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From: "robin" <robin_v@bigpond.com>
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Subject: Re: ONES COMPLEMENT
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Message-ID: <aszvg.7784$tE5.149@news-server.bigpond.net.au>
Date: Wed, 19 Jul 2006 23:43:02 GMT
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Date: 2006-07-19T23:43:02+00:00
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glen herrmannsfeldt wrote in message <5qednejm5MHL9SPZnZ2dnUVZ_oSdnZ2d@comcast.com>...
>Peter Flass wrote:
>
>> Shmuel (Seymour J.) Metz wrote:
>
>(snip on negative zero)
>
>>> I never saw a need to test for it regardless. Every 1s complement
>>> machine I know of lets you test for zero in a single instruction.
>
>> What happens on a test for negative?  Did the machines just test the
>> sign bit, making -0 a negative number?
>
>Well, consider the 704, which is actually sign magnitude but has the
>same problem.  (The easiest way to do sign magnitude arithmetic is
>to convert to ones complement first, and convert back later.)

It doesn't follow.
Twos complement for neg. values is just as easy.
In fact, for a serial machine, not only it [twos complement] easier,
it is done in less time! when consideration of the ensuing arithmetic
is considered.

>The 704 has a three way test instruction recently discussed in some
>newsgroup, with branch destinations for negative, zero, and positive.
>Any questions about the origin of the arithmetic IF statement?

This is off-topic, and completely irrelevant.
It has nothing to do with ones complement.