9455507 Biermann A modern trend in computer science education is to include in the first course a rigorous and broad coverage of the field. This is in contrast to teaching a traditional literacy course which emphasizes software packages, vocabulary, and computers and society or to teaching a standard introduction to programming. The new style course is especially demanding on both students and instructor because of the great complexity of the ideas to be transmitted in a short time. This project continues ongoing work to provide a major aid to teaching breadth in the first course; it will develop the "This-is-how-a-computer-works" system which simulates levels of processing in an idealized machine. It enables students to view and manipulate the internals of the compiler, machine architecture at the register level, the switching circuits that implement the machine operations. The system is able to function in the simulation mode for viewing computations, the training mode for instructing a student on what is happening at each step, or the testing mode which will query students at random points and score the quality of their answers. The system is a general tool for teaching at the early college level; it is useful for lecture demonstrations, laboratory exercises, or individual study.