Trivia

Why are the rows on a calculator arranged with the lowest numbers at the bottom, and why are telephone keypads arranged the other way, with the lowest numbers at the top?

Mechanical adding machines, based on rotating wheels, always have the 0 button adjacent to the 1 button. By convention, most old adding machines had the numbers increasing in value from the bottom. When the numbers were put onto a pad arranged as a 3 by 3 grid with one left over, the order of the numbers was kept the same.

On a rotary telephone dial, the 0 comes adjacent to the 9 because a 0 in the telephone number is signalled by 10 pulses on the line. When telephones acquired push buttons in a grid, the ordering of the buttons was carried over from the old telephone dial.