An empirical comparison of modularity of procedural and object-oriented software

A commonly held belief is that applications written in object-oriented languages are more modular than those written in procedural languages. This paper presents results from an experiment that examines this hypothesis. Open source and industrial program modules written in the procedural languages of Fortran and C were compared with open source program modules written in the object-oriented languages of C++ and Java. The metrics examined in this study were lines of code per module and number of parameters per module. The results of the investigation support the hypothesis. The modules of the object-oriented programs were found to be half the size of those of the procedural programs and the average number of parameters per module for the object-oriented programs was approximately half that of the procedural programs. Thus the object-oriented programs were twice as modular as the procedural programs. An unexpected result was that the C++ programs were found to be no more modular than the C programs.