Exact difference between Call by Reference and Call by value

shrikanth_m · New User Joined: 19 Jan 2007 Posts: 5 Location: bangalore

Please explain me What is the difference between Call the sub-program BY REFERENCE AND CALL VALUE.....

though i read about it in the book, but i couldn't able to understand exactly....

Please some one help me out in this!

Thanks!
Regards
Shrikanth

William Thompson · Posted: Sun Jan 21, 2007 11:41 pm

By reference is the default (and the only way back in the olden days) and means that if the data item is in the calling program's working storage, the called program can alter it directly.
By value means that if the calling program refered to an item in its working storage, the called program ihas access to a duplicate of it, not the actual item.