Fn key

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Fn key can also refer to the function keys on a computer keyboard.

Fn is a modifier key on PC keyboards used in a compact layout to combine keys which are usually kept separate. It is typically found on laptops, since a full sized keyboard would be difficult to fit in a laptop chassis.

[edit] Compact layouts

Typically, in a compact layout the main area of the keyboard (containing the letter keys) 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 colour.

This 78-key UK layout is taken from the Apple iBook. Characters in blue are accessed through the Fn key.

[edit] Technical details

Unlike other modifier keys such as Shift or AltGr, the control processor inside the keyboard typically sends out a different keycode depending on whether the Fn key is depressed. This allows the keyboard to emulate a full sized keyboard and means that specialised keymaps do not need to be created; the operating system can use standard keymaps designed for a full sized keyboard.

In addition to being mapped to standard keyboard keys like Scroll Lock and Num Lock, the Fn key combinations may also be mapped to control system interfaces to change the LCD brightness, VGA output, or speaker volume on most laptop computers.