80-Bus News

  

November–December 1983, Volume 2, Issue 6











Page 36 of 67











Dis-assembly of NASCOM ROM BASIC Ver 4.7                PAGE    48

EE33 0600       FNOFST: LD      B,0             ; Get address of function
EE35 07                 RLCA                    ; Double function offset
EE36 4F                 LD      C,A             ; BC = Offset in function table
EE37 C5                 PUSH    BC              ; Save adjusted token value
EE38 CD36E8             CALL    GETCHR          ; Get next character
EE3B 79                 LD      A,C             ; Get adjusted token value
EE3C FE22               CP      2*(ZPOINT-ZSGN) ; Adjusted "POINT" token?
EE3E CA79FF             JP      Z,POINTB        ; Yes - Do "POINT" (not POINTB)
EE41 FE2D               CP      2*(ZLEFT-ZSGN)-1; Adj' LEFT$,RIGHT$ or MID$ ?
EE43 DA5FEE             JP      C,FNVAL         ; No - Do function
EE46 CD56ED             CALL    OPNPAR          ; Evaluate expression  (X,...
EE49 CD90E6             CALL    CHKSYN          ; Make sure "," follows
EE4C 2C                 DEFB    ","
EE4D CD45ED             CALL    TSTSTR          ; Make sure it's a string
EE50 EB                 EX      DE,HL           ; Save code string address
EE51 2AE410             LD      HL,(FPREG)      ; Get address of string
EE54 E3                 EX      (SP),HL         ; Save address of string
EE55 E5                 PUSH    HL              ; Save adjusted token value
EE56 EB                 EX      DE,HL           ; Restore code string address
EE57 CD84F4             CALL    GETINT          ; Get integer 0-255
EE5A EB                 EX      DE,HL           ; Save code string address
EE5B E3                 EX      (SP),HL         ; Save integer,HL = adj' token
EE5C C367EE             JP      GOFUNC          ; Jump to string function

EE5F CD09EE     FNVAL:  CALL    EVLPAR          ; Evaluate expression
EE62 E3                 EX      (SP),HL         ; HL = Adjusted token value
EE63 111DEE             LD      DE,RETNUM       ; Return number from function
EE66 D5                 PUSH    DE              ; Save on stack
EE67 010FE1     GOFUNC: LD      BC,FNCTAB       ; Function routine addresses
EE6A 09                 ADD     HL,BC           ; Point to right address
EE6B 4E                 LD      C,(HL)          ; Get LSB of address
EE6C 23                 INC     HL              ;
EE6D 66                 LD      H,(HL)          ; Get MSB of address
EE6E 69                 LD      L,C             ; Address to HL
EE6F E9                 JP      (HL)            ; Jump to function

EE70 15         SGNEXP: DEC     D               ; Dee to flag negative exponent
EE71 FEAD               CP      ZMINUS          ; "-" token ?
EE73 C8                 RET     Z               ; Yes - Return
EE74 FE2D               CP      "-"             ; "-" ASCII ?
EE76 C8                 RET     Z               ; Yes - Return
EE77 14                 INC     D               ; Inc to flag positive exponent
EE78 FE2B               CP      "+"             ; "+" ASCII ?
EE7A C8                 RET     Z               ; Yes - Return
EE7B FEAC               CP      ZPLUS           ; "+" token ?
EE7D C8                 RET     Z               ; Yes - Return
EE7E 2B                 DEC     HL              ; DEC 'cos GETCHR INCs
EE7F C9                 RET                     ; Return "NZ"
Dis-assembly of NASCOM ROM BASIC Ver 4.7                PAGE    49

EE80 F6         POR:    DEFB    (OR n)          ; Flag "OR"
EE81 AF         PAND:   XOR     A               ; Flag "AND"
EE82 F5                 PUSH    AF              ; Save "AND" / "OR" flag
EE83 CD44ED             CALL    TSTNUM          ; Make sure it's a number
EE86 CD8BE9             CALL    DEINT           ; Get integer -32768 to 32767
EE89 F1                 POP     AF              ; Restore "AND" / "OR" flag
EE8A EB                 EX      DE,HL           ; <- Get last
EE8B C1                 POP     BC              ; <-  value
EE8C E3                 EX      (SP),HL         ; <-  from
EE8D EB                 EX      DE,HL           ; <-  stack
EE8E CD54F8             CALL    FPBCDE          ; Move last value to FPREG
EE91 F5                 PUSH    AF              ; Save "AND" / "OR" flag
EE92 CD8BE9             CALL    DEINT           ; Get integer -32768 to 32767
EE95 F1                 POP     AF              ; Restore "AND" / "OR" flag
EE96 C1                 POP     BC              ; Get value
EE97 79                 LD      A,C             ; Get LSB
EE98 21F1F0             LD      HL,ACPASS       ; Address of save AC as current
EE9B C2A3EE             JP      NZ,POR1         ; Jump if OR
EE9E A3                 AND     E               ; "AND" LSBs
EE9F 4F                 LD      C,A             ; Save LSB
EEA0 78                 LD      A,B             ; Get MBS
EEA1 A2                 AND     D               ; "AND" MSBs
EEA2 E9                 JP      (HL)            ; Save AC as current (ACPASS)

EEA3 B3         POR1:   OR      E               ; "OR" LSBs
EEA4 4F                 LD      C,A             ; Save LSB
EEA5 78                 LD      A,B             ; Get MSB
EEA6 B2                 OR      D               ; "OR" MSBs
EEA7 E9                 JP      (HL)            ; Save AC as current (ACPASS)

EEA8 21BAEE     TSTRED: LD      HL,CMPLOG       ; Logical compare routine
EEAB 3AAD10             LD      A,(TYPE)        ; Get data type
EEAE 1F                 RRA                     ; Carry set = string
EEAF 7A                 LD      A,D             ; Get last precedence value
EEB0 17                 RLA                     ; Times 2 plus carry
EEB1 5F                 LD      E,A             ; To E
EEB2 1664               LD      D,64H           ; Relational precedence
EEB4 78                 LD      A,B             ; Get current precedence
EEB5 BA                 CP      D               ; Compare with last
EEB6 D0                 RET     NC              ; Eval if last was rel' or log'
EEB7 C3BAED             JP      STKTHS          ; Stack this one and get next

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











Page 36 of 67