C needs BCD -- why BCD? Accountants!

[Barry Margolin]

In article <4611 at utzoo.UUCP> henry at 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 at MIT-Multics
    UUCP: ..!genrad!mit-eddie!barmar