#include <iostream>

void
myfunc (double la, double lb, double &lc)
{
// a and b are parameters called by value, c is called by reference
  double x = 2 * la;		// x is a local variable, only available in this function
  lb = x;
  lc = x;
}

main ()
{
  double a = 3;
  double b = 0;
  double c = 0;
  myfunc (a, b, c);  // call the function c and lc are identified
                     // a is copies into la, b is copied into lb
  cout << a << "\t" << b << "\t" << c << "\n";	// this will print 3 0 6
}