From:	Stephen Liu <stephen_liu AT bigfoot DOT com>
Newsgroups:	comp.os.msdos.djgpp
Subject:	Writing directly to vga memory in DJGPP
Date:	Thu, 27 Feb 1997 21:59:28 -0500
Organization:	Kadoorie Corp.
Lines:	39
Message-ID:	<33164A10.1D88@bigfoot.com>
NNTP-Posting-Host:	128.226.101.87
Mime-Version:	1.0
To:	djgpp AT delorie DOT com
DJ-Gateway:	from newsgroup comp.os.msdos.djgpp

The following program clears the screen in VGA mode (13h) in each 
of the 255 colors.  My buffer is declared as:

unsigned char *vidbuffer=(unsigned char *)0xA0000;

Is this correct? When I run it under Win95, it creates
a memory exception and quits the program.


//*******************************************************************

#include <stdio.h>
#include <dos.h>

unsigned char *vidbuffer=(unsigned char *)0xA0000;

void setmode(int mode)
{ union REGS regs;
  regs.h.al = mode;
  regs.h.ah = 0;
  int86(0x10, &regs, &regs);
}

void clrvidbuffer(unsigned char color)
{ int i;
  for (i=0; i<32000; i++)
  { vidbuffer[i]=color;     // Write pixel to buffer
  }
}

void main()
{ int i;
  setmode(0x13);        // Set VGA mode

  for (i=0; i<256; i++) 
   clrvidbuffer(i);     // Clear the screen in each color
}

//*******************************************************************

- Raw text -