COM Interface Information

When a COM component is loaded into memory, its functions are mapped to internal memory addresses. A COM interface is simply a pointer to a location in memory where a set of functions is stored. Functions are called methods by COM programmers.

By convention, COM interface names begin with the letter "I", which stands for "interface". All COM objects implement an interface named IUnknown, which exposes three functions:

• AddRef increments an internal counter each time the object is referenced.

• Release decrements an internal counter each time that an object is released. When the internal reference counter becomes zero, Windows deletes the object.

• QueryInterface allows you to query a COM object to find out if it supports a particular interface. If it does, QueryInterface provides a pointer to the set of functions exposed by the interface.

It is unlikely that you will ever need to use IUnknown to query an IEIC COM component, since all IEIC interfaces, methods, and properties are fully documented. However, each IEIC component supports the standard IUnknown interface and its methods. Since IUnknown is defined by the COM specification, it is not described elsewhere in this documentation.