Re: IEEE-754-2008 2's complement question

From	MitchAlsup <MitchAlsup@aol.com>
Newsgroups	comp.arch
Subject	Re: IEEE-754-2008 2's complement question
Date	2012-03-04 11:46 -0800
Organization	http://groups.google.com
Message-ID	<25219818.707.1330890410962.JavaMail.geo-discussion-forums@ynll40> (permalink)
References	<999f8083-6a41-4c59-b42f-883d8c8e9192@pz2g2000pbc.googlegroups.com>

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On Sunday, March 4, 2012 7:12:57 AM UTC-6, Daku wrote:
> Could some computer architecture guru please
> clarify this a bit ?
> Suppose I have a signed fraction as -0.25
> The IEEE-754-2008 representation(with
> "hidden bit") of it is:
> 
> Sign       Exponent       Mantissa
> 1            01111110       1.0000000000000000000000
> 
> Now suppose I wish to add it to 100.0
> First of all, the 2's complement of the
> mantissa has to be obtained. 

No, in general, the math is performed in signed magnitude (not 2's complement.) The Add/Subtractor is implemented in such a way as to take the signs of the operands into account while mangling the bits on the way through.

>                               The
> question is whether the "hidden bit" is
> also inverted.

You are thinking in 2's complement form, its not done that way in hardware.

Mitch

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IEEE-754-2008 2's complement question Daku <dakupoto@gmail.com> - 2012-03-04 05:12 -0800
  Re: IEEE-754-2008 2's complement question Mark Thorson <nospam@sonic.net> - 2012-03-04 10:37 -0800
    Re: IEEE-754-2008 2's complement question BGB <cr88192@hotmail.com> - 2012-03-04 13:21 -0700
      Re: IEEE-754-2008 2's complement question BGB <cr88192@hotmail.com> - 2012-03-04 13:49 -0700
    Re: IEEE-754-2008 2's complement question Quadibloc <jsavard@ecn.ab.ca> - 2012-03-04 13:08 -0800
      Re: IEEE-754-2008 2's complement question BGB <cr88192@hotmail.com> - 2012-03-04 14:43 -0700
      Re: IEEE-754-2008 2's complement question Mark Thorson <nospam@sonic.net> - 2012-03-04 16:35 -0800
        Re: IEEE-754-2008 2's complement question John Levine <johnl@iecc.com> - 2012-03-05 01:39 +0000
          Re: IEEE-754-2008 2's complement question Mark Thorson <nospam@sonic.net> - 2012-03-04 18:53 -0800
            Re: IEEE-754-2008 2's complement question John Levine <johnl@iecc.com> - 2012-03-05 04:04 +0000
              Re: IEEE-754-2008 2's complement question Mark Thorson <nospam@sonic.net> - 2012-03-04 21:13 -0800
                Re: IEEE-754-2008 2's complement question Terje Mathisen <"terje.mathisen at tmsw.no"> - 2012-03-05 08:27 +0100
                Re: IEEE-754-2008 2's complement question BGB <cr88192@hotmail.com> - 2012-03-05 01:21 -0700
                Re: IEEE-754-2008 2's complement question Jean-Marc Bourguet <jm@bourguet.org> - 2012-03-08 16:57 +0100
                Re: IEEE-754-2008 2's complement question Terje Mathisen <"terje.mathisen at tmsw.no"> - 2012-03-08 18:55 +0100
                Re: IEEE-754-2008 2's complement question Stefan Monnier <monnier@iro.umontreal.ca> - 2012-03-05 17:01 -0500
        Re: IEEE-754-2008 2's complement question Joe Pfeiffer <pfeiffer@cs.nmsu.edu> - 2012-03-04 22:32 -0700
  Re: IEEE-754-2008 2's complement question MitchAlsup <MitchAlsup@aol.com> - 2012-03-04 11:46 -0800
  Re: IEEE-754-2008 2's complement question bert <bert.hutchings@btinternet.com> - 2012-03-04 12:05 -0800
    Re: IEEE-754-2008 2's complement question dakupoto@gmail.com - 2012-03-04 19:40 -0800
      Re: IEEE-754-2008 2's complement question Joe Pfeiffer <pfeiffer@cs.nmsu.edu> - 2012-03-04 22:33 -0700
      Re: IEEE-754-2008 2's complement question bert <bert.hutchings@btinternet.com> - 2012-03-05 02:16 -0800
  Re: IEEE-754-2008 2's complement question Quadibloc <jsavard@ecn.ab.ca> - 2012-03-04 13:09 -0800

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