[danprager]

Side-track: The Romans used IIII for 4, not IV, etc. which was introduced by early printers (not dot-matrixes ;-) to save space, so the original system was more additive.

Looked at in this light, you can see more easily how humanity progressed from tallying, to counting on fingers -- use fingers to tally up to four, take the thumb to represent five -- to the abacus and Roman numerals.

[dhimes]

I had exactly the same thought as I started skimming this: uh oh, first decide what convention you are going to use. Or do you do that last?