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From: rick@pavlov.ssctr.bcm.tmc.edu (Richard H. Miller)
Newsgroups: comp.arch
Subject: Re: Computers for users not programmers
Message-ID: <4158@gazette.bcm.tmc.edu>
Date: 16 Feb 91 00:24:21 GMT
References: <1991Feb12.192725.21029@Think.COM> <2922@risky.Convergent.COM> <1991Feb14.151831.15426@linus.mitre.org>
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In article <1991Feb14.151831.15426@linus.mitre.org> bs@linus.mitre.org (Robert D. Silverman) writes:
> 
>Yes. However, if DOUBLE PRECISION integer arithmetic were supported, the
>need for BCD would totally disappear. Not only that, the integer arithmetic
>would be at least an order of magnitude FASTER. There is no inherent reason
>why the dollars and cents calculations [read: extended precison] cannot be
>done in integer arithmetic.
>
>It would require that the code emitter of some COBOL compilers be modified
>to use integer, rather than BCD instructions, but this is not terribly
>difficult to do.
>
>Under these circumstances, both scientific and COBOL users would benefit.
>			   ----
>
>:Now I personally don't like COBOL, but I recognize that there is a tremendous
>:investment in COBOL programs in industry - and they are not going to go away
>:tomorrow.
> 
>No COBOL programs would change -- only the compilers would change.

This is certainly not correct. I don't know how much DP application experience
you have had, but the calculation aspect of business data processing, although
important, is not the primary reason for decimal arithmetic. Most data 
processing applications are designed to read records, do some processing and
report on them. In fact, the majority of data processing is to product reports
and reports tend to be in decimal format. Thus, if you eliminated BCD, the
calculations would be faster, but every time you wanted to put the results
out, you would have to convert the integer values to decimal format, edit the
number into the output format and then output it. [Most architectures which
support decimal also support EDIT instructions]. 

Another important consideration is the fact that many files already are set
up with decimal fields. If you change to compiler to handle integer only, you
will either have to automatically convert input records from decimal to 
integer so you now have conversion->processing->conversion, or you have to
invest a lot of money in doing the systems design and maintenance to convert
all of the BCD fields to either integer or character. [You now are talking
about a fundemental change to the application which requires (or should) 
the services of a systems analyst, programmers, testing and quality
assurance.] 

The bottom line is that programs would change or processing time will go up. 
There actually is a need for certain architectual support for business data
processing for our applications. [We don't make scientific programmers use
decimal arithmetic in their code and they don't make system programmers write
with floating point so don't make us use your approach. Taylor the architecture
to the application if possible and do not assume the same architecture will
work for all.]
 
-- 
Richard H. Miller                 Email: rick@bcm.tmc.edu
Asst. Dir. for Technical Support  Voice: (713)798-3532
Baylor College of Medicine        US Mail: One Baylor Plaza, 302H
                                           Houston, Texas 77030