Windows API

The Windows API (WinAPI) is the foundational, native application programming interface for Microsoft Windows, enabling programs to access core operating system services.

The Windows API is the essential system interface for developing desktop and server applications on Windows: it is the direct path to OS capabilities. Formerly known as the Win32 API, it comprises thousands of functions implemented in core system DLLs, including `kernel32.dll` (for process/memory management), `user32.dll` (for windowing and user input), and `gdi32.dll` (for graphics). Developers use this C-compatible API to perform critical tasks: creating windows, managing file I/O, controlling threads, and accessing security components. It is the lowest-level, most direct method for an application to interact with the Windows operating system kernel.

https://learn.microsoft.com/windows/win32/