Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP
Posting-Version: version B 2.10.1 6/24/83; site mit-eddie.UUCP
Path: utzoo!watmath!clyde!burl!ulysses!allegra!mit-eddie!barmar
From: barmar@mit-eddie.UUCP (Barry Margolin)
Newsgroups: net.lang.c
Subject: Re: C needs BCD -- why BCD?  Accountants!
Message-ID: <3123@mit-eddie.UUCP>
Date: Wed, 14-Nov-84 01:52:16 EST
Article-I.D.: mit-eddi.3123
Posted: Wed Nov 14 01:52:16 1984
Date-Received: Thu, 15-Nov-84 02:27:56 EST
References: <105@ISM780B.UUCP> <869@ihuxn.UUCP>  <904@umcp-cs.UUCP> <4611@utzoo.UUCP>
Reply-To: barmar@mit-eddie.UUCP (Barry Margolin)
Organization: MIT, Cambridge, MA
Lines: 30

In article <4611@utzoo.UUCP> henry@utzoo.UUCP (Henry Spencer) writes:
>> I have always been surprised that business people didn't just use 64
>> bit integers, and keep the amounts in CENTS.  No BCD required, can
>> take advantage of nice fast machine instructions, etc.
>
>It's not hard to figure out.  I once read an excellent paper -- alas,
>I don't have it handy -- that pointed out a basic behavior pattern:
>new tools, when applied to old problems, are invariably applied in a
>way that mimics the old methods as closely as possible.  Evolution
>toward new methods, better suited to the new tools, comes much later.
>
>One of the prime examples in the paper -- I think it was in one of the
>Joint Computer Conferences, which would make it nearly 20 years ago --
>was the continuing dominance of decimal arithmetic in business computing.
>Of course the business people use decimal arithmetic; it never occurred
>to them to do anything else.  And now the albatross of being "backward
>compatible with all previous mistakes" has locked them into it, but good.
>-- 
>				Henry Spencer @ U of Toronto Zoology
>				{allegra,ihnp4,linus,decvax}!utzoo!henry

I think it is inertia.  Two decades ago, when business computing habits
were being formed, there probably was not very good hardware available
on computers for doing 64-bit integer arithmetic.  However, because of
the reasons cited above by Henry Spencer, large-precision decimal units
were invented.
-- 
    Barry Margolin
    ARPA: barmar@MIT-Multics
    UUCP: ..!genrad!mit-eddie!barmar