SWin and VRuby are the two primary components of the VisualuRuby project. SWin is a Ruby extension module, written in C, that exposes much of the Win32 API to the Ruby interpreter. VRuby is a library of pure Ruby modules built on top of SWin, that provides a higher-level interface to the Win32 programming environment.

As is the case with many Ruby extensions, most of the documentation for SWin and VRuby is only available in Japanese. And although the example programs from the VisualuRuby Web site will give you some idea about what's possible with SWin and VRuby, there's an implicit assumption that you're already familiar with basic Windows programming concepts. This section provides enough of an overview of the VRuby API to develop our sample application, but for a real appreciation of SWin/VRuby you need a stronger background in Windows programming. There are some excellent books on this subject, and although they may discuss the Win32 API from a C programming standpoint, they should help you to fill in a lot of the blanks about programming with VRuby as well. Along those lines, another invaluable reference is the Win32 API reference from the Microsoft Developer Network (MSDN) CDs and DVDs.