Classes are used for two main reasons: (1) it makes it much easier to organize your programs if you can group together data with the functions that manipulate that data, and (2) the use of private members makes it possible to do information hiding, so that you can be more confident about the way information flows in your programs (if you want to impress people, you call this enforcing invariants).

These are electronic books in HTML on C++ and Java, along with the source code. The HTML books are fully indexed, use Frames for easy navigation through the chapters, and have color syntax highlighting on all the source-code listings. Each HTML download contains an entire book and source code in a single zipped file.