Modifier key

In computing, a modifier key is a special key on a computer keyboard that modifies the normal action of another key the two are pressed in combination.

For example, <Alt> + <F4> in Microsoft Windows will automatically close the program in an active window. In contrast, pressing just <F4> will probably do nothing unless assigned a specific function in a particular program. By themselves, modifier keys usually do do nothing.

The most common modifier keys are:

• <Shift>
• <Ctrl> -- "control"
• <Alt> -- "alternative"
• <Alt Gr> -- "alternative graphic", used to obtain special symbols from the keyboard. If a key has a third symbol on it (sometimes in a different colour or on the vertical edge of the key), then <Alt Gr> will elicit that symbol. Under Microsoft Windows, <Alt Gr> is equivalent to <Ctrl><Alt>.

<Shift>, of course, is the oldest in terms of keyboards in general as it originates from typewriters and is usually used to make uppercase letters when typing.

Apple Macintosh computers also have the special <Command> key with the Apple Computer logo and a proprietary symbol that looks like a hash mark with the lines connected in a way that looks somewhat like a flower. <Alt> is also replaced with the <Option> key; however modern Apple keyboards label this key with both "option" and "alt".

Sun Microsystems keyboards have two <Meta> keys, which look like a square rotated 45 degrees (like a diamond shape).

Amiga computers[?] has two <Amiga> keys with the Amiga logo on them. They are mostly used in the same way as <Alt> is on the PC.

See also: Bucky bit[?]