Beginning C# 2008 Objects: From Concept to Code

5.4. Three Distinguishing Features of an Object-Oriented Programming Language, Revisited

In Chapter 3, we called out three key mechanisms that are required of a programming language in order to be considered truly object-oriented. We've now defined two of the three features required of a true OOPL:

• (Programmer creation of) User-defined types—discussed in Chapter 3

• Inheritance—discussed in this chapter

• Polymorphism

All that remains is to discuss polymorphism, one of the subjects of an upcoming chapter (Chapter 7, to be precise!). We're going to take a bit of a detour first, however, to discuss what we can do to gather up and organize groups of objects as we create them through the use of a special type of object called a collection.