Fn key

For operating system or programmable keys, see Function key.

Fn key on the Dell Inspiron 1150 Laptop

Fn, or '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, since a full-sized keyboard would be difficult to fit in a laptop chassis. It is also found in many full-sized 'multimedia' and 'office' keyboards, named 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.

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 (usually blue).

This 78-key UK layout is taken from the Apple iBook. Characters in blue are accessed through the Fn key, but functions on the top row can be accessed without Fn key in Mac OS X.

Technical details

Unlike other modifier keys such as Ctrl, Shift and AltGr, the microcontroller 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, so that specialised keymaps do not need to be created; the operating system can use standard keymaps designed for a full-sized keyboard. Because the operating system has no notion of the Fn key, the key can not be remapped in software, unlike all other standard keyboard keys.

In many designs, pressing F-Lock or Fn key itself does not generate a scancode. However, if it does, the key may be remapped by modifying the interrupt handler in BIOS that maps scancodes to characters, a technique that has proven successful on Lenovo laptops.^{[citation needed]}

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.

Displacement of the Control key

The Fn key is usually placed either to the right or to the left of the left Control key. In the latter case, it displaces the control key from the lower left corner of the keyboard, below the left shift key. This is where the control key sits on keyboards without the Fn key.

Displacement of the control key has caused considerable user annoyance. The control key, being by convention the entry point of keyboard shortcuts (such as Ctrl+Alt+Del), with a handy corner position of the keyboard, may for some users serve as the origin of the keyboard when doing combined keypresses, as far as the left hand is concerned. In particular, when learning these handy keystrokes, the position of the control key relative to nearby keys (such as the mentioned shift key) will determine the mapping from fingers to keys. If for example the user is accustomed to using the little finger for Ctrl, and ring finger for shift, then pressing Ctrl+shift when the Fn and control keys are swapped, requires a near ninety degree outward twist of the wrist, alternatively crossing the fingers, before eventually getting used to the opposite mapping of these fingers to keys.

One workaround is to modify the point of origin by using the ring finger for the Shift key, the thumb for the displaced Control key and index and middle fingers for everything else, leaving the little finger out entirely. Such change to the point of origin does reduce the useful radius of the first four fingers across the keyboard, yet may be more ergonomic for the hand.

Apple keyboards

Newer Apple Keyboards have an Fn key that modifies the function of the function keys from those printed to a normal function key.

External links

• Microsoft Keyboards - F Lock Key
• What the F-Key?