Reuse through inheritance: a quantitative study of C++ software

According to proponents of object-oriented programming, inheritance is an excellent way to organize abstraction and a superb tool for reuse. Yet, few quantitative studies of the actual use of inheritance have been conducted. Quantitative studies are necessary to evaluate the actual usefulness of structures such as inheritance. We characterize the use of inheritance in 19 existing C++ software systems containing 2,744 classes. We measure the class depth in the inheritance hierarchies, and the number of child and parent classes in the software. We find that inheritance is used far less frequently than expected.