The paper describes concepts and principles resulting in successful applications of computer technology to the needs of the disabled. The first part describes what a microcomputer is and is not, emphasizing the microcomputer as a machine that simply carries out instructions, the role of programming, and the use of prepared application programs. The second part examines three roles for the computer in the communication rehabilitation of the disabled: (1) temporary use of a computer for assessment, education, therapy, or training; (2) long-term use of a computer as a personal aid (usually of a prosthetic nature); and (3) use of the same computers running the same programs as everyone else. The effective use of computers as personal communication aids is stressed, with particular emphasis on the importance of portability, the computer as a component of a communication system, and the computer's role in writing. Among the possible future trends identified are technical advances (such as headpointing, eyegaze and voice input) and social advances (such as more successful competitive employment by disabled individuals and better information and service delivery). (DB)