Xref: news2.mv.net comp.os.msdos.djgpp:2424
From: fnunez AT cs DOT uct DOT ac DOT za (Fabian Nunez)
Newsgroups: comp.os.msdos.djgpp
Subject: Re: How to code Interrupts in C?
Date: 3 Apr 1996 06:23:28 GMT
Organization: University of Cape Town
Lines: 37
Message-ID: <4jt5h0$6p5@groa.uct.ac.za>
References: <4ji0s3$t4i AT news DOT nevada DOT edu> <315F1AEF DOT 5A083C32 AT alcyone DOT com>
NNTP-Posting-Host: dione.cs.uct.ac.za
To: djgpp AT delorie DOT com
DJ-Gateway: from newsgroup comp.os.msdos.djgpp

In <315F1AEF DOT 5A083C32 AT alcyone DOT com> Erik Max Francis <max AT alcyone DOT com> writes:

>GEORGE GAGHON wrote:

>> int w_stuff
>> long l_stufftoo
>> byte b_stuffalso
>> 
>> w_stuff = *p    <---- will this grab a word at location p
>> l_stufftoo = *(p+2)<---- will this grab a long ?
>> b_stuffalso = *(p+6) <--- and this will grab a byte, right?

>No.  It depends on what kind of pointer p is.  Say that p is declared as a
>char *.  Then *p (or, equivalently, p[0]) would get the char at p, *(p + 2)
>(or p[2]) would get the char at p + 2, and *(p + 6) (p[6]) would get the char
>at p + 6.  Since the pointer is a char * (or whatever), dereferencing it gives
>you a char (or whatever).  If you want to dereference to get other values, you
>have to explicitly cast it before dereferencing; i.e., *(int *) p.

>-- 
>Erik Max Francis &tSftDotIotE && http://www.alcyone.com/max && max AT alcyone DOT com
>San Jose, California, U.S.A. && 37 20 07 N 121 53 38 W && the 4th R is respect
>H.3`S,3,P,3$S,#$Q,C`Q,3,P,3$S,#$Q,3`Q,3,P,C$Q,#(Q.#`-"C`- && 1love && folasade
>Omnia quia sunt, lumina sunt. && Dominion, GIGO, GOOGOL, Omega, Psi, Strategem
>"Out from his breast/his soul went to seek/the doom of the just." -- _Beowulf_

also, don't forget that DJGPP is a 32bit compiler, so data sizes are different:

int = 4 bytes = dword
short = 2 bytes = word
char = 1 byte = byte

--
Fabian Nunez, Bsc(hons) student, University of Cape Town                     
email:fnunez AT cs DOT uct DOT ac DOT za   web:http//www.cs.uct.ac.za/~fnunez
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