User interface expert Jef Raskin coined the term ' quasimode' to describe the state a computer enters into when a modifier key is pressed. In contrast, pressing just ⇧ Shift or Alt will probably do nothing unless assigned a specific function in a particular program (for example, activating input aids or the toolbar of the active window in Windows). A combination of Alt+ F4 in Microsoft Windows will close the active window in this instance, Alt is the modifier key. By themselves, modifier keys usually do nothing that is, pressing any of the ⇧ Shift, Alt, or Ctrl keys alone does not (generally) trigger any action from the computer.įor example, in most keyboard layouts the Shift key combination ⇧ Shift+ A will produce a capital letter 'A' instead of the default lower-case letter 'a' (unless in Caps lock or Shift lock mode). In computing, a modifier key is a special key (or combination) on a computer keyboard that temporarily modifies the normal action of another key when pressed together.
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