COM Clients and Servers

COM is a refinement of the thinking behind OLE, DDE, and ActiveX. COM makes it possible to create truly reusable software components that are compatible across programming languages. COM provides some relief from version conflicts associated with software updates, and creates a platform for truly distributed network computing. As with DDE, there are COM clients and COM servers. However, in the world of COM, these terms have new meaning.

• A COM client is a program or object that calls methods in one or more interfaces provided by a COM server.

• A COM server interacts with clients by implementing interfaces that direct the client to methods supported by the interface. In-process COM servers are DLLs that run on the local machine. Out-of-process COM servers are .EXE files that can reside on the local machine, or on a networked computer. The COM specification has been extended to provide support for distributed processes (DCOM) running on remote computers. The term COM is now synonymous with both COM and DCOM.