A graphics-based operating system interface that uses icons, menus and a mouse (to click on the icon or pull down the menus) to manage interaction with the system. Developed by Xerox, the GUI was popularized by the Apple Macintosh in the 1980s. At the time, Microsoft’s operating system, MS-DOS, required the user to type specific commands, but the company’s GUI, Microsoft Windows, is now the dominant user interface for personal computers (PCs). A comprehensive GUI environment includes four components: a graphics library, a user interface toolkit, a user interface style guide and consistent applications. The graphics library provides a high-level graphics programming interface. The user interface toolkit, built on top of the graphics library, provides application programs with mechanisms for creating and managing the dialogue elements of the windows, icons, menus, pointers and scroll bars (WIMPS) interface. The user interface style guide specifies how applications should employ the dialogue elements to present a consistent, easy-to-use environment (i.e., “look and feel”) to the user. Application program conformance with a single user interface style is the primary determinant of ease of learning and use, and thus, of application effectiveness and user productivity.