Win32 API (hereinafter WinAPI) – a set of functions (API – application programming interfaces), running under Windows environment. These functions are contained in windows.h library.
Windows API is designed to be used with C language to write the applications under MS Windows operating system environment. Windows API is the closest way to interact with operating system from the application level. The lower level access is required only for device drivers in the current versions of Windows and is available through the Windows Driver Model.
Windows API is a set of functions, data structures and numerical constants, that follow C language conventions. All programming languages that can call to such functions and to operate these types of data in the programs executed under Windows, can use this API. In particular, the languages C++,
Pascal, Visual Basic, and many others.
Using WinAPI functions you can easily create different window procedures, dialog boxes, software and even games. This library, so far, is the base for the development of Windows Forms programming,
MFC, because these interfaces are add-ons for that library. If you master it, you will easily create forms and understand how this happens.