So far we have been using only standard classes such as System, String, and others
when we wrote programs. For a basic program, that is fine. However, we need to
to learn how to write programs using our own classes (in addition to using the standard
classes) when the programs become large and complex. In this chapter, we
learn the basics of how to define our own classes. And, in Chapter 7, we will cover
more advanced topics on defining classes.
