A window manager is system software that controls the placement and appearance of windows within a windowing system in a graphical user interface. Most window managers are designed to help provide a desktop environment. They work in conjunction with the underlying graphical system that provides required functionality—support for graphics hardware, pointing devices, and a keyboard—and are often written and created using a widget toolkit.
Few window managers are designed with a clear distinction between the windowing system and the window manager. Every graphical user interface based on a windows metaphor has some form of window management. In practice, the elements of this functionality vary greatly. Elements usually associated with window managers allow the user to open, close, minimize, maximize, move, resize, and keep track of running windows, including window decorators. Many window managers also come with various utilities and features such as task bars, program launchers, docks to facilitate halving or quartering windows on screen, workspaces for grouping windows, desktop icons, wallpaper, an ability to keep select windows in foreground, the ability to "roll up" windows to show only their title bars, to cascade windows, to stack windows into a grid, to group windows of the same program in the task bar in order to save space, and optional multi-row taskbars.
History of the graphical user interface
In 1973, the Xerox Alto became the first computer shipped with a working WIMP GUI. It used a stacking window manager that allowed overlapping windows. However, this was so far ahead of its time that its design paradigm would not become widely adopted until more than a decade later. While it is unclear if Microsoft Windows contains designs copied from Apple's classic Mac OS, it is clear that neither was the first to produce a GUI using stacking windows. In the early 1980s, the Xerox Star, successor to the Alto, used tiling for most main application windows, and used overlapping only for dialogue boxes, removing most of the need for stacking.