Subject: Pointer Arithmetic + physical address mapping
From: Bryanston School <MOLESWORTH DOT THOMAS AT bryanston DOT co DOT uk>
Date: Mon, 06 May 1996 16:55:15 +0100
Message-Id: <000000137472914242915@bryanston.co.uk>
Organization: Bryanston School
To: DJGPP <djgpp AT delorie DOT com>
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Does pointer arithmetic only work with ints in DJGPP? I tried using
pointer arithmetic on unsigned ints and longs, and my program gave
a whole list of runtime errors; when I called a subroutine with a pointer
to a variable, it could not access the correct area of memory (the actual
pointer passed to the function was wrong; the value printed in the main
procedure and the function were different)

Also, is it possible to map an area of physical memory (a reserved area of
extended memory at about 1.25 Mb, 1 Mb in size) to a logical address in
DJGPP v1? I found some code which adds 0xE0000000 to the address, is this
right and if so how does it work? The docs say that the 0xE0000000 address
is simply a copy of the first 1 Mb.

Thanks in advance,

Thomas Molesworth
mailto:MOLESWORTH DOT THOMAS AT bryanston DOT co DOT uk