An array of keys that may be captioned buttons or marked areas on a plane, each of which can cause a discrete signal or action when pressed with a finger. In current systems the operation of the key is detected and turned into a coded electrical signal; in the past mechanical coupling was used to allow depression of keys to directly punch a pattern of holes in a punch card or paper tape, as in a keypunch, or to print a character.
Computer keyboards consist of the standard typewriter layout — the QWERTY keyboard (in the English variants) — plus some additional keys. These can include a control key, function keys, arrow keys, and a numeric keypad. The control key operates in the same way as a shift key but allows noncharacter information to be sent to the computer; the function keys send not one but a whole sequence of characters to the computer at a time, and can often be programmed by the user to send commonly used sequences; the arrow keys are used, for example, to move the screen cursor to a new position. Modern keyboards often include additional ‘shift’ keys, e.g. Alt, Function, Alt Gr, and Window keys, which operate in conjunction with other keys to produce specific effects.
The numeric keypad duplicates the normal typewriter number keys and speeds up the entry of numerical data, the layout following a typical calculator keypad. The keypad may be switched to provide numeric or cursor keys by means of the numlock key.