80-Bus News

  

January–February 1984, Volume 3, Issue 1











Page 24 of 55











Dis-assembly of NASCOM ROM BASIC Ver 4.7                PAGE    55

F04A 110400     CREARY: LD      DE,4            ; 4 Bytes per entry
F04D F1                 POP     AF              ; Array to save or 0 dim'ns?
F04E CAA0E9             JP      Z,FCERR         ; Yes - ?FC Error
F051 71                 LD      (HL),C          ; Save second byte of name
F052 23                 INC     HL
F053 70                 LD      (HL),B          ; Save first byte of name
F054 23                 INC     HL
F055 4F                 LD      C,A             ; Number of dimensions to C
F056 CD8AE3             CALL    CHKSTK          ; Check if enough memory
F059 23                 INC     HL              ; Point to number of dimensions
F05A 23                 INC     HL
F05B 22C510             LD      (CUROPR),HL     ; Save address of pointer
F05E 71                 LD      (HL),C          ; Set number of dimensions
F05F 23                 INC     HL
F060 3AAC10             LD      A,(LCRFLG)      ; Locate of Create?
F063 17                 RLA                     ; Carry set = Create
F064 79                 LD      A,C             ; Get number of dimensions
F065 010B00     CRARLP: LD      BC,10+1         ; Default dimension size 10
F068 D26DF0             JP      NC,DEFSIZ       ; Locate - Set default size
F06B C1                 POP     BC              ; Get specified dimension size
F06C 03                 INC     BC              ; Include zero element
F06D 71         DEFSIZ: LD      (HL),C          ; Save LSB of dimension size
F06E 23                 INC     HL
F06F 70                 LD      (HL),B          ; Save MSB of dimension size
F070 23                 INC     HL
F071 F5                 PUSH    AF              ; Save num' of dim'ns an status
F072 E5                 PUSH    HL              ; Save address of dim'n size
F073 CDFFF8             CALL    MLDEBC          ; Multiply DE by BC to find
F076 EB                 EX      DE,HL           ; amount of mem needed (to DE)
F077 E1                 POP     HL              ; Restore address of dimension
F078 F1                 POP     AF              ; Restore number of dimensions
F079 3D                 DEC     A               ; Count them
F07A C265F0             JP      NZ,CRARLP       ; Do next dimension if more
F07D F5                 PUSH    AF              ; Save locate/create flag
F07E 42                 LD      B,D             ; MSB of memory needed
F07F 4B                 LD      C,E             ; LSB of memory needed
F080 EB                 EX      DE,HL
F081 19                 ADD     HL,DE           ; Add bytes to array start
F082 DAA2E3             JP      C,OMERR         ; Too big - Error
F085 CD93E3             CALL    ENFMEM          ; See if enough memory
F088 22DA10             LD      (ARREND),HL     ; Save new end of array
Dis-assembly of NASCOM ROM BASIC Ver 4.7                PAGE    56

F08B 2B         ZERARY: DEC     HL              ; Back through array data
F08C 3600               LD      (HL),0          ; Set array element to zero
F08E CD8AE6             CALL    CPDEHL          ; All elements zeroed?
F091 C28BF0             JP      NZ,ZERARY       ; No - Keep on going
F094 03                 INC     BC              ; Number of bytes + 1
F095 57                 LD      D,A             ; A=0
F096 2AC510             LD      HL,(CUROPR)     ; Get address of array
F099 5E                 LD      E,(HL)          ; Number of dimensions
F09A EB                 EX      DE,HL           ; To HL
F09B 29                 ADD     HL,HL           ; Two bytes per dimension size
F09C 09                 ADD     HL,BC           ; Add number of bytes
F09D EB                 EX      DE,HL           ; Bytes needed to DE
F09E 2B                 DEC     HL
F09F 2B                 DEC     HL
F0A0 73                 LD      (HL),E          ; Save LSB of bytes needed
F0A1 23                 INC     HL
F0A2 72                 LD      (HL),D          ; Save MSB of bytes needed
F0A3 23                 INC     HL
F0A4 F1                 POP     AF              ; Locate / Create?
F0A5 DACCF0             JP      C,ENDDIM        ; A is 0 , End if create
F0A8 47         FINDEL: LD      B,A             ; Find array element
F0A9 4F                 LD      C,A
F0AA 7E                 LD      A,(HL)          ; Number of dimensions
F0AB 23                 INC     HL
F0AC 16                 DEFB    (LD D,n)        ; Skip "POP HL"
F0AD E1         FNDELP: POP     HL              ; Address of next dim' size
F0AE 5E                 LD      E,(HL)          ; Get LSB of dim'n size
F0AF 23                 INC     HL
F0B0 56                 LD      D,(HL)          ; Get MSB of dim'n size
F0B1 23                 INC     HL
F0B2 E3                 EX      (SP),HL         ; Save address - Get index
F0B3 F5                 PUSH    AF              ; Save number of dim'ns
F0B4 CD8AE6             CALL    CPDEHL          ; Dimension too large?
F0B7 D245F0             JP      NC,BSERR        ; Yes - ?BS Error
F0BA E5                 PUSH    HL              ; Save index
F0BB CDFFF8             CALL    MLDEBC          ; Multiply previous by size
F0BE D1                 POP     DE              ; Index supplied to DE
F0BF 19                 ADD     HL,DE           ; Add index to pointer
F0C0 F1                 POP     AF              ; Number of dimensions
F0C1 3D                 DEC     A               ; Count them
F0C2 44                 LD      B,H             ; MSB of pointer
F0C3 4D                 LD      C,L             ; LSB of pointer
F0C4 C2ADF0             JP      NZ,FNDELP       ; More - Keep going
F0C7 29                 ADD     HL,HL           ; 4 Bytes per element
F0C8 29                 ADD     HL,HL
F0C9 C1                 POP     BC              ; Start of array
F0CA 09                 ADD     HL,BC           ; Point to element
F0CB EB                 EX      DE,HL           ; Address of element to DE
F0CC 2AD010     ENDDIM: LD      HL,(NXTOPR)     ; Got code string address
F0CF C9                 RET

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

NASCOM ROM BASIC source code is available in ASM and LST file format.











Page 24 of 55