The graphical user interface, or "GUI", is a computer interface that uses graphic icons and controls in addition to text. The user of the computer utilizes a pointing device, like a mouse, to manipulate these icons and controls. This was a great leap forward from the command line interface used in other operating systems, in which the user types a series of text commands to the computer.

Initial Developments
The first concept of a windowing system begins with the first real-time graphic display systems for computers, namely the SAGE Project and Ivan Sutherland’s Sketchpad.

Augmentation of Human Intellect
Doug 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.

Xerox PARC
Engelbart’s work directly led to the advances at Xerox PARC. Several people went from SRI to Xerox PARC in the early 1970’s. The Xerox PARC team codified the WIMP (windows, icons, menus and pointers/pull-down menus) paradigm, first pioneered on the Xerox Alto experimental computer, but which eventually appeared commercially in the Xerox 8010 (’Star’) system in 1981.

Apple Lisa and Macintosh
Beginning in 1979, led by Jef Raskin, the Lisa and Macintosh teams at Apple Computer (which included former members of the Xerox PARC group) continued to develop such ideas. The Macintosh, released in 1984, was the first commercially successful product to use a GUI. A desktop metaphor was used, in which files looked like pieces of paper; directories looked like file folders; there were a set of desk accessories like a calculator, notepad, and alarm clock that the user could place around the screen as desired; and the user could delete files and folders by dragging them to a trash can on the screen.
There is still some controversy over the amount of influence that Xerox’s PARC work, as opposed to previous academic research, had on the GUIs of Apple’s Lisa and Macintosh, but it is clear that the influence was extensive.

The Macintosh’s GUI has been revised with time since 1984, with a major update with System 7, and underwent its largest revision with the introduction of the "Aqua" interface in 2001’s Mac OS X.