Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!usc!wuarchive!emory!att!att!ima!dirtydog!karl
From: karl@ima.isc.com (Karl Heuer)
Newsgroups: comp.lang.c
Subject: Re: % operator with negatives
Message-ID: <1990Dec14.064305.4491@dirtydog.ima.isc.com>
Date: 14 Dec 90 06:43:05 GMT
References: <1990Dec12.185714.7169@mp.cs.niu.edu> <1990Dec12.205416.26622@zoo.toronto.edu> <7461:Dec1310:04:0990@kramden.acf.nyu.edu> <18140@neptune.inf.ethz.ch>
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Reply-To: karl@ima.isc.com (Karl Heuer)
Organization: Interactive Systems
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In article <18140@neptune.inf.ethz.ch> brandis@inf.ethz.ch (Marc Brandis) writes:
>Did somebody ever try it on the VAX? A guy told me once that integer division
>rounds toward zero on the VAX while the MOD instruction delivers always a
>positive result...

Sounds like you're refering to what the Pascal compiler does, rather than
the machine language.  When I first encountered the VAX, one of my first
complaints was that it didn't *have* a 32-bit MOD instruction (or
equivalently, a DIV that generated remainder as well as quotient).  The
compiler must either generate a-(a/b)*b, or extend a into a double word% and
use the 64-bit EDIV (which *does* generate both quotient and remainder).

Karl W. Z. Heuer (karl@ima.isc.com or uunet!ima!karl), The Walking Lint
% DEC, out of loyalty to their 16-bit line, called their halfwords `words'
  and so they called this thing a `quadword'.