The only time you might include source files is if you're using templates, and then it should be at the bottom of your header file. There's been plenty of examples of how to split your project into multiple source files, but here you go:
Code:
//program.cpp
#include "func.hpp" //hpp extension might be preferable
int main()
{
//...
}
Code:
//func.hpp
#ifndef FUNC_H_ //arbitrary macro name for include guard
#define FUNC_H_
//function prototypes and inline and template function definitions in headers
void Func();
inline void Func2()
{
//...
}
template <class T>
void Func3()
{
//...
}
#endif
Code:
//func.cpp
#include "func.hpp"
void Func()
{
//...
}
Edit: And if this doesn't help, I think we might need a more specific/complete example from you.