Dealing exclusively with instructional computing, this paper describes how computers are delivering instruction in a wide variety of subjects to students of all ages and explains why computer-based education is currently having a profound impact on education. After a discussion of roots and origins, computer applications are described for educational, government, professional, and instructional markets. Examples of higher education applications are given for the sciences, the arts, humanities, medicine, agriculture, business, engineering and counseling, and for mathematics, reading, language arts, and computer science at the pre-college level. Examples of applications are from the PLATO system and include diagrams. Benefits and characteristics of computer-based instruction are enumerated and explained, and an overview of instructional computers on the current market is provided, including online mainframe systems, offline microcomputer systems, and hybrid systems. Six main categories of system-selection criteria for good computer-based instruction are discussed: (1) support for instructional strategies; (2) student learning station requirements; (3) features for instructors and authors; (4) general operational characteristics; (5) dissemination networks; and (6) future viability. Final sections examine contemporary trends and issues in the future related to computer-based instruction. Eighteen references are listed. (LMM)