Windows API

Windows API
	The Win32 subsystem shown next to the POSIX and OS/2 subsystem in the architecture of Windows NT (later Win64 is also available.)
Developer(s)	Microsoft
Initial release	November 20, 1985
Operating system	Microsoft Windows, OS/2
Predecessor	DOS API
Type	API
License	Proprietary
Website	https://learn.microsoft.com/en-us/windows/apps/

The Windows API, informally WinAPI, is the foundational application programming interface (API) that allows a computer program to access the features of the Microsoft Windows operating system in which the program is running.

Each major version of the Windows API has another name that identifies a compatibility aspect of that version. For example, Win32 is the major version of Windows API that runs on 32-bit systems. The name, Windows API, collectively refers to all versions of this capability of Windows.

Microsoft provides developer support via a software development kit, Microsoft Windows SDK, which includes documentation and tools for building software based on the Windows API.