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Why do we have two different numeric pads?

 

Original Question:

Observe that on telephones the numbers are arranged in a grid with 1-2-3 at the top, and on calculators the grid has 1-2-3 at the bottom.  How did this happen?

telephone keypad calculator keypad
Telephone Calculator

The Answers:

Ray Bois, after looking things up, confirms the opinion of most others that the calculator pad came first and was designed for professionals, while the telephone pad came later and had to be adapted to the casual user who reads from left to right and top to bottom.

I have two comments on this:  (1) indeed the digit 1 occurs more often at the start of a number than any other digit (they are distributed logarithmically) and so it pays to have the smaller digits at the bottom if you use a calculator a lot; (2) the trend for the casual user can also be seen on some keyboards on public information terminals where the letter keys appear in alphabetical order rather than the professional QWERTY style.

Frode Tennebø supplied this link:  telephone keypad, leading to a number of articles where the idea that the layout needed to be adapted to casual users is confirmed.

Unfortunately the link from Rob Phelps's answer is now dead, but the argument there was to arrange it so that the telephone network could keep up with the speed of typing:  it slowed down the professionals to have to dial on a pad that was the inverse of that on their calculators.

A more intriguing answer was found by George Laughead:  the letters associated with the numbers would have to be in alphabetic order, putting the 1 at the top left.

Murray Anderegg sent a link which the American Scientist site has now decreed to be accessible only to members and subscribers. Long live micropayments…

Josh Bude wrote that on simpler calculators there was a row with ten digit buttons for each position (I worked on one of those) and obviously the 1s were at the bottom and the 9s at the top.  This stuck when they were replaced with a single button for each digit.  Josh also mentions the digit-letter correspondence as the reason to have 1 at the top on telephones.

James Soshea has a very similar story to the ones above and Tim Reid found a link to DTMF in the Wikipedia that has a partial explanation.

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