From:	"M. Schulter" <mschulter AT value DOT net>
Newsgroups:	comp.os.msdos.djgpp
Subject:	Re: BEGINNER -address of arrays etc - Help
Date:	2 Oct 1997 18:58:41 GMT
Organization:	Value Net Internetwork Services Inc.
Lines:	25
Message-ID:	<610qt1$j8f$2@vnetnews.value.net>
References:	<EHFIz7 DOT 4DH AT cix DOT compulink DOT co DOT uk>
NNTP-Posting-Host:	value.net
To:	djgpp AT delorie DOT com
DJ-Gateway:	from newsgroup comp.os.msdos.djgpp

"Peter Scargill" <pscargill AT cix DOT compulink DOT co DOT uk> wrote:

: Remember I've never used a 32 bit compiler before. Seems like a valid 32 
: bit address would be sent but obviously not. Comments anyone?

Protected mode is a horse of another color <grin>, and getting a "valid
address" gets into a world of descriptor tables, protection levels, page
directories and tables, and the like.

In other words, getting a _valid_ 32-bit address is a nontrivial matter,
because the essence of "protected" mode is that you cannot just
arbitrarily access a desired location in memory. You have to go through
a validation process.

Fortunately, there are some common DJGPP techniques to cope with these
issues, discussed in an uncommonly informative document: see Sections 10
and 18 of the DJGPP FAQ on graphics and hardware programming. These
sections discuss some methods for accessing video memory or handling DOS
interrupts, for example.

Most respectfully,

Margo Schulter
mschulter AT value DOT net

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