Path: utzoo!attcan!uunet!lll-winken!lll-tis!ames!ncar!tank!uxc!uxc.cso.uiuc.edu!uxg.cso.uiuc.edu!uxe.cso.uiuc.edu!mcdonald
From: mcdonald@uxe.cso.uiuc.edu
Newsgroups: comp.sys.ibm.pc
Subject: Re: VGA routines   (wanted)
Message-ID: <45900167@uxe.cso.uiuc.edu>
Date: 10 Oct 88 14:40:00 GMT
References: <490@fabscal.UUCP>
Lines: 40
Nf-ID: #R:fabscal.UUCP:490:uxe.cso.uiuc.edu:45900167:000:1034
Nf-From: uxe.cso.uiuc.edu!mcdonald    Oct 10 09:40:00 1988


>I am looking for routines useable under DOS and/or XENIX on a 80386
>based system to do the following:

>   1) switch my VGA from text to 320x200x256color mode

>   2) write information to the graphics screen either pixel at a time
>      or in blocks.

>   3) switch  the screen back to 80x24 text mode.
For DOS this is truly trivial. The display is bitmapped, one unsigned
char per pixel, starting at 0xa0000000 (that is a000:0000).
The following program fills the screen with the first 200 default colors.
#include <dos.h>
#include <conio.h>
#include <stdio.h>

main(){
union REGS rg;
unsigned char far *screenptr;
int i,j;

    rg.x.ax = 19;
    int86(16,&rg,&rg);

    screenptr = (unsigned char far *)(0xa0000000l);

    for (i = 0; i < 200; i++)
        for(j = 0; j < 320; j++)*screenptr++ = i;

    while(!kbhit);
    (void)getchar();
    rg.x.ax = 3;
    int86(16,&rg,&rg);
}
The translation to assembly is obvious.

Xenix is of course another thing ENTIRELY. I'll bet it isn't so easy.


Doug McDonald (mcdonald@uiucuxe)