Keypad

A keypad is a set of buttons arranged in a block or "pad" which bear digits, symbols or alphabetical letters. Pads mostly containing numbers are called a numeric keypad. Numeric keypads are found on alphanumeric keyboards and on other devices which require mainly numeric input such as calculators, push-button telephones, vending machines, ATMs, Point of Sale devices, combination locks, and digital door locks. Many devices follow the E.161 standard for their arrangement.

A computer keyboard usually has a small numeric keypad on the side, in addition to the other number keys on the top, but with a calculator-style arrangement of buttons that allow more efficient entry of numerical data. This number pad (commonly abbreviated to "numpad") is usually positioned on the right side of the keyboard because most people are right-handed.

Many laptop computers have special function keys which turn part of the alphabetical keyboard into a numerical keypad as there is insufficient space to allow a separate keypad to be built into the laptop's chassis. Separate external plug-in keypads can be purchased.

Keypads for the entry of PINs and for product selection appear on many devices including ATMs, vending machines, Point of Sale payment devices, time clocks, combination locks and digital door locks.

The first key-activated mechanical calculators and many cash registers used "parallel" keys with one column of 0 to 9 for each position the machine could use.

Mechanical calculators used 10-key input first beginning with the Facit-T in 1932. The Facit had two-rows of digits 24579 and 13068. Olivetti introduced the "MC 4S Summa" with the 789, 456, 123 top to bottom order in 1940. The Olivetti ordering became standard so that the keys on modern calculator-style keypads are arranged so that the digits 0 through 9 increase from bottom upwards with 0 on the lowest row and 123 on the next row increasing from left to right. There is no standard for the layout of the four arithmetic operations, the decimal point equal sign or other more advanced mathematical functions on the keypad of a calculator.

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