#include<iostream>
#include<string>

using namespace std;

void main(void){

string a;
string b;
string output;

// Fill the two strings
a = “Hello”;
b = ” World!”;

// Normal append of two strings
output = a + b;
cout << output << endl;

// Or without the output string variable
cout << (a + b) << endl;

// Using compound assignments += operator
output = a;
output += b;
// In fact you are saying output = output + b;
// So if you fill the string variables you get:
// Hello + World! = result in output.
cout << output << endl;
}

I hope that this joining strings example is somewhat easier to understand.