Component Object Model (COM) refers to both a specification and implementation developed by Microsoft Corporation which provides a framework for integrating components. This framework supports interoperability and reusabilityof distributed objects by allowing developers to build systems by assembling reusable components from different vendors which communicate via COM.

COM defines an application programming interface (API) to allow for the creation of components for use in integrating custom applications or to allow diverse components to interact. The COM library is key to implementing this common interface between objects. The COM library maintains information about available classes in the system registry. The interface definition language used to define COM interfaces and methods is borrowed from DCE. COM also defines a binary interface standard. This standard helps to promote language-independence.

The Distributed Component Object Model (DCOM), based on COM, is Microsoft's approach to developing distributed systems. DCOM allows COM objects executing on one computer to create COM objects on other computers and access their methods. The location of the remote object is transparent. Using DCOM, remote objects are accessed in exactly the same manner as local objects.

Although DCOM is a Microsoft product, it is an open standard and has been ported to other platforms, such as UNIX.

COM & DCOM: Component Object Model and Distributed Component Object Model

Related Terms: API, Remote Procedure Call (RPC), Distributed Computing Environment (DCE), Distributed Component Object Model (DCOM), Common Object Request Broker Architecture (COBRA)