Window class

In computer programming a window class is a structure fundamental to the Microsoft Windows (Win16, Win32, and Win64) operating systems and its Application Programming Interface (API).

The structure provides a template, from which windows may be created, by specifying a window's icons, menu, background color and a few other features. It also holds a pointer to a procedure that controls how the window behaves in response to user interaction. It finally tells the operating system how much additional storage space is needed for the class itself and for each window created from it.