Graphical user interface
The graphical user interface (often referred to as a GUI), now the almost universal form of user interface to computing devices, is based on images, now displayed on a bit-mapped display, but initially with vector graphics on a CRT.
The user interacts with the operating system and applications with a pointing input device, which is the main input form (although the keyboard is still used). The first pointing device was the light pen; then came the mouse, and now the touch-pad. Recently, the pointing device has been used to supplant the keyboard in some systems, by means of hand-writing recognition.
The next steps were taken by Douglas Engelbart of the Augmentation Research Center at the Stanford Research Institute. That work was then taken up at the nearby Xerox PARC, with the ground-breaking Xerox Alto project, the first personal computer of modern form.
Work at PARC introduced the window concept, to allow multiple simultaneous applications to share the screen. A number of companies, including Microsoft and Apple Computer, then produced products based on PARC's work, which popularized the concept.