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.

For example, Alt+F4 in Microsoft Windows will close the program in the active window ; in this instance, Alt is the modifier key. In contrast, pressing just F4 will probably do nothing unless assigned a specific function in a particular program. By themselves, modifier keys usually do nothing, that is, pressing Alt alone does not trigger any action from the computer.

User interface expert Jef Raskin coined the term "quasimode" to describe the state a computer enters into when a modifier key is pressed.

Modifier keys on typewriters

• ⇧ Shift

Modifier keys on personal computers

The most common are:

• ⇧ Shift
• Ctrl (Control)
• Alt (Alternate) - also labelled "Opt" on Apple keyboards
• AltGr (Alternate Graphic)
• ◆ - Meta key, found on Sun Microsystems keyboards
• (Windows logo) – found on Windows keyboards
• ⌘ Cmd – Command key, found on Apple Macintosh keyboards. On older keyboards marked with the Apple logo.
• Fn (Function) – present on small-layout keyboard, usually on notebooks.

The (Sun) Meta key, Windows key, (Apple) Cmd key, and the analogous "Amiga key" on Amiga computers, are usually handled equivalently. Under the GNU/Linux operating system, desktop environments such as KDE and GNOME call this key, neutrally, Super. (This is a bit confusing, since the original space cadet keyboard and the X Window System recognize a "Meta" modifier distinct from "Super".)

The Sinclair ZX Spectrum has a Symbol Shift key in addition to Caps Shift. This was used to access additional punctuation and keywords.

Compact keyboards, such as those used in laptops, often have a Fn key to save space by combining two functions that are normally on separate keys. On laptops, pressing Fn plus one of the function keys, e.g., F2, often control hardware functions.

The MIT space-cadet keyboard had additional Top, Front, Super and Hyper modifier keys. Combined with standard modifiers, it could enter as many as 8,000 different characters.

Accented characters

Some non-English language keyboards have special keys to produce accented modifications of the standard letter keys. In fact, the standard British keyboard layout includes an accent key on the top-left corner to produce àèìòù, although this is a two step procedure, press the accent key and release, then the letter key. These kinds of keys are called dead keys. The AltGr modifier produces the áéíóú sequence, or in conjunction with the Shift key, ÁÉÍÓÚ. Keyboards of some languages simply include the accented characters on their own keys. Some keyboards also have a Compose key for typing accented and other special characters. By pressing Compose, and then two other keys, something similar to a combination of the glyphs of the two previous keys will appear on the screen.

User interface difficulties

In old, 1990s MS-DOS games, modifer keys such as Ctrl, Alt, Shift were often used extensively. For example, id Software's original DOOM series by default mapped the Ctrl key to fire a weapon, hold down Alt in conjunction with the arrow keys to strafe (move sideways), hold Shift and up or back arrow to run forwards and backwards. This kind of control scheme was copied by various game companies across multiple genres, including first-person shooters, fighting games, and others. With the introduction and standardization of the Windows key after Windows 95, this kind of control scheme became faulty because players could accidentally press the Windows key while trying to press Ctrl or Alt, and this in turn could interfere with DOS games run on top of Windows via the Dos prompt. The addition of the Windows Key to keyboards may have been part of the reason why most current games have evolved their control schemes, and most first person shooters generally use the mouse in conjunction with a "Half-Life" style of control (W,A,S,D, Space, Shift, Ctrl) named apparently because it may have been the first widespread game to popularize such an interface, and because usage of the Alt button would nowadays heighten the risk of accidentally pressing the Windows Key. To cope with this problem, some newer games (like Doom 3) disable the Windows Key while in the game.

See also

• Control character
• Function key
• Keyboard layout
• Space-cadet keyboard
• Emacs

• Table of keyboard shortcuts

External links

• Bucky bits in the Jargon file