For anything larger than a sample program  it is a good idea to break  it
up into several classes. You should try your best to design your system
so that each class  is a black box component which can be reused as
necessary.

One thing though: I hope you are not confusing methods with classes. It
is hard to tell from your message below.

What do you mean by a black box component? Could you
care to elaborate this a little tad more?

create his classes  so they can easily be re-
used. Black Box is frequently mentioned in testing. BlackBox refers
to knowing the input and output without knowing the inner workings of
the class. Another programmer can take Tim's class  and use it in
thier program  without worrying about how it works, just that it works
correctly. Of course Tim can re-use his class in other programs as
well. The class should be a free standing component. By contrast,
White Box aka "Glass Box" refers to knowing the code inside the
class.