"Changing" parameter and "Tables" parameter defintions in function module
If one defines "Changing" or "tables" parameters, they are treated as reference parameters.
It becomes obvious for "tables" parameters where one does not have option to check box for "Pass by Value". But for "Changing" parameters, they provide the checkbox for "Pass by Value". Even when you select this option, the function module seems to handle the parameter as a reference parameter (whatever changes you make to it in the function module are retained when you return back to a calling program).
My question is why then SAP has provided the checkbox of "Pass by Value" for "Changing" parameter?