IUnknown
The new home for Visual Studio documentation is Visual Studio 2017 Documentation on docs.microsoft.com.
The latest version of this topic can be found at IUnknown.
IUnknown](https://msdn.microsoft.com/library/windows/desktop/ms680509) is the base interface of every other COM interface. This interface defines three methods: QueryInterface, AddRef, and Release. QueryInterface allows an interface user to ask the object for a pointer to another of its interfaces. AddRef and Release implement reference counting on the interface.