The Visual Basic language provides a rich set of functions, commands, and objects, but in many cases they don't meet all the needs of a professional programmer. Just to name a few shortcomings, Visual Basic doesn't allow you to retrieve system information—such as the name of the current user—and most Visual Basic controls expose only a fraction of the features that they potentially have.
Expert programmers have learned to overcome most of these limitations by directly calling one or more Windows API functions. In this book, I've resorted to API functions on many occasions, and it's time to give these functions the attention they deserve. In contrast to my practice in most other chapters in this book, however, I won't even try to exhaustively describe all you can do with this programming technique, for one simple reason: The Windows operating system exposes several thousands different functions, and the number grows almost weekly.
Instead, I'll give you some ready-to-use routines that perform specific tasks and that remedy a few of the deficiencies of Visual Basic. You won't see much theory in these pages because there are many other good sources of information available, such as the Microsoft Developer Network (MSDN), a product that should always have a place on the desktop of any serious developer, regardless of his or her programming language.