### Source for a Simple C++ Program

    /************************************************************************
    *

The following is a simple C++ program containing declarations, expressions, statements, and two functions:

                                                                            *
    ************************************************************************/

    /**
     ** A simple C++ program containing declarations,
     ** expressions, statements, and two functions:
     **/

    #include <math.h>                         // contains definition of abs()
    double multiplier, common_ratio;          // variable declarations
    double geo_series(double a, double r)     // function definition
    {
          if (r == 1)                         // if statement
                return -1.0;                  // return statement
          else if (abs(r) < 1.0)              // else if statement
                return (a / (1 - r));         // statement containing
                                              // expression
          else return -2.0;
    }
    void main()                // program execution begins here
    {
          double sum;          // variable declaration
          multiplier = 2.2;    // initialization of external variable
          common_ratio = 3.1;  // initialization of external variable
          sum = geo_series(multiplier, common_ratio); // function call
          // ..
    }