Is #include <ctime> necessary?

Question

I've done some programs that use rand(), but I've never included ctime library.
Do I need to include that?
I usually do include iostream and cstdlib and use:
rand(time(NULL))

Can anyone explain me that please? Tanks!

Answer 1

To use time() you need to include the time header.

Answer 2

There is a difference between compilers.