Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!crdgw1!uunet!midway!quads.uchicago.edu!tisu
From: tisu@quads.uchicago.edu (Seth Tisue)
Newsgroups: comp.sys.mac.programmer
Subject: Re: 68000 Assembly question -- overflow
Message-ID: <1991May29.210531.7174@midway.uchicago.edu>
Date: 29 May 91 21:05:31 GMT
References: <12423.284125F3@stjhmc.fidonet.org>
Sender: news@midway.uchicago.edu (NewsMistress)
Organization: Plaster Cramp Press
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In article <12423.284125F3@stjhmc.fidonet.org> Lawson.English@p88.f15.n300.z1.fidonet.org (Lawson English) writes:
>Think about it: you have 2^32 numbers available (an even number), this gives
>one either an equal number of positive and negative numbers and 2 possible zeros
>(one's compliment) or an even number of negative numbers, an odd number of positive
>numbers and only one zero (two's compliment). It seems to me that the average
>"user" would worry more about the existance of two zeros than about the imbalance
>of positive and negative.

>After all, one might have (and ofen does) a use for
>that last odd number, but how many times do you need a second way of representing
>"zero?" And for that matter, imagine the headaches of the chip designer who
>must add a second test for zero if one's compliment arithmatic were standard.

I wasn't advocating one's complement arithmetic -- I'm not that naive.  What
I was wondering was, why not have $80000000 (-2^31) be an invalid number
rather than -2^31, thus removing the asymmetry?  I'm assuming there's some
good reason for this...  What uses does one "often have" for the extra
number?



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---- Seth Tisue                     USMail: c/o Plaster Cramp Press  
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"Please to be restful.  It is only a few           Chicago IL 60680
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