parameters value reference

Question 1

what is passing a parameter by value

Answer 1

A local copy of the data is used
Data is discarded when the
subprogram exits
Does not override/change the original
data

Question 2

what is passing a parameter by reference

Answer 2

address of the parameter is given to the subroutine, so the
value of the parameter will be updated at the given address. Changes remain after the subprogram
exits