Xref: news2.mv.net comp.os.msdos.djgpp:1633
From: Chris Dial <cdial AT jeffnet DOT org>
Newsgroups: comp.os.msdos.djgpp
Subject: WHY DOESN'T IT WORK!?
Date: Sat, 02 Mar 1996 19:53:42 -0800
Organization: Oregon Public Networking
Lines: 42
Message-ID: <313917C6.5574@jeffnet.org>
NNTP-Posting-Host: 204.214.98.28
Mime-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Transfer-Encoding: 7bit
To: djgpp AT delorie DOT com
DJ-Gateway: from newsgroup comp.os.msdos.djgpp

I have a question about DJGPP 2.0:

char *screen;
char screen2[65536];
short our_global_selector;


int main(void) {
 if (__djgpp_nearptr_enable()==0) return 1;
 screen= 0xa0000+ __djgpp_conventional_base;

 our_global_selector = _dos_ds;

 /*     This sends 1 byte to the VGA screen..... */
 screen[0]=(char)255;

 /*     Just like doing this will send one byte to the screen */
 asm ("
  pushw %es
  movw _our_global_selector,%es
  movl $0xa0000,%edi
  movb $255,%es:(%edi)
  popw %es
 ");

 /*     This puts 1 byte in the array 'screen2' */
 screen2[0]=(char)255;

 /*     So how come this does not send one byte to 'screen2'? */
 asm ("
  pushw %es
  movw _our_global_selector,%es
  movl _screen2,%edi
  movb $255,%es:(%edi)
  popw %es
 ");

 return 0;
};


-Chris Dial