80-Bus News

  

March-April 1984, Volume 3, Issue 2











Page 27 of 51











Dis-assembly of NASCOM ROM BASIC Ver 4.7                PAGE    84

F965 C259F9     ENDCON: JP      NZ,SCALMI       ; More to do
F968 D1                 POP     DE              ; Restore code string address
F969 F1                 POP     AF              ; Restore sign of number
F96A CC3CF8             CALL    Z,INVSGN        ; Negative - Negate number
F96D EB                 EX      DE,HL           ; Code string address to HL
F96E C9                 RET

F96F C8         SCALPL: RET     Z               ; Exit if no scaling needed
F970 F5         MULTEN: PUSH    AF              ; Save count
F971 CDFCF7             CALL    MLSP10          ; Multiply number by 10
F974 F1                 POP     AF              ; Restore count
F975 3D                 DEC     A               ; Count multiplies
F976 C9                 RET

F977 D5         ADDIG:  PUSH    DE              ; Save sign of exponent
F978 57                 LD      D,A             ; Save digit
F979 78                 LD      A,B             ; Get digits after point
F97A 89                 ADC     A,C             ; Add one if after point
F97B 47                 LD      B,A             ; Re-save counter
F97C C5                 PUSH    BC              ; Save point flags
F97D E5                 PUSH    HL              ; Save code string address
F97E D5                 PUSH    DE              ; Save digit
F97F CDFCF7             CALL    MLSP10          ; Multiply number by 10
F982 F1                 POP     AF              ; Restore digit
F983 D630               SUB     "0"             ; Make it absolute
F985 CD8EF9             CALL    RSCALE          ; Re-scale number
F988 E1                 POP     HL              ; Restore code string address
F989 C1                 POP     BC              ; Restore point flags
F98A D1                 POP     DE              ; Restore sign of exponent
F98B C32EF9             JP      MANLP           ; Get another digit

F98E CD44F8     RSCALE: CALL    STAKFP          ; Put number on stack
F991 CD25F8             CALL    FLGREL          ; Digit to add to FPREG
F994 C1         PADD:   POP     BC              ; Restore number
F995 D1                 POP     DE
F996 C3CDF5             JP      FPADD           ; Add BCDE to FPREG and return

F999 7B         EDIGIT: LD      A,E             ; Get digit
F99A 07                 RLCA                    ; Times 2
F99B 07                 RLCA                    ; Times 4
F99C 83                 ADD     A,E             ; Times 5
F99D 07                 RLCA                    ; Times 10
F99E 86                 ADD     A,(HL)          ; Add next digit
F99F D630               SUB     "0"             ; Make it absolute
F9A1 5F                 LD      E,A             ; Save new digit
F9A2 C344F9             JP      EXPLP           ; Look for another digit

Dis-assembly of NASCOM ROM BASIC Ver 4.7                PAGE    85

F9A5 E5         LINEIN: PUSH    HL              ; Save code string address
F9A6 2146E3             LD      HL,INMSG        ; Output " in "
F9A9 CD10F2             CALL    PRS             ; Output string at HL
F9AC E1                 POP     HL              ; Restore code string address
F9AD EB         PRNTHL: EX      DE,HL           ; Code string address to DE
F9AE AF                 XOR     A
F9AF 0698               LD      B,80H+24        ; 24 bits
F9B1 CD2AF8             CALL    RETINT          ; Return the integer
F9B4 210FF2             LD      HL,PRNUMS       ; Print number string
F9B7 E5                 PUSH    HL              ; Save for return
F9B8 21E910     NUMASC: LD      HL,PBUFF        ; Convert number to ASCII
F9BB E5                 PUSH    HL              ; Save for return
F9BC CD13F8             CALL    TSTSGN          ; Test sign of FPREG
F9BF 3620               LD      (HL)," "        ; Space at start
F9C1 F2C6F9             JP      P,SPCFST        ; Positive - Space to start
F9C4 362D               LD      (HL),"-"        ; "-" sign at start
F9C6 23         SPCFST: INC     HL              ; First byte of number
F9C7 3630               LD      (HL),"0"        ; "0" if zero
F9C9 CA7CFA             JP      Z,JSTZER        ; Return "0" if zero
F9CC E5                 PUSH    HL              ; Save buffer address
F9CD FC3CF8             CALL    M,INVSGN        ; Negate FPREG if negative
F9D0 AF                 XOR     A               ; Zero A
F9D1 F5                 PUSH    AF              ; Save it
F9D2 CD82FA             CALL    RNGTST          ; Test number is in range
F9D5 014391     SIXDIG: LD      BC,9143H        ; BCDE - 99999.9
F9D8 11F84F             LD      DE,4FF8H
F9DB CD8EF8             CALL    CMPNUM          ; Compare numbers
F9DE B7                 OR      A
F9DF E2F3F9             JP      PO,INRNG        ; > 99999.9 - Sort it out
F9E2 F1                 POP     AF              ; Restore count
F9E3 CD70F9             CALL    MULTEN          ; Multiply by ten
F9E6 F5                 PUSH    AF              ; Re-save count
F9E7 C3D5F9             JP      SIXDIG          ; Test it again

F9EA CD5BF7     GTSIXD: CALL    DIV10           ; Divide by 10
F9ED F1                 POP     AF              ; Get count
F9EE 3C                 INC     A               ; Count divides
F9EF F5                 PUSH    AF              ; Re-save count
F9F0 CD82FA             CALL    RNGTST          ; Test number is in range
F9F3 CDBBF5     INRNG:  CALL    ROUND           ; Add 0.5 to FPREG
F9F6 3C                 INC     A
F9F7 CDBBF8             CALL    FPINT           ; F.P to integer
F9FA CD54F8             CALL    FPBCDE          ; Move BCDE to FPREG
F9FD 010603             LD      BC,0306H        ; 1E+06 to 1E-03 range
FA00 F1                 POP     AF              ; Restore count
FA01 81                 ADD     A,C             ; 6 digits before point
FA02 3C                 INC     A               ; Add one
FA03 FA0FFA             JP      M,MAKNUM        ; Do it in "E" form if < 1E-02
FA06 FE08               CP      6+1+1           ; More than 999999 ?
FA08 D20FFA             JP      NC,MAKNUM       ; Yes - Do it in "E" form
FA0B 3C                 INC     A               ; Adjust for exponent
FA0C 47                 LD      B,A             ; Exponent of number
FA0D 3E02               LD      A,2             ; Make it zero after


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











Page 27 of 51