C needs BCD -- why BCD? Accountants!

[Henry Spencer]

> 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