---- ---- - COM -- موسوعة علوم الحاسب: COM

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الخميس، 28 يناير 2010

COM

Component Object Model (COM) is a binary-interface standard for software componentryMicrosoft in 1993. It is used to enable interprocess communication and dynamic objectprogramming languages. The term COM is often used in the Microsoft software development industry as an umbrella term that encompasses the OLE, OLE Automation, ActiveX, COM+ and DCOM technologies introduced by creation in a large range of


Overview

The essence of COM is a language-neutral way of implementing objects that can be used in environments different from the one they were created in, even across machine boundaries. For well-authored components, COM allows reuse of objects with no knowledge of their internal implementation, as it forces component implementers to provide well-defined interfaces that are separate from the implementation. The different allocation semantics of languages are accommodated by making objects responsible for their own creation and destruction through reference-counting. Casting between different interfaces of an object is achieved through the QueryInterface() function. The preferred method of inheritance within COM is the creation of sub-objects to which method calls are delegated.
Although the interface standard has been implemented on several platforms[citation needed], COM is primarily used with Microsoft Windows. For some applications, COM has been replaced at least to some extent by the Microsoft .NET framework, and support for Web Services through the Windows Communication Foundation (WCF). However, COM objects can be used with all .NET languages through .NET COM Interop.
Networked DCOM uses binary proprietary formats, while WCF encourages the use of XML-based SOAP messaging. COM is very similar to other component software interface standards, such as CORBA and Java Beans, although each has its own strengths and weaknesses. The characteristics of COM make it most suitable for the development and deployment of desktop applications, for which it was originally designed.

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