User Interfaces for Articles on Related Subjects, See Human Factors in Computing Systems; Interactive Input Devices; Interactive System; and Window Environ- Ments

A user interface is that portion of an interactive computer system that communicates with the user. Design of the user interface includes any aspect of the system that is visible to the user. Once, all computer user were specialists in computing, and interfaces consisted of jumper wires in patch boards, punched cards prepared offline, and batch printouts. Today a wide range of nonspecialists use computers, and keyboards, mice, and graphical displays are the most common interface hardware. The user interface is becoming a larger and larger portion of the software in a computer system—and a more important portion, as broader groups of people use computers. As computers become more powerful, the critical bottleneck in applying computer-based systems to solve problems is now more often in the user interface, rather than the computer hardware or software. Because the design of the user interface includes anything that is visible to the user, interface design extends deep into the design of the interactive system as a whole. A good user interface cannot be applied to a system after it is built but must be part of the design process from the beginning. Proper design of a user interface can make a substantial difference in training time, performance speed, error rates, user satisfaction, and the user's retention of knowledge of operations over time. The poor designs of the past are giving way to elegant systems. Descriptive taxonomies of users and tasks, predictive models of performance, and explanatory theories are being developed to guide designers and evaluators. Haphazard and intuitive development strategies with claims of ''user friendliness'' are yielding to a more scientific