Windows API - Versions

Versions

Almost every new version of Microsoft Windows has introduced its own additions and changes to the Windows API. The name of the API, however, remained consistent between different Windows versions, and name changes were kept limited to major architectural and platform changes for Windows. Microsoft eventually changed the name of the then current Win32 API family into Windows API, and made it into a catch-all term for both past and future versions of the API.

• Win16 is the API for the first, 16-bit versions of Microsoft Windows. These were initially referred to as simply the "Windows API", but were later renamed to Win16 in an effort to distinguish them from the newer, 32-bit version of the Windows API. The functions of Win16 API mainly reside in the core files of the OS: kernel.exe (or krnl286.exe or krnl386.exe), user.exe and gdi.exe. Despite the file extension of exe, these actually are dynamically linked libraries.
• Win32 is the 32-bit API for modern versions of Windows. The API consists of functions implemented, as with Win16, in system DLLs. The core DLLs of Win32 are kernel32.dll, user32.dll, and gdi32.dll. Win32 was introduced with Windows NT. The version of Win32 shipped with Windows 95 was initially referred to as Win32c, with the "c" standing for "compatibility", but this term was later abandoned by Microsoft in favour 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 variant of the API implemented on 64-bit platforms of the Windows architecture (as of 2011 AMD64 and IA-64.) Both 32-bit and 64-bit versions of an application can be still compiled from a single codebase, although some older APIs have been deprecated, and some of the APIs that were already deprecated in Win32 were entirely removed. All memory pointers are 64-bit by default (the LLP64 model), so the source code has to be checked for compatibility with 64-bit pointer arithmetic and rewritten as necessary.
• WinCE is the implementation of the Windows API for the Windows CE operating system.