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From: psc@lznv.ATT.COM (Paul S. R. Chisholm)
Newsgroups: comp.sys.ibm.pc
Subject: Re: How do I point to the frame buffer?
Summary: paragraph is not address
Keywords: C, far pointers, frame buffer,ibm pc
Message-ID: <1391@lznv.ATT.COM>
Date: 1 Jul 88 02:23:14 GMT
References: <2784@juniper.UUCP>
Organization: AT&T
Lines: 26

< "Would you buy a used operating system from these guys?" >

In article <2784@juniper.UUCP>, dan@juniper.UUCP (Dan Galewsky) writes:
> Could someone please tell me how to set up a  pointer to the frame buffer
> on my PC's CGA from Microsoft C? I know that the frame buffer starts at 
> 0xb800. So I tried the following :
> 
> far char *Screen;
> Screen = (char *)0Xb800;
 Dan Galewsky, {...}sun!austsun!galewsky, galewsky%asc@sdr.slb.com

The frame buffer starts at B800:0000, which would be 0xB8000 if the
8088 had a linear address space.  It doesn't.  The right way to do this
in MS or Turbo C is

	#include <dos.h>
	far char * const Screen = MK_FP( 0xB800, 0 );

(The "const" is optional; it tells the compiler that Screen is a
constant, and that no one should be allowed to muck with it.)

Comments?

-Paul S. R. Chisholm, {ihnp4,cbosgd,allegra,rutgers}!mtune!lznv!psc
AT&T Mail !psrchisholm, Internet psc@lznv.att.com
I'm not speaking for my employer, I'm just speaking my mind.