30 Input/output library [input.output]

30.4 Standard iostream objects [iostream.objects]

30.4.4 Wide stream objects [wide.stream.objects]

wistream wcin;
The object wcin controls input from a stream buffer associated with the object stdin, declared in <cstdio>.
After the object wcin is initialized, wcin.tie() returns &wcout.
Its state is otherwise the same as required for basic_­ios<wchar_­t>​::​init.
wostream wcout;
The object wcout controls output to a stream buffer associated with the object stdout, declared in <cstdio>.
wostream wcerr;
The object wcerr controls output to a stream buffer associated with the object stderr, declared in <cstdio>.
After the object wcerr is initialized, wcerr.flags() & unitbuf is nonzero and wcerr.tie() returns &wcout.
Its state is otherwise the same as required for basic_­ios<wchar_­t>​::​init.
wostream wclog;
The object wclog controls output to a stream buffer associated with the object stderr, declared in <cstdio>.