Visualizing roles of variables in program animation

Visualizations may be used to assist in learning elementary computer programming— a skill that is hard to acquire by many students. This article presents a program animation system, PlanAni, that is based on the concept of the roles of variables. Roles represent schematic uses of variables that occur in programs over and over again, and a set of nine roles covers practically all variables in novice-level programs. PlanAni has been evaluated in a classroom experiment comparing traditional teaching with role-based teaching and animation. The results suggest that the introduction of roles provides students with a new conceptual framework that enables them to mentally process program information in a way similar to that of good code comprehenders. The use of role-based animation seems to assist in the adoption of role knowledge and expert-like programming strategies. A semi-structured interview with the teacher indicates that students like to work with the animator and that the system clarifies many concepts in programming.