This paper introduces an Abstract Machine Simulator (AMS) for assisting students to learn abstract machines such as finite automata, Mealy machines and Moore machines. With AMS, topics related to abstract machines which are often included in introductory courses on Theory of Computation can be mastered more easily since it allows the learner to simulate any machine s/he can think of. The program supports learning by discovery. Through interacting with a simulation, the learner can acquire indepth knowledge about the nature of the machine. The general problem-solver approach adopted in developing the program can be employed to construct other simulation and animation based CAI applications. The program also demonstrates the effectiveness of a multi-paradigm programming approach to the implementation of tutoring programs.