Simple, stop using Borland Turbo C - it was old when I first pickd up version 3.1 nearly 20 years ago. Turbo C from that era doesn't have a iostream (no extension) file because it was released at a time before the stl was. Prior to that time, the functions were indeed found in iostream.h
As such, I'd expect that it also didn't define wchar_t - I don't even remember if multibyte stuff was around then, unicode certainly wasn't a consideration..
For what it's worth, I've still got a copy of Turbo C on 5 1/4" floppy discs - yes! The floppy floppies... Get a compiler from this century!
Get Code::Blocks with MinGW (~70MB download), or Visual Studio Express (couple hundred), hell - even DevCpp is less archaic than Turbo C.
(Oh, and you've indicated to me that it's overwhelmingly likely your compiler of choice through the inclusion of conio.h)