Parameter Modes
To define the behavior of formal parameters you use the parameter modes. The 3 parameter modes, IN, OUT, & IN OUT, can be used with any subprogram. Though, avoid using the OUT and IN OUT modes with functions. The aim of a function is to take zero or more arguments and return a single value. To have a return function, multiple values is a bad programming practice. The functions should also be free from the side effects that change the values of variables not local to the subprogram.