Category : Files from Magazines
Archive   : PJ-VGA.ZIP
Filename : VGA62-L3.ASM

 
Output of file : VGA62-L3.ASM contained in archive : PJ-VGA.ZIP
Code from "Yet Another VGA Write Mode" by Michael Abrash, PJ,
Volume 6.2. Copyright 1987 Michael Abrash
;
; *** Listing 3 ***
;
; Program to illustrate flipping from bit-mapped graphics mode to
; text mode and back without losing any of the graphics bit-map.
;
; Assembled with MASM 5.0, linked with MS-LINK 3.60.
;
; By Michael Abrash 11/8/87
;
Stack segment para stack 'STACK'
db 512 dup(0)
Stack ends

GRAPHICS_SEGMENT equ 0a000h ;mode 10 bit-map segment
TEXT_SEGMENT equ 0b800h ;mode 3 bit-map segment
SC_INDEX equ 3c4h ;Sequence Controller Index register
MAP_MASK equ 2 ;index of Map Mask register
GC_INDEX equ 3ceh ;Graphics Controller Index register
READ_MAP equ 4 ;index of Read Map register

Data segment para common 'DATA'

GStrikeAnyKeyMsg0 label byte
db 0dh, 0ah, 'Graphics mode', 0dh, 0ah
db 'Strike any key to continue...', 0dh, 0ah, '$'

GStrikeAnyKeyMsg1 label byte
db 0dh, 0ah, 'Graphics mode again', 0dh, 0ah
db 'Strike any key to continue...', 0dh, 0ah, '$'

TStrikeAnyKeyMsg label byte
db 0dh, 0ah, 'Text mode', 0dh, 0ah
db 'Strike any key to continue...', 0dh, 0ah, '$'

Plane2Save db 2000h dup (?) ;save area for plane 2 data
; where font gets loaded
CharAttSave db 4000 dup (?) ;save area for memory wiped
; out by character/attribute
; data in text mode
Data ends

Code segment para public 'CODE'
assume cs:Code, ds:Data
Start proc near
mov ax,10h
int 10h ;select video mode 10h (640x350)
;
; Fill the graphics bit-map with a colored pattern.
;
cld
mov ax,GRAPHICS_SEGMENT
mov es,ax
mov ah,3 ;initial fill pattern
mov cx,4 ;four planes to fill
mov dx,SC_INDEX
mov al,MAP_MASK
out dx,al ;leave the SC Index pointing to the
inc dx ; Map Mask register

FillBitMap:
mov al,10h
shr al,cl ;generate map mask for this plane
out dx,al ;set map mask for this plane
sub di,di ;start at offset 0
mov al,ah ;get the fill pattern
push cx ;preserve plane count
mov cx,8000h ;fill 32K words
rep stosw ;do fill for this plane
pop cx ;get back plane count
shl ah,1
shl ah,1
loop FillBitMap
;
; Put up "strike any key" message.
;
mov ax,Data
mov ds,ax
mov dx,offset GStrikeAnyKeyMsg0
mov ah,9
int 21h
;
; Wait for a key.
;
mov ah,01h
int 21h
;
; Save the 8K of plane 2 that will be used by the font.
;
mov dx,GC_INDEX
mov al,READ_MAP
out dx,al
inc dx
mov al,2
out dx,al ;set up to read from plane 2
mov ax,Data
mov es,ax
mov ax,GRAPHICS_SEGMENT
mov ds,ax
sub si,si
mov di,offset Plane2Save
mov cx,2000h/2 ;save 8K (length of default font)
rep movsw
;
; Go to text mode without clearing display memory.
;
mov ax,083h
int 10h
;
; Save the text mode bit-map.
;
mov ax,Data
mov es,ax
mov ax,TEXT_SEGMENT
mov ds,ax
sub si,si
mov di,offset CharAttSave
mov cx,4000/2 ;length of one text screen in words
rep movsw
;
; Fill the text mode screen with dots and put up "strike any key"
; message.
;
mov ax,TEXT_SEGMENT
mov es,ax
sub di,di
mov al,'.' ;fill character
mov ah,7 ;fill attribute
mov cx,4000/2 ;length of one text screen in words
rep stosw
mov ax,Data
mov ds,ax
mov dx,offset TStrikeAnyKeyMsg
mov ah,9
int 21h
;
; Wait for a key.
;
mov ah,01h
int 21h
;
; Restore the text mode screen to the state it was in on entering
; text mode.
;
mov ax,Data
mov ds,ax
mov ax,TEXT_SEGMENT
mov es,ax
mov si,offset CharAttSave
sub di,di
mov cx,4000/2 ;length of one text screen in words
rep movsw
;
; Return to mode 10h without clearing display memory.
;
mov ax,90h
int 10h
;
; Restore the portion of plane 2 that was wiped out by the font.
;
mov dx,SC_INDEX
mov al,MAP_MASK
out dx,al
inc dx
mov al,4
out dx,al ;set up to write to plane 2
mov ax,Data
mov ds,ax
mov ax,GRAPHICS_SEGMENT
mov es,ax
mov si,offset Plane2Save
sub di,di
mov cx,2000h/2 ;restore 8K (length of default font)
rep movsw
;
; Put up "strike any key" message.
;
mov ax,Data
mov ds,ax
mov dx,offset GStrikeAnyKeyMsg1
mov ah,9
int 21h
;
; Wait for a key before returning to text mode and ending.
;
mov ah,01h
int 21h
mov ax,03h
int 10h
mov ah,4ch
int 21h
Start endp
Code ends
end Start



  3 Responses to “Category : Files from Magazines
Archive   : PJ-VGA.ZIP
Filename : VGA62-L3.ASM

  1. Very nice! Thank you for this wonderful archive. I wonder why I found it only now. Long live the BBS file archives!

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