Q31573: QuickBASIC/MASM Programs in "PC Magazine" Incorrect

Article: Q31573
Product(s): See article
Version(s): 4.00 4.00b 4.50
Operating System(s): MS-DOS
Keyword(s): ENDUSER | B_BasicCom | mspl13_basic
Last Modified: 28-DEC-1989

The sample QuickBASIC and MASM programs discussed in "PC Magazine"
October 13, 1987, on Pages 389-399 will not correctly work with
QuickBASIC Version 4.00.

The modified programs are as follows:

   === QP.BAS ===

   'QPrint.Bas - quick print demonstration for QuickBASIC

   Test$ = STRING$(20 * 80, "X")              'make a long string
   Colr% = 7
   LOCATE 1, 1
   CALL QPrint(Test$, Colr%)

   === QP.ASM ===

   ;QPRINT.ASM - performs Quick Printing in the QuickBASIC
   ;Note: Assemble this with MASM (2.00 or later)
   ;Copyright 1987, Ziff Communications Co.

   Code        Segment Byte Public 'Code'
               Assume  CS:Code
               Public  QPrint

   QPrint      Proc    Far

   Begin:      Push  BP         ;save registers for BASIC
               MOV   BP,SP      ;* ADD THIS LINE
               PUSH  DS         ;* ADD THIS LINE
               PUSH  ES         ;* ADD THIS LINE

               Mov   AH,3       ;specify BIOS service to read cursor position
               Mov   BH,0       ;on text page zero
               Int   10h        ;this service returns row/column in DH/DL

               Mov   AL,DH      ;put the current row number into AL
               Mov   CL,160     ;multiply by 160 to get start address of row
               Mul   CL         ;do the multiplication, answer ends up in AX
               Mov   DH,0       ;clear DH for the Add below, we only want DL
               Add   AX,DX      ;add the column once for the character byte
               Add   AX,DX      ;and once more for the attribute byte
               Mov   DI,AX      ;now DI holds starting address on the screen

               Xor   DX,DX      ;zero out DX to look at low memory using ES
               Mov   ES,DX
               Mov   BX,0B000h     ;assume the mono screen segment for now
               Mov   AL,ES:[463h]  ;look at the video controller port address
               Cmp   AL,0B4h     ;is it mono?
               JZ    Get_Params ;yes, skip over adding 800h to video segment
               Add   BX,800h    ;no, adjust BX for a color monitor
               Push  BX         ;and save it because the EGA test destroys BX

               Mov   AH,12h     ;specify EGA BIOS EGA special function servic
               Mov   BL,10h     ;request EGA information
               Int   10h        ;call the BIOS
               Cmp   BL,10h     ;if BL is still 10h, there's no EGA
               JNZ   EGA        ;it is an EGA, skip ahead
               Mov   DX,3DAh    ;not EGA, specify port to check for retrace

   EGA:        Pop   BX         ;get the video segment again

   Get_Params: ;* Mov   BP,SP   ;get stack pointer so you can find variables
               Mov   ES,BX      ;move whatever segment is correct into ES

               Mov   SI,[BP+06] ;get the color that was passed
               Mov   AH,[SI]    ;and put it into AH for screen writing below
               Mov   SI,[BP+08] ;put descriptor to X$ into SI
               Mov   CX,[SI]    ;put Len(X$) into CX for loop counter
               JCXZ  Exit       ;if CX is zero it's a null string, exit now
               Mov   SI,[SI+02] ;put address of first character in X$ into SI
               Cld              ;clear the direction flag to move data forwar

   Check_Mon:  Cmp   DL,0       ;are we on a mono or EGA system?
               JZ    Mono       ;yes, skip over the retrace stuff

   No_Retrace: In    AL,DX      ;get the video status byte from port number D
               Test  AL,1       ;test just the horizontal retrace bit
               JNZ   No_Retrace ;if doing a retrace, wait until it's not

   Retrace:    In    AL,DX      ;get the status byte again
               Test  AL,1       ;are we doing a retrace now?
               JZ    Retrace    ;no, wait until we are

   Mono:       Lodsb            ;get the character from X$ and increment SI
               Stosw            ;store both the character and attribute
               Loop  Check_Mon  ;loop until CX is zero

   Exit:       POP   ES         ;* ADD THIS LINE
               POP   DS         ;* ADD THIS LINE
               Pop   BP         ;restore BP for BASIC
               Ret   4          ;return skipping the passed parameters

   QPrint      Endp
   Code        Ends
               End   ;* remove this label Begin

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