Maybe you don’t want to just use a sub-procedure in your program. Maybe you actually want to write the sub-procedure up as a small program and then call it from another program. Granted, that is not technically a sub-procedure, but we will let that go for the moment and concentrate on the call of one program by another.

By David Shirey

Editor's Note: This article is excerpted from article 8 of 21st Century RPG: /Free, ILE, and MVC, by David Shirey.

Back in the olden days, we would have used a CALL with a PARM list. But the regular, old CALL was not carried over into /Free. It wasn’t efficient enough. And so the new way to call from one program to another is via the CALLP, a prototyped call.

What is a prototyped call? Well, as we have already seen, it is a structured call where the parameters are defined in both the calling and the called program.