If you're trying to use plain C, without MFC, WTL, .NET, ATL, C#, or even any C++ code at all, then there is a dirth of examples and information how to deal with COM objects. This book teaches how to create a COM component in plain C, without using any of the above frameworks. As such, it allows a programmer the fullest control over the minute details of implementing a COM component, is not confined to using any particular C compiler, and may be used to create custom COM frameworks including those that run upon platforms other than Windows.