COM Concepts

This page defines some concepts that are fundamental to the entire technology of COM.
COM is a standard that describes how a binary component can communicate with the outside world.


The component communicates through well-defined interfaces. Each interface is a specification of a group of properties and methods. It is important that the interface does not contain the implementation of the properties and methods, only their specifications (signatures).


The actual implementation lies in the coclass. There can be different implementations of the same interface in different coclasses.

Class Objects or Class Factories

Finally, each coclass can be instantiated using a class object or class factory.

These notions will be discussed further in the upcoming sections.

See Also:
EiffelCOM library
COM Interfaces
Component Location
Access Type
Deeper into COM