Active Template Library
The Active Template Library (ATL) is a collection of C++ templates included in Microsoft Visual C++ version 4.0 and greater. This template library is intended specifically to facilitate the creation of Component Object Model (COM) objects.
Although you can create a pipeline component using any development environment that supports the creation of COM components, the use of the ATL is recommended because it creates small, fast code. COM components created using the ATL are smaller and faster than other approaches to component creation, including approaches supported by Visual C++. Although you can easily create COM components using the Microsoft Foundation Classes (MFC) library, you incur the significant memory overhead that is occasioned by using a large class library.
For information about the Active Template Library, see the ATL tutorial, which is included with Microsoft Visual C++.
See Also
Building the ATL Pipeline Component Wizard