Microsoft’s docs are a self-contradictory tangled incomplete and sometimes even downright erroneous mess, I wouldn’t put too much stock in what they say.
If I say “CreateFile is the Win32 API analog of NtCreateFile in the NT native API”, everyone experienced with low-level Windows development will know what I am talking about. If I started talking about “Native System Services”, I’m not sure as many would.
Similarly, the distinction between APIs which are easy to call from C code (and simpler FFI frameworks from scripting languages, e.g. libffi) and COM/Automation/.Net/WinRT APIs which are a lot more difficult to use from C (as opposed to C++), and which require more advanced FFI support, is still important in Windows development (or at least some parts of it.) And in practice the term “Win32 API” is often defined to exclude those higher-level harder-to-call-from-plain-old-C APIs.
It goes back to the original design of Windows NT, where you had a primary environment subsystem (Win32), secondary environment subsystems (OS/2 and POSIX), and integral subsystems (local security authority, session manager, etc). The primary environment subsystem is still called Win32, and the Win32 API is its public API. (It also has private APIs, most notably the CSRSS LPC interface, but that’s unstable from version to version.). As I said “Windows API” is insufficiently specific because (especially nowadays) Windows has lots of other APIs. WinRT and Win32 are both Windows APIs but very different. WinRT is largely built on top of Win32, but some documented WinRT APIs are built on undocumented Win32 APIs, leaving WinRT the only officially supported API to access certain functions.
Microsoft intentionally didn’t rename Win32 to Win64 when they added 64-bit support because it is 99% the same API just with some highly regular changes (mainly widening pointers). By contrast, Win32 was a much more radical change to Win16 - the Win16 API directly incorporates notions of segmented memory, which it uses to implement movable memory blocks (rather similar to Classic MacOS, albeit that did it in a 24/32-bit flat memory model rather than a 16-bit segmented one). Microsoft could have done a more straightforward port of Win16 to 32-bit x86, e.g. using a 32-bit segmented memory model instead of 32-bit flat memory, keeping movable memory; but (thankfully) they didn’t. It would have made it a lot harder to move to 64-bit or non-x86 platforms.
If I say “CreateFile is the Win32 API analog of NtCreateFile in the NT native API”, everyone experienced with low-level Windows development will know what I am talking about. If I started talking about “Native System Services”, I’m not sure as many would.
Similarly, the distinction between APIs which are easy to call from C code (and simpler FFI frameworks from scripting languages, e.g. libffi) and COM/Automation/.Net/WinRT APIs which are a lot more difficult to use from C (as opposed to C++), and which require more advanced FFI support, is still important in Windows development (or at least some parts of it.) And in practice the term “Win32 API” is often defined to exclude those higher-level harder-to-call-from-plain-old-C APIs.
It goes back to the original design of Windows NT, where you had a primary environment subsystem (Win32), secondary environment subsystems (OS/2 and POSIX), and integral subsystems (local security authority, session manager, etc). The primary environment subsystem is still called Win32, and the Win32 API is its public API. (It also has private APIs, most notably the CSRSS LPC interface, but that’s unstable from version to version.). As I said “Windows API” is insufficiently specific because (especially nowadays) Windows has lots of other APIs. WinRT and Win32 are both Windows APIs but very different. WinRT is largely built on top of Win32, but some documented WinRT APIs are built on undocumented Win32 APIs, leaving WinRT the only officially supported API to access certain functions.
Microsoft intentionally didn’t rename Win32 to Win64 when they added 64-bit support because it is 99% the same API just with some highly regular changes (mainly widening pointers). By contrast, Win32 was a much more radical change to Win16 - the Win16 API directly incorporates notions of segmented memory, which it uses to implement movable memory blocks (rather similar to Classic MacOS, albeit that did it in a 24/32-bit flat memory model rather than a 16-bit segmented one). Microsoft could have done a more straightforward port of Win16 to 32-bit x86, e.g. using a 32-bit segmented memory model instead of 32-bit flat memory, keeping movable memory; but (thankfully) they didn’t. It would have made it a lot harder to move to 64-bit or non-x86 platforms.