Re: subtraction between unsigned ints

Article View: comp.std.c

Article #525

#525

From: Henry Spencer
Date: Wed, 06 Sep 1989 15:34

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In article <KURO.89Sep5111940@shochu.Sun.Com> kuro@shochu.Sun.Com (Teruhiko Kurosaka - Sun Intercon) writes:
>Does pANSI defines the datatype of the result of subtraction
>between unsigned integers?  Would it be also unsigned?  Then
>what would be the result of subtraction of a number from a
>smaller number? ...

Unsigned - unsigned gives unsigned.  Unsigned arithmetic is done modulo the
type size, roughly speaking, so carries and borrows off the top end are
ignored.  The value of "(unsigned)3 - (unsigned)5" depends on how big the
unsigned type is, but on a 16-bit machine it's probably (unsigned)65534.
-- 
V7 /bin/mail source: 554 lines.|     Henry Spencer at U of Toronto Zoology
1989 X.400 specs: 2200+ pages. | uunet!attcan!utzoo!henry henry@zoo.toronto.edu

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Newsgroups: comp.std.c
Path: arc1-ca.pugleaf.net!utzoo!henry
From: henry@utzoo.uucp (Henry Spencer)
Subject: Re: subtraction between unsigned ints
Message-ID: <1989Sep6.153407.18638@utzoo.uucp>
Organization: U of Toronto Zoology
References: <KURO.89Sep5111940@shochu.Sun.Com>
Date: Wed, 6 Sep 89 15:34:07 GMT

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