In computing, a window is a graphical control element. It consists of a visual area containing some of the graphical user interface of the program it belongs to and is framed by a . It usually has a rectangular shape that can overlap with the area of other windows. It displays the output of and may allow input to one or more processes. A graphical user interface (GUI) using windows as one of its main "metaphors" is called a windowing system, whose main components are the display server and the window manager.