Date: Sun, 7 Apr 1996 09:16:08 +0200 (IST)
From: Eli Zaretskii <eliz AT is DOT elta DOT co DOT il>
To: George Foot <gfoot AT mymail DOT com>
Cc: djgpp AT delorie DOT com
Subject: Re: GRX20 Help!
In-Reply-To: <4k3vit$20m@soap.news.pipex.net>
Message-Id: <Pine.SUN.3.91.960407091209.22284M-100000@is>
Mime-Version: 1.0
Content-Type: TEXT/PLAIN; charset=US-ASCII


On Fri, 5 Apr 1996, George Foot wrote:

> >of the screen. But be aware that you'll have to manage *far* pointers, which
> >is not obvious with gcc. PutPixel and others libgrx functions are REALLY fast,
> 
> What's this about far pointers? I thought they didn't exist under gcc.
> AFAIK all pointers are capable of specifying any memory address...

You can only access memory addresses that are in your program's address
space.  That is what protected mode is all about.  Memory-mapped devices
generally *aren't* in your address space, so you should use special
techniques to get at them.  Using ``far pointers'' (that don't imply the
``far'' keyword, btw) is one of these techniques, but there are others. 
The FAQ list explains this in detail in section 18.4.