Why are the keys on my mobile phone arranged 123 456 789 but the keys on my computer keyboard arrang

Why are the keys on my mobile phone arranged 123 456 789 but the keys on my computer keyboard arranged 789 456 123 ?

James Cook, Sydney, Australia

• I imagine that a phone keypad is derived from the rotary telephone dial (remember those?) in which the number '1' is at the top, and number '9' at the bottom. The PC numeric keypad is modelled on desk calculators which were primarily produced for accounting purposes. The digit '0' is at the bottom presumably because this is the most frequently-entered digit in that situation, and hence needs to be nearest the hand for convenience. The rest of the digits then follow in ascending order.

  Mike Whittaker, Peplow Shropshire

• Hmm,simple question, long answer. Basically, the 2 styles may loosely be termed consumer electronics and computer. The computer style is the original one, going all the way back to 19th C. mechanical adding machines,and is used by computers (obviously), calculators, cash registers, etc. In the 1950's, AT&T were about to introduce the push button phone and got an ergonomics consultant to do some research into which style was the more efficient. He decided that "123 at the top" was better, and hence the consumer electronic style was born.The research was bitterly disputed among those who care about these things, by the way. In any event, consumer electronics (phones, remote controls, alarm system keypads etc,) has tended to follow the AT&T research. As an aside, medical equipment falls between the two stools and there are documented cases of fatalities caused by doctors in a hurry assuming the wrong pattern.

  William Baskerville, Dublin