Fn key
Encyclopedia
Modifier key
In computing, a modifier key is a special key on a computer keyboard that modifies the normal action of another key when the two are pressed in combination....
on many keyboards
Computer keyboard
In computing, a keyboard is a typewriter-style keyboard, which uses an arrangement of buttons or keys, to act as mechanical levers or electronic switches...
, especially on laptops, used in a compact layout
Keyboard layout
A keyboard layout is any specific mechanical, visual, or functional arrangement of the keys, legends, or key–meaning associations of a computer, typewriter, or other typographic keyboard....
to combine keys which are usually kept separate. It is typically found on laptop
Laptop
A laptop, also called a notebook, is a personal computer for mobile use. A laptop integrates most of the typical components of a desktop computer, including a display, a keyboard, a pointing device and speakers into a single unit...
s, 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
F-Lock
The F-Lock key, introduced by Microsoft in 2001 toggles the state of the function keys. When on, keys F1 to F12 behave as standard, with meanings defined by the application being used at the time. When off, new behaviour is used: F5 means "open", F10 means "spell" etc...
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 keypadNumeric keypad
A numeric keypad, numpad or tenkey for short, is the small, palm-sized, seventeen key section of a computer keyboard, usually on the very far right. The numeric keypad features digits 0 to 9, addition , subtraction , multiplication and division symbols, a decimal point and Num Lock and Enter keys...
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).
Apple Computer
Apple Inc. is an American multinational corporation that designs and markets consumer electronics, computer software, and personal computers. The company's best-known hardware products include the Macintosh line of computers, the iPod, the iPhone and the iPad...
iBook
IBook
The iBook was a line of laptop computers sold by Apple Computer from 1999 to 2006. The line targeted the consumer and education markets, with lower specifications and prices than the PowerBook, Apple's higher-end line of laptop computers....
. 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
Mac OS X
Mac OS X is a series of Unix-based operating systems and graphical user interfaces developed, marketed, and sold by Apple Inc. Since 2002, has been included with all new Macintosh computer systems...
.
Technical details
Unlike other modifier keys such as CtrlControl key
In computing, a Control key is a modifier key which, when pressed in conjunction with another key, will perform a special operation ; similar to the Shift key, the Control key rarely performs any function when pressed by itself...
, Shift
Shift key
The shift key is a modifier key on a keyboard, used to type capital letters and other alternate "upper" characters. There are typically two shift keys, on the left and right sides of the row below the home row...
and AltGr
AltGr key
AltGr is a modifier key found on many computer keyboards and primarily used to type characters that are unusual for the locale of the keyboard layout, such as currency symbols and accented letters...
, the microcontroller
Microcontroller
A microcontroller is a small computer on a single integrated circuit containing a processor core, memory, and programmable input/output peripherals. Program memory in the form of NOR flash or OTP ROM is also often included on chip, as well as a typically small amount of RAM...
inside the keyboard typically sends out a different keycode depending on whether the Fn key is depressed. This allows the keyboard to emulate
Emulator
In computing, an emulator is hardware or software or both that duplicates the functions of a first computer system in a different second computer system, so that the behavior of the second system closely resembles the behavior of the first system...
a full-sized keyboard, so that specialised keymaps do not need to be created; the operating system
Operating system
An operating system is a set of programs that manage computer hardware resources and provide common services for application software. The operating system is the most important type of system software in a computer 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
Scancode
A scancode is the data that most computer keyboards send to a computer to report which keys have been pressed. A number, or sequence of numbers, is assigned to each key on the keyboard.- Variants :...
. However, if it does, the key may be remapped by modifying the interrupt handler
Interrupt handler
An interrupt handler, also known as an interrupt service routine , is a callback subroutine in microcontroller firmware, operating system or device driver whose execution is triggered by the reception of an interrupt...
in BIOS
BIOS
In IBM PC compatible computers, the basic input/output system , also known as the System BIOS or ROM BIOS , is a de facto standard defining a firmware interface....
that maps scancodes to characters, a technique that has proven successful on Lenovo laptops.
In addition to being mapped to standard keyboard keys like Scroll Lock
Scroll lock
Scroll lock is a keyboard button on some computer keyboards. The key is not frequently used and therefore some keyboards lack Scroll Lock altogether....
and Num Lock
Num lock
Num Lock is a key on the numeric keypad of most computer keyboards. It is a toggle key, like Caps Lock and Scroll Lock. Its state is commonly represented by an LED light built into the keyboard....
, 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 keyControl key
In computing, a Control key is a modifier key which, when pressed in conjunction with another key, will perform a special operation ; similar to the Shift key, the Control key rarely performs any function when pressed by itself...
. 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
Control-Alt-Delete
Control-Alt-Delete is a computer keyboard command on IBM PC compatible systems that can be used to reboot the computer, and summon the task manager or Windows Security in more recent versions of the Microsoft Windows operating system...
), with a handy corner position of the keyboard, may for some users serve as the origin
Origin (mathematics)
In mathematics, the origin of a Euclidean space is a special point, usually denoted by the letter O, used as a fixed point of reference for the geometry of the surrounding space. In a Cartesian coordinate system, the origin is the point where the axes of the system intersect...
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 KeyboardApple keyboard
The Apple Keyboard is a keyboard designed by Apple first for the Apple line, then the Macintosh line of computers. It is available in both wired and Bluetooth models.- Layout :...
s have an Fn key that modifies the function of the function keys from those printed to a normal function key.