IUnknown
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The published COM specification (http://www.microsoft.com/com/resources/comdocs.asp) mandates that COM objects must minimally implement the IUnknown interface. This interface is comprised of three functions - QueryInterface, AddRef and Release.
- QueryInterface is used to retrieve a pointer to a vector containing pointers to object methods
- AddRef is used by clients to indicate that a COM object is being referenced. This is necessary to ensure that a COM object is not disposed prematurely
- Release is used by clients to indicate that they have finished using the COM object. An unreferenced COM object may be safely disposed