I am puzzled with one question for years … have you ever wondered “Why calculator and phone number layouts differ ?”. Check your desk calculator and desktop / mobile phone to find out; or here are two pictures:
As you can see, the calculator keypads start from 7, 8 and 9, line up from upper left corner. The phone number keypads, however, start from 1, 2 and 3, also line up from upper left corner. So the question – why the difference ?
I searched, searched and searched again … finally found the plausible answer to that.
Decades ago in last century, the first calculators were actually resembled old cash registers. Those cash registers had columns of keys numbering 9 on top down to 0 on the bottom. The next column had another set of keys with 90 on top and 10 on the bottom, the next row to the right had 900 on top, 100 on the bottom, and so on. As you can see from the pictures of an old cash register below.
Therefore, it is logical to design a hand-held calculators with the number 9 on the top row, and 0 in the bottom row. Well then, the next question – “why did we place 7-8-9 in the top row, instead of 9-8-7 ?” Sorry, I don’t have the answer, so please leave your comments if you know.
For the phone … there are two theories. One is about the rotary phones – before the touch-tone phone, of course, rotary dials were the rule. This theory states that the touch-tone key pad was designed to mimic the rotary dial with the “1” on top and the 7-8-9 on the bottom; as in the following picture.
Another theory is that the design is from Human Factors Engineering Studies in Bell Laboratories. See below for the layout designs in the study. And turned out the one with 1-2-3 on top role was the selected design.
To me both are good answers, don’t you think ?