From:	Damian Yerrick <DONT DOT YOU DOT DAREd_yerrick AT hotmail DOT comSEND DOT SPAM>
Newsgroups:	comp.os.msdos.djgpp
Subject:	Re: odd or even?
Organization:	Pin Eight Software http://pineight.8m.com/
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NNTP-Posting-Date:	Mon, 06 Mar 2000 00:43:04 GMT
Distribution:	world
Date:	Mon, 06 Mar 2000 00:43:04 GMT
To:	djgpp AT delorie DOT com
DJ-Gateway:	from newsgroup comp.os.msdos.djgpp
Reply-To:	djgpp AT delorie DOT com

On 5 Mar 2000 13:39:56 GMT, eplmst AT lu DOT erisoft DOT se (Martin Stromberg)
wrote:

>Chris Mears (chris_mears AT softhome DOT net) wrote:
>: That "Campbell, Rolf [SKY:1U32:EXCH]" <moscoop AT americasm01 DOT nt DOT com>
>: really knows where his towel is.  On Thu, 02 Mar 2000 09:45:01 -0500,
>: he wrote:
>
>Ha-ha! Good reference!
>
>: >It should work fine with signed integers....
>: >-1 = 0xFFFFFFFF (lowest bit set)
>: >-2 = 0xFFFFFFFE (lowest bit not set)
>
>: Might not work on other machines, though.  (I honestly don't know,
>: I've never used a machine that wasn't 2's-complement)
>
>One's complement works as well:
>+0 = 0x00000000 (lowest bit not set)
>-0 = 0x80000000 (lowest bit not set)
>-1 = 0x80000001 (lowest bit set)
>-2 = 0x80000002 (lowest bit not set)

This isn't ones' complement.  This is called "sign bit" representation
and is one of the first things taught in Intro to Digital Logic
(EC130) here at Rose.

>What other interesting representations are there? 

There's ones' complement, where -foo = 0xffffffff xor foo

-2 0xfffffffd
-1 0xfffffffe
-0 0xffffffff
+0 0x00000000
+1 0x00000001
+2 0x00000002

When you add two ones' complement numbers, you also add the carry-out
to the final result.  This is slow; that's one reason why two's
complement was introduced.

And then there's floating point.  I'm not touching that
with a proverbial fifteen-millifurlong (3 m; 10 ft) pole.

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