WINAPI

WinAPI, short for Windows API, is the core set of application programming interfaces provided by Microsoft Windows that enables native applications to interact with the operating system. The term most often refers to the Win32 API, the 32-bit API that forms the foundation for Windows desktop applications; these interfaces continue to be available on 64-bit editions and newer Windows versions.

The Win32 API is composed of a large collection of functions exposed by system DLLs such as kernel32.dll, user32.dll, gdi32.dll, and advapi32.dll, among others. Applications traditionally include Windows.h to access these declarations and link against the corresponding libraries to call the APIs. The API covers a wide range of subsystems, including window creation and message handling, file and I/O operations, process and thread management, synchronization, networking, registry access, graphics, multimedia, and security.

Programs written against the Win32 API are typically written in C or C++, though other languages provide bindings or wrappers and can call the APIs via language-level interop. The API is event-driven, relies on a message loop, and uses a window procedure to process messages such as paint, input, and system notifications.

Over time, Windows introduced complementary interfaces such as the Windows Runtime for modern apps; however, the Win32 API remains the standard for traditional desktop applications and is preserved for backward compatibility. The API is well documented by Microsoft and supported across Windows versions, with new features added in tandem with Windows releases.