VC++ automatically adds external dependencies

[Indyishere]

I am learning c++ and am working on a homework I found somewhere. I have some exp with c and have read about c++.
The picture found following the link contains the entire code.
The thing that puzzles me is the External Dependencies.

I have included <ctime> in my header file and therefore it is defined wherever it is used, but my VC++ adds this external dependencies. What is it for anyway?

I am working in (somewhat old) Microsoft VC++ (1994-1998).

[Indyishere]

I guess the link is to a tag, so here is the link to the image:
http://img529.imageshack.us/img529/6223/prob.jpg