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Re: IBM STRETCH repricing decision?

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On 2016-01-13, hancock4@bbs.cpcn.com <hancock4@bbs.cpcn.com> wrote:

> I don't think the choice of decimal instruction was because certain
> heritage machines used it.  Rather, I think it was because decimal
> was more efficient for business calculations.  There wasn't a waste
> of CPU to convert the number to binary and back.  While decimal
> was slower, it didn't matter as much for the simpler business calculations.
>
> Decimal would be used regardless if the business operation was small
> or large.

The other reason packed decimal was used was the size of the fields.
A 32-bit binary field was just not enough to hold financial amounts
of any size; if you used integer pennies you couldn't handle amounts
over $21,474,836.47 - and several orders of magnitude less if you
left room for the guard digits that many calculations require.
Packed decimal fields, on the other hand, could hold up to 31 digits.

(If anyone mentions floating point for monetary amounts, I'll send
a couple of guys from the accounting department over to beat you up.)

> For S/360, amazingly, many younger COBOL programmers were not aware
> of COMP-3 (packed decimal), which would save memory and time.  (Now,
> it doesn't matter).

I once came across just the opposite in a program whose excessive
CPU usage I was called in to analyze - some bright bulb had declared
all subscripts as COMP-3.  Changing them to COMP-4 (binary) cut the
CPU usage by 30%.

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IBM STRETCH repricing decision? hancock4@bbs.cpcn.com - 2016-01-12 09:37 -0800
  Re: IBM STRETCH repricing decision? Quadibloc <jsavard@ecn.ab.ca> - 2016-01-12 15:59 -0800
    Re: IBM STRETCH repricing decision? Quadibloc <jsavard@ecn.ab.ca> - 2016-01-12 16:01 -0800
    Re: IBM STRETCH repricing decision? hancock4@bbs.cpcn.com - 2016-01-12 18:50 -0800
      Re: IBM STRETCH repricing decision? Quadibloc <jsavard@ecn.ab.ca> - 2016-01-12 23:37 -0800
        Re: IBM STRETCH repricing decision? hancock4@bbs.cpcn.com - 2016-01-13 07:24 -0800
          Re: IBM STRETCH repricing decision? Quadibloc <jsavard@ecn.ab.ca> - 2016-01-13 14:37 -0800
      Re: IBM STRETCH repricing decision? Morten Reistad <first@last.name.invalid> - 2016-01-13 08:37 +0100
        Re: IBM STRETCH repricing decision? hancock4@bbs.cpcn.com - 2016-01-13 07:39 -0800
          Re: IBM STRETCH repricing decision? Anne & Lynn Wheeler <lynn@garlic.com> - 2016-01-13 08:17 -0800
            Re: IBM STRETCH repricing decision? Jon Elson <elson@pico-systems.com> - 2016-01-13 18:02 -0600
          Re: IBM STRETCH repricing decision? Quadibloc <jsavard@ecn.ab.ca> - 2016-01-13 12:58 -0800
            Re: IBM STRETCH repricing decision? hancock4@bbs.cpcn.com - 2016-01-13 13:53 -0800
              Re: IBM STRETCH repricing decision? Quadibloc <jsavard@ecn.ab.ca> - 2016-01-13 14:31 -0800
                Re: IBM STRETCH repricing decision? hancock4@bbs.cpcn.com - 2016-01-13 18:38 -0800
              Re: IBM STRETCH repricing decision? Charlie Gibbs <cgibbs@kltpzyxm.invalid> - 2016-01-13 22:43 +0000
                Re: IBM STRETCH repricing decision? "J. Clarke" <j.clarke.873638@gmail.com> - 2016-01-13 20:13 -0500
                Re: IBM STRETCH repricing decision? Gene Wirchenko <genew@telus.net> - 2016-01-13 17:17 -0800
                Re: IBM STRETCH repricing decision? hancock4@bbs.cpcn.com - 2016-01-13 18:32 -0800
                Re: IBM STRETCH repricing decision? "J. Clarke" <j.clarke.873638@gmail.com> - 2016-01-13 21:51 -0500
                Re: IBM STRETCH repricing decision? Charlie Gibbs <cgibbs@kltpzyxm.invalid> - 2016-01-14 18:24 +0000
              Re: IBM STRETCH repricing decision? "J. Clarke" <j.clarke.873638@gmail.com> - 2016-01-13 20:04 -0500
            Re: IBM STRETCH repricing decision? Peter Flass <peter_flass@yahoo.com> - 2016-01-14 08:03 -0500
          Re: IBM STRETCH repricing decision? Jon Elson <elson@pico-systems.com> - 2016-01-13 17:49 -0600
            Re: IBM STRETCH repricing decision? Peter Flass <peter_flass@yahoo.com> - 2016-01-14 08:03 -0500

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