#include <string> under iostream. At the end put string value in the parentheses, as your function declarations don't match. Then cout value. Actually, you'll probably learn more if I show you how to do this:
Now look over this and try to understand the changes I made. You'll learn more this way. Good luck
#include <string> //Need this for string
using namespace std;
string input ();
void output (string value);
int main ()
string thename = input();
output(thename); //Need this to get name. Notice the placement of input.
string input() //Move outside main
cout << "Enter your name" << endl;
cin >> name;
void output(string value) //Get the value in a parameter.
cout << "Hello " << value << endl;