Hi Brent,
This is great advice from James.
I've been writing in RPG for the last 37 years and started out with the RPG Cycle. Having written in Assembler & Cobol before, it was hard to understand, but once you grasp that you don't need to worry about Opening & Closing files and other mundane programming tasks, it becomes very useful. Send any messages my way and I will be only too happy to help.
One area that I am very poor on is developing programs using sub-files with interactive screens.
Rgrds,
Alan McKenzie
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From: RPG400-L [mailto:rpg400-l-bounces@xxxxxxxxxxxx] On Behalf Of James H. H. Lampert
Sent: 27 April 2017 06:39 PM
To: RPG programming on the IBM i (AS/400 and iSeries) <rpg400-l@xxxxxxxxxxxx>
Subject: Re: New to RPG
The only thing I can think of to add is this:
DON'T BE AFRAID TO TAKE A RIDE ON "THE CYCLE."
Because of RPG's history (it's name means "Report Program Generator"),
it's designed to process entire files, and as such, every RPG program
(unless, in the more recent versions of RPG, you explicitly disable it)
runs inside an implicit "DO UNTIL *INLR = TRUE" loop, and if you
designate a file as the "Primary File," each iteration of that implicit
do-loop begins with a read operation on that file, raising the "LR"
indicator when the last record of the file is read.
If you designate a Primary File, then The Cycle allows you to "ride"
through the file, processing each record in sequence, instead of having
to "walk" through it.
And if you don't designate a Primary File, then The Cycle can be used as
a built-in event loop for an interactive program: all you need to do is
raise the LR indicator whenever the user is ready to exit.
If you don't have a use for The Cycle in a given program, then you need
to either disable it explicitly, or else make sure LR gets raised.
WHAT YOU DO NOT WANT TO DO IS IGNORE "THE CYCLE." If you ignore The
Cycle, it will run over you.
--
JHHL
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