Why are calculator keypads and telephone keypads laid out differently?
Keyboards first appeared on calculators well over a century ago and I don’t believe anyone knows for sure how the 9 at the top became a standard, but they were clearly set in their ways long before touch tone phones appeared. My best guess is that Felt set the de facto standard with the Comptometer 1887 and this model was so wildly successful that everyone copied it. Older calculators were set using levers but some machines had 9 at the top and others at the bottom. (For example, compare the Burkhardt and Odhner pictures, However, if you look at all the keyboarded models, you’ll see that they are consistent with current designs.) Touch tone telephones are much more recent and according to AT&T/Bell documents, they were designed that way to be closer to dial phones which had 1, 2, 3 at the top of the dial and because testing showed that people made fewer dialing errors that way.
