Graphical User Interface (GUI), in computer science, a display format that enables the user to choose commands, start programs, and see lists of files and other options by pointing to pictorial representations (icons) and lists of menu items on the screen (see User Interface). Choices can generally be activated either with the keyboard or with a mouse. GUIs were inspired from the pioneering research of computer scientists at the Xerox Corporation's Palo Alto Research Center in the 1970s. Modern GUIs are used on the Macintosh operating system, Microsoft Windows, and the OS/2 Presentation Manager.

For application developers, GUIs offer an environment that processes the direct interaction with the computer. This frees the developer to concentrate on the application without worrying about the details of screen display, mouse control, or keyboard input. It also provides programmers standard controlling mechanisms for frequently repeated tasks such as opening windows and dialog boxes. Another benefit is that applications written for a GUI are device-independent: As the interface changes to support new input and output devices, such as a large-screen monitor or an optical storage device, the applications can, without modification, use those devices.