LD B,C CALL INT_FETCH ; routine INT_FETCH LD A,B XOR C LD C,A POP HL CALL HL_HL_DE ; routine HL_HL_DE EX DE,HL POP HL JR C,MULT_OFLW ; to MULT_OFLW LD A,D OR E JR NZ,MULT_RSLT ; to MULT_RSLT LD C,A ;;;$30EA MULT_RSLT: CALL INT_STORE ; routine INT_STORE POP DE RET ;;;$30EF MULT_OFLW: POP DE ;;;$30F0 MULT_LONG: CALL RE_ST_TWO ; routine RE_ST_TWO XOR A CALL PREP_M_D ; routine PREP_M_D RET C EXX PUSH HL EXX PUSH DE EX DE,HL CALL PREP_M_D ; routine PREP_M_D EX DE,HL JR C,ZERO_RSLT ; to ZERO_RSLT PUSH HL CALL FETCH_TWO ; routine FETCH_TWO LD A,B AND A SBC HL,HL EXX PUSH HL SBC HL,HL EXX LD B,$21 JR STRT_MLT ; to STRT_MLT ;;;$3114 MLT_LOOP: JR NC,NO_ADD ; to NO_ADD ADD HL,DE EXX ADC HL,DE EXX ;;;$311B NO_ADD: EXX RR H RR L EXX RR H RR L ;;;$3125 STRT_MLT: EXX RR B RR C EXX RR C RRA DJNZ MLT_LOOP ; to MLT_LOOP EX DE,HL EXX EX DE,HL EXX POP BC POP HL LD A,B ADD A,C JR NZ,MAKE_EXPT ; to MAKE_EXPT AND A ;;;$313B MAKE_EXPT: DEC A CCF ; Complement Carry Flag ;;;$313D DIVN_EXPT: RLA CCF ; Complement Carry Flag RRA JP P,OFLW1_CLR ; to OFLW1_CLR JR NC,REPORT_6 ; to REPORT_6 AND A ;;;$3146 OFLW1_CLR: INC A ; JR NZ,OFLW2_CLR ; to OFLW2_CLR JR C,OFLW2_CLR ; to OFLW2_CLR EXX BIT 7,D EXX JR NZ,REPORT_6 ; to REPORT_6 ;;;$3151 OFLW2_CLR: LD (HL),A EXX LD A,B EXX ;;;$3155 TEST_NORM: JR NC,NORMALISE ; to NORMALISE LD A,(HL) AND A ;;;$3159 NEAR_ZERO: LD A,$80 JR Z,SKIP_ZERO ; to SKIP_ZERO ;;;$315D ZERO_RSLT: XOR A ;;;$315E SKIP_ZERO: EXX AND D CALL ZEROS_4_5 ; routine ZEROS_4_5 RLCA LD (HL),A JR C,OFLOW_CLR ; to OFLOW_CLR INC HL LD (HL),A DEC HL JR OFLOW_CLR ; to OFLOW_CLR ;;;$316C NORMALISE: LD B,$20 ;;;$316E SHIFT_ONE: EXX BIT 7,D EXX JR NZ,NORML_NOW ; to NORML_NOW RLCA RL E RL D EXX RL E RL D EXX DEC (HL) JR Z,NEAR_ZERO ; to NEAR_ZERO DJNZ SHIFT_ONE ; to SHIFT_ONE JR ZERO_RSLT ; to ZERO_RSLT ;;;$3186 NORML_NOW: RLA JR NC,OFLOW_CLR ; to OFLOW_CLR CALL ADD_BACK ; routine ADD_BACK JR NZ,OFLOW_CLR ; to OFLOW_CLR EXX LD D,$80 EXX INC (HL) JR Z,REPORT_6 ; to REPORT_6 ;;;$3195 OFLOW_CLR: PUSH HL INC HL EXX PUSH DE EXX POP BC LD A,B RLA RL (HL) RRA LD (HL),A INC HL LD (HL),C INC HL LD (HL),D INC HL LD (HL),E POP HL POP DE EXX POP HL EXX RET ;;;$31AD REPORT_6: RST 08H ; ERROR_1 DEFB $05 ; Error Report: Number too big ;---------------------- ; Handle division ($05) ;---------------------- ;;;$31AF DIVISION: CALL RE_ST_TWO ; routine RE_ST_TWO EX DE,HL XOR A CALL PREP_M_D ; routine PREP_M_D JR C,REPORT_6 ; to REPORT_6 EX DE,HL CALL PREP_M_D ; routine PREP_M_D RET C EXX PUSH HL EXX PUSH DE PUSH HL CALL FETCH_TWO ; routine FETCH_TWO EXX PUSH HL LD H,B LD L,C EXX LD H,C LD L,B XOR A LD B,$DF JR DIV_START ; to DIV_START ;;;$31D2 DIV_LOOP: RLA RL C EXX RL C RL B EXX ;;;$31DB DIV_34TH: ADD HL,HL EXX ADC HL,HL EXX JR C,SUBN_ONLY ; to SUBN_ONLY ;;;$31E2 DIV_START: SBC HL,DE EXX SBC HL,DE EXX JR NC,NO_RSTORE ; to NO_RSTORE ADD HL,DE EXX ADC HL,DE EXX AND A JR COUNT_ONE ; to COUNT_ONE ;;;$31F2 SUBN_ONLY: AND A SBC HL,DE EXX SBC HL,DE EXX ;;;$31F9 NO_RSTORE: SCF ; Set Carry Flag ;;;$31FA COUNT_ONE: INC B JP M,DIV_LOOP ; to DIV_LOOP PUSH AF JR Z,DIV_START ; to DIV_START LD E,A LD D,C EXX LD E,C LD D,B POP AF RR B POP AF RR B EXX POP BC POP HL LD A,B SUB C JP DIVN_EXPT ; to DIVN_EXPT ;-------------------------------------- ; Integer truncation towards zero ($3A) ;-------------------------------------- ;;;$3214 TRUNCATE: LD A,(HL) AND A RET Z CP $81 JR NC,T_GR_ZERO ; to T_GR_ZERO LD (HL),$00 LD A,$20 JR NIL_BYTES ; to NIL_BYTES ;;;$3221 T_GR_ZERO: CP $91 JR NZ,T_SMALL ; to T_SMALL INC HL INC HL INC HL LD A,$80 AND (HL) DEC HL OR (HL) DEC HL JR NZ,T_FIRST ; to T_FIRST LD A,$80 XOR (HL) ;;;$3233 T_FIRST: DEC HL JR NZ,T_EXPNENT ; to T_EXPNENT LD (HL),A INC HL LD (HL),$FF DEC HL LD A,$18 JR NIL_BYTES ; to NIL_BYTES ;;;$323F T_SMALL: JR NC,X_LARGE ; to X_LARGE PUSH DE CPL ADD A,$91 INC HL LD D,(HL) INC HL LD E,(HL) DEC HL DEC HL LD C,$00 BIT 7,D JR Z,T_NUMERIC ; to T_NUMERIC DEC C ;;;$3252 T_NUMERIC: SET 7,D LD B,$08 SUB B ADD A,B JR C,T_TEST ; to T_TEST LD E,D LD D,$00 SUB B ;;;$325E T_TEST: JR Z,T_STORE ; to T_STORE LD B,A ;;;$3261 T_SHIFT: SRL D RR E DJNZ T_SHIFT ; to T_SHIFT ;;;$3267 T_STORE: CALL INT_STORE ; routine INT_STORE POP DE RET ;;;$326C T_EXPNENT: LD A,(HL) ;;;$326D X_LARGE: SUB $A0 RET P NEG ; Negate ;;;$3272 NIL_BYTES: PUSH DE EX DE,HL DEC HL LD B,A SRL B SRL B SRL B JR Z,BITS_ZERO ; to BITS_ZERO ;;;$327E BYTE_ZERO: LD (HL),$00 DEC HL DJNZ BYTE_ZERO ; to BYTE_ZERO ;; BITS_ZERO BITS_ZERO: AND $07 JR Z,IX_END ; to IX_END LD B,A LD A,$FF ;;;$328A LESS_MASK: SLA A DJNZ LESS_MASK ; to LESS_MASK AND (HL) LD (HL),A ;;;$3290 IX_END: EX DE,HL POP DE RET ; ---------------------------------- ; Storage of numbers in 5 byte form. ; ================================== ; Both integers and floating-point numbers can be stored in five bytes. ; Zero is a special case stored as 5 zeros. ; For integers the form is ; Byte 1 - zero, ; Byte 2 - sign byte, $00 +ve, $FF -ve. ; Byte 3 - Low byte of integer. ; Byte 4 - High byte ; Byte 5 - unused but always zero. ; ; it seems unusual to store the low byte first but it is just as easy either ; way. Statistically it just increases the chances of trailing zeros which ; is an advantage elsewhere in saving ROM code. ; ; zero sign low high unused ; So +1 is 00000000 00000000 00000001 00000000 00000000 ; ; and -1 is 00000000 11111111 11111111 11111111 00000000 ; ; much of the arithmetic found in basic lines can be done using numbers ; in this form using the Z80's 16 bit register operation ADD. ; (multiplication is done by a sequence of additions). ; ; Storing -ve integers in two's complement form, means that they are ready for ; addition and you might like to add the numbers above to prove that the ; answer is zero. If, as in this case, the carry is set then that denotes that ; the result is positive. This only applies when the signs don't match. ; With positive numbers a carry denotes the result is out of integer range. ; With negative numbers a carry denotes the result is within range. ; The exception to the last rule is when the result is -65536 ; ; Floating point form is an alternative method of storing numbers which can ; be used for integers and larger (or fractional) numbers. ; ; In this form 1 is stored as ; 10000001 00000000 00000000 00000000 00000000 ; ; When a small integer is converted to a floating point number the last two ; bytes are always blank so they are omitted in the following steps ; ; first make exponent +1 +16d (bit 7 of the exponent is set if positive) ; 10010001 00000000 00000001 ; 10010000 00000000 00000010 <- now shift left and decrement exponent ; ... ; 10000010 01000000 00000000 <- until a 1 abuts the imaginary point ; 10000001 10000000 00000000 to the left of the mantissa. ; ; however since the leftmost bit of the mantissa is always set then it can ; be used to denote the sign of the mantissa and put back when needed by the ; PREP routines which gives ; ; 10000001 00000000 00000000 ;------------------------------ ; Re-stack two `small' integers ;------------------------------ ; This routine is called to re-stack two numbers in full floating point form ; e.g. from MULTIPLY when integer multiplication has overflowed. ;;;$3293 RE_ST_TWO: CALL RESTK_SUB ; routine RESTK_SUB below and continue ; into the routine to do the other one. ;;;$3296 RESTK_SUB: EX DE,HL ; swap pointers ;--------------------------------- ; Re-stack one number in full form ;--------------------------------- ; This routine re-stacks an integer usually on the calculator stack ; in full floating point form. ; HL points to first byte. ;;;$3297 RE_STACK: LD A,(HL) ; Fetch Exponent byte to A AND A ; test it RET NZ ; return if not zero as already in full ; floating-point form. PUSH DE ; preserve DE. CALL INT_FETCH ; routine INT_FETCH ; integer to DE, sign to C. ; HL points to 4th byte. XOR A ; clear accumulator. INC HL ; point to 5th. LD (HL),A ; and blank. DEC HL ; point to 4th. LD (HL),A ; and blank. LD B,$91 ; set exponent byte +ve $81 ; and imaginary dec point 16 bits to right ; of first bit. ; we could skip to normalize now but it's quicker to avoid ; normalizing through an empty D. LD A,D ; fetch the high byte D AND A ; is it zero ? JR NZ,RS_NRMLSE ; skip to RS_NRMLSE if not. OR E ; low byte E to A and test for zero LD B,D ; set B exponent to 0 JR Z,RS_STORE ; forward to RS_STORE if value is zero. LD D,E ; transfer E to D LD E,B ; set E to 0 LD B,$89 ; reduce the initial exponent by eight. ;;;$32B1 RS_NRMLSE: EX DE,HL ; integer to HL, addr of 4th byte to DE. ;;;$32B2 RSTK_LOOP: DEC B ; decrease exponent ADD HL,HL ; shift DE left JR NC,RSTK_LOOP ; loop back to RSTK_LOOP ; until a set bit pops into carry RRC C ; now rotate the sign byte $00 or $FF ; into carry to give a sign bit RR H ; rotate the sign bit to left of H RR L ; rotate any carry into L EX DE,HL ; address 4th byte, normalized int to DE ;;;$32BD RS_STORE: DEC HL ; address 3rd byte LD (HL),E ; place E DEC HL ; address 2nd byte LD (HL),D ; place D DEC HL ; address 1st byte LD (HL),B ; store the exponent POP DE ; restore initial DE. RET ; return. ;**************************************** ;** Part 10. FLOATING-POINT CALCULATOR ** ;**************************************** ; As a general rule the calculator avoids using the IY register. ; exceptions are VAL, VAL$ and STR$. ; So an assembly language programmer who has disabled interrupts to use ; IY for other purposes can still use the calculator for mathematical ; purposes. ;------------------- ; Table of constants ;------------------- ; used 11 times ;;;$32C5 00 00 00 00 00 STK_ZERO: DEFB $00 ;;Bytes: 1 DEFB $B0 ;;Exponent $00 DEFB $00 ;;(+00,+00,+00) ; used 19 times ;;;$32C8 00 00 01 00 00 STK_ONE: DEFB $40 ;;Bytes: 2 DEFB $B0 ;;Exponent $00 DEFB $00,$01 ;;(+00,+00) ; used 9 times ;;;$32CC 80 00 00 00 00 STK_HALF: DEFB $30 ;;Exponent: $80, Bytes: 1 DEFB $00 ;;(+00,+00,+00) ; used 4 times ;;;$32CE ;; stk-pi/2 81 49 0F DA A2 STK_PI_2: DEFB $F1 ;;Exponent: $81, Bytes: 4 DEFB $49,$0F,$DA,$A2 ; used 3 times ;;;$32D3 00 00 0A 00 00 STK_TEN: DEFB $40 ;;Bytes: 2 DEFB $B0 ;;Exponent $00 DEFB $00,$0A ;;(+00,+00) ;------------------- ; Table of addresses ;------------------- ; ; starts with binary operations which have two operands and one result. ; three pseudo binary operations first. ;;;$32D7 TBL_ADDRS: DEFW JUMP_TRUE ; $00 Address: $368F - JUMP_TRUE DEFW EXCHANGE ; $01 Address: $343C - EXCHANGE DEFW DELETE ; $02 Address: $33A1 - DELETE ; true binary operations. DEFW SUBTRACT ; $03 Address: $300F - SUBTRACT DEFW MULTIPLY ; $04 Address: $30CA - MULTIPLY DEFW DIVISION ; $05 Address: $31AF - DIVISION DEFW TO_POWER ; $06 Address: $3851 - TO_POWER DEFW OR_ ; $07 Address: $351B - OR DEFW NO_AND_NO ; $08 Address: $3524 - NO_AND_NO DEFW NO_L_EQL ; $09 Address: $353B - NO_L_EQL DEFW NO_GR_EQL ; $0A Address: $353B - NO_GR_EQL DEFW NOS_NEQL ; $0B Address: $353B - NOS_NEQL DEFW NO_GRTR ; $0C Address: $353B - NO_GRTR DEFW NO_LESS ; $0D Address: $353B - NO_LESS DEFW NOS_EQL ; $0E Address: $353B - NOS_EQL DEFW ADDITION ; $0F Address: $3014 - ADDITION DEFW STR_AND_NO ; $10 Address: $352D - STR_AND_NO DEFW STR_L_EQL ; $11 Address: $353B - STR_L_EQL DEFW STR_GR_EQL ; $12 Address: $353B - STR_GR_EQL DEFW STRS_NEQL ; $13 Address: $353B - STRS_NEQL DEFW STR_GRTR ; $14 Address: $353B - STR_GRTR DEFW STR_LESS ; $15 Address: $353B - STR_LESS DEFW STRS_EQL ; $16 Address: $353B - STRS_EQL DEFW STRS_ADD ; $17 Address: $359C - STRS_ADD ; unary follow DEFW VALS ; $18 Address: $35DE - VAL$ DEFW USR_ ; $19 Address: $34BC - USR-$ DEFW READ_IN ; $1A Address: $3645 - READ_IN DEFW NEGATE ; $1B Address: $346E - NEGATE DEFW CODE ; $1C Address: $3669 - CODE DEFW VAL ; $1D Address: $35DE - VAL DEFW LEN ; $1E Address: $3674 - LEN DEFW SIN_ ; $1F Address: $37B5 - SIN DEFW COS_ ; $20 Address: $37AA - COS DEFW TAN ; $21 Address: $37DA - TAN DEFW ASN ; $22 Address: $3833 - ASN DEFW ACS ; $23 Address: $3843 - ACS DEFW ATN ; $24 Address: $37E2 - ATN DEFW LN ; $25 Address: $3713 - LN DEFW EXP ; $26 Address: $36C4 - EXP DEFW INT ; $27 Address: $36AF - INT DEFW SQR ; $28 Address: $384A - SQR DEFW SGN ; $29 Address: $3492 - SGN DEFW @ABS ; $2A Address: $346A - ABS DEFW PEEK ; $2B Address: $34AC - PEEK DEFW IN_ ; $2C Address: $34A5 - IN DEFW USR_NO ; $2D Address: $34B3 - USR_NO DEFW STRS ; $2E Address: $361F - STR$ DEFW CHRS ; $2F Address: $35C9 - CHR$ DEFW NOT_ ; $30 Address: $3501 - NOT ; end of true unary DEFW DUPLICATE ; $31 Address: $33C0 - DUPLICATE DEFW N_MOD_M ; $32 Address: $36A0 - N_MOD_M DEFW JUMP ; $33 Address: $3686 - JUMP DEFW STK_DATA ; $34 Address: $33C6 - STK_DATA DEFW DEC_JR_NZ ; $35 Address: $367A - DEC_JR_NZ DEFW LESS_0 ; $36 Address: $3506 - LESS_0 DEFW GREATER_0 ; $37 Address: $34F9 - GREATER_0 DEFW END_CALC ; $38 Address: $369B - END_CALC DEFW GET_ARGT ; $39 Address: $3783 - GET_ARGT DEFW TRUNCATE ; $3A Address: $3214 - TRUNCATE DEFW FP_CALC_2 ; $3B Address: $33A2 - FP_CALC_2 DEFW E_TO_FP ; $3C Address: $2D4F - E_TO_FP DEFW RE_STACK ; $3D Address: $3297 - RE_STACK ; the following are just the next available slots for the 128 compound literals ; which are in range $80 - $FF. DEFW SERIES_XX ; $3E Address: $3449 - SERIES_XX $80 - $9F. DEFW STK_CONST_XX ; $3F Address: $341B - STK_CONST_XX $A0 - $BF. DEFW ST_MEM_XX ; $40 Address: $342D - ST_MEM_XX $C0 - $DF. DEFW GET_MEM_XX ; $41 Address: $340F - GET_MEM_XX $E0 - $FF. ; Aside: $3E - $7F are therefore unused calculator literals. ; $3E - $7B would be available for expansion. ;--------------- ; The Calculator ;--------------- ;;;$335B CALCULATE: CALL STK_PNTRS ; routine STK_PNTRS is called to set up the ; calculator stack pointers for a default ; unary operation. HL = last value on stack. ; DE = STKEND first location after stack. ; the calculate routine is called at this point by the series generator... ;;;$335E GEN_ENT_1: LD A,B ; fetch the Z80 B register to A LD (BREG),A ; and store value in system variable BREG. ; this will be the counter for DEC_JR_NZ ; or if used from FP_CALC2 the calculator ; instruction. ; ... and again later at this point ;;;$3362 GEN_ENT_2: EXX ; switch sets EX (SP),HL ; and store the address of next instruction, ; the return address, in H'L'. ; If this is a recursive call the the H'L' ; of the previous invocation goes on stack. ; c.f. END_CALC. EXX ; switch back to main set ; this is the re-entry looping point when handling a string of literals. ;;;$3365 RE_ENTRY: LD (STKEND),DE ; save end of stack in system variable STKEND EXX ; switch to alt LD A,(HL) ; get next literal INC HL ; increase pointer' ; single operation jumps back to here ;;;$336C SCAN_ENT: PUSH HL ; save pointer on stack AND A ; now test the literal JP P,FIRST_3D ; forward to FIRST_3D if in range $00 - $3D ; anything with bit 7 set will be one of ; 128 compound literals. ; compound literals have the following format. ; bit 7 set indicates compound. ; bits 6-5 the subgroup 0-3. ; bits 4-0 the embedded parameter $00 - $1F. ; The subgroup 0-3 needs to be manipulated to form the next available four ; address places after the simple literals in the address table. LD D,A ; save literal in D AND $60 ; and with 01100000 to isolate subgroup RRCA ; rotate bits RRCA ; 4 places to right RRCA ; not five as we need offset * 2 RRCA ; 00000xx0 ADD A,$7C ; add ($3E * 2) to give correct offset. ; alter above if you add more literals. LD L,A ; store in L for later indexing. LD A,D ; bring back compound literal AND $1F ; use mask to isolate parameter bits JR ENT_TABLE ; forward to ENT_TABLE ; the branch was here with simple literals. ;;;$3380 FIRST_3D: CP $18 ; compare with first unary operations. JR NC,DOUBLE_A ; to DOUBLE_A with unary operations ; it is binary so adjust pointers. EXX LD BC,$FFFB ; the value -5 LD D,H ; transfer HL, the last value, to DE. LD E,L ADD HL,BC ; subtract 5 making HL point to second value. EXX ;;;$338C DOUBLE_A: RLCA ; double the literal LD L,A ; and store in L for indexing ;;;$338E ENT_TABLE: LD DE,TBL_ADDRS ; Address: TBL_ADDRS LD H,$00 ; prepare to index ADD HL,DE ; add to get address of routine LD E,(HL) ; low byte to E INC HL LD D,(HL) ; high byte to D LD HL,RE_ENTRY ; Address: RE_ENTRY EX (SP),HL ; goes to stack PUSH DE ; now address of routine EXX ; main set ; avoid using IY register. LD BC,(STKEND_HI) ; STKEND_hi ; nothing much goes to C but BREG to B ; and continue into next ret instruction ; which has a dual identity ;-------------------- ; Handle delete ($02) ;-------------------- ; A simple return but when used as a calculator literal this ; deletes the last value from the calculator stack. ; On entry, as always with binary operations, ; HL=first number, DE=second number ; On exit, HL=result, DE=stkend. ; So nothing to do ;;;$33A1 DELETE: RET ; return - indirect jump if from above. ;----------------------- ; Single operation ($3B) ;----------------------- ; this single operation is used, in the first instance, to evaluate most ; of the mathematical and string functions found in Basic expressions. ;;;$33A2 FP_CALC_2: POP AF ; drop return address. LD A,(BREG) ; load accumulator from system variable BREG ; value will be literal eg. 'TAN' EXX ; switch to alt JR SCAN_ENT ; back to SCAN_ENT ; next literal will be END_CALC at $2758 ;----------------- ; Test five-spaces ;----------------- ; This routine is called from MOVE_FP, STK_CONST and STK_STORE to ; test that there is enough space between the calculator stack and the ; machine stack for another five-byte value. It returns with BC holding ; the value 5 ready for any subsequent LDIR. ;;;$33A9 TEST_5_SP: PUSH DE ; save PUSH HL ; registers LD BC,$0005 ; an overhead of five bytes CALL TEST_ROOM ; routine TEST_ROOM tests free RAM raising an error if not. POP HL ; else restore POP DE ; registers. RET ; return with BC set at 5. ;------------- ; Stack number ;------------- ; This routine is called to stack a hidden floating point number found in ; a Basic line. It is also called to stack a numeric variable value, and ; from BEEP, to stack an entry in the semi-tone table. It is not part of the ; calculator suite of routines. ; On entry HL points to the number to be stacked. ;;;$33B4 STACK_NUM: LD DE,(STKEND) ; load destination from STKEND system variable. CALL MOVE_FP ; routine MOVE_FP puts on calculator stack with a memory check. LD (STKEND),DE ; set STKEND to next free location. RET ; return. ;----------------------------------- ; Move a floating point number ($31) ;----------------------------------- ; This simple routine is a 5-byte LDIR instruction ; that incorporates a memory check. ; When used as a calculator literal it duplicates the last value on the ; calculator stack. ; Unary so on entry HL points to last value, DE to stkend ;;;$33C0 DUPLICATE: MOVE_FP: CALL TEST_5_SP ; routine TEST_5_SP test free memory and sets BC to 5. LDIR ; copy the five bytes. RET ; return with DE addressing new STKEND ; and HL addressing new last value. ;--------------------- ; Stack literals ($34) ;--------------------- ; When a calculator subroutine needs to put a value on the calculator ; stack that is not a regular constant this routine is called with a ; variable number of following data bytes that convey to the routine ; the integer or floating point form as succinctly as is possible. ;;;$33C6 STK_DATA: LD H,D ; transfer STKEND LD L,E ; to HL for result. ;;;$33C8 STK_CONST: CALL TEST_5_SP ; routine TEST_5_SP tests that room exists ; and sets BC to $05. EXX ; switch to alternate set PUSH HL ; save the pointer to next literal on stack EXX ; switch back to main set EX (SP),HL ; pointer to HL, destination to stack. PUSH BC ; save BC - value 5 from test room ??. LD A,(HL) ; fetch the byte following 'STK_DATA' AND $C0 ; isolate bits 7 and 6 RLCA ; rotate RLCA ; to bits 1 and 0 range $00 - $03. LD C,A ; transfer to C INC C ; and increment to give number of bytes ; to read. $01 - $04 LD A,(HL) ; reload the first byte AND $3F ; mask off to give possible exponent. JR NZ,FORM_EXP ; forward to FORM_EXP if it was possible to ; include the exponent. ; else byte is just a byte count and exponent comes next. INC HL ; address next byte and LD A,(HL) ; pick up the exponent ( - $50). ;;;$33DE FORM_EXP: ADD A,$50 ; now add $50 to form actual exponent LD (DE),A ; and load into first destination byte. LD A,$05 ; load accumulator with $05 and SUB C ; subtract C to give count of trailing zeros plus one. INC HL ; increment source INC DE ; increment destination LD B,$00 ; prepare to copy LDIR ; copy C bytes POP BC ; restore 5 counter to BC ??. EX (SP),HL ; put HL on stack as next literal pointer ; and the stack value - result pointer - to HL. EXX ; switch to alternate set. POP HL ; restore next literal pointer from stack to H'L'. EXX ; switch back to main set. LD B,A ; zero count to B XOR A ; clear accumulator ;;;$33F1 STK_ZEROS: DEC B ; decrement B counter RET Z ; return if zero. >> ; DE points to new STKEND ; HL to new number. LD (DE),A ; else load zero to destination INC DE ; increase destination JR STK_ZEROS ; loop back to STK_ZEROS until done. ;--------------- ; Skip constants ;--------------- ; This routine traverses variable-length entries in the table of constants, ; stacking intermediate, unwanted constants onto a dummy calculator stack, ; in the first five bytes of ROM. ;;;$33F7 SKIP_CONS: AND A ; test if initially zero. ;;;$33F8 SKIP_NEXT: RET Z ; return if zero. >> PUSH AF ; save count. PUSH DE ; and normal STKEND LD DE,$0000 ; dummy value for STKEND at start of ROM ; Note. not a fault but this has to be ; moved elsewhere when running in RAM. ; e.g. with Expandor Systems 'Soft Rom'. CALL STK_CONST ; routine STK_CONST works through variable length records. POP DE ; restore real STKEND POP AF ; restore count DEC A ; decrease JR SKIP_NEXT ; loop back to SKIP_NEXT ;---------------- ; Memory location ;---------------- ; This routine, when supplied with a base address in HL and an index in A ; will calculate the address of the A'th entry, where each entry occupies ; five bytes. It is used for reading the semi-tone table and addressing ; floating-point numbers in the calculator's memory area. ;;;$3406 LOC_MEM: LD C,A ; store the original number $00-$1F. RLCA ; double. RLCA ; quadruple. ADD A,C ; now add original to multiply by five. LD C,A ; place the result in C. LD B,$00 ; set B to 0. ADD HL,BC ; add to form address of start of number in HL. RET ; return. ;-------------------------------- ; Get from memory area ($E0 etc.) ;-------------------------------- ; Literals $E0 to $FF ; A holds $00-$1F offset. ; The calculator stack increases by 5 bytes. ;;;$340F GET_MEM_XX: PUSH DE ; save STKEND LD HL,(MEM) ; MEM is base address of the memory cells. CALL LOC_MEM ; routine LOC_MEM so that HL = first byte CALL MOVE_FP ; routine MOVE_FP moves 5 bytes with memory check. ; DE now points to new STKEND. POP HL ; original STKEND is now RESULT pointer. RET ; return. ;---------------------------- ; Stack a constant ($A0 etc.) ;---------------------------- ; This routine allows a one-byte instruction to stack up to 32 constants ; held in short form in a table of constants. In fact only 5 constants are ; required. On entry the A register holds the literal ANDed with 1F. ; It isn't very efficient and it would have been better to hold the ; numbers in full, five byte form and stack them in a similar manner ; to that used for semi-tone table values. ;;;$341B STK_CONST_XX: LD H,D ; save STKEND - required for result LD L,E EXX ; swap PUSH HL ; save pointer to next literal LD HL,STK_ZERO ; Address: STK_ZERO - start of table of constants EXX CALL SKIP_CONS ; routine SKIP_CONS CALL STK_CONST ; routine STK_CONST EXX POP HL ; restore pointer to next literal. EXX RET ; return. ;---------------------------------- ; Store in a memory area ($C0 etc.) ;---------------------------------- ; Offsets $C0 to $DF ; Although 32 memory storage locations can be addressed, only six ; $C0 to $C5 are required by the ROM and only the thirty bytes (6*5) ; required for these are allocated. Spectrum programmers who wish to ; use the floating point routines from assembly language may wish to ; alter the system variable MEM to point to 160 bytes of RAM to have ; use the full range available. ; A holds derived offset $00-$1F. ; Unary so on entry HL points to last value, DE to STKEND. ;;;$342D ST_MEM_XX: PUSH HL ; save the result pointer. EX DE,HL ; transfer to DE. LD HL,(MEM) ; fetch MEM the base of memory area. CALL LOC_MEM ; routine LOC_MEM sets HL to the destination. EX DE,HL ; swap - HL is start, DE is destination. CALL MOVE_FP ; routine MOVE_FP. ; note. a short ld bc,5; ldir ; the embedded memory check is not required ; so these instructions would be faster. EX DE,HL ; DE = STKEND POP HL ; restore original result pointer RET ; return. ;------------------------------------- ; Swap first number with second number ;------------------------------------- ; This routine exchanges the last two values on the calculator stack ; On entry, as always with binary operations, ; HL=first number, DE=second number ; On exit, HL=result, DE=stkend. ;;;$343C EXCHANGE: LD B,$05 ; there are five bytes to be swapped ; start of loop. ;;;$343E SWAP_BYTE: LD A,(DE) ; each byte of second LD C,(HL) ; each byte of first EX DE,HL ; swap pointers LD (DE),A ; store each byte of first LD (HL),C ; store each byte of second INC HL ; advance both INC DE ; pointers. DJNZ SWAP_BYTE ; loop back to SWAP_BYTE until all 5 done. EX DE,HL ; even up the exchanges ; so that DE addresses STKEND. RET ; return. ;---------------------------- ; Series generator ($86 etc.) ;---------------------------- ; The Spectrum uses Chebyshev polynomials to generate approximations for ; SIN, ATN, LN and EXP. These are named after the Russian mathematician ; Pafnuty Chebyshev, born in 1821, who did much pioneering work on numerical ; series. As far as calculators are concerned, Chebyshev polynomials have an ; advantage over other series, for example the Taylor series, as they can ; reach an approximation in just six iterations for SIN, eight for EXP and ; twelve for LN and ATN. The mechanics of the routine are interesting but ; for full treatment of how these are generated with demonstrations in ; Sinclair Basic see "The Complete Spectrum ROM Disassembly" by Dr Ian Logan ; and Dr Frank O'Hara, published 1983 by Melbourne House. ;;;$3449 SERIES_XX: LD B,A ; parameter $00 - $1F to B counter CALL GEN_ENT_1 ; routine GEN_ENT_1 is called. ; A recursive call to a special entry point ; in the calculator that puts the B register ; in the system variable BREG. The return ; address is the next location and where ; the calculator will expect it's first ; instruction - now pointed to by HL'. ; The previous pointer to the series of ; five-byte numbers goes on the machine stack. ; The initialization phase. DEFB $31 ;;DUPLICATE x,x DEFB $0F ;;ADDITION x+x DEFB $C0 ;;st-mem-0 x+x DEFB $02 ;;DELETE . DEFB $A0 ;;STK_ZERO 0 DEFB $C2 ;;st-mem-2 0 ; a loop is now entered to perform the algebraic calculation for each of ; the numbers in the series ;; G_LOOP G_LOOP: DEFB $31 ;;DUPLICATE v,v. DEFB $E0 ;;get-mem-0 v,v,x+2 DEFB $04 ;;MULTIPLY v,v*x+2 DEFB $E2 ;;get-mem-2 v,v*x+2,v DEFB $C1 ;;st-mem-1 DEFB $03 ;;SUBTRACT DEFB $38 ;;END_CALC ; the previous pointer is fetched from the machine stack to H'L' where it ; addresses one of the numbers of the series following the series literal. CALL STK_DATA ; routine STK_DATA is called directly to ; push a value and advance H'L'. CALL GEN_ENT_2 ; routine GEN_ENT_2 recursively re-enters ; the calculator without disturbing ; system variable BREG ; H'L' value goes on the machine stack and is ; then loaded as usual with the next address. DEFB $0F ;;ADDITION DEFB $01 ;;EXCHANGE DEFB $C2 ;;st-mem-2 DEFB $02 ;;DELETE DEFB $35 ;;DEC_JR_NZ DEFB $EE ;;back to G_LOOP ; when the counted loop is complete the final subtraction yields the result ; for example SIN X. DEFB $E1 ;;get-mem-1 DEFB $03 ;;SUBTRACT DEFB $38 ;;END_CALC RET ; return with H'L' pointing to location ; after last number in series. ;------------------------- ; Absolute magnitude ($2A) ;------------------------- ; This calculator literal finds the absolute value of the last value, ; integer or floating point, on calculator stack. ;;;$346A ABS: LD B,$FF ; signal abs JR NEG_TEST ; forward to NEG_TEST ;------------------------- ; Handle unary minus ($1B) ;------------------------- ; Unary so on entry HL points to last value, DE to STKEND. ;;;$346E NEGATE: CALL TEST_ZERO ; call routine TEST_ZERO and RET C ; return if so leaving zero unchanged. LD B,$00 ; signal negate required before joining ; common code. ;;;$3474 NEG_TEST: LD A,(HL) ; load first byte and AND A ; test for zero JR Z,INT_CASE ; forward to INT_CASE if a small integer ; for floating point numbers a single bit denotes the sign. INC HL ; address the first byte of mantissa. LD A,B ; action flag $FF=abs, $00=neg. AND $80 ; now $80 $00 OR (HL) ; sets bit 7 for abs RLA ; sets carry for abs and if number negative CCF ; complement carry flag RRA ; and rotate back in altering sign LD (HL),A ; put the altered adjusted number back DEC HL ; HL points to result RET ; return with DE unchanged ; for integer numbers an entire byte denotes the sign. ;;;$3483 INT_CASE: PUSH DE ; save STKEND. PUSH HL ; save pointer to the last value/result. CALL INT_FETCH ; routine INT_FETCH puts integer in DE and the sign in C. POP HL ; restore the result pointer. LD A,B ; $FF=abs, $00=neg OR C ; $FF for abs, no change neg CPL ; $00 for abs, switched for neg LD C,A ; transfer result to sign byte. CALL INT_STORE ; routine INT_STORE to re-write the integer. POP DE ; restore STKEND. RET ; return. ;------------- ; Signum ($29) ;------------- ; This routine replaces the last value on the calculator stack, ; which may be in floating point or integer form, with the integer values ; zero if zero, with one if positive and with -minus one if negative. ;;;$3492 SGN: CALL TEST_ZERO ; call routine TEST_ZERO and RET C ; exit if so as no change is required. PUSH DE ; save pointer to STKEND. LD DE,$0001 ; the result will be 1. INC HL ; skip over the exponent. RL (HL) ; rotate the sign bit into the carry flag. DEC HL ; step back to point to the result. SBC A,A ; byte will be $FF if negative, $00 if positive. LD C,A ; store the sign byte in the C register. CALL INT_STORE ; routine INT_STORE to overwrite the last value with 0001 and sign. POP DE ; restore STKEND. RET ; return. ;------------------------- ; Handle IN function ($2C) ;------------------------- ; This function reads a byte from an input port. ;;;$34A5 IN_: CALL FIND_INT2 ; routine FIND_INT2 puts port address in BC. ; all 16 bits are put on the address line. IN A,(C) ; read the port. JR IN_PK_STK ; exit to STACK_A (via IN_PK_STK to save a byte ; of instruction code). ;-------------------------- ; Handle PEEK function ($2B) ;-------------------------- ; This function returns the contents of a memory address. ; The entire address space can be peeked including the ROM. ;;;$34AC PEEK: CALL FIND_INT2 ; routine FIND_INT2 puts address in BC. LD A,(BC) ; load contents into A register. ;;;$34B0 IN_PK_STK: JP STACK_A ; exit via STACK_A to put value on the ; calculator stack. ;----------------- ; USR number ($2D) ;----------------- ; The USR function followed by a number 0-65535 is the method by which ; the Spectrum invokes machine code programs. This function returns the ; contents of the BC register pair. ; Note. that STACK_BC re-initializes the IY register if a user-written ; program has altered it. ;; USR_NO USR_NO: CALL FIND_INT2 ; routine FIND_INT2 to fetch the supplied address into BC. LD HL,STACK_BC ; address: STACK_BC is PUSH HL ; pushed onto the machine stack. PUSH BC ; then the address of the machine code routine. RET ; make an indirect jump to the routine ; and, hopefully, to STACK_BC also. ;----------------- ; USR string ($19) ;----------------- ; The user function with a one-character string argument, calculates the ; address of the User Defined Graphic character that is in the string. ; As an alternative, the ascii equivalent, upper or lower case, ; may be supplied. This provides a user-friendly method of redefining ; the 21 User Definable Graphics e.g. ; POKE USR "a", BIN 10000000 will put a dot in the top left corner of the ; character 144. ; Note. the curious double check on the range. With 26 UDGs the first check ; only is necessary. With anything less the second check only is required. ; It is highly likely that the first check was written by Steven Vickers. ;;;$34BC USR_: CALL STK_FETCH ; routine STK_FETCH fetches the string parameters. DEC BC ; decrease BC by LD A,B ; one to test OR C ; the length. JR NZ,REPORT_A ; to REPORT_A if not a single character. LD A,(DE) ; fetch the character CALL ALPHA ; routine ALPHA sets carry if 'A-Z' or 'a-z'. JR C,USR_RANGE ; forward to USR_RANGE if ascii. SUB $90 ; make udgs range 0-20d JR C,REPORT_A ; to REPORT_A if too low. e.g. usr " ". CP $15 ; Note. this test is not necessary. JR NC,REPORT_A ; to REPORT_A if higher than 20. INC A ; make range 1-21d to match LSBs of ascii ;;;$34D3 USR_RANGE: DEC A ; make range of bits 0-4 start at zero ADD A,A ; multiply by eight ADD A,A ; and lose any set bits ADD A,A ; range now 0 - 25*8 CP $A8 ; compare to 21*8 JR NC,REPORT_A ; to REPORT_A if originally higher ; than 'U','u' or graphics U. LD BC,(UDG) ; fetch the UDG system variable value. ADD A,C ; add the offset to character LD C,A ; and store back in register C. JR NC,USR_STACK ; forward to USR_STACK if no overflow. INC B ; increment high byte. ;;;$34E4 USR_STACK: JP STACK_BC ; jump back and exit via STACK_BC to store ;;;$34E7 REPORT_A: RST 08H ; ERROR_1 DEFB $09 ; Error Report: Invalid argument ;-------------- ; Test for zero ;-------------- ; Test if top value on calculator stack is zero. ; The carry flag is set if the last value is zero but no registers are altered. ; All five bytes will be zero but first four only need be tested. ; On entry HL points to the exponent the first byte of the value. ;;;$34E9 TEST_ZERO: PUSH HL ; preserve HL which is used to address. PUSH BC ; preserve BC which is used as a store. LD B,A ; preserve A in B. LD A,(HL) ; load first byte to accumulator INC HL ; advance. OR (HL) ; OR with second byte and clear carry. INC HL ; advance. OR (HL) ; OR with third byte. INC HL ; advance. OR (HL) ; OR with fourth byte. LD A,B ; restore A without affecting flags. POP BC ; restore the saved POP HL ; registers. RET NZ ; return if not zero and with carry reset. SCF ; set the carry flag. RET ; return with carry set if zero. ;------------------------ ; Greater than zero ($37) ;------------------------ ; Test if the last value on the calculator stack is greater than zero. ; This routine is also called directly from the end-tests of the comparison ; routine. ;;;$34F9 GREATER_0: CALL TEST_ZERO ; routine TEST_ZERO RET C ; return if was zero as this ; is also the Boolean 'false' value. LD A,$FF ; prepare XOR mask for sign bit JR SIGN_TO_C ; forward to SIGN_TO_C ; to put sign in carry ; (carry will become set if sign is positive) ; and then overwrite location with 1 or 0 ; as appropriate. ;-------------------------- ; Handle NOT operator ($30) ;-------------------------- ; This overwrites the last value with 1 if it was zero else with zero ; if it was any other value. ; ; e.g NOT 0 returns 1, NOT 1 returns 0, NOT -3 returns 0. ; ; The subroutine is also called directly from the end-tests of the comparison ; operator. ;;;$3501 NOT_: CALL TEST_ZERO ; routine TEST_ZERO sets carry if zero JR FP_0_1 ; to FP_0_1 to overwrite operand with ; 1 if carry is set else to overwrite with zero. ;--------------------- ; Less than zero ($36) ;--------------------- ; Destructively test if last value on calculator stack is less than zero. ; Bit 7 of second byte will be set if so. ;;;$3506 LESS_0: XOR A ; set xor mask to zero ; (carry will become set if sign is negative). ; transfer sign of mantissa to Carry Flag. ;;;$3507 SIGN_TO_C: INC HL ; address 2nd byte. XOR (HL) ; bit 7 of HL will be set if number is negative. DEC HL ; address 1st byte again. RLCA ; rotate bit 7 of A to carry. ;------------ ; Zero or one ;------------ ; This routine places an integer value zero or one at the addressed location ; of calculator stack or MEM area. The value one is written if carry is set on ; entry else zero. ;;;$350B ;; FP-0/1 FP_0_1: PUSH HL ; save pointer to the first byte LD A,$00 ; load accumulator with zero - without disturbing flags. LD (HL),A ; zero to first byte INC HL ; address next LD (HL),A ; zero to 2nd byte INC HL ; address low byte of integer RLA ; carry to bit 0 of A LD (HL),A ; load one or zero to low byte. RRA ; restore zero to accumulator. INC HL ; address high byte of integer. LD (HL),A ; put a zero there. INC HL ; address fifth byte. LD (HL),A ; put a zero there. POP HL ; restore pointer to the first byte. RET ; return. ;------------------------- ; Handle OR operator ($07) ;------------------------- ; The Boolean OR operator. eg. X OR Y ; The result is zero if both values are zero else a non-zero value. ; ; e.g. 0 OR 0 returns 0. ; -3 OR 0 returns -3. ; 0 OR -3 returns 1. ; -3 OR 2 returns 1. ; ; A binary operation. ; On entry HL points to first operand (X) and DE to second operand (Y). ;;;$351B OR_: EX DE,HL ; make HL point to second number CALL TEST_ZERO ; routine TEST_ZERO EX DE,HL ; restore pointers RET C ; return if result was zero - first operand, ; now the last value, is the result. SCF ; set carry flag JR FP_0_1 ; back to FP_0_1 to overwrite the first operand ; with the value 1. ;------------------------------- ; Handle number AND number ($08) ;------------------------------- ; The Boolean AND operator. ; ; e.g. -3 AND 2 returns -3. ; -3 AND 0 returns 0. ; 0 AND -2 returns 0. ; 0 AND 0 returns 0. ; ; Compare with OR routine above. ;;;$3524 NO_AND_NO: EX DE,HL ; make HL address second operand. CALL TEST_ZERO ; routine TEST_ZERO sets carry if zero. EX DE,HL ; restore pointers. RET NC ; return if second non-zero, first is result. AND A ; else clear carry. JR FP_0_1 ; back to FP_0_1 to overwrite first operand ; with zero for return value. ;------------------------------- ; Handle string AND number ($10) ;------------------------------- ; e.g. "You Win" AND score>99 will return the string if condition is true ; or the null string if false. ;;;$352D STR_AND_NO: EX DE,HL ; make HL point to the number. CALL TEST_ZERO ; routine TEST_ZERO. EX DE,HL ; restore pointers. RET NC ; return if number was not zero - the string is the result. ; if the number was zero (false) then the null string must be returned by ; altering the length of the string on the calculator stack to zero. PUSH DE ; save pointer to the now obsolete number ; (which will become the new STKEND) DEC DE ; point to the 5th byte of string descriptor. XOR A ; clear the accumulator. LD (DE),A ; place zero in high byte of length. DEC DE ; address low byte of length. LD (DE),A ; place zero there - now the null string. POP DE ; restore pointer - new STKEND. RET ; return. ;------------------------------------ ; Perform comparison ($09-$0E, $11-$16) ;------------------------------------ ; True binary operations. ; ; A single entry point is used to evaluate six numeric and six string ; comparisons. On entry, the calculator literal is in the B register and ; the two numeric values, or the two string parameters, are on the ; calculator stack. ; The individual bits of the literal are manipulated to group similar ; operations although the SUB 8 instruction does nothing useful and merely ; alters the string test bit. ; Numbers are compared by subtracting one from the other, strings are ; compared by comparing every character until a mismatch, or the end of one ; or both, is reached. ; ; Numeric Comparisons. ; -------------------- ; The 'x>y' example is the easiest as it employs straight-thru logic. ; Number y is subtracted from x and the result tested for GREATER_0 yielding ; a final value 1 (true) or 0 (false). ; For 'x0? NOT ; NO_GR_EQL x>=y 0A 00000010 dec 00000001 10000000c swap y-x ? --- >0? NOT ; NOS_NEQL x<>y 0B 00000011 dec 00000010 00000001 ---- x-y ? NOT --- NOT ; NO_GRTR x>y 0C 00000100 - 00000100 00000010 ---- x-y ? --- >0? --- ; NO_LESS x0? --- ; NOS_EQL x=y 0E 00000110 - 00000110 00000011 ---- x-y ? NOT --- --- ; ; comp -> C/F ; ==== === ; STR_L_EQL x$<=y$ 11 00001001 dec 00001000 00000100 ---- x$y$ 0 !or >0? NOT ; STR_GR_EQL x$>=y$ 12 00001010 dec 00001001 10000100c swap y$x$ 0 !or >0? NOT ; STRS_NEQL x$<>y$ 13 00001011 dec 00001010 00000101 ---- x$y$ 0 !or >0? NOT ; STR_GRTR x$>y$ 14 00001100 - 00001100 00000110 ---- x$y$ 0 !or >0? --- ; STR_LESS x$0? --- ; STRS_EQL x$=y$ 16 00001110 - 00001110 00000111 ---- x$y$ 0 !or >0? --- ; ; String comparisons are a little different in that the eql/neql carry flag ; from the 2nd RRCA is, as before, fed into the first of the end tests but ; along the way it gets modified by the comparison process. The result on the ; stack always starts off as zero and the carry fed in determines if NOT is ; applied to it. So the only time the GREATER_0 test is applied is if the ; stack holds zero which is not very efficient as the test will always yield ; zero. The most likely explanation is that there were once separate end tests ; for numbers and strings. ;;;$353B NO_L_EQL: NO_GR_EQL: NOS_NEQL: NO_GRTR: NO_LESS: NOS_EQL: STR_L_EQL: STR_GR_EQL: STRS_NEQL: STR_GRTR: STR_LESS: STRS_EQL: LD A,B ; transfer literal to accumulator. SUB $08 ; subtract eight - which is not useful. BIT 2,A ; isolate '>', '<', '='. JR NZ,EX_OR_NOT ; skip to EX_OR_NOT with these. DEC A ; else make $00-$02, $08-$0A to match bits 0-2. ;;;$3543 EX_OR_NOT: RRCA ; the first RRCA sets carry for a swap. JR NC,NU_OR_STR ; forward to NU_OR_STR with other 8 cases ; for the other 4 cases the two values on the calculator stack are exchanged. PUSH AF ; save A and carry. PUSH HL ; save HL - pointer to first operand. ; (DE points to second operand). CALL EXCHANGE ; routine EXCHANGE swaps the two values. ; (HL = second operand, DE = STKEND) POP DE ; DE = first operand EX DE,HL ; as we were. POP AF ; restore A and carry. ; Note. it would be better if the 2nd RRCA preceded the string test. ; It would save two duplicate bytes and if we also got rid of that sub 8 ; at the beginning we wouldn't have to alter which bit we test. ;;;$354E NU_OR_STR: BIT 2,A ; test if a string comparison. JR NZ,STRINGS ; forward to STRINGS if so. ; continue with numeric comparisons. RRCA ; 2nd RRCA causes eql/neql to set carry. PUSH AF ; save A and carry CALL SUBTRACT ; routine SUBTRACT leaves result on stack. JR END_TESTS ; forward to END_TESTS ;;;$3559 STRINGS: RRCA ; 2nd RRCA causes eql/neql to set carry. PUSH AF ; save A and carry. CALL STK_FETCH ; routine STK_FETCH gets 2nd string params PUSH DE ; save start2 *. PUSH BC ; and the length. CALL STK_FETCH ; routine STK_FETCH gets 1st string ; parameters - start in DE, length in BC. POP HL ; restore length of second to HL. ; A loop is now entered to compare, by subtraction, each corresponding character ; of the strings. For each successful match, the pointers are incremented and ; the lengths decreased and the branch taken back to here. If both string ; remainders become null at the same time, then an exact match exists. ;;;$3564 BYTE_COMP: LD A,H ; test if the second string OR L ; is the null string and hold flags. EX (SP),HL ; put length2 on stack, bring start2 to HL *. LD A,B ; hi byte of length1 to A JR NZ,SEC_PLUS ; forward to SEC_PLUS if second not null. OR C ; test length of first string. ;;;$356B SECND_LOW: POP BC ; pop the second length off stack. JR Z,BOTH_NULL ; forward to BOTH_NULL if first string is also ; of zero length. ; the true condition - first is longer than second (SECND-LESS) POP AF ; restore carry (set if eql/neql) CCF ; complement carry flag. ; Note. equality becomes false. ; Inequality is true. By swapping or applying ; a terminal 'not', all comparisons have been ; manipulated so that this is success path. JR STR_TEST ; forward to leave via STR_TEST ; the branch was here with a match ;;;$3572 BOTH_NULL: POP AF ; restore carry - set for eql/neql JR STR_TEST ; forward to STR_TEST ; the branch was here when 2nd string not null and low byte of first is yet ; to be tested. ;;;$3575 SEC_PLUS: OR C ; test the length of first string. JR Z,FRST_LESS ; forward to FRST_LESS if length is zero. ; both strings have at least one character left. LD A,(DE) ; fetch character of first string. SUB (HL) ; subtract with that of 2nd string. JR C,FRST_LESS ; forward to FRST_LESS if carry set JR NZ,SECND_LOW ; back to SECND_LOW and then STR_TEST ; if not exact match. DEC BC ; decrease length of 1st string. INC DE ; increment 1st string pointer. INC HL ; increment 2nd string pointer. EX (SP),HL ; swap with length on stack DEC HL ; decrement 2nd string length JR BYTE_COMP ; back to BYTE_COMP ; the false condition. ;;;$3585 FRST_LESS: POP BC ; discard length POP AF ; pop A AND A ; clear the carry for false result. ; exact match and x$>y$ rejoin here ;;;$3588 STR_TEST: PUSH AF ; save A and carry RST 28H ;; FP_CALC DEFB $A0 ;;STK_ZERO an initial false value. DEFB $38 ;;END_CALC ; both numeric and string paths converge here. ;;;$358C END_TESTS: POP AF ; pop carry - will be set if eql/neql PUSH AF ; save it again. CALL C,NOT_ ; routine NOT sets true(1) if equal(0) ; or, for strings, applies true result. POP AF ; pop carry and PUSH AF ; save A CALL NC,GREATER_0 ; routine GREATER_0 tests numeric subtraction ; result but also needlessly tests the string ; value for zero - it must be. POP AF ; pop A RRCA ; the third RRCA - test for '<=', '>=' or '<>'. CALL NC,NOT_ ; apply a terminal NOT if so. RET ; return. ;--------------------------- ; String concatenation ($17) ;--------------------------- ; This literal combines two strings into one e.g. LET a$ = b$ + c$ ; The two parameters of the two strings to be combined are on the stack. ;;;$359C STRS_ADD: CALL STK_FETCH ; routine STK_FETCH fetches string parameters ; and deletes calculator stack entry. PUSH DE ; save start address. PUSH BC ; and length. CALL STK_FETCH ; routine STK_FETCH for first string POP HL ; re-fetch first length PUSH HL ; and save again PUSH DE ; save start of second string PUSH BC ; and it's length. ADD HL,BC ; add the two lengths. LD B,H ; transfer to BC LD C,L ; and create RST 30H ; BC_SPACES in workspace. ; DE points to start of space. CALL STK_STO_D ; routine STK_STO_D stores parameters ; of new string updating STKEND. POP BC ; length of first POP HL ; address of start LD A,B ; test for OR C ; zero length. JR Z,OTHER_STR ; to OTHER_STR if null string LDIR ; copy string to workspace. ;;;$35B7 OTHER_STR: POP BC ; now second length POP HL ; and start of string LD A,B ; test this one OR C ; for zero length JR Z,STK_PNTRS ; skip forward to STK_PNTRS if so as complete. LDIR ; else copy the bytes. ; and continue into next routine which ; sets the calculator stack pointers. ;--------------------- ; Check stack pointers ;--------------------- ; Register DE is set to STKEND and HL, the result pointer, is set to five ; locations below this. ; This routine is used when it is inconvenient to save these values at the ; time the calculator stack is manipulated due to other activity on the ; machine stack. ; This routine is also used to terminate the VAL and READ_IN routines for ; the same reason and to initialize the calculator stack at the start of ; the CALCULATE routine. ;;;$35BF STK_PNTRS: LD HL,(STKEND) ; fetch STKEND value from system variable. LD DE,$FFFB ; the value -5 PUSH HL ; push STKEND value. ADD HL,DE ; subtract 5 from HL. POP DE ; pop STKEND to DE. RET ; return. ;------------------ ; Handle CHR$ ($2F) ;------------------ ; This function returns a single character string that is a result of ; converting a number in the range 0-255 to a string e.g. CHR$ 65 = "A". ;;;$35C9 CHRS: CALL FP_TO_A ; routine FP_TO_A puts the number in A. JR C,REPORT_BD ; forward to REPORT_BD if overflow JR NZ,REPORT_BD ; forward to REPORT_BD if negative PUSH AF ; save the argument. LD BC,$0001 ; one space required. RST 30H ; BC_SPACES makes DE point to start POP AF ; restore the number. LD (DE),A ; and store in workspace CALL STK_STO_D ; routine STK_STO_D stacks descriptor. EX DE,HL ; make HL point to result and DE to STKEND. RET ; return. ;;;$35DC REPORT_BD: RST 08H ; ERROR_1 DEFB $0A ; Error Report: Integer out of range ;------------------------------- ; Handle VAL and VAL$ ($1D, $18) ;------------------------------- ; VAL treats the characters in a string as a numeric expression. ; e.g. VAL "2.3" = 2.3, VAL "2+4" = 6, VAL ("2" + "4") = 24. ; VAL$ treats the characters in a string as a string expression. ; e.g. VAL$ (z$+"(2)") = a$(2) if z$ happens to be "a$". ;;;$35DE VAL: VALS: LD HL,(CH_ADD) ; fetch value of system variable CH_ADD PUSH HL ; and save on the machine stack. LD A,B ; fetch the literal $1D or $18. ADD A,$E3 ; add $E3 to form $00 (setting carry) or $FB. SBC A,A ; now form $FF bit 6 = numeric result ; or $00 bit 6 = string result. PUSH AF ; save this mask on the stack CALL STK_FETCH ; routine STK_FETCH fetches the string operand ; from calculator stack. PUSH DE ; save the address of the start of the string. INC BC ; increment the length for a carriage return. RST 30H ; BC_SPACES creates the space in workspace. POP HL ; restore start of string to HL. LD (CH_ADD),DE ; load CH_ADD with start DE in workspace. PUSH DE ; save the start in workspace LDIR ; copy string from program or variables or ; workspace to the workspace area. EX DE,HL ; end of string + 1 to HL DEC HL ; decrement HL to point to end of new area. LD (HL),$0D ; insert a carriage return at end. RES 7,(IY+$01) ; update FLAGS - signal checking syntax. CALL SCANNING ; routine SCANNING evaluates string ; expression and result. RST 18H ; GET_CHAR fetches next character. CP $0D ; is it the expected carriage return ? JR NZ,V_RPORT_C ; forward to V_RPORT_C if not ; 'Nonsense in Basic'. POP HL ; restore start of string in workspace. POP AF ; restore expected result flag (bit 6). XOR (IY+$01) ; xor with FLAGS now updated by SCANNING. AND $40 ; test bit 6 - should be zero if result types match. ;;;$360C V_RPORT_C: JP NZ,REPORT_C ; jump back to REPORT_C with a result mismatch. LD (CH_ADD),HL ; set CH_ADD to the start of the string again. SET 7,(IY+$01) ; update FLAGS - signal running program. CALL SCANNING ; routine SCANNING evaluates the string ; in full leaving result on calculator stack. POP HL ; restore saved character address in program. LD (CH_ADD),HL ; and reset the system variable CH_ADD. JR STK_PNTRS ; back to exit via STK_PNTRS. ; resetting the calculator stack pointers ; HL and DE from STKEND as it wasn't possible ; to preserve them during this routine. ;------------------ ; Handle STR$ ($2E) ;------------------ ;;;$361F STRS: LD BC,$0001 ; create an initial byte in workspace RST 30H ; using BC_SPACES restart. LD (K_CUR),HL ; set system variable K_CUR to new location. PUSH HL ; and save start on machine stack also. LD HL,(CURCHL) ; fetch value of system variable CURCHL PUSH HL ; and save that too. LD A,$FF ; select system channel 'R'. CALL CHAN_OPEN ; routine CHAN_OPEN opens it. CALL PRINT_FP ; routine PRINT_FP outputs the number to ; workspace updating K-CUR. POP HL ; restore current channel. CALL CHAN_FLAG ; routine CHAN_FLAG resets flags. POP DE ; fetch saved start of string to DE. LD HL,(K_CUR) ; load HL with end of string from K_CUR. AND A ; prepare for true subtraction. SBC HL,DE ; subtract start from end to give length. LD B,H ; transfer the length to LD C,L ; the BC register pair. CALL STK_STO_D ; routine STK_STO_D stores string parameters ; on the calculator stack. EX DE,HL ; HL = last value, DE = STKEND. RET ; return. ;-------------- ; Read-in ($1A) ;-------------- ; This is the calculator literal used by the INKEY$ function when a '#' ; is encountered after the keyword. ; INKEY$ # does not interact correctly with the keyboard, #0 or #1, and ; it's uses are for other channels. ;;;$3645 READ_IN: CALL FIND_INT1 ; routine FIND_INT1 fetches stream to A CP $10 ; compare with 16 decimal. JP NC,REPORT_BB ; jump to REPORT_BB if not in range 0 - 15. ; 'Integer out of range' ; (REPORT_BD is within range) LD HL,(CURCHL) ; fetch current channel CURCHL PUSH HL ; save it CALL CHAN_OPEN ; routine CHAN_OPEN opens channel CALL INPUT_AD ; routine INPUT_AD - the channel must have an ; input stream or else error here from stream stub. LD BC,$0000 ; initialize length of string to zero JR NC,R_I_STORE ; forward to R_I_STORE if no key detected. INC C ; increase length to one. RST 30H ; BC_SPACES creates space for one character in workspace. LD (DE),A ; the character is inserted. ;;;$365F R_I_STORE: CALL STK_STO_D ; routine STK_STO_D stacks the string parameters. POP HL ; restore current channel address CALL CHAN_FLAG ; routine CHAN_FLAG resets current channel ; system variable and flags. JP STK_PNTRS ; jump back to STK_PNTRS ;------------------ ; Handle CODE ($1C) ;------------------ ; Returns the ascii code of a character or first character of a string ; e.g. CODE "Aardvark" = 65, CODE "" = 0. ;;;$3669 CODE: CALL STK_FETCH ; routine STK_FETCH to fetch and delete the ; string parameters. ; DE points to the start, BC holds the length. LD A,B ; test length OR C ; of the string. JR Z,STK_CODE ; skip to STK_CODE with zero if the null string. LD A,(DE) ; else fetch the first character. ;;;$3671 STK_CODE: JP STACK_A ; jump back to STACK_A (with memory check) ;----------------- ; Handle LEN ($1E) ;----------------- ; Returns the length of a string. ; In Sinclair Basic strings can be more than twenty thousand characters long ; so a sixteen-bit register is required to store the length ;;;$3674 LEN: CALL STK_FETCH ; routine STK_FETCH to fetch and delete the ; string parameters from the calculator stack. ; register BC now holds the length of string. JP STACK_BC ; jump back to STACK_BC to save result on the ; calculator stack (with memory check). ;--------------------------- ; Decrease the counter ($35) ;--------------------------- ; The calculator has an instruction that decrements a single-byte ; pseudo-register and makes consequential relative jumps just like ; the Z80's DJNZ instruction. ;;;$367A DEC_JR_NZ: EXX ; switch in set that addresses code PUSH HL ; save pointer to offset byte LD HL,BREG ; address BREG in system variables DEC (HL) ; decrement it POP HL ; restore pointer JR NZ,JUMP_2 ; to JUMP_2 if not zero INC HL ; step past the jump length. EXX ; switch in the main set. RET ; return. ; Note. as a general rule the calculator avoids using the IY register ; otherwise the cumbersome 4 instructions in the middle could be replaced by ; dec (iy+$2d) - three bytes instead of six. ;----------- ; Jump ($33) ;----------- ; This enables the calculator to perform relative jumps just like ; the Z80 chip's JR instruction ;;;$3686 JUMP: EXX ;switch in pointer set ;;;$3687 JUMP_2: LD E,(HL) ; the jump byte 0-127 forward, 128-255 back. LD A,E ; transfer to accumulator. RLA ; if backward jump, carry is set. SBC A,A ; will be $FF if backward or $00 if forward. LD D,A ; transfer to high byte. ADD HL,DE ; advance calculator pointer forward or back. EXX ; switch back. RET ; return. ;------------------- ; Jump on true ($00) ;------------------- ; This enables the calculator to perform conditional relative jumps ; dependent on whether the last test gave a true result ;;;$368F JUMP_TRUE: INC DE ; collect the INC DE ; third byte LD A,(DE) ; of the test DEC DE ; result and DEC DE ; backtrack. AND A ; is result 0 or 1 ? JR NZ,JUMP ; back to JUMP if true (1). EXX ; else switch in the pointer set. INC HL ; step past the jump length. EXX ; switch in the main set. RET ; return. ;------------------------- ; End of calculation ($38) ;------------------------- ; The END_CALC literal terminates a mini-program written in the Spectrum's ; internal language. ;;;$369B END_CALC: POP AF ; drop the calculator return address RE_ENTRY EXX ; switch to the other set. EX (SP),HL ; transfer H'L' to machine stack for the ; return address. ; when exiting recursion then the previous ; pointer is transferred to H'L'. EXX ; back to main set. RET ; return. ;------------- ; Modulus ($32) ;------------- ;;;$36A0 N_MOD_M: RST 28H ;; FP_CALC 17, 3. DEFB $C0 ;;st-mem-0 17, 3. DEFB $02 ;;DELETE 17. DEFB $31 ;;DUPLICATE 17, 17. DEFB $E0 ;;get-mem-0 17, 17, 3. DEFB $05 ;;DIVISION 17, 17/3. DEFB $27 ;;INT 17, 5. DEFB $E0 ;;get-mem-0 17, 5, 3. DEFB $01 ;;EXCHANGE 17, 3, 5. DEFB $C0 ;;st-mem-0 17, 3, 5. DEFB $04 ;;MULTIPLY 17, 15. DEFB $03 ;;SUBTRACT 2. DEFB $E0 ;;get-mem-0 2, 5. DEFB $38 ;;END_CALC 2, 5. RET ; return. ;----------------- ; Handle INT ($27) ;----------------- ; This function returns the integer of x, which is just the same as truncate ; for positive numbers. The truncate literal truncates negative numbers ; upwards so that -3.4 gives -3 whereas the Basic INT function has to ; truncate negative numbers down so that INT -3.4 is 4. ; It is best to work through using +-3.4 as examples. ;;;$36AF INT: RST 28H ;; FP_CALC x. (= 3.4 or -3.4). DEFB $31 ;;DUPLICATE x, x. DEFB $36 ;;LESS_0 x, (1/0) DEFB $00 ;;JUMP_TRUE x, (1/0) DEFB $04 ;;to X_NEG DEFB $3A ;;TRUNCATE trunc 3.4 = 3. DEFB $38 ;;END_CALC 3. RET ; return with + int x on stack. ;;;$36B7 X_NEG: DEFB $31 ;;DUPLICATE -3.4, -3.4. DEFB $3A ;;TRUNCATE -3.4, -3. DEFB $C0 ;;st-mem-0 -3.4, -3. DEFB $03 ;;SUBTRACT -.4 DEFB $E0 ;;get-mem-0 -.4, -3. DEFB $01 ;;EXCHANGE -3, -.4. DEFB $30 ;;NOT -3, (0). DEFB $00 ;;JUMP_TRUE -3. DEFB $03 ;;to EXIT -3. DEFB $A1 ;;STK_ONE -3, 1. DEFB $03 ;;SUBTRACT -4. ;;;$36C2 EXIT: DEFB $38 ;;END_CALC -4. RET ; return. ;----------------- ; Exponential ($26) ;----------------- ;;;$36C4 EXP: RST 28H ;; FP_CALC DEFB $3D ;;RE_STACK DEFB $34 ;;STK_DATA DEFB $F1 ;;Exponent: $81, Bytes: 4 DEFB $38,$AA,$3B,$29 ;; DEFB $04 ;;MULTIPLY DEFB $31 ;;DUPLICATE DEFB $27 ;;INT DEFB $C3 ;;st-mem-3 DEFB $03 ;;SUBTRACT DEFB $31 ;;DUPLICATE DEFB $0F ;;ADDITION DEFB $A1 ;;STK_ONE DEFB $03 ;;SUBTRACT DEFB $88 ;;series-08 DEFB $13 ;;Exponent: $63, Bytes: 1 DEFB $36 ;;(+00,+00,+00) DEFB $58 ;;Exponent: $68, Bytes: 2 DEFB $65,$66 ;;(+00,+00) DEFB $9D ;;Exponent: $6D, Bytes: 3 DEFB $78,$65,$40 ;;(+00) DEFB $A2 ;;Exponent: $72, Bytes: 3 DEFB $60,$32,$C9 ;;(+00) DEFB $E7 ;;Exponent: $77, Bytes: 4 DEFB $21,$F7,$AF,$24 ;; DEFB $EB ;;Exponent: $7B, Bytes: 4 DEFB $2F,$B0,$B0,$14 ;; DEFB $EE ;;Exponent: $7E, Bytes: 4 DEFB $7E,$BB,$94,$58 ;; DEFB $F1 ;;Exponent: $81, Bytes: 4 DEFB $3A,$7E,$F8,$CF ;; DEFB $E3 ;;get-mem-3 DEFB $38 ;;END_CALC CALL FP_TO_A ; routine FP_TO_A JR NZ,N_NEGTV ; to N_NEGTV JR C,REPORT_6B ; to REPORT_6B ADD A,(HL) ; JR NC,RESULT_OK ; to RESULT_OK ;;;$3703 REPORT_6B: RST 08H ; ERROR_1 DEFB $05 ; Error Report: Number too big ;; N_NEGTV N_NEGTV: JR C,RSLT_ZERO ; to RSLT_ZERO SUB (HL) JR NC,RSLT_ZERO ; to RSLT_ZERO NEG ; Negate ;;;$370C RESULT_OK: LD (HL),A RET ; return. ;;;$370E RSLT_ZERO: RST 28H ;; FP_CALC DEFB $02 ;;DELETE DEFB $A0 ;;STK_ZERO DEFB $38 ;;END_CALC RET ; return. ;------------------------ ; Natural logarithm ($25) ;------------------------ ;;;$3713 LN: RST 28H ;; FP_CALC DEFB $3D ;;RE_STACK DEFB $31 ;;DUPLICATE DEFB $37 ;;GREATER_0 DEFB $00 ;;JUMP_TRUE DEFB $04 ;;to VALID DEFB $38 ;;END_CALC ;;;$371A REPORT_AB: RST 08H ; ERROR_1 DEFB $09 ; Error Report: Invalid argument ;;;$371C VALID: DEFB $A0 ;;STK_ZERO DEFB $02 ;;DELETE DEFB $38 ;;END_CALC LD A,(HL) LD (HL),$80 CALL STACK_A ; routine STACK_A RST 28H ;; FP_CALC DEFB $34 ;;STK_DATA DEFB $38 ;;Exponent: $88, Bytes: 1 DEFB $00 ;;(+00,+00,+00) DEFB $03 ;;SUBTRACT DEFB $01 ;;EXCHANGE DEFB $31 ;;DUPLICATE DEFB $34 ;;STK_DATA DEFB $F0 ;;Exponent: $80, Bytes: 4 DEFB $4C,$CC,$CC,$CD ;; DEFB $03 ;;SUBTRACT DEFB $37 ;;GREATER_0 DEFB $00 ;;JUMP_TRUE DEFB $08 ;;to GRE_8 DEFB $01 ;;EXCHANGE DEFB $A1 ;;STK_ONE DEFB $03 ;;SUBTRACT DEFB $01 ;;EXCHANGE DEFB $38 ;;END_CALC INC (HL) RST 28H ;; FP_CALC ;;;$373D GRE_8: DEFB $01 ;;EXCHANGE DEFB $34 ;;STK_DATA DEFB $F0 ;;Exponent: $80, Bytes: 4 DEFB $31,$72,$17,$F8 ;; DEFB $04 ;;MULTIPLY DEFB $01 ;;EXCHANGE DEFB $A2 ;;STK_HALF DEFB $03 ;;SUBTRACT DEFB $A2 ;;STK_HALF DEFB $03 ;;SUBTRACT DEFB $31 ;;DUPLICATE DEFB $34 ;;STK_DATA DEFB $32 ;;Exponent: $82, Bytes: 1 DEFB $20 ;;(+00,+00,+00) DEFB $04 ;;MULTIPLY DEFB $A2 ;;STK_HALF DEFB $03 ;;SUBTRACT DEFB $8C ;;series-0C DEFB $11 ;;Exponent: $61, Bytes: 1 DEFB $AC ;;(+00,+00,+00) DEFB $14 ;;Exponent: $64, Bytes: 1 DEFB $09 ;;(+00,+00,+00) DEFB $56 ;;Exponent: $66, Bytes: 2 DEFB $DA,$A5 ;;(+00,+00) DEFB $59 ;;Exponent: $69, Bytes: 2 DEFB $30,$C5 ;;(+00,+00) DEFB $5C ;;Exponent: $6C, Bytes: 2 DEFB $90,$AA ;;(+00,+00) DEFB $9E ;;Exponent: $6E, Bytes: 3 DEFB $70,$6F,$61 ;;(+00) DEFB $A1 ;;Exponent: $71, Bytes: 3 DEFB $CB,$DA,$96 ;;(+00) DEFB $A4 ;;Exponent: $74, Bytes: 3 DEFB $31,$9F,$B4 ;;(+00) DEFB $E7 ;;Exponent: $77, Bytes: 4 DEFB $A0,$FE,$5C,$FC ;; DEFB $EA ;;Exponent: $7A, Bytes: 4 DEFB $1B,$43,$CA,$36 ;; DEFB $ED ;;Exponent: $7D, Bytes: 4 DEFB $A7,$9C,$7E,$5E ;; DEFB $F0 ;;Exponent: $80, Bytes: 4 DEFB $6E,$23,$80,$93 ;; DEFB $04 ;;MULTIPLY DEFB $0F ;;ADDITION DEFB $38 ;;END_CALC RET ; return. ;---------------------- ; Reduce argument ($39) ;---------------------- ;;;$3783 GET_ARGT: RST 28H ;; FP_CALC DEFB $3D ;;RE_STACK DEFB $34 ;;STK_DATA DEFB $EE ;;Exponent: $7E, Bytes: 4 DEFB $22,$F9,$83,$6E DEFB $04 ;;MULTIPLY DEFB $31 ;;DUPLICATE DEFB $A2 ;;STK_HALF DEFB $0F ;;ADDITION DEFB $27 ;;INT DEFB $03 ;;SUBTRACT DEFB $31 ;;DUPLICATE DEFB $0F ;;ADDITION DEFB $31 ;;DUPLICATE DEFB $0F ;;ADDITION DEFB $31 ;;DUPLICATE DEFB $2A ;;ABS DEFB $A1 ;;STK_ONE DEFB $03 ;;SUBTRACT DEFB $31 ;;DUPLICATE DEFB $37 ;;GREATER_0 DEFB $C0 ;;st-mem-0 DEFB $00 ;;JUMP_TRUE DEFB $04 ;;to ZPLUS DEFB $02 ;;DELETE DEFB $38 ;;END_CALC RET ; return. ;;;$37A1 ZPLUS: DEFB $A1 ;;STK_ONE DEFB $03 ;;SUBTRACT DEFB $01 ;;EXCHANGE DEFB $36 ;;LESS_0 DEFB $00 ;;JUMP_TRUE DEFB $02 ;;to YNEG DEFB $1B ;;NEGATE ;;;$37A8 YNEG: DEFB $38 ;;END_CALC RET ; return. ;-------------------- ; Handle cosine ($20) ;-------------------- ;;;$37AA COS_: RST 28H ;; FP_CALC DEFB $39 ;;GET_ARGT DEFB $2A ;;ABS DEFB $A1 ;;STK_ONE DEFB $03 ;;SUBTRACT DEFB $E0 ;;get-mem-0 DEFB $00 ;;JUMP_TRUE DEFB $06 ;;fwd to C_ENT DEFB $1B ;;NEGATE DEFB $33 ;;jump DEFB $03 ;;fwd to C_ENT ;------------------ ; Handle sine ($1F) ;------------------ ;;;$37B5 SIN_: RST 28H ;; FP_CALC DEFB $39 ;;GET_ARGT ;;;$37B7 C_ENT: DEFB $31 ;;DUPLICATE DEFB $31 ;;DUPLICATE DEFB $04 ;;MULTIPLY DEFB $31 ;;DUPLICATE DEFB $0F ;;ADDITION DEFB $A1 ;;STK_ONE DEFB $03 ;;SUBTRACT DEFB $86 ;;series-06 DEFB $14 ;;Exponent: $64, Bytes: 1 DEFB $E6 ;;(+00,+00,+00) DEFB $5C ;;Exponent: $6C, Bytes: 2 DEFB $1F,$0B ;;(+00,+00) DEFB $A3 ;;Exponent: $73, Bytes: 3 DEFB $8F,$38,$EE ;;(+00) DEFB $E9 ;;Exponent: $79, Bytes: 4 DEFB $15,$63,$BB,$23 ;; DEFB $EE ;;Exponent: $7E, Bytes: 4 DEFB $92,$0D,$CD,$ED ;; DEFB $F1 ;;Exponent: $81, Bytes: 4 DEFB $23,$5D,$1B,$EA ;; DEFB $04 ;;MULTIPLY DEFB $38 ;;END_CALC RET ; return. ;--------------------- ; Handle tangent ($21) ;--------------------- ; Evaluates tangent x as sin x/cos x. ;;;$37DA TAN: RST 28H ;; FP_CALC x. DEFB $31 ;;DUPLICATE x, x. DEFB $1F ;;SIN_ x, sin x. DEFB $01 ;;EXCHANGE sin x, x. DEFB $20 ;;COS_ sin x, cos x. DEFB $05 ;;DIVISION sin x/cos x (= tan x). DEFB $38 ;;END_CALC tan x. RET ; return. ;------------------- ; Handle arctan ($24) ;------------------- ; the inverse tangent function with the result in radians. ;;;$37E2 ATN: CALL RE_STACK ; routine RE_STACK LD A,(HL) CP $81 JR C,SMALL ; to SMALL RST 28H ;; FP_CALC DEFB $A1 ;;STK_ONE DEFB $1B ;;NEGATE DEFB $01 ;;EXCHANGE DEFB $05 ;;DIVISION DEFB $31 ;;DUPLICATE DEFB $36 ;;LESS_0 DEFB $A3 ;;STK_PI_2 DEFB $01 ;;EXCHANGE DEFB $00 ;;JUMP_TRUE DEFB $06 ;;to CASES DEFB $1B ;;NEGATE DEFB $33 ;;jump DEFB $03 ;;to CASES ;;;$37F8 SMALL: RST 28H ;; FP_CALC DEFB $A0 ;;STK_ZERO ;;;$37FA CASES: DEFB $01 ;;EXCHANGE DEFB $31 ;;DUPLICATE DEFB $31 ;;DUPLICATE DEFB $04 ;;MULTIPLY DEFB $31 ;;DUPLICATE DEFB $0F ;;ADDITION DEFB $A1 ;;STK_ONE DEFB $03 ;;SUBTRACT DEFB $8C ;;series-0C DEFB $10 ;;Exponent: $60, Bytes: 1 DEFB $B2 ;;(+00,+00,+00) DEFB $13 ;;Exponent: $63, Bytes: 1 DEFB $0E ;;(+00,+00,+00) DEFB $55 ;;Exponent: $65, Bytes: 2 DEFB $E4,$8D ;;(+00,+00) DEFB $58 ;;Exponent: $68, Bytes: 2 DEFB $39,$BC ;;(+00,+00) DEFB $5B ;;Exponent: $6B, Bytes: 2 DEFB $98,$FD ;;(+00,+00) DEFB $9E ;;Exponent: $6E, Bytes: 3 DEFB $00,$36,$75 ;;(+00) DEFB $A0 ;;Exponent: $70, Bytes: 3 DEFB $DB,$E8,$B4 ;;(+00) DEFB $63 ;;Exponent: $73, Bytes: 2 DEFB $42,$C4 ;;(+00,+00) DEFB $E6 ;;Exponent: $76, Bytes: 4 DEFB $B5,$09,$36,$BE ;; DEFB $E9 ;;Exponent: $79, Bytes: 4 DEFB $36,$73,$1B,$5D ;; DEFB $EC ;;Exponent: $7C, Bytes: 4 DEFB $D8,$DE,$63,$BE ;; DEFB $F0 ;;Exponent: $80, Bytes: 4 DEFB $61,$A1,$B3,$0C ;; DEFB $04 ;;MULTIPLY DEFB $0F ;;ADDITION DEFB $38 ;;END_CALC RET ; return. ;-------------------- ; Handle arcsin ($22) ;-------------------- ; the inverse sine function with result in radians. ; Error A unless the argument is between -1 and +1. ;;;$3833 ASN: RST 28H ;; FP_CALC DEFB $31 ;;DUPLICATE DEFB $31 ;;DUPLICATE DEFB $04 ;;MULTIPLY DEFB $A1 ;;STK_ONE DEFB $03 ;;SUBTRACT DEFB $1B ;;NEGATE DEFB $28 ;;SQR DEFB $A1 ;;STK_ONE DEFB $0F ;;ADDITION DEFB $05 ;;DIVISION DEFB $24 ;;ATN DEFB $31 ;;DUPLICATE DEFB $0F ;;ADDITION DEFB $38 ;;END_CALC RET ; return. ;-------------------- ; Handle arccos ($23) ;-------------------- ; the inverse cosine function with the result in radians. ; Error A unless the argument is between -1 and +1. ;;;$3843 ACS: RST 28H ;; FP_CALC DEFB $22 ;;ASN DEFB $A3 ;;STK_PI_2 DEFB $03 ;;SUBTRACT DEFB $1B ;;NEGATE DEFB $38 ;;END_CALC RET ; return. ;------------------------- ; Handle square root ($28) ;------------------------- ; This routine is remarkable only in it's brevity - 7 bytes. ; It wasn't written here but in the ZX81 where the programmers had to squeeze ; a bulky operating sytem into an 8K ROM. it simply calculates ; ;;;$384A SQR: RST 28H ;; FP_CALC DEFB $31 ;;DUPLICATE DEFB $30 ;;NOT DEFB $00 ;;JUMP_TRUE DEFB $1E ;;to LAST DEFB $A2 ;;STK_HALF DEFB $38 ;;END_CALC ;------------------------- ; Handle exponential ($06) ;------------------------- ;;;$3851 TO_POWER: RST 28H ;; FP_CALC DEFB $01 ;;EXCHANGE DEFB $31 ;;DUPLICATE DEFB $30 ;;NOT DEFB $00 ;;JUMP_TRUE DEFB $07 ;;to XISO DEFB $25 ;;LN DEFB $04 ;;MULTIPLY DEFB $38 ;;END_CALC JP EXP ; to EXP ;;;$385D XISO: DEFB $02 ;;DELETE DEFB $31 ;;DUPLICATE DEFB $30 ;;NOT DEFB $00 ;;JUMP_TRUE DEFB $09 ;;to ONE DEFB $A0 ;;STK_ZERO DEFB $01 ;;EXCHANGE DEFB $37 ;;GREATER_0 DEFB $00 ;;JUMP_TRUE DEFB $06 ;;to LAST DEFB $A1 ;;STK_ONE DEFB $01 ;;EXCHANGE DEFB $05 ;;DIVISION ;;;$386A ONE: DEFB $02 ;;DELETE DEFB $A1 ;;STK_ONE ;;;$386C LAST: DEFB $38 ;;END_CALC RET ; return ;---------------- ; Spare Locations ;---------------- ;;;$386E SPARE: DEFB $FF, $FF DEFB $FF, $FF, $FF, $FF, $FF, $FF, $FF, $FF; DEFB $FF, $FF, $FF, $FF, $FF, $FF, $FF, $FF; DEFB $FF, $FF, $FF, $FF, $FF, $FF, $FF, $FF; DEFB $FF, $FF, $FF, $FF, $FF, $FF, $FF, $FF; DEFB $FF, $FF, $FF, $FF, $FF, $FF, $FF, $FF; DEFB $FF, $FF, $FF, $FF, $FF, $FF, $FF, $FF; DEFB $FF, $FF, $FF, $FF, $FF, $FF, $FF, $FF; DEFB $FF, $FF, $FF, $FF, $FF, $FF, $FF, $FF; DEFB $FF, $FF, $FF, $FF, $FF, $FF, $FF, $FF; DEFB $FF, $FF, $FF, $FF, $FF, $FF, $FF, $FF; DEFB $FF, $FF, $FF, $FF, $FF, $FF, $FF, $FF; DEFB $FF, $FF, $FF, $FF, $FF, $FF, $FF, $FF; DEFB $FF, $FF, $FF, $FF, $FF, $FF, $FF, $FF; DEFB $FF, $FF, $FF, $FF, $FF, $FF, $FF, $FF; DEFB $FF, $FF, $FF, $FF, $FF, $FF, $FF, $FF; DEFB $FF, $FF, $FF, $FF, $FF, $FF, $FF, $FF; DEFB $FF, $FF, $FF, $FF, $FF, $FF, $FF, $FF; DEFB $FF, $FF, $FF, $FF, $FF, $FF, $FF, $FF; DEFB $FF, $FF, $FF, $FF, $FF, $FF, $FF, $FF; DEFB $FF, $FF, $FF, $FF, $FF, $FF, $FF, $FF; DEFB $FF, $FF, $FF, $FF, $FF, $FF, $FF, $FF; DEFB $FF, $FF, $FF, $FF, $FF, $FF, $FF, $FF; DEFB $FF, $FF, $FF, $FF, $FF, $FF, $FF, $FF; DEFB $FF, $FF, $FF, $FF, $FF, $FF, $FF, $FF; DEFB $FF, $FF, $FF, $FF, $FF, $FF, $FF, $FF; DEFB $FF, $FF, $FF, $FF, $FF, $FF, $FF, $FF; DEFB $FF, $FF, $FF, $FF, $FF, $FF, $FF, $FF; DEFB $FF, $FF, $FF, $FF, $FF, $FF, $FF, $FF; DEFB $FF, $FF, $FF, $FF, $FF, $FF, $FF, $FF; DEFB $FF, $FF, $FF, $FF, $FF, $FF, $FF, $FF; DEFB $FF, $FF, $FF, $FF, $FF, $FF, $FF, $FF; DEFB $FF, $FF, $FF, $FF, $FF, $FF, $FF, $FF; DEFB $FF, $FF, $FF, $FF, $FF, $FF, $FF, $FF; DEFB $FF, $FF, $FF, $FF, $FF, $FF, $FF, $FF; DEFB $FF, $FF, $FF, $FF, $FF, $FF, $FF, $FF; DEFB $FF, $FF, $FF, $FF, $FF, $FF, $FF, $FF; DEFB $FF, $FF, $FF, $FF, $FF, $FF, $FF, $FF; DEFB $FF, $FF, $FF, $FF, $FF, $FF, $FF, $FF; DEFB $FF, $FF, $FF, $FF, $FF, $FF, $FF, $FF; DEFB $FF, $FF, $FF, $FF, $FF, $FF, $FF, $FF; DEFB $FF, $FF, $FF, $FF, $FF, $FF, $FF, $FF; DEFB $FF, $FF, $FF, $FF, $FF, $FF, $FF, $FF; DEFB $FF, $FF, $FF, $FF, $FF, $FF, $FF, $FF; DEFB $FF, $FF, $FF, $FF, $FF, $FF, $FF, $FF; DEFB $FF, $FF, $FF, $FF, $FF, $FF, $FF, $FF; DEFB $FF, $FF, $FF, $FF, $FF, $FF, $FF, $FF; DEFB $FF, $FF, $FF, $FF, $FF, $FF, $FF, $FF; DEFB $FF, $FF, $FF, $FF, $FF, $FF, $FF, $FF; DEFB $FF, $FF, $FF, $FF, $FF, $FF, $FF, $FF; DEFB $FF, $FF, $FF, $FF, $FF, $FF, $FF, $FF; DEFB $FF, $FF, $FF, $FF, $FF, $FF, $FF, $FF; DEFB $FF, $FF, $FF, $FF, $FF, $FF, $FF, $FF; DEFB $FF, $FF, $FF, $FF, $FF, $FF, $FF, $FF; DEFB $FF, $FF, $FF, $FF, $FF, $FF, $FF, $FF; DEFB $FF, $FF, $FF, $FF, $FF, $FF, $FF, $FF; DEFB $FF, $FF, $FF, $FF, $FF, $FF, $FF, $FF; DEFB $FF, $FF, $FF, $FF, $FF, $FF, $FF, $FF; DEFB $FF, $FF, $FF, $FF, $FF, $FF, $FF, $FF; DEFB $FF, $FF, $FF, $FF, $FF, $FF, $FF, $FF; DEFB $FF, $FF, $FF, $FF, $FF, $FF, $FF, $FF; DEFB $FF, $FF, $FF, $FF, $FF, $FF, $FF, $FF; DEFB $FF, $FF, $FF, $FF, $FF, $FF, $FF, $FF; DEFB $FF, $FF, $FF, $FF, $FF, $FF, $FF, $FF; DEFB $FF, $FF, $FF, $FF, $FF, $FF, $FF, $FF; DEFB $FF, $FF, $FF, $FF, $FF, $FF, $FF, $FF; DEFB $FF, $FF, $FF, $FF, $FF, $FF, $FF, $FF; DEFB $FF, $FF, $FF, $FF, $FF, $FF, $FF, $FF; DEFB $FF, $FF, $FF, $FF, $FF, $FF, $FF, $FF; DEFB $FF, $FF, $FF, $FF, $FF, $FF, $FF, $FF; DEFB $FF, $FF, $FF, $FF, $FF, $FF, $FF, $FF; DEFB $FF, $FF, $FF, $FF, $FF, $FF, $FF, $FF; DEFB $FF, $FF, $FF, $FF, $FF, $FF, $FF, $FF; DEFB $FF, $FF, $FF, $FF, $FF, $FF, $FF, $FF; DEFB $FF, $FF, $FF, $FF, $FF, $FF, $FF, $FF; DEFB $FF, $FF, $FF, $FF, $FF, $FF, $FF, $FF; DEFB $FF, $FF, $FF, $FF, $FF, $FF, $FF, $FF; DEFB $FF, $FF, $FF, $FF, $FF, $FF, $FF, $FF; DEFB $FF, $FF, $FF, $FF, $FF, $FF, $FF, $FF; DEFB $FF, $FF, $FF, $FF, $FF, $FF, $FF, $FF; DEFB $FF, $FF, $FF, $FF, $FF, $FF, $FF, $FF; DEFB $FF, $FF, $FF, $FF, $FF, $FF, $FF, $FF; DEFB $FF, $FF, $FF, $FF, $FF, $FF, $FF, $FF; DEFB $FF, $FF, $FF, $FF, $FF, $FF, $FF, $FF; DEFB $FF, $FF, $FF, $FF, $FF, $FF, $FF, $FF; DEFB $FF, $FF, $FF, $FF, $FF, $FF, $FF, $FF; DEFB $FF, $FF, $FF, $FF, $FF, $FF, $FF, $FF; DEFB $FF, $FF, $FF, $FF, $FF, $FF, $FF, $FF; DEFB $FF, $FF, $FF, $FF, $FF, $FF, $FF, $FF; DEFB $FF, $FF, $FF, $FF, $FF, $FF, $FF, $FF; DEFB $FF, $FF, $FF, $FF, $FF, $FF, $FF, $FF; DEFB $FF, $FF, $FF, $FF, $FF, $FF, $FF, $FF; DEFB $FF, $FF, $FF, $FF, $FF, $FF, $FF, $FF; DEFB $FF, $FF, $FF, $FF, $FF, $FF, $FF, $FF; DEFB $FF, $FF, $FF, $FF, $FF, $FF, $FF, $FF; DEFB $FF, $FF, $FF, $FF, $FF, $FF, $FF, $FF; DEFB $FF, $FF, $FF, $FF, $FF, $FF, $FF, $FF; DEFB $FF, $FF, $FF, $FF, $FF, $FF, $FF, $FF; DEFB $FF, $FF, $FF, $FF, $FF, $FF, $FF, $FF; DEFB $FF, $FF, $FF, $FF, $FF, $FF, $FF, $FF; DEFB $FF, $FF, $FF, $FF, $FF, $FF, $FF, $FF; DEFB $FF, $FF, $FF, $FF, $FF, $FF, $FF, $FF; DEFB $FF, $FF, $FF, $FF, $FF, $FF, $FF, $FF; DEFB $FF, $FF, $FF, $FF, $FF, $FF, $FF, $FF; DEFB $FF, $FF, $FF, $FF, $FF, $FF, $FF, $FF; DEFB $FF, $FF, $FF, $FF, $FF, $FF, $FF, $FF; DEFB $FF, $FF, $FF, $FF, $FF, $FF, $FF, $FF; DEFB $FF, $FF, $FF, $FF, $FF, $FF, $FF, $FF; DEFB $FF, $FF, $FF, $FF, $FF, $FF, $FF, $FF; DEFB $FF, $FF, $FF, $FF, $FF, $FF, $FF, $FF; DEFB $FF, $FF, $FF, $FF, $FF, $FF, $FF, $FF; DEFB $FF, $FF, $FF, $FF, $FF, $FF, $FF, $FF; DEFB $FF, $FF, $FF, $FF, $FF, $FF, $FF, $FF; DEFB $FF, $FF, $FF, $FF, $FF, $FF, $FF, $FF; DEFB $FF, $FF, $FF, $FF, $FF, $FF, $FF, $FF; DEFB $FF, $FF, $FF, $FF, $FF, $FF, $FF, $FF; DEFB $FF, $FF, $FF, $FF, $FF, $FF, $FF, $FF; DEFB $FF, $FF, $FF, $FF, $FF, $FF, $FF, $FF; DEFB $FF, $FF, $FF, $FF, $FF, $FF, $FF, $FF; DEFB $FF, $FF, $FF, $FF, $FF, $FF, $FF, $FF; DEFB $FF, $FF, $FF, $FF, $FF, $FF, $FF, $FF; DEFB $FF, $FF, $FF, $FF, $FF, $FF, $FF, $FF; DEFB $FF, $FF, $FF, $FF, $FF, $FF, $FF, $FF; DEFB $FF, $FF, $FF, $FF, $FF, $FF, $FF, $FF; DEFB $FF, $FF, $FF, $FF, $FF, $FF, $FF, $FF; DEFB $FF, $FF, $FF, $FF, $FF, $FF, $FF, $FF; DEFB $FF, $FF, $FF, $FF, $FF, $FF, $FF, $FF; DEFB $FF, $FF, $FF, $FF, $FF, $FF, $FF, $FF; DEFB $FF, $FF, $FF, $FF, $FF, $FF, $FF, $FF; DEFB $FF, $FF, $FF, $FF, $FF, $FF, $FF, $FF; DEFB $FF, $FF, $FF, $FF, $FF, $FF, $FF, $FF; DEFB $FF, $FF, $FF, $FF, $FF, $FF, $FF, $FF; DEFB $FF, $FF, $FF, $FF, $FF, $FF, $FF, $FF; DEFB $FF, $FF, $FF, $FF, $FF, $FF, $FF, $FF; DEFB $FF, $FF, $FF, $FF, $FF, $FF, $FF, $FF; DEFB $FF, $FF, $FF, $FF, $FF, $FF, $FF, $FF; DEFB $FF, $FF, $FF, $FF, $FF, $FF, $FF, $FF; DEFB $FF, $FF, $FF, $FF, $FF, $FF, $FF, $FF; DEFB $FF, $FF, $FF, $FF, $FF, $FF, $FF, $FF; DEFB $FF, $FF, $FF, $FF, $FF, $FF, $FF, $FF; DEFB $FF, $FF, $FF, $FF, $FF, $FF, $FF, $FF; DEFB $FF, $FF, $FF, $FF, $FF, $FF, $FF, $FF; DEFB $FF, $FF, $FF, $FF, $FF, $FF, $FF, $FF; DEFB $FF, $FF, $FF, $FF, $FF, $FF, $FF, $FF; DEFB $FF, $FF, $FF, $FF, $FF, $FF, $FF, $FF; DEFB $FF, $FF, $FF, $FF, $FF, $FF, $FF, $FF; DEFB $FF, $FF, $FF, $FF, $FF, $FF, $FF, $FF; ;-------------- ; Character set ;-------------- ;;;$3D00 CHAR_SET: DEFB %00000000 DEFB %00000000 DEFB %00000000 DEFB %00000000 DEFB %00000000 DEFB %00000000 DEFB %00000000 DEFB %00000000 ; Character: ! DEFB %00000000 DEFB %00010000 DEFB %00010000 DEFB %00010000 DEFB %00010000 DEFB %00000000 DEFB %00010000 DEFB %00000000 ; Character: " DEFB %00000000 DEFB %00100100 DEFB %00100100 DEFB %00000000 DEFB %00000000 DEFB %00000000 DEFB %00000000 DEFB %00000000 ; Character: # DEFB %00000000 DEFB %00100100 DEFB %01111110 DEFB %00100100 DEFB %00100100 DEFB %01111110 DEFB %00100100 DEFB %00000000 ; Character: $ DEFB %00000000 DEFB %00001000 DEFB %00111110 DEFB %00101000 DEFB %00111110 DEFB %00001010 DEFB %00111110 DEFB %00001000 ; Character: % DEFB %00000000 DEFB %01100010 DEFB %01100100 DEFB %00001000 DEFB %00010000 DEFB %00100110 DEFB %01000110 DEFB %00000000 ; Character: & DEFB %00000000 DEFB %00010000 DEFB %00101000 DEFB %00010000 DEFB %00101010 DEFB %01000100 DEFB %00111010 DEFB %00000000 ; Character: ' DEFB %00000000 DEFB %00001000 DEFB %00010000 DEFB %00000000 DEFB %00000000 DEFB %00000000 DEFB %00000000 DEFB %00000000 ; Character: ( DEFB %00000000 DEFB %00000100 DEFB %00001000 DEFB %00001000 DEFB %00001000 DEFB %00001000 DEFB %00000100 DEFB %00000000 ; Character: ) DEFB %00000000 DEFB %00100000 DEFB %00010000 DEFB %00010000 DEFB %00010000 DEFB %00010000 DEFB %00100000 DEFB %00000000 ; Character: * DEFB %00000000 DEFB %00000000 DEFB %00010100 DEFB %00001000 DEFB %00111110 DEFB %00001000 DEFB %00010100 DEFB %00000000 ; Character: + DEFB %00000000 DEFB %00000000 DEFB %00001000 DEFB %00001000 DEFB %00111110 DEFB %00001000 DEFB %00001000 DEFB %00000000 ; Character: , DEFB %00000000 DEFB %00000000 DEFB %00000000 DEFB %00000000 DEFB %00000000 DEFB %00001000 DEFB %00001000 DEFB %00010000 ; Character: - DEFB %00000000 DEFB %00000000 DEFB %00000000 DEFB %00000000 DEFB %00111110 DEFB %00000000 DEFB %00000000 DEFB %00000000 ; Character: . DEFB %00000000 DEFB %00000000 DEFB %00000000 DEFB %00000000 DEFB %00000000 DEFB %00011000 DEFB %00011000 DEFB %00000000 ; Character: / DEFB %00000000 DEFB %00000000 DEFB %00000010 DEFB %00000100 DEFB %00001000 DEFB %00010000 DEFB %00100000 DEFB %00000000 ; Character: 0 DEFB %00000000 DEFB %00111100 DEFB %01000110 DEFB %01001010 DEFB %01010010 DEFB %01100010 DEFB %00111100 DEFB %00000000 ; Character: 1 DEFB %00000000 DEFB %00011000 DEFB %00101000 DEFB %00001000 DEFB %00001000 DEFB %00001000 DEFB %00111110 DEFB %00000000 ; Character: 2 DEFB %00000000 DEFB %00111100 DEFB %01000010 DEFB %00000010 DEFB %00111100 DEFB %01000000 DEFB %01111110 DEFB %00000000 ; Character: 3 DEFB %00000000 DEFB %00111100 DEFB %01000010 DEFB %00001100 DEFB %00000010 DEFB %01000010 DEFB %00111100 DEFB %00000000 ; Character: 4 DEFB %00000000 DEFB %00001000 DEFB %00011000 DEFB %00101000 DEFB %01001000 DEFB %01111110 DEFB %00001000 DEFB %00000000 ; Character: 5 DEFB %00000000 DEFB %01111110 DEFB %01000000 DEFB %01111100 DEFB %00000010 DEFB %01000010 DEFB %00111100 DEFB %00000000 ; Character: 6 DEFB %00000000 DEFB %00111100 DEFB %01000000 DEFB %01111100 DEFB %01000010 DEFB %01000010 DEFB %00111100 DEFB %00000000 ; Character: 7 DEFB %00000000 DEFB %01111110 DEFB %00000010 DEFB %00000100 DEFB %00001000 DEFB %00010000 DEFB %00010000 DEFB %00000000 ; Character: 8 DEFB %00000000 DEFB %00111100 DEFB %01000010 DEFB %00111100 DEFB %01000010 DEFB %01000010 DEFB %00111100 DEFB %00000000 ; Character: 9 DEFB %00000000 DEFB %00111100 DEFB %01000010 DEFB %01000010 DEFB %00111110 DEFB %00000010 DEFB %00111100 DEFB %00000000 ; Character: : DEFB %00000000 DEFB %00000000 DEFB %00000000 DEFB %00010000 DEFB %00000000 DEFB %00000000 DEFB %00010000 DEFB %00000000 ; Character: ; DEFB %00000000 DEFB %00000000 DEFB %00010000 DEFB %00000000 DEFB %00000000 DEFB %00010000 DEFB %00010000 DEFB %00100000 ; Character: < DEFB %00000000 DEFB %00000000 DEFB %00000100 DEFB %00001000 DEFB %00010000 DEFB %00001000 DEFB %00000100 DEFB %00000000 ; Character: = DEFB %00000000 DEFB %00000000 DEFB %00000000 DEFB %00111110 DEFB %00000000 DEFB %00111110 DEFB %00000000 DEFB %00000000 ; Character: > DEFB %00000000 DEFB %00000000 DEFB %00010000 DEFB %00001000 DEFB %00000100 DEFB %00001000 DEFB %00010000 DEFB %00000000 ; Character: ? DEFB %00000000 DEFB %00111100 DEFB %01000010 DEFB %00000100 DEFB %00001000 DEFB %00000000 DEFB %00001000 DEFB %00000000 ; Character: @ DEFB %00000000 DEFB %00111100 DEFB %01001010 DEFB %01010110 DEFB %01011110 DEFB %01000000 DEFB %00111100 DEFB %00000000 ; Character: A DEFB %00000000 DEFB %00111100 DEFB %01000010 DEFB %01000010 DEFB %01111110 DEFB %01000010 DEFB %01000010 DEFB %00000000 ; Character: B DEFB %00000000 DEFB %01111100 DEFB %01000010 DEFB %01111100 DEFB %01000010 DEFB %01000010 DEFB %01111100 DEFB %00000000 ; Character: C DEFB %00000000 DEFB %00111100 DEFB %01000010 DEFB %01000000 DEFB %01000000 DEFB %01000010 DEFB %00111100 DEFB %00000000 ; Character: D DEFB %00000000 DEFB %01111000 DEFB %01000100 DEFB %01000010 DEFB %01000010 DEFB %01000100 DEFB %01111000 DEFB %00000000 ; Character: E DEFB %00000000 DEFB %01111110 DEFB %01000000 DEFB %01111100 DEFB %01000000 DEFB %01000000 DEFB %01111110 DEFB %00000000 ; Character: F DEFB %00000000 DEFB %01111110 DEFB %01000000 DEFB %01111100 DEFB %01000000 DEFB %01000000 DEFB %01000000 DEFB %00000000 ; Character: G DEFB %00000000 DEFB %00111100 DEFB %01000010 DEFB %01000000 DEFB %01001110 DEFB %01000010 DEFB %00111100 DEFB %00000000 ; Character: H DEFB %00000000 DEFB %01000010 DEFB %01000010 DEFB %01111110 DEFB %01000010 DEFB %01000010 DEFB %01000010 DEFB %00000000 ; Character: I DEFB %00000000 DEFB %00111110 DEFB %00001000 DEFB %00001000 DEFB %00001000 DEFB %00001000 DEFB %00111110 DEFB %00000000 ; Character: J DEFB %00000000 DEFB %00000010 DEFB %00000010 DEFB %00000010 DEFB %01000010 DEFB %01000010 DEFB %00111100 DEFB %00000000 ; Character: K DEFB %00000000 DEFB %01000100 DEFB %01001000 DEFB %01110000 DEFB %01001000 DEFB %01000100 DEFB %01000010 DEFB %00000000 ; Character: L DEFB %00000000 DEFB %01000000 DEFB %01000000 DEFB %01000000 DEFB %01000000 DEFB %01000000 DEFB %01111110 DEFB %00000000 ; Character: M DEFB %00000000 DEFB %01000010 DEFB %01100110 DEFB %01011010 DEFB %01000010 DEFB %01000010 DEFB %01000010 DEFB %00000000 ; Character: N DEFB %00000000 DEFB %01000010 DEFB %01100010 DEFB %01010010 DEFB %01001010 DEFB %01000110 DEFB %01000010 DEFB %00000000 ; Character: O DEFB %00000000 DEFB %00111100 DEFB %01000010 DEFB %01000010 DEFB %01000010 DEFB %01000010 DEFB %00111100 DEFB %00000000 ; Character: P DEFB %00000000 DEFB %01111100 DEFB %01000010 DEFB %01000010 DEFB %01111100 DEFB %01000000 DEFB %01000000 DEFB %00000000 ; Character: Q DEFB %00000000 DEFB %00111100 DEFB %01000010 DEFB %01000010 DEFB %01010010 DEFB %01001010 DEFB %00111100 DEFB %00000000 ; Character: R DEFB %00000000 DEFB %01111100 DEFB %01000010 DEFB %01000010 DEFB %01111100 DEFB %01000100 DEFB %01000010 DEFB %00000000 ; Character: S DEFB %00000000 DEFB %00111100 DEFB %01000000 DEFB %00111100 DEFB %00000010 DEFB %01000010 DEFB %00111100 DEFB %00000000 ; Character: T DEFB %00000000 DEFB %11111110 DEFB %00010000 DEFB %00010000 DEFB %00010000 DEFB %00010000 DEFB %00010000 DEFB %00000000 ; Character: U DEFB %00000000 DEFB %01000010 DEFB %01000010 DEFB %01000010 DEFB %01000010 DEFB %01000010 DEFB %00111100 DEFB %00000000 ; Character: V DEFB %00000000 DEFB %01000010 DEFB %01000010 DEFB %01000010 DEFB %01000010 DEFB %00100100 DEFB %00011000 DEFB %00000000 ; Character: W DEFB %00000000 DEFB %01000010 DEFB %01000010 DEFB %01000010 DEFB %01000010 DEFB %01011010 DEFB %00100100 DEFB %00000000 ; Character: X DEFB %00000000 DEFB %01000010 DEFB %00100100 DEFB %00011000 DEFB %00011000 DEFB %00100100 DEFB %01000010 DEFB %00000000 ; Character: Y DEFB %00000000 DEFB %10000010 DEFB %01000100 DEFB %00101000 DEFB %00010000 DEFB %00010000 DEFB %00010000 DEFB %00000000 ; Character: Z DEFB %00000000 DEFB %01111110 DEFB %00000100 DEFB %00001000 DEFB %00010000 DEFB %00100000 DEFB %01111110 DEFB %00000000 ; Character: [ DEFB %00000000 DEFB %00001110 DEFB %00001000 DEFB %00001000 DEFB %00001000 DEFB %00001000 DEFB %00001110 DEFB %00000000 ; Character: \ DEFB %00000000 DEFB %00000000 DEFB %01000000 DEFB %00100000 DEFB %00010000 DEFB %00001000 DEFB %00000100 DEFB %00000000 ; Character: ] DEFB %00000000 DEFB %01110000 DEFB %00010000 DEFB %00010000 DEFB %00010000 DEFB %00010000 DEFB %01110000 DEFB %00000000 ; Character: ^ DEFB %00000000 DEFB %00010000 DEFB %00111000 DEFB %01010100 DEFB %00010000 DEFB %00010000 DEFB %00010000 DEFB %00000000 ; 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