Experiments in software reengineering

Program restructuring is frequently part of software reengineering and maintenance activities. There are several goals: reduce future system life cycle costs and improve quality by reducing software faults. An important sub goal is to reduce the number of non-traversable program execution paths. The conjecture is that non-traversable execution paths make programs hard to understand and maintain. Unfortunately, reducing the number of non-traversable paths frequently produces unstructured programs, which are also commonly believed to make program understanding and maintenance more difficult. Pleszkoch, Linger, and Hevner (1992) described a technique in which the final result of a restructuring process is an equivalent system that is both structured and has fewer non-traversable paths. Their restructuring technique involves creation of a set of intermediate transformations, some of which may produce unstructured programs, even though the final output is structured. We describe the results of a series of experiments on the effect of program restructuring on comprehension. There were several objectives: to determine if this technique produced programs that were easier to understand than their original versions, to see if understanding was the same in intermediate as well as the final versions, and to see if the programming language in which the programs were written had any effect on the results. Applicability of the results to industrial environments is also discussed