Essential things to remember from today's class (class 6, 11th September)

Features of class definitions:

   class/static members (variables), constants, and methods.

   Why we have both copy constructors and assignment operators,
      and how to define them correctly.

   How to define other operators like +, *, %, ++, *=, <, ==, etc correctly.

   Why << for use on cout or any other ostream has to be an ordinary function,
      not a member, and how to define it properly.

How to make use of exceptions: throw, try, catch.