Thread: Get sense of internal linkage and external linkage

Took me ages to get a handle on this.

Say you have a main file and you want to use a function that prints a string:

Code:

//  main.cpp
#include <string>
#include "MyHeader.h"
using namespace std;

int main()
{
     string Welcome("Welcome to my program!");

     PrintString(Welcome);

     return 0;
}

Then you have a header file, which provides the link for the compiler to the PrintString() function.

Code:

//  MyHeader.h
#ifndef MYHEADER_H
#define MYHEADER_H

#include <string>
using namespace std;

void PrintString(string ToPrint);

#endif

Then you have the .cpp file that contains the code to PrintString()

Code:

//  PrintStr.cpp
#include <string>
#include <iostream>
#include "MyHeader.h"
using namespace std;

void PrintString(string ToPrint)
{
     cout << ToPrint;
}

The #ifndef and #define ensure that the file isn't included multiple times per file (i.e some other include also includes this header).
edit: Like how my .cpps include <string> but MyHeader also includes <string>