W32

W32 commonly refers to Win32, the 32-bit application programming interface for Microsoft Windows. It denotes the set of functions, data structures, and conventions that native Windows applications use to interact with the operating system. The term is used in both a historical and practical sense to describe software written for 32-bit Windows environments.

The Win32 API originated with Windows NT and became the standard programming interface for Windows in the 1990s, extending into Windows 95/98 in its 32-bit capacity. It provides core subsystems for user interface and input (such as User32 and related messaging), graphics (GDI and GDI+), and system services (Kernel32, Advapi32), as well as file I/O, networking, threading, synchronization, and more. Programs are traditionally built as 32-bit PE executables that run in user mode and may invoke kernel-mode services through defined system calls.

On modern systems, Win32 software remains widely used for desktop and server applications. 64-bit Windows supports Win32 applications through compatibility layers such as WoW64, enabling 32-bit executables to operate on 64-bit hardware. While newer Windows APIs and frameworks, such as the Windows Runtime, exist, Win32 continues to provide a broad and mature foundation for application development and maintenance.

Terminology note: W32 is sometimes used informally to refer to the Win32 API, but the abbreviation can also appear in different contexts, including the naming of certain Windows-based malware families. When encountered, it is important to confirm the intended reference to avoid confusion.