Source : WordNet®

graphical user interface
     n : a user interface based on graphics (icons and pictures and
         menus) instead of text; uses a mouse as well as a
         keyboard as an input device [syn: {GUI}]

Source : Free On-Line Dictionary of Computing

Graphical User Interface
     
         (GUI) The use of pictures rather than just
        words to represent the input and output of a program.  A
        program with a GUI runs under some {windowing system}
        (e.g. The {X Window System}, {MacOS}, {Microsoft Windows},
        {Acorn} {RISC OS}, {NEXTSTEP}).  The program displays certain
        {icons}, {buttons}, {dialogue boxes}, etc. in its {windows} on
        the screen and the user controls it mainly by moving a
        {pointer} on the screen (typically controlled by a {mouse})
        and selecting certain objects by pressing buttons on the mouse
        while the pointer is pointing at them.  This contrasts with a
        {command line interface} where communication is by exchange of
        strings of text.
     
        Windowing systems started with the first {real}-time graphic
        display systems for computers, namely the {SAGE} Project
        [Dates?] and {Ivan Sutherland}'s {Sketchpad} (1963).  {Douglas
        Engelbart}'s {Augmentation of Human Intellect} project at
        {SRI} in the 1960s developed the {On-Line System}, which
        incorporated a mouse-driven cursor and multiple windows.
        Several people from Engelbart's project went to Xerox PARC in
        the early 1970s, most importantly his senior engineer, {Bill
        English}.  The Xerox PARC team established the {WIMP} concept,
        which appeared commercially in the {Xerox 8010} (Star) system
        in 1981.
     
        Beginning in 1980(?), led by {Jef Raskin}, the {Macintosh}
        team at {Apple Computer} (which included former members of the
        Xerox PARC group) continued to develop such ideas in the first
        commercially successful product to use a GUI, the Apple
        Macintosh, released in January 1984.  In 2001 Apple introduced
        {Mac OS X}.
     
        {Microsoft} modeled the first version of {Windows}, released
        in 1985, on Mac OS.  Windows was a GUI for {MS-DOS} that had
        been shipped with {IBM PC} and compatible computers since
        1981.  Apple sued Microsoft over infringement of the
        look-and-feel of the MacOS.  The court case ran for many
        years.
     
        [Wikipedia].
     
        (2002-03-25)