摘要
The notions of class, subclass, superclass and inheritance were first introduced into programming languages by Simula 67, and further developed in languages like Smalltalk and C++ to form a special programming style, known as object-oriented programming: by means of the inheritance mechanism, subclass shares the code defined in its superclass, thus encouraging the incremental development of programs and improving the extensionability of software product.
基金
Project supported by the National Natural Science Foundation of China.
