Xref: news2.mv.net comp.os.msdos.djgpp:2419
From: Eli Zaretskii <eliz AT is DOT elta DOT co DOT il>
Newsgroups: comp.os.msdos.djgpp
Subject: Re: DJGPP v2 and direct memory writing
Date: Wed, 3 Apr 1996 07:40:17 +0200
Organization: NetVision LTD.
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References: <4jqo2o$7ud AT news DOT mdata DOT fi>
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To: djgpp AT delorie DOT com
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On 1 Apr 1996, Vesa-Matti Heino wrote:

> I use in my programs direct screen writing routines. When I upgradet to version
> 2 of djgpp, my programs wont work anymore. GCC compiles them just right, but
> when I run these files Gcc gives error and register values. What is wrong...
> 
> Here is one of functions, whitch wont work:
> 
> char *screen=(char *)0xD0000000;
> 
> void inline plot(short x,short y,char col){
>             screen[(y<<8)+(y<<6)+x]=col;
>             }
> 
> Also my direct textmode routines wont work... :(

Direct access to video RAM (and any other memory-mapped device) by poking 
a constant address like 0xD0000000 doesn't work in v2.0.  In fact, it 
didn't even work in v1.x in DPMI mode, and v2.0 is DPMI-only 
environment.  Read the __djgpp_nearptr_enable section in the libc.a 
on-line Info docs, or point your Web browser to this URL:

   http://www.delorie.com/djgpp/doc/libc-2.00/libc_111.html#SEC111.

Section 18.4 in the FAQ list (available as v2/faq200b.zip from the same 
place you get DJGPP) tells you about other available methods of accessing 
conventional memory and memory-mapped devices.  I suggest you read it.