[FIXED] How was non-decimal money represented in software?

Issue

A lot of the answers to the questions about the accuracy of float and double recommend the use of decimal for monetary amounts. This works because today all currencies are decimal except MGA and MRO, and those have subunits of 1/5 so are still decimal-friendly.

But what about the software used in U.S. stock markets when prices were in 1/16ths of dollar? The accuracy of binary data types wouldn't have been an issue, right?

Going further back, how did pre-1971 British accounting software deal with pounds, shillings, and pence? Did their versions of COBOL have a special PIC clause for it? Were all amounts stored in pence? How was decimalisation handled?

Solution

PL/I had a type specifically for British currency - I don't know about COBOL. The British currency at one time incorporated farthings, or a quarter of a penny; I'm not sure though that computers had to deal with those, just with half pennies or ha'pennies.

Accurate accounting usually uses special types - representing decimals exactly. The new IEEE 754 has support for floating-point decimals, and some chips (notably IBM pSeries) have such support in hardware.

Answered By - Jonathan Leffler

Answer Checked By - Marie Seifert (PHPFixing Admin)