See computer output microfilm
odel) A Microsoft architecture for building software modules (objects) that are executed in Windows. Parts of Windows itself and Microsoft's own applications are built as COM objects. Beginning with Windows 95 and Windows NT, COM provides the interfaces between objects, and Distributed COM (DCOM) allows them to run remotely.
COM objects can be small or large. They can be written in several programming languages and perform any kind of processing. Whenever it needs its services, a program can call the object, which can be run remotely over a network, originally known as "Distributed COM" (DCOM).
Automation (OLE automation)
Standard applications, such as word processors and spreadsheets, can be written to expose their internal functions as COM objects, allowing them to be "automated" instead of manually selected from a menu. For example, a script could be written to extract data from a database, summarize and chart it in a spreadsheet and place the results into a text document. See COM automation
Controls (OLE controls, ActiveX controls)
Applications can invoke COM objects, called "controls," that blend in and become just another part of the program. An industry of third-party, ready-made controls for the Windows programmer has been created. ActiveX controls can also be downloaded from the Internet to make a Web page perform any kind of processing. See ActiveX control
Compound Documents and ActiveX Documents
Microsoft's OLE compound documents are based on COM, which lets one document be embedded within or linked to another (see OLE
). ActiveX Documents are extensions to OLE that allow a Web browser, for example, to view not only Web pages, but any kind of document (see ActiveX Documents
Increasingly, Microsoft is making its standard programming interfaces conform to the COM object model so that there is continuity between all interfaces. See DAO
and OLE DB
It Can Be Confusing
Microsoft first used the term OLE to refer to its COM-based architecture, then later dropped that designation in favor of ActiveX. Since both OLE and ActiveX are based on COM, the term COM is also used. As a result, any combination of the words COM, OLE and ActiveX followed by the words control, object and component may mean the same thing, or they may not, depending on context.
Any kind of program, small or large, can be written as a COM object. It can be run locally or remotely via DCOM. The terms COM object, ActiveX object and ActiveX component are synonymous.