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From: dave@cs.arizona.edu (Dave P. Schaumann)
Newsgroups: comp.lang.c
Subject: Re: The use of unsigned int
Keywords: unsigned int, C
Message-ID: <819@caslon.cs.arizona.edu>
Date: 9 Feb 91 01:30:23 GMT
References: <1255@tredysvr.Tredydev.Unisys.COM>
Organization: U of Arizona CS Dept, Tucson
Lines: 26

In article <1255@tredysvr.Tredydev.Unisys.COM> paul@tredysvr.Tredydev.Unisys.COM (Paul Siu) writes:
>The most commonly use, and commonly returned type in C is probably int.  
>In some cases, wouldn't it be more appropriate if unsigned int was used
>instead, such as when you are indexing an array, or returning a length?
>
>I heard that int is usually declared as the most efficent type in C, would
>using unsigned int cause any problems such as slow things down or cause
>type-conversation problems?

There is no general answer to this question.  On a twos-complement machine,
the instructions generated for int/unsigned int (of the same size) should
be virtually identical.  The only differences would be in checking for overflow
and checking for sequence (ie less/greater).  Even here, I would expect the
differences in instruction execution speed would be very small, if not 0.

I've never written assembly code on a sign/magnatude machine, so I don't know
about those.  (Are there any 1's complement machines out there?)

>Paul Siu
>paul@tredysvr.tredydev.unisys.com


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