COM objects and interfaces
In principle, a COM object is a piece of software that implements one or more functions. Different COM objects support different functions. The functions of a COM object are accessible by means of the interface of the COM object. The COM object itself is regarded as a black box that implements one or more functions accessible through its interfaces.
Applications that support COM can create COM objects. By accessing the interface functions of the COM object, the functions of the COM object are executed by the calling application. The syntax to create COM objects and access the interface functions of a COM object is extremely general: this is the main reason why COM objects can be used by so many different applications: The same COM object can be created and used in ASP-pages, Word documents and Visual Basic scripts.
All applications that support COM use some kind of programming or script language to implement COM. The procedure used is always the same:
The COM object is created;
The interface functions of the COM object are accessed;
Returned variables can be processed in the application.
An application can use multiple COM objects and COM objects can use other COM objects.
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