From: John Cowan <cowan@ccil.org>
To: Paul Winalski <paul.winalski@gmail.com>
Cc: The Eunuchs Hysterical Society <tuhs@tuhs.org>
Subject: Re: [TUHS] reviving a bit of WWB
Date: Thu, 24 Sep 2020 14:17:07 -0400 [thread overview]
Message-ID: <CAD2gp_Sh4Ymrn9xRVUCSePYX4Ppqrmqmmyk=HjwHSXQuP1tmKQ@mail.gmail.com> (raw)
In-Reply-To: <CABH=_VSd4uijgx6OhxNfhKGRHH_7JOSE-jJBmcrh0eewW7Oimw@mail.gmail.com>
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On Thu, Sep 24, 2020 at 1:19 PM Paul Winalski <paul.winalski@gmail.com>
wrote:
Or separate-sign numerical representations, for that matter, such as
> the IBM 1620 had. And packed decimal on the S/360/370 and the VAX.
> Negative zero in packed decimal is responsible for a lot of the
> "computerized bill for $0.00" bugs that were rife in the 1960s.
>
IEEE floats are still sign-magnitude, for that matter, both the binary ones
and the little-used decimal ones, which is why MAX_FLOAT and MAX_DOUBLE are
the same in both positive and negative directions.
I once had to deal with some mainframe data that had been transferred to
our PDP-11 or Vax (not sure which), and I noticed right away that some of
the allegedly numeric data had a non-digit immediately following and one
fewer significant digit than the rest. A little digging in my memory (I
think this was before I got access to the Internet in 1985 or so), plus a
little experimentation, established that these were
trailing-overpunched-sign numbers that had been mechanically translated
from EBCDIC to ASCII. So on the principle of "If a problem is not
interesting, generalize it until it is", I wrote a little filter that
looked for such numbers in its input and rewrote them as
leading-separate-sign (i.e. the Usual Way), copying everything else.
Unfortunately the source is long since lost, but I wouldn't write it in C
today anyway.
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next prev parent reply other threads:[~2020-09-24 18:18 UTC|newest]
Thread overview: 60+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-09-19 1:51 Doug McIlroy
2020-09-20 18:42 ` arnold
2020-09-20 19:28 ` Will Senn
2020-09-20 20:12 ` Steve Nickolas
2020-09-20 20:26 ` Doug McIlroy
2020-09-20 20:57 ` Doug McIlroy
2020-09-20 22:13 ` Clem Cole
2020-09-21 20:43 ` Steffen Nurpmeso
2020-09-20 20:58 ` Steve Nickolas
2020-09-20 21:33 ` Brantley Coile
2020-10-07 5:43 ` scj
2020-09-20 21:35 ` John Cowan
2021-02-02 23:08 ` Greg A. Woods
2021-02-02 23:47 ` Larry McVoy
2021-02-03 0:11 ` Dave Horsfall
2021-02-03 0:19 ` Larry McVoy
2021-02-03 2:04 ` Richard Salz
2021-02-03 3:32 ` Dave Horsfall
2021-02-03 4:32 ` M Douglas McIlroy
2021-02-03 11:27 ` Peter Jeremy via TUHS
2021-02-03 20:09 ` Dave Horsfall
2021-02-03 20:13 ` Niklas Karlsson
2021-02-03 23:46 ` Tom Lyon
2021-02-03 22:19 ` Dave Horsfall
2021-02-03 22:55 ` M Douglas McIlroy
2020-09-20 22:15 ` Clem Cole
2020-09-20 22:47 ` John Cowan
2020-09-21 20:48 ` Steffen Nurpmeso
2020-09-21 20:46 ` Steffen Nurpmeso
2020-09-24 2:25 ` Dave Horsfall
2020-09-24 2:33 ` Clem Cole
2020-09-25 0:18 ` [TUHS] One's complement (was: reviving a bit of WWB) Greg 'groggy' Lehey
2020-09-25 0:22 ` Warner Losh
2020-09-25 1:39 ` John Cowan
2020-09-27 5:54 ` [TUHS] reviving a bit of WWB Dave Horsfall
2020-09-24 17:19 ` Paul Winalski
2020-09-24 18:17 ` John Cowan [this message]
2020-10-07 5:47 ` scj
2020-10-07 9:20 ` arnold
2020-10-08 0:27 ` Dave Horsfall
2020-10-08 3:08 ` John Cowan
2020-09-20 22:51 Norman Wilson
2020-09-20 23:00 Norman Wilson
2020-09-20 23:53 ` Clem Cole
2020-09-21 0:00 ` Clem Cole
2020-09-21 2:24 ` John Cowan
2020-09-21 0:09 ` Warner Losh
2020-09-21 1:05 ` Clem Cole
2020-09-21 5:55 ` Steve Nickolas
2020-09-21 5:59 ` Warner Losh
2020-09-21 18:40 ` Paul Winalski
2020-09-21 19:56 ` Dan Cross
2020-09-21 20:50 ` John Cowan
2020-09-21 21:22 ` Rob Pike
2020-09-21 21:57 ` Clem Cole
2020-09-21 23:56 ` John Cowan
2020-09-22 0:54 ` Richard Salz
2020-09-21 21:39 ` Steve Nickolas
2020-09-25 14:19 Doug McIlroy
2020-09-28 17:35 ` Angelo Papenhoff
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