Component Object Model

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Related to Component Object Model: Distributed Component Object Model

Component Object Model

(COM) An open software architecture from DEC and Microsoft, allowing interoperation between ObjectBroker and OLE. Microsoft evolved COM into DCOM.

On page XV of Box's book in the foreword by Charlie Kindel he says, "It is Mark Ryland's fault that some people call COM the 'Common Object Model.' He deeply regrets it and apologizes profusely."

["Essential COM", Don Box].

This article is provided by FOLDOC - Free Online Dictionary of Computing (


(1) See computer-on-module.

(2) See computer output microfilm.

(3) (Component Object Model) 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
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).

Programming Interfaces
Increasingly, Microsoft is making its standard programming interfaces conform to the COM object model so that there is continuity between all interfaces. See DAO, ADO 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.

COM Objects
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.
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References in periodicals archive ?
When the Component Object Model Add-In is loaded, it automatically calls the previously described function afiseazaNumarCurent, but it does so only at the moment when the module is loaded.
The two vulnerabilities are in the components of Windows that deal with remote procedure calls (RPC) to distributed component object model (DCOM) services.
Finnish IT company Tekla Corporation said today (13 June) that it had signed a license contract with German utility company Hamburgische Electricitats-Werke HEW (Hamburg electricity utility) for the COM (Component Object Model) interface for the Tekla Xpower network information system.
The software supports Microsoft's Component Object Model programming, which allows users to create programs that interact to exchange data with other software, such as Microsoft Office applications.
The Origin C language built into OriginPro offers support for Microsoft's Component Object Model (COM) programming.
By connecting to, the Object Factory offers an environment that combines local application development with remote financial market data, complex financial analytical business objects and data storage services using open standards, including component object model (COM), eXtensible markup language (XML) and simple object access protocol (SOAP).
Additionally, i/Lytics supports XML, CORBA(R), JNI and Component Object Model (COM)-based technologies, including COM+ and DCOM.
The PNA Series instruments also allow programming using Standard Commands for Programmable Instruments (SCPI) or Component object Model (COM) and Distributed Component Object Model (DCOM) commands, which can be executed over a LAN interface or within the instrument (SCPI can also be executed over GPIB).
These industry standards are Microsoft's Component Object Model (COM) architecture and ActiveX technology.
The DCOM (Distributed Component Object Model) model from Microsoft has gone through several iterations and continues to evolve.

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