Component Object Model (COM)

What is COM ?

COM stands for Component Object Model, which is binary specification for software code re-use. It has a standard that is imposed for the interfaces through which client talks to the component classes. The component’s IUnknown interface helps to maintain a reference count of the number of clients using the component. When this count falls below zero, the component is unloaded.

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All components should implement the IUnknown interface. The reference count is maintained by the following methods
IUnknown::AddRef()
IUnknown::Release()
and interface discovery is handled through IUnknown::QueryInterface().

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