Page #37 (References)

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Chapter 2. Designing Interfaces

In the previous chapter we observed that in order to write a reusable component we need to separate the interface from details of implementation. We also learned that the first step in developing a COM component is defining the interfaces the component intends to expose.

The interfaces in the previous chapter were defined as C++ classes. This lets the vendor pick a C++ compiler of its choice and lets the client pick a vendor of its choice. However, in defining the architecture for COM, the COM committee had goals beyond C++ compiler independence and vendor independence. C++ language was not adequate to define an interface that would meet many of the goals. Therefore, COM specifies a language to define interfaces. This language is called the Interface Definition Language (IDL).

In this chapter we examine several goals that the COM committee wanted to achieve and their impact on the design of IDL. We then examine various keywords and data types defined in the language and show their usage from a programming perspective. The primary goal of this chapter is to make the developers feel comfortable defining fairly complex interfaces in IDL. A secondary goal is to help the developers write correct code in using the interfaces.

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