Re: Externally-Described Field used as array name.

["Peter Dow" <pcdow@xxxxxxxxx>]

Hi Barbara, Hans,

Thanks for correcting me! I knew that. I don't know what I was thinking when
I sent that. Must be the heat -- gotta keep that a/c off so we have
electricity for the computers...

Regards,
Peter Dow
Dow Software Services, Inc.
909 425-0194 voice
909 425-0196 fax

----- Original Message -----
From: <bmorris@ca.ibm.com>
To: <rpg400-l@midrange.com>
Sent: Friday, August 24, 2001 10:05 AM
Subject: Re: Externally-Described Field used as array name.


>
> >From: "Peter Dow" <pcdow@yahoo.com>
> >Date: Thu, 23 Aug 2001 15:30:17 -0700
> >
> >The compiler sees PDLB02 in the data structure first, and allocates
memory
> >for it there.
> >
> >Then it sees PDLB02 in the input specs and wants to allocate memory for
it
> >within the input buffer, but it can't have a unique field name pointing
to
> >two different memory locations.
>
> Peter, the compiler doesn't allocate memory for input fields in the
> input buffer.  The input specs actually describe "move" operations
> from the input buffer to program fields.  The compiler uses the
> input spec information to generate definitions for you, if you don't
> already have explicit definitions.  (The memory for the input buffer
> is already allocated by database.)
>
> So it's perfectly normal and reasonable to have a D-spec definition
> for a field that appears in an input spec.  Just like it's normal and
> reasonable to have the same field in two different input specs, for
> two different files.
>
> Example:
>
> D FLD1        S        5P 0
> I              S   11   15 0  FLD1
>
> FLD1 is zoned(5,0) in the input spec.
> FLD1 is packed(5,0) on the D spec.
> The input spec says "move the zoned field in positions
> 11-15 of the input buffer to FLD1, whereever FLD1 happens
> to be".  This is one of the central features of RPG that
> makes it different from other languages.
>
> (You're not alone in thinking that I-specs are definitions.  It's
> one of the most common misconceptions about RPG.  The more common
> symptom of this misconception is thinking that if a field is zoned
> in the database, it must also be zoned in RPG.)
>
> Barbara Morris
>
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