===========================================================================
 BBS: The Abacus * HST/DS * Potterville, MI
Date: 04-23-93 (19:01)             Number: 84
From: ROBERT CHURCH                Refer#: NONE
  To: ALL                           Recvd: NO  
Subj: Assembley direct screen w      Conf: (35) Quick Basi
---------------------------------------------------------------------------
Here's an assembly routine I wrote for writing a QB near string directly to vide
o ram.  If anyone notices any room for improvement, please let me know. I'd like
 to hear your comments.

; fprint - writes a string directly to the video buffer

; DECLARE SUB FPrint (S$, BYVAL Attr%, BYVAL Row%, BYVAL Col%)

.Model Medium, Basic
.Data
VidSegment dw 0

.Code

fprint proc uses SI DI, str_ptr:word, attr:word, row:word, col:word

    Mov   AX, row
    Dec   AX             ; (160 * (row - 1)) + (2 * (col - 1))
    Mov   DX, 160
    Imul  DX
    Mov   DX, col
    Dec   DX
    Shl   DX, 1
    Add   AX, DX
    Mov   DI, AX         ; the offset into video memory in which to
                                ; print is now in DI

    Mov   BX, VidSegment ; figure out if the routine has been called yet
    Cmp   BX, 0
    Je    GetVidSegment  ; call the initionaliztion routine

SetupLoop:
    Mov   ES, BX         ; load the video buffer's segment into ES
    Mov   AX, Attr       ; put the attribute in AX
    Mov   SI, str_ptr    ; load the QB string, length in CX, ptr in SI
    Mov   CX, [SI]
    Mov   SI, [SI+2]

    ; Current register contents:
    ;  AX = Attribute word
    ;  CX = string length
    ;  SI = pointer to string
    ;  DI = offset into video memory at which to print
    ;  ES = video memory segment

    Cld
LoopHere:               ; entry point of loop
    Movsb                ; copy the next char in the string to vid ram
    Mov   ES:[DI], AL    ; copy the attribute to vid ram
    Inc   DI             ; move to the next position on the screen
    Loop  LoopHere       ; loop until CX = 0
    Jmp   ExitProc

GetVidSegment:

    Xor   AX, AX            ; set ES to segment 0
    Mov   ES, AX
    Mov   AX, ES:[463h]     ; figure out if we're mono or color
    Cmp   AH, 0B4h
    Jne   Color             ; if not equal, color
    Mov   VidSegment, 0B000h ;Set the VidSegment to 0B000h, monochrome
    Jmp   Return
Color:
    Mov   VidSegment, 0B800h ;color
Return:
    Mov   BX, VidSegment    ; either way, load BX with the segment
    Jmp   SetupLoop

ExitProc:
    Ret

fprint endp
end


Here's the .OBJ file for those of you without assemblers.

'Save this script to a file, edit out all of the non-QB related text and
'execute it in a QB environment to retrieve FPRINT.OBJ.
DEFINT A-Z:FOR A=0 TO 6:P(A)=2^A:NEXT:OPEN "B",1,"FPRINT.OBJ"
T$="abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789()"
G"aYaakygCYLMB05sqt1eYwwcaayarhj1tvbfbefevbrWqprurf8frbrvqlyeusLKt
G"u9fvfHfvXG5baGuyayabb0kMhaascaqbdeGdAsaac8VaFbzdaaqagyeusLKtubaa
G"aKiIeaaaIgq0GAaacaaaaaawGwgabaaavTi7wD1IgHas6cka3R(IwzGsrl(acVi(
G"l6baam4(aqhgoo8IgPWI2XWImSiDcWpPMGybhjE(RpcKZaSJaBsOJraG8tBDjCSb
G"aaaaWU(bqESbaaaa4UOhaaW6g)LxDPmcaShNvaaXAqracqmsueGaehffbiaXxrra
G"cKTIcaaa0b"
N=247:K=255:IF LEN(C$)<>330 THEN ?"Bad script file!":BEEP:END
FOR A=1 TO N:LOCATE,1:?(100&*A)\N"% Done";:IF L=0 THEN GOSUB G:L=6
W=T\P(6-L):GOSUB G:W=W OR T*P(L):L=L-2:B$=CHR$(W AND K):PUT 1,,B$:NEXT
?:IF C<>244 THEN ?"Bad checksum!":BEEP:END ELSE ?"Success!":END
G:I=I+1:T=INSTR(T$,MID$(C$,I,1))-1:C=(C+T)*2:C=C\256+(C AND K):RETURN
SUB G(A$):SHARED C$:C$=C$+RTRIM$(A$):END SUB


>-= Rob =-<

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