IUnknown

In computer programming, the IUnknown interface is the fundamental interface in the Component Object Model (COM). The COM specification[1] mandates that COM objects must implement this interface. Furthermore, every other COM interface must be derived from IUnknown. IUnknown exposes two essential features of all COM objects: object lifetime management through reference counting, and access to object functionality through other interfaces.

An IUnknown (or IUnknown-derived) interface consists of a pointer to a virtual method table that contains a list of pointers to the functions that implement the functions declared in the interface, in the order that they are declared in the interface. The in-process invocation call overhead is therefore identical to virtual method calls in C++.[2]

  1. ^ The Component Object Model Specification, archived from the original on 2004-02-15
  2. ^ "The Component Object Model". microsoft.com. Microsoft. 30 May 2018. Retrieved 12 February 2019.