Argument passing

• Arguments are passed from the calling function to the called function in two possible ways:
  1. by value
  2. by reference
• Passing by value (default): the calling function makes a copy of the argument and passes the copy to the called function; the called function cannot change the argument
  double performSum(double op1, double op2);
• Passing by reference (prepend a &): the calling function passes the argument directly to the called function; the called function can change the argument
  void increaseArgument(double& arg) { arg++; }