80-Bus News

  

July–August 1983, Volume 2, Issue 4











Page 31 of 55











Dis-assembly of NASCOM ROM BASIC Ver 4.7                PAGE    16

E3F8 AF         PRNTOK: XOR     A               ; Output "Ok" and get command
E3F9 324510             LD      (CTLOFG),A      ; Enable output
E3FC CD74EB             CALL    STTLIN          ; Start new line
E3FF 214BE3             LD      HL,OKMSG        ; "Ok" message
E402 CD10F2             CALL    PRS             ; Output "Ok"
E405 21FFFF     GETCMD: LD      HL,-1           ; Flag direct mode
E408 225C10             LD      (LINEAT),HL     ; Save as current line
E40B CDF2E5             CALL    GETLIN          ; Get an input line
E40E DA05E4             JP      C,GETCMD        ; Get line again if break
E411 CD36E8             CALL    GETCHR          ; Get first character
E414 3C                 INC     A               ; Test if end of line
E415 3D                 DEC     A               ; Without affecting Carry
E416 CA05E4             JP      Z,GETCMD        ; Nothing entered - Get another
E419 F5                 PUSH    AF              ; Save Carry status
E41A CDA5E9             CALL    ATOH            ; Get line number into DE
E41D D5                 PUSH    DE              ; Save line number
E41E CD09E5             CALL    CRUNCH          ; Tokenise rest of line
E421 47                 LD      B,A             ; Length of tokenised line
E422 D1                 POP     DE              ; Restore line number
E423 F1                 POP     AF              ; Restore Carry
E424 D216E8             JP      NC,EXCUTE       ; No line number - Direct mode
E427 D5                 PUSH    DE              ; Save line number
E428 C5                 PUSH    BC              ; Save length of tokenised line
E429 AF                 XOR     A
E42A 32CC10             LD      (LSTBIN),A      ; Clear last byte input
E42D CD36E8             CALL    GETCHR          ; Get next character
E430 B7                 OR      A               ; Set flags
E431 F5                 PUSH    AF              ; And save them
E432 CD99E4             CALL    SRCHLN          ; Search for line number in DE
E435 DA3EE4             JP      C,LINFND        ; Jump if line found
E438 F1                 POP     AF              ; Get status
E439 F5                 PUSH    AF              ; And re-save
E43A CA46EA             JP      Z,ULERR         ; Nothing after number - Error
E43D B7                 OR      A               ; Clear Carry
E43E C5         LINFND: PUSH    BC              ; Save address of line in prog
E43F D255E4             JP      NC,INEWLN       ; Line not found - Insert new
E442 EB                 EX      DE,HL           ; Next line address in DE
E443 2AD610             LD      HL,(PROGND)     ; End of program
E446 1A         SFTPRG: LD      A,(DE)          ; Shift rest of program down
E447 02                 LD      (BC),A
E448 03                 INC     BC              ; Next destination
E449 13                 INC     DE              ; Next source
E44A CD8AE6             CALL    CPDEHL          ; All done?
E44D C246E4             JP      NZ,SFTPRG       ; More to do
E450 60                 LD      H,B             ; HL - New end of program
E451 69                 LD      L,C
E452 22D610             LD      (PROGND),HL     ; Update end of program
Dis-assembly of NASCOM ROM BASIC Ver 4.7                PAGE    17

E455 D1         INEWLN: POP     DE              ; Get address of line,
E456 F1                 POP     AF              ; Get status
E457 CA7CE4             JP      Z,SETPTR        ; No text - Set up pointers
E45A 2AD610             LD      HL,(PROGND)     ; Get end of program
E45D E3                 EX      (SP),HL         ; Get length of input line
E45E C1                 POP     BC              ; End of program to BC
E45F 09                 ADD     HL,BC           ; Find new end
E460 E5                 PUSH    HL              ; Save new end
E461 CD79E3             CALL    MOVUP           ; Make space for line
E464 E1                 POP     HL              ; Restore new end
E465 22D610             LD      (PROGND),HL     ; Update end of program pointer
E468 EB                 EX      DE,HL           ; Get line to move up in HL
E469 74                 LD      (HL),H          ; Save MSB
E46A D1                 POP     DE              ; Get new line number
E46B 23                 INC     HL              ; Skip pointer
E46C 23                 INC     HL
E46D 73                 LD      (HL),E          ; Save LSB of line number
E46E 23                 INC     HL
E46F 72                 LD      (HL),D          ; Save MSB of line number
E470 23                 INC     HL              ; To first byte in line
E471 116110             LD      DE,BUFFER       ; Copy buffer to program
E474 1A         MOVBUF: LD      A,(DE)          ; Get source
E475 77                 LD      (HL),A          ; Save destinations
E476 23                 INC     HL              ; Next source
E477 13                 INC     DE              ; Next destination
E478 B7                 OR      A               ; Done?
E479 C274E4             JP      NZ,MOVBUF       ; No - Repeat
E47C CDC5E4     SETPTR: CALL    RUNFST          ; Set line pointers
E47F 23                 INC     HL              ; To LSB of pointer
E480 EB                 EX      DE,HL           ; Address to DE
E481 62         PTRLP:  LD      H,D             ; Address to HL
E482 6B                 LD      L,E
E483 7E                 LD      A,(HL)          ; Get LSB of pointer
E484 23                 INC     HL              ; To MSB of pointer
E485 B6                 OR      (HL)            ; Compare with MSB pointer
E486 CA05E4             JP      Z,GETCMD        ; Get command line if end
E489 23                 INC     HL              ; To LSB of line number
E48A 23                 INC     HL              ; Skip line number
E48B 23                 INC     HL              ; Point to first byte in line
E48C AF                 XOR     A               ; Looking for 00 byte
E48D BE         FNDEND: CP      (HL)            ; Found end of line?
E48E 23                 INC     HL              ; Move to next byte
E48F C28DE4             JP      NZ,FNDEND       ; No - Keep looking
E492 EB                 EX      DE,HL           ; Next line address to HL
E493 73                 LD      (HL),E          ; Save LSB of pointer
E494 23                 INC     HL
E495 72                 LD      (HL),D          ; Save MSB of pointer
E496 C381E4             JP      PTRLP           ; Do next line

This is an OCR’d version of the scanned page and likely contains recognition errors.











Page 31 of 55