Win16

Major versions

• Win16 is in the 16-bit versions of Windows. The functions reside mainly in core files of the OS: kernel.exe (or krnl286.exe or krnl386.exe), user.exe and gdi.exe. Despite the file extension being EXE, such a file is accessed as a DLL.
• Win32 is in the 32-bit versions of Windows (NT, 95, and later). The functions are implemented in system DLL files including kernel32.dll, user32.dll, and gdi32.dll. Win32 was introduced with Windows NT. In Windows 95, it was initially referred to as Win32c, with c meaning compatibility or chicago. This term was later abandoned by Microsoft in favor of Win32.
• Win32s is an extension for the Windows 3.1x family of Microsoft Windows that implemented a subset of the Win32 API for these systems. The "s" stands for "subset".
• Win64 is the version in the 64-bitplatforms of the Windows architecture (as of 2021, x86-64 and AArch64). Both 32-bit and 64-bit versions of an application can be compiled from one codebase, although some older API functions have been deprecated, and some of the API functions that were deprecated in Win32 were removed. All memory pointers are 64-bit by default (the LLP64 model), so porting Win32-compatible source code includes updating for 64-bit pointer arithmetic.
• WinCE is the version in the Windows CE operating system.