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 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.
User interface expert Jef Raskin coined the term "quasimode" to describe the state a computer enters into when a modifier key is pressed.
Common modifier keys
The most common modifier keys, as used by PCs, are:
, 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.
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. These kinds of keys are called dead keys. 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. Some keyboards also have a Compose key for typing accented and other special characters. By pressing , and then two other keys, something similar to a combination of the glyphs of the two previous keys will appear on the screen.
"Modifier key"