Well ok, the two standards are overlapping where it makes sense, I stand corrected there. But nothing prevents me from writing C or C++ programs on Windows whi

Well ok, the two standards are overlapping where it makes sense, I stand corrected there. But nothing prevents me from writing C or C++ programs on Windows which don't have a single POSIX (or even libc call) in them, but exclusively use Windows system DLL calls - and those are still entirely valid C or C++ programs (although I'm aware that the situation is muddy for some libc calls which some compilers treat like builtins, e.g. memset and memcpy).