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exec.asm
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; TITLE BBC BASIC (C) R.T.RUSSELL 1987
;
;BBC BASIC INTERPRETER - Z80 VERSION
;STATEMENT EXECUTION & ASSEMBLER MODULE - "EXEC"
;(C) COPYRIGHT R.T.RUSSELL 1984
;VERSION 2.1, 22-01-1984
;VERSION 3.0, 02-03-1987
;VERSION 3.1, 11-06-1987
;
PUBLIC XEQ
PUBLIC RUN0
PUBLIC CHAIN0
PUBLIC CHECK
PUBLIC MUL16
PUBLIC X4OR5
PUBLIC TERMQ
PUBLIC STORE4
PUBLIC STORE5
PUBLIC FILL
PUBLIC FN
PUBLIC USR
PUBLIC ESCAPE
PUBLIC SYNTAX
PUBLIC CHANEL
;
EXTERN ERROR
EXTERN REPORT
EXTERN WARM
EXTERN CLOOP
EXTERN SAYLN
EXTERN LOAD0
EXTERN CRLF
EXTERN PBCDL
EXTERN TELL
EXTERN FINDL
EXTERN SETLIN
EXTERN CLEAR
EXTERN GETVAR
EXTERN PUTVAR
EXTERN GETDEF
EXTERN CREATE
EXTERN OUTCHR
EXTERN OUT
EXTERN AUTO
EXTERN DELETE
EXTERN LOAD
EXTERN LIST
EXTERN NEW
EXTERN OLD
EXTERN RENUM
EXTERN SAVE
;
EXTERN OSWRCH
EXTERN OSLINE
EXTERN OSSHUT
EXTERN OSBPUT
EXTERN OSBGET
EXTERN CLRSCN
EXTERN PUTCSR
EXTERN PUTIME
EXTERN PUTIMS
EXTERN PUTPTR
EXTERN OSCALL
EXTERN OSCLI
EXTERN TRAP
;
EXTERN SOUND
EXTERN CLG
EXTERN DRAW
EXTERN ENVEL
EXTERN GCOL
EXTERN MODE
EXTERN MOVE
EXTERN PLOT
EXTERN COLOUR
;
EXTERN STR
EXTERN HEXSTR
EXTERN EXPR
EXTERN EXPRN
EXTERN EXPRI
EXTERN EXPRS
EXTERN ITEMI
EXTERN CONS
EXTERN LOADS
EXTERN VAL0
EXTERN SFIX
EXTERN TEST
EXTERN NXT
EXTERN SWAP
EXTERN LOAD4
EXTERN LOADN
EXTERN DLOAD5
EXTERN FPP
EXTERN COMMA
EXTERN BRAKET
EXTERN PUSHS
EXTERN POPS
EXTERN ZERO
;
EXTERN ACCS
EXTERN PAGE
EXTERN LOMEM
EXTERN HIMEM
EXTERN FREE
EXTERN BUFFER
EXTERN ERRTRP
EXTERN ERRLIN
EXTERN COUNT
EXTERN WIDTH
EXTERN STAVAR
EXTERN DATPTR
EXTERN RANDOM
EXTERN TRACEN
EXTERN LISTON
EXTERN PC
EXTERN OC
;
TAND: EQU 80H
TOR: EQU 84H
TERROR: EQU 85H
LINE: EQU 86H
OFF: EQU 87H
STEP: EQU 88H
SPC: EQU 89H
TAB: EQU 8AH
ELSE: EQU 8BH
THEN: EQU 8CH
LINO: EQU 8DH
TO: EQU 0B8H
TCMD: EQU 0C6H
TCALL: EQU 0D6H
DATA: EQU 0DCH
DEF: EQU 0DDH
TGOSUB: EQU 0E4H
TGOTO: EQU 0E5H
TON: EQU 0EEH
TPROC: EQU 0F2H
TSTOP: EQU 0FAH
;
CMDTAB: DEFW AUTO
DEFW DELETE
DEFW LOAD
DEFW LIST
DEFW NEW
DEFW OLD
DEFW RENUM
DEFW SAVE
DEFW PUT
DEFW PTR
DEFW PAGEV
DEFW TIMEV
DEFW LOMEMV
DEFW HIMEMV
DEFW SOUND
DEFW BPUT
DEFW CALL
DEFW CHAIN
DEFW CLR
DEFW CLOSE
DEFW CLG
DEFW CLS
DEFW REM ;DATA
DEFW REM ;DEF
DEFW DIM
DEFW DRAW
DEFW END
DEFW ENDPRO
DEFW ENVEL
DEFW FOR
DEFW GOSUB
DEFW GOTO
DEFW GCOL
DEFW IF
DEFW INPUT
DEFW LET
DEFW LOCAL
DEFW MODE
DEFW MOVE
DEFW NEXT
DEFW ON
DEFW VDU
DEFW PLOT
DEFW PRINT
DEFW PROC
DEFW READ
DEFW REM
DEFW REPEAT
DEFW REPOR
DEFW RESTOR
DEFW RETURN
DEFW RUN
DEFW STOP
DEFW COLOUR
DEFW TRACE
DEFW UNTIL
DEFW WIDTHV
DEFW CLI ;OSCLI
;
RUN: CALL TERMQ
JR Z,RUN0
CHAIN: CALL EXPRS
LD A,CR
LD (DE),A
CHAIN0: LD SP,(HIMEM)
CALL LOAD0
RUN0: LD SP,(HIMEM) ;PREPARE FOR RUN
LD IX,RANDOM
LD A,R ;RANDOMISE (CARE!)
JR NZ,RAND
INC A
RAND: RLCA
RLCA
LD (IX+3),A
SBC A,A
LD (IX+4),A
CALL CLEAR
LD HL,0
LD (ERRTRP),HL
LD HL,(PAGE)
LD A,DATA
CALL SEARCH ;LOOK FOR "DATA"
LD (DATPTR),HL ;SET DATA POINTER
LD IY,(PAGE)
XEQ0: CALL NEWLIN
XEQ: LD (ERRLIN),IY ;ERROR POINTER
CALL TRAP ;CHECK KEYBOARD
XEQ1: CALL NXT
INC IY
CP ':' ;SEPARATOR
JR Z,XEQ1
CP CR
JR Z,XEQ0 ;NEW PROGRAM LINE
SUB TCMD
JR C,LET0 ;IMPLIED "LET"
ADD A,A
LD C,A
LD B,0
LD HL,CMDTAB
ADD HL,BC
LD A,(HL) ;TABLE ENTRY
INC HL
LD H,(HL)
LD L,A
CALL NXT
JP (HL) ;EXECUTE STATEMENT
;
;END
;
END: CALL SETLIN ;FIND CURRENT LINE
LD A,H
OR L ;DIRECT?
JP Z,CLOOP
LD E,0
CALL OSSHUT ;CLOSE ALL FILES
JP WARM ;"Ready"
;
NEWLIN: LD A,(IY+0) ;A=LINE LENGTH
LD BC,3
ADD IY,BC
OR A
JR Z,END ;LENGTH=0, EXIT
LD HL,(TRACEN)
LD A,H
OR L
RET Z
LD D,(IY-1) ;DE = LINE NUMBER
LD E,(IY-2)
SBC HL,DE
RET C
EX DE,HL
LD A,'[' ;TRACE
CALL OUTCHR
CALL PBCDL
LD A,']'
CALL OUTCHR
LD A,' '
JP OUTCHR
;
;ROUTINES FOR EACH STATEMENT:
;
;OSCLI
;
CLI: CALL EXPRS
LD A,CR
LD (DE),A
LD HL,ACCS
CALL OSCLI
JR XEQ
;
;REM, *
;
EXT: PUSH IY
POP HL
CALL OSCLI
REM: PUSH IY
POP HL
LD A,CR
LD B,A
CPIR ;FIND LINE END
PUSH HL
POP IY
JP XEQ0
;
;[LET] var = expr
;
LET0: CP ELSE-TCMD
JR Z,REM
CP '*'-TCMD+100H
JR Z,EXT
CP '='-TCMD+100H
JR Z,FNEND
CP '['-TCMD
JR Z,ASM
DEC IY
LET: CALL ASSIGN
JP Z,XEQ
JR C,SYNTAX ;"Syntax error"
PUSH AF ;SAVE STRING TYPE
CALL EQUALS
PUSH HL
CALL EXPRS
POP IX
POP AF
CALL STACCS
XEQR: JP XEQ
;
ASM0: CALL NEWLIN
ASM: LD (ERRLIN),IY
CALL TRAP
CALL ASSEM
JR C,SYNTAX
CP CR
JR Z,ASM0
LD HL,LISTON
LD A,(HL)
AND 0FH
OR 30H
LD (HL),A
JR XEQR
;
VAR: CALL GETVAR
RET Z
JP NC,PUTVAR
SYNTAX: LD A,16 ;"Syntax error"
DEFB 21H
ESCAPE: LD A,17 ;"Escape"
ERROR0: JP ERROR
;
;=
;
FNEND: CALL EXPR ;FUNCTION RESULT
LD B,E
EX DE,HL
EXX ;SAVE RESULT
EX DE,HL ; IN DEB'C'D'E'
FNEND5: POP BC
LD HL,LOCCHK
OR A
SBC HL,BC
JR Z,FNEND0 ;LOCAL VARIABLE
LD HL,FNCHK
OR A
SBC HL,BC
LD A,7
JR NZ,ERROR0 ;"No FN"
POP IY
LD (ERRLIN),IY ;IN CASE OF ERROR
EX DE,HL
EXX
EX DE,HL
LD DE,ACCS
LD E,B
EX AF,AF'
RET
;
FNEND0: POP IX
POP BC
LD A,B
OR A
JP M,FNEND1 ;STRING
POP HL
EXX
POP HL
EXX
CALL STORE
JR FNEND5
FNEND1: LD HL,0
ADD HL,SP
PUSH DE
LD E,C
CALL STORES
POP DE
LD SP,HL
JR FNEND5
;
;DIM var(dim1[,dim2[,...]])[,var(...]
;DIM var expr[,var expr...]
;
DIM: CALL GETVAR ;VARIABLE
JR C,BADDIM
JP Z,DIM4
CALL CREATE
PUSH HL
POP IX
LD A,(IY)
CP '('
LD A,D
JR NZ,DIM4
PUSH HL
PUSH AF ;SAVE TYPE
LD DE,1
LD B,D ;DIMENSION COUNTER
DIM1: INC IY
PUSH BC
PUSH DE
PUSH IX
CALL EXPRI ;DIMENSION SIZE
BIT 7,H
JR NZ,BADDIM
EXX
INC HL
POP IX
INC IX
LD (IX),L ;SAVE SIZE
INC IX
LD (IX),H
POP BC
CALL MUL16 ;HL=HL*BC
JR C,NOROOM ;TOO LARGE
EX DE,HL ;DE=PRODUCT
POP BC
INC B ;DIMENSION COUNTER
LD A,(IY)
CP ',' ;ANOTHER
JR Z,DIM1
CALL BRAKET ;CLOSING BRACKET
POP AF ;RESTORE TYPE
INC IX
EX (SP),IX
LD (IX),B ;NO. OF DIMENSIONS
CALL X4OR5 ;DE=DE*n
POP HL
JR C,NOROOM
DIM3: ADD HL,DE
JR C,NOROOM
PUSH HL
INC H
JR Z,NOROOM
SBC HL,SP
JR NC,NOROOM ;OUT OF SPACE
POP HL
LD (FREE),HL
DIM2: LD A,D
OR E
JR Z,DIM5
DEC HL
LD (HL),0 ;INITIALISE ARRAY
DEC DE
JR DIM2
DIM5: CALL NXT
CP ',' ;ANOTHER VARIABLE?
JP NZ,XEQ
INC IY
CALL NXT
JR DIM
;
BADDIM: LD A,10 ;"Bad DIM"
DEFB 21H
NOROOM: LD A,11 ;"DIM space"
ERROR1: JP ERROR
;
DIM4: OR A
JR Z,BADDIM
JP M,BADDIM
LD B,A
LD A,(IY-1)
CP ')'
LD A,B
JR Z,BADDIM
LD HL,(FREE)
EXX
LD HL,0
LD C,H
CALL STORE ;RESERVED AREA
CALL EXPRI
EXX
INC HL
EX DE,HL
LD HL,(FREE)
JR DIM3
;
;PRINT list...
;PRINT #channel,list...
;
PRINT: CP '#'
JR NZ,PRINT0
CALL CHNL ;CHANNEL NO. = E
PRNTN1: CALL NXT
CP ','
JP NZ,XEQ
INC IY
PUSH DE
CALL EXPR ;ITEM TO PRINT
EX AF,AF'
JP M,PRNTN2 ;STRING
POP DE
PUSH BC
EXX
LD A,L
EXX
CALL OSBPUT
EXX
LD A,H
EXX
CALL OSBPUT
LD A,L
CALL OSBPUT
LD A,H
CALL OSBPUT
POP BC
LD A,C
CALL OSBPUT
JR PRNTN1
PRNTN2: LD C,E
POP DE
LD HL,ACCS
INC C
PRNTN3: DEC C
JR Z,PRNTN4
LD A,(HL)
INC HL
PUSH BC
CALL OSBPUT
POP BC
JR PRNTN3
PRNTN4: LD A,CR
CALL OSBPUT
JR PRNTN1
;
PRINT6: LD B,2
JR PRINTC
PRINT8: LD BC,100H
JR PRINTC
PRINT9: LD HL,STAVAR
XOR A
CP (HL)
JR Z,PRINT0
LD A,(COUNT)
OR A
JR Z,PRINT0
PRINTA: SUB (HL)
JR Z,PRINT0
JR NC,PRINTA
NEG
CALL FILL
PRINT0: LD A,(STAVAR)
LD C,A ;PRINTS
LD B,0 ;PRINTF
PRINTC: CALL TERMQ
JR Z,PRINT4
RES 0,B
INC IY
CP '~'
JR Z,PRINT6
CP ';'
JR Z,PRINT8
CP ','
JR Z,PRINT9
CALL FORMAT ;SPC, TAB, '
JR Z,PRINTC
DEC IY
PUSH BC
CALL EXPR ;VARIABLE TYPE
EX AF,AF'
JP M,PRINT3 ;STRING
POP DE
PUSH DE
BIT 1,D
PUSH AF
CALL Z,STR ;DECIMAL
POP AF
CALL NZ,HEXSTR ;HEX
POP BC
PUSH BC
LD A,C
SUB E
CALL NC,FILL ;RIGHT JUSTIFY
PRINT3: POP BC
CALL PTEXT ;PRINT
JR PRINTC
PRINT4: BIT 0,B
CALL Z,CRLF
JP XEQ
;
;
ONERR: INC IY ;SKIP "ERROR"
LD HL,0
LD (ERRTRP),HL
CALL NXT
CP OFF
INC IY
JP Z,XEQ
DEC IY
LD (ERRTRP),IY
JP REM
;
;ON expr GOTO line[,line...] [ELSE statement]
;ON expr GOTO line[,line...] [ELSE line]
;ON expr GOSUB line[,line...] [ELSE statement]
;ON expr GOSUB line[,line...] [ELSE line]
;ON expr PROCone [,PROCtwo..] [ELSE PROCotherwise]
;ON ERROR statement [:statement...]
;ON ERROR OFF
;
ON: CP TERROR
JR Z,ONERR ;"ON ERROR"
CALL EXPRI
LD A,(IY)
INC IY
LD E,',' ;SEPARATOR
CP TGOTO
JR Z,ON1
CP TGOSUB
JR Z,ON1
LD E,TPROC
CP E
LD A,39
JR NZ,ERROR2 ;"ON syntax"
ON1: LD D,A
EXX
PUSH HL
EXX
POP BC ;ON INDEX
LD A,B
OR H
OR L
JR NZ,ON4 ;OUT OF RANGE
OR C
JR Z,ON4
DEC C
JR Z,ON3 ;INDEX=1
ON2: CALL TERMQ
JR Z,ON4 ;OUT OF RANGE
INC IY ;SKIP DELIMITER
CP E
JR NZ,ON2
DEC C
JR NZ,ON2
ON3: LD A,E
CP TPROC
JR Z,ONPROC
PUSH DE
CALL ITEMI ;LINE NUMBER
POP DE
LD A,D
CP TGOTO
JR Z,GOTO2
CALL SPAN ;SKIP REST OF LIST
JR GOSUB1
;
ON4: LD A,(IY)
INC IY
CP ELSE
JP Z,IF1 ;ELSE CLAUSE
CP CR
JR NZ,ON4
LD A,40
ERROR2: JP ERROR ;"ON range"
;
ONPROC: LD A,TON
JP PROC
;
;GOTO line
;
GOTO: CALL ITEMI ;LINE NUMBER
GOTO1: CALL TERMQ
JP NZ,SYNTAX
GOTO2: EXX
CALL FINDL
PUSH HL
POP IY
JP Z,XEQ0
LD A,41
JR ERROR2 ;"No such line"
;
;GOSUB line
;
GOSUB: CALL ITEMI ;LINE NUMBER
GOSUB1: PUSH IY ;TEXT POINTER
CALL CHECK ;CHECK ROOM
CALL GOTO1 ;SAVE MARKER
GOSCHK EQU $
;
;RETURN
;
RETURN: POP DE ;MARKER
LD HL,GOSCHK
OR A
SBC HL,DE
POP IY
JP Z,XEQ
LD A,38
JR ERROR2 ;"No GOSUB"
;
;REPEAT
;
REPEAT: PUSH IY
CALL CHECK
CALL XEQ
REPCHK EQU $
;
;UNTIL expr
;
UNTIL: POP BC
PUSH BC
LD HL,REPCHK
OR A
SBC HL,BC
LD A,43
JR NZ,ERROR2 ;"No REPEAT"
CALL EXPRI
CALL TEST
POP BC
POP DE
JR NZ,XEQ2 ;TRUE
PUSH DE
PUSH BC
PUSH DE
POP IY
XEQ2: JP XEQ
;
;FOR var = expr TO expr [STEP expr]
;
FORVAR: LD A,34
JR ERROR2 ;"FOR variable"
;
FOR: CALL ASSIGN
JR NZ,FORVAR ;"FOR variable"
PUSH AF ;SAVE TYPE
LD A,(IY)
CP TO
LD A,36
JR NZ,ERROR2 ;"No TO"
INC IY
PUSH IX
CALL EXPRN ;LIMIT
POP IX
POP AF
LD B,A ;TYPE
PUSH BC ;SAVE ON STACK
PUSH HL
LD HL,0
LD C,H
EXX
PUSH HL
LD HL,1 ;PRESET STEP
EXX
LD A,(IY)
CP STEP
JR NZ,FOR1
INC IY
PUSH IX
CALL EXPRN ;STEP
POP IX
FOR1: PUSH BC
PUSH HL
EXX
PUSH HL
EXX
PUSH IY ;SAVE TEXT POINTER
PUSH IX ;LOOP VARIABLE
CALL CHECK
CALL XEQ
FORCHK EQU $
;
;NEXT [var[,var...]]
;
NEXT: POP BC ;MARKER
LD HL,FORCHK
OR A
SBC HL,BC
LD A,32
JR NZ,ERROR3 ;"No FOR"
CALL TERMQ
POP HL
PUSH HL
PUSH BC
PUSH HL
CALL NZ,GETVAR ;VARIABLE
POP DE
EX DE,HL
OR A
NEXT0: SBC HL,DE
JR NZ,NEXT1
PUSH DE
LD IX,6+2
ADD IX,SP
CALL DLOAD5 ;STEP
LD A,(IX+11) ;TYPE
POP IX
CALL LOADN ;LOOP VARIABLE
BIT 7,D ;SIGN?
PUSH AF
LD A,'+' & 0FH
CALL FPP ;ADD STEP
JR C,ERROR3
POP AF ;RESTORE TYPE
PUSH AF
CALL STORE ;UPDATE VARIABLE
LD IX,12+2
ADD IX,SP
CALL DLOAD5 ;LIMIT
POP AF
CALL Z,SWAP
LD A,0+('<'-4) & 0FH
CALL FPP ;TEST AGAINST LIMIT
JR C,ERROR3
INC H
JR NZ,LOOP ;KEEP LOOPING
LD HL,18
ADD HL,SP
LD SP,HL
CALL NXT
CP ','
JP NZ,XEQ
INC IY
JR NEXT
;
LOOP: POP BC
POP DE
POP IY
PUSH IY
PUSH DE
PUSH BC
JP XEQ
;
NEXT1: LD HL,18
ADD HL,SP
LD SP,HL ;"POP" THE STACK
POP BC
LD HL,FORCHK
SBC HL,BC
POP HL ;VARIABLE POINTER
PUSH HL
PUSH BC
JR Z,NEXT0
LD A,33
ERROR3: JP ERROR ;"Can"t match FOR"
;
;FNname
;N.B. ENTERED WITH A <> TON
;
FN: PUSH AF ;MAKE SPACE ON STACK
CALL PROC1
FNCHK EQU $
;
;PROCname
;N.B. ENTERED WITH A = ON PROC FLAG
;
PROC: PUSH AF ;MAKE SPACE ON STACK
CALL PROC1
PROCHK EQU $
PROC1: CALL CHECK
DEC IY
PUSH IY
CALL GETDEF
POP BC
JR Z,PROC4
LD A,30
JR C,ERROR3 ;"Bad call"
PUSH BC
LD HL,(PAGE)
PROC2: LD A,DEF
CALL SEARCH ;LOOK FOR "DEF"
JR C,PROC3
PUSH HL
POP IY
INC IY ;SKIP DEF
CALL NXT
CALL GETDEF
PUSH IY
POP DE
JR C,PROC6
CALL NZ,CREATE
PUSH IY
POP DE
LD (HL),E
INC HL
LD (HL),D ;SAVE ADDRESS
PROC6: EX DE,HL
LD A,CR
LD B,A
CPIR ;SKIP TO END OF LINE
JR PROC2
PROC3: POP IY ;RESTORE TEXT POINTER
CALL GETDEF
LD A,29
JR NZ,ERROR3 ;"No such FN/PROC"
PROC4: LD E,(HL)
INC HL
LD D,(HL) ;GET ADDRESS
LD HL,2
ADD HL,SP
CALL NXT ;ALLOW SPACE BEFORE (
PUSH DE ;EXCHANGE DE,IY
EX (SP),IY
POP DE
CP '(' ;ARGUMENTS?
JR NZ,PROC5
CALL NXT ;ALLOW SPACE BEFORE (
CP '('
JP NZ,SYNTAX ;"Syntax error"
PUSH IY
POP BC ;SAVE IY IN BC
EXX
CALL SAVLOC ;SAVE DUMMY VARIABLES
CALL BRAKET ;CLOSING BRACKET
EXX
PUSH BC
POP IY ;RESTORE IY
PUSH HL
CALL ARGUE ;TRANSFER ARGUMENTS
POP HL
PROC5: LD (HL),E ;SAVE "RETURN ADDRESS"
INC HL
LD A,(HL)
LD (HL),D
CP TON ;WAS IT "ON PROC" ?
JP NZ,XEQ
PUSH DE
EX (SP),IY
CALL SPAN ;SKIP REST OF ON LIST
EX (SP),IY
POP DE
LD (HL),D
DEC HL
LD (HL),E
JP XEQ
;
;LOCAL var[,var...]
;
LOCAL: POP BC
PUSH BC
LD HL,FNCHK
OR A
SBC HL,BC
JR Z,LOCAL1
LD HL,PROCHK
OR A
SBC HL,BC
JR Z,LOCAL1
LD HL,LOCCHK
OR A
SBC HL,BC
LD A,12
JP NZ,ERROR ;"Not LOCAL"
LOCAL1: PUSH IY
POP BC
EXX
DEC IY
CALL SAVLOC
EXX
PUSH BC
POP IY
LOCAL2: CALL GETVAR
JP NZ,SYNTAX
OR A ;TYPE
EX AF,AF'
CALL ZERO
EX AF,AF'
PUSH AF
CALL P,STORE ;ZERO
POP AF
LD E,C
CALL M,STORES
CALL NXT
CP ','
JP NZ,XEQ
INC IY
CALL NXT
JR LOCAL2
;
;ENDPROC
;
ENDPRO: POP BC
LD HL,LOCCHK
OR A
SBC HL,BC
JR Z,UNSTK ;LOCAL VARIABLE
LD HL,PROCHK ;PROC MARKER
OR A
SBC HL,BC
POP IY
JP Z,XEQ
LD A,13
JP ERROR ;"No PROC"
;
UNSTK: POP IX
POP BC