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, 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 default actions printed on/besides them, or they may have the more common F-number designation, short for function, is a modifier key on many keyboards, especially on laptops, used in a compact layout to combine keys which are usually kept separate. It is typically found on laptops due to their keyboard size restrictions. It is also found on many full-sized multimedia keyboards as the F-Lock key. It is mainly for the purpose of changing display or audio settings quickly, such as brightness, contrast, or volume, and is held down in conjunction with the appropriate key to change the settings.
Typically, in a compact layout the main area of the keyboard is kept in much the same layout as with a full-sized keyboard, and the numeric keypad is moved to share a group of central keys. This allows typists to enter text without having to learn a new layout. The symbol that is accessed through pressing Fn is often printed on the key in a smaller font or different color