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, + in Microsoft Windows will automatically close the program in an active window. In contrast, pressing just will probably do nothing unless assigned a specific function in a particular program. By themselves, modifier keys usually do nothing.
1 Common modifier keys
The most common modifier keys, as used by PCs, are:
– Alt Gr key (Alternative Graphics key) – 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 will elicit that symbol. Under Microsoft Windows, is equivalent to .
, 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.
1.1 Accented characters
Some foreign 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. The Alt Gr modifier produces the áéíóú sequence, or in conjunction with the Shift key, ÁÉÍÓÚ. Some foreign language keyboards simply include the accented characters on their own keys.
2 Other modifier keys
Apple Macintosh computers also have the special key with the Apple Computer logo and the place of interest sign ( Unicode code point U+2318, or ⌘). is also replaced with the