80-Bus News

  

January–February 1984, Volume 3, Issue 1











Page 28 of 55











Dis-assembly of NASCOM ROM BASIC Ver 4.7                PAGE    63

F2E1 D1         SCNEND: POP     DE              ; Addresses of strings
F2E2 E1                 POP     HL              ;
F2E3 7D                 LD      A,L             ; HL = 0 if no more to do
F2E4 B4                 OR      H
F2E5 C8                 RET     Z               ; No more to do - Return
F2E6 2B                 DEC     HL
F2E7 46                 LD      B,(HL)          ; MSB of address of string
F2E8 2B                 DEC     HL
F2E9 4E                 LD      C,(HL)          ; LSB of address of string
F2EA E5                 PUSH    HL              ; Save variable address
F2EB 2B                 DEC     HL
F2EC 2B                 DEC     HL
F2ED 6E                 LD      L,(HL)          ; HL = Length of string
F2EE 2600               LD      H,0
F2F0 09                 ADD     HL,BC           ; Address of end of string+1
F2F1 50                 LD      D,B             ; String address to DE
F2F2 59                 LD      E,C
F2F3 2B                 DEC     HL              ; Last byte in string
F2F4 44                 LD      B,H             ; Address to BC
F2F5 4D                 LD      C,L
F2F6 2AC310             LD      HL,(STRBOT)     ; Current bottom of string area
F2F9 CD7CE3             CALL    MOVSTR          ; Move string to new address
F2FC E1                 POP     HL              ; Restore variable address
F2FD 71                 LD      (HL),C          ; Save new LSB of address
F2FE 23                 INC     HL
F2FF 70                 LD      (HL),B          ; Save new MSB of address
F300 69                 LD      L,C             ; Next string area+1 to HL
F301 60                 LD      H,B
F302 2B                 DEC     HL              ; Next string area address
F303 C356F2             JP      GARBLP          ; Look for more strings

F306 C5         CONCAT: PUSH    BC              ; Save prec' opr & code string
F307 E5                 PUSH    HL              ;
F308 2AE410             LD      HL,(FPREG)      ; Get first string
F30B E3                 EX      (SP),HL         ; Save first string
F30C CDD1ED             CALL    OPRND           ; Get second string
F30F E3                 EX      (SP),HL         ; Restore first string
F310 CD45ED             CALL    TSTSTR          ; Make sure it's a string
F313 7E                 LD      A,(HL)          ; Get length of second string
F314 E5                 PUSH    HL              ; Save first string
F315 2AE410             LD      HL,(FPREG)      ; Get second string
F318 E5                 PUSH    HL              ; Save second string
F319 86                 ADD     A,(HL)          ; Add length of second string
F31A 1E1C               LD      E,LS            ; ?LS Error
F31C DAC1E3             JP      C,ERROR         ; String too long - Error
F31F CDBFF1             CALL    MKTMST          ; Make temporary string
F322 D1                 POP     DE              ; Get second string to DE
F323 CD57F3             CALL    GSTRDE          ; Move to string pool if needed
F326 E3                 EX      (SP),HL         ; Get first string
F327 CD56F3             CALL    GSTRHL          ; Move to string pool if needed
F32A E5                 PUSH    HL              ; Save first string
F32B 2AC110             LD      HL,(TMPSTR+2)   ; Temporary string address
F32E EB                 EX      DE,HL           ; To DE
F32F CD3DF3             CALL    SSTSA           ; First string to string area
F332 CD3DF3             CALL    SSTSA           ; Second string to string area
F335 2166ED             LD      HL,EVAL2        ; Return to evaluation loop
F338 E3                 EX      (SP),HL         ; Save return,get code string
F339 E5                 PUSH    HL              ; Save code string address
F33A C3F0F1             JP      TSTOPL          ; To temporary string to pool
Dis-assembly of NASCOM ROM BASIC Ver 4.7                PAGE    64

F33D E1         SSTSA:  POP     HL              ; Return address
F33E E3                 EX      (SP),HL         ; Get string block,save return
F33F 7E                 LD      A,(HL)          ; Get length of string
F340 23                 INC     HL
F341 23                 INC     HL
F342 4E                 LD      C,(HL)          ; Get LSB of string address
F343 23                 INC     HL
F344 46                 LD      B,(HL)          ; Get MSB of string address
F345 6F                 LD      L,A             ; Length to L
F346 2C         TOSTRA: INC     L               ; INC - DECed after
F347 2D         TSALP:  DEC     L               ; Count bytes moved
F348 C8                 RET     Z               ; End of string - Return
F349 0A                 LD      A,(BC)          ; Get source
F34A 12                 LD      (DE),A          ; Save destination
F34B 03                 INC     BC              ; Next source
F34C 13                 INC     DE              ; Next destination
F34D C347F3             JP      TSALP           ; Loop until string moved

F350 CD45ED     GETSTR: CALL    TSTSTR          ; Make sure it's a string
F353 2AE410     GSTRCU: LD      HL,(FPREG)      ; Get current string
F356 EB         GSTRHL: EX      DE,HL           ; Save DE
F357 CD71F3     GSTRDE: CALL    BAKTMP          ; Was it last tmp-str?
F35A EB                 EX      DE,HL           ; Restore DE
F35B C0                 RET     NZ              ; No - Return
F35C D5                 PUSH    DE              ; Save string
F35D 50                 LD      D,B             ; String block address to DE
F35E 59                 LD      E,C
F35F 1B                 DEC     DE              ; Point to length
F360 4E                 LD      C,(HL)          ; Get string length
F361 2AC310             LD      HL,(STRBOT)     ; Current bottom of string area
F364 CD8AE6             CALL    CPDEHL          ; Last one in string area?
F367 C26FF3             JP      NZ,POPHL        ; No - Return
F36A 47                 LD      B,A             ; Clear B (A=0)
F36B 09                 ADD     HL,BC           ; Remove string from str' area
F36C 22C310             LD      (STRBOT),HL     ; Save new bottom of str' area
F36F E1         POPHL:  POP     HL              ; Restore string
F370 C9                 RET

F371 2AB110     BAKTMP: LD      HL,(TMSTPT)     ; Get temporary string pool top
F374 2B                 DEC     HL              ; Back
F375 46                 LD      B,(HL)          ; Get MSB of address
F376 2B                 DEC     HL              ; Back
F377 4E                 LD      C,(HL)          ; Get LSB of address
F378 2B                 DEC     HL              ; Back
F379 2B                 DEC     HL              ; Back
F37A CD8AE6             CALL    CPDEHL          ; String last in string pool?
F37D C0                 RET     NZ              ; Yes - Leave it
F37E 22B110             LD      (TMSTPT),HL     ; Save new string pool top
F381 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 28 of 55