Function key
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A function key is a key on a computer or terminal keyboard which can be programmed so as to cause an operating system command interpreter or application program to perform certain actions. On some keyboards/computers, function keys may have default actions, accessible on power-on.
Function keys on a terminal may either generate short fixed sequences of characters, often beginning with the escape character (ASCII 27), or the characters they generate may be configured by sending special character sequences to the terminal. On a standard computer keyboard, the function keys may generate a fixed, single byte code, outside the normal ASCII range, which is translated into some other configurable sequence by the keyboard device driver or interpreted directly by the application program. Function keys may have (abbreviations of) default actions printed on/besides them, or they may have the more common "F-number" designations.
Function key schemes on various computer keyboards
- Apple Macintosh: variously no function keys, or function keys F1 through F12, F1 through F15, or F1 through F16 across the top of the keyboard, depending on model.
- Apple Macintosh Laptops: F1 through F12, with pre-defined actions for F1 through F7.
- BBC Micro: red/orange keys f0 to f9 in a horizontal row above the number keys on top of the computer/keyboard
- Commodore Amiga: ten keys arranged in a row of two 5-key groups across the top of the keyboard (flush with the ordinary keyboard top row); function keys are 1.5× the width of ordinary keys
- Commodore VIC-20 and C64: F1/F2 to F7/F8 in a vertical row of four keys ascending downwards on the computer/keyboard's right hand side, odd-numbered functions accessed unshifted, even-numbered shifted; orange, beige/brown, or grey key color, depending on VIC/64 'submodel'
- Commodore 128: essentially same as VIC-20/C64, but with (grey) function keys placed in a horizontal row above the numeric keypad right of the main QWERTY-keyboard
- IBM 3270: Early models, 12 function keys 3*4 at the right of keyboard, later 24 in two rows on top of the keyboard
- IBM PC AT and PS/2 keyboard: F1 to F12 in three 4-key groups across the top of the keyboard (the original IBM PC and PC XT keyboards had function keys F1 through F10, in two adjacent vertical rows on the left hand side; F1|F2, F3|F4, ..., F9|F10, ascending downwards)
- Sharp MZ-700: blue keys F1 to F5 in a horizontal row across the top left side of the keyboard, the keys are vertically half the size of ordinary keys and twice the width; there's also a dedicated 'slot' for changeable key legend overlays (paper/plastic) above the function key row