Did you ever notice that the numeric keypads on phones and calculators are reversed? The only thing that is common in all the numeric pads is the ‘0’ button that is at the bottom. The remaining numbers go from top to the bottom in a phone whereas from bottom to the top in calculators. If you’ve been confused about this, you have come to the right place. Here’s why they are in reverse directions.
The theory lies in the most used buttons being on the bottom. Old mechanical cash registers were designed in such a way that the ‘0’ button was at the bottom. Because of its high usage, the designers thought that it must be accessible to the fingers easily and visible to eyes just at a glance. And then the numbers followed i.e. 1-2-3 in the next row, followed by 4-5-6 in the row above it, and finally 7-8-9.
Later, when the electronic calculators were designed, they used the existing calculator’s keypad arrangement with ‘0’ at the bottom, ‘1’ at the bottom left corner, and ‘9’ in the top right corner.
Before the invention of the touch-tone phones, telephones had rotary dials. So, instead of buttons, they used to be numbered from 1 to 9 followed by 0, and when you had to dial any number, you had to insert your finger in the hole of that number and then spin it. However, when the touch-tone telephones were invented, the designers decided to change the layout rather than replicating the design of the calculators.
After testing several designs, they came to the conclusion that a three-by-three matrix with 1,2,3 at the top was the most suitable and convenient design to use with the lowest error rate. The same design has been in use till date and even smartphones follow the same format.
So, this is the reason why numbers on phones and calculators are reversed.
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