A mainline CAI system is an individualized instructional system of major scope which uses the computer as a tool for instructional management and information transmission. Such systems are developed according to a design science approach and used as a less costly alternative to conventional instruction. In contrast, adjunctive systems have a much smaller scope and are used in support of regular classroom or laboratory instruction. TICCIT is classified as a mainline CAI system because (1) it was not designed by a single faculty author for a single course, (2) it is not used on existing computer systems, (3) it does not use existing languages, and (4) it does not employ normative grading. (CMV)