Computer Guided Instruction. 1,2] - refers to the aspects of computer use in education to guide the instructional process. Two subclasses of CGI indicate the form of decision making or guidance involved: CGIT refers to tactical guidance of individual presentation choices. An example of a tactical choice is selecting a particular fact, problem, or example for presentation. CGIS refers to strategic or overall guidance that affects higher level instructional decisions or modes. An example of a strategic instructional decision is choosing parameters for the relative importance of different concepts or facts, or determining what to do about a student's point of confusion or lack of knowledge. The distinction between "guiding" or "managing" instruction is based on whether the choice or advice is given on-line and automatically (guidance) or off-line and for consideration by the teacher (CMI). The adaptive tutor developed in this work exemplifies all three approaches: CGIS, CGIT, and CMI.