for the predefined streams, it's safe to mix C stdio and C++ iostreams. you can safely use stdin and std::cin in the same program; the C++ Standard guarantees that it will work the way you would expect it to.
if you don't need to mix C stdio and C++ iostreams on the same stream, you can get better performance by turning this feature off std::ios_base::sync_with_stdio(false); however, if you need to open a file with C++ iostreams, and at the same time access that file as a C FILE*, there's nothing in the C++ standard to support that usage by default. however, the library is extensible, and a std::streambuf derived class that supports this is just a couple of dozen lines of code.
im creating a program with both stdio.h and iostream.h in the include header.
Can the program run with them both? or others?
As Ancient Dragon mentioned: change <iostream.h> to <iostream>. If this doesn't work on your compiler (probably Turbo...), you need to update your compiler to a modern one. Visual Studio (c++) 2008free for example.
Here's a nice thread with some explanation about headers and also a list of which header are c/c++ standard and what they do.