Chapter 7. Introduction to the Standard Widget Toolkit
Object-oriented software at its technical core is constructed from objects that receive method calls, change their internal state, and compute some return value. Part II created a solid and detailed conceptual basis for reasoning about these method calls and about the correctness of software in general. Such a basis is indispensable for developing any substantial software product: If we are not able to capture the expected behavior of its different components precisely, we will never be able to divide the work among a team and still be confident that the parts will fit together seamlessly in the end.