    //  Cout is used to print to the standard output device which
    //  is usually a terminal window.

        cout << "Hello world" << endl;

    //  Technically endl is a strange beast, but it basically ends
    //  up being like using a new-line character.

        cout << "Hello world\n";

    //  Using endl will send a new-line and it will force data to be
    //  written to the device or file.  Usually '\n' does the same
    //  thing but not always.

        cout << "The sum is " << sum << endl;

    //  Notice the space in the string before printing the variable
    //  sum.  It looks nicer to have a space before a number.