Since COM components can be created in a number of high-level programming languages, such as Visual C++, Java, and Visual Basic, if you are proficient in any of these languages, you can create your own custom COM components (or COM objects, as they are sometimes called). For an object to be considered a COM object (and therefore to be able to be instantiated from the wide range of development tools and programming languages), it must follow certain guidelines. These low-level guidelines are far past the scope of this book, and will not be discussed in detail.
Thankfully, high-level programming languages ensure that most of these low-level implementation details are taken care of for you. For example, when creating a COM component in Visual Basic, these low-level details can be completely ignored, and the developer can focus on creating classes that will be translated into full-fledged COM components by Visual Basic.
This book also refrains from stepping through the process of creating a COM object with any programming language. There are already several great books on the topic. If you are looking for an entire book dedicated to building COM objects in various languages, let me recommend Shelly Powers’s Developing ASP Components (O’Reilly), which shows how to create components in Java, Visual C++, and Visual Basic in great detail.
What this book does focus on is a particular type of custom COM component, one used to ensure business logic integrity.