// hello.h
// Header files should ONLY contain
// declarations (prototypes) and
// constants, but not variables.
void say_greeting(string name);
#include <iostream>
using namespace std;
#include "hello.h"
void say_greeting(string name)
{
    cout << "Hello " << name << endl;
}#include <iostream>
using namespace std;
#include "hello.h"
int main()
{
    say_greeting("Chris");
    return 0;
}