NYGAARD'S MODEL OF PROGRAM EXECUTION: A FRAMEWORK FOR PROGRAM VISUALIZATION

Abstract

This paper presents a dynamic model for understanding and visualizing how computer programs are executed in a block structured domain. Useful in its present form, it also provides a framework for implementing a program visualization system and can be generalized to most imperative languages. The model is used to explain such topics as dynamic program structure, (including recursion) the binding rule, procedure entry and exit, and the passing of arguments to procedures. The model also serves as a good introduction to implementation techniques since it closely mimics the way programs are executed. The sequence of presentation and examples used rely heavily on extensive classroom experience dating back to the 1960's. The programming language used in the examples is Pascal.