RE: Need for separate Input and Output Areas in Display File

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Cobol, RPG, and all AS/400 languages have separate input and output buffers.
It is not a language-dependent issue.  The 5250 data stream protocol outputs
one set of fields, and receives a [normally] smaller set of fields back.

In RPG, the programmer never sees the input and output buffers - the RPG
data handler moves fields from the buffers to fields that are mapped from
the buffers.

Cobol can probably simulate RPG - simply code a file layout record into
working storage.

For reads,
Read into the buffer, then move corr into working storage.

For writes, move corr to the buffer, then write from the buffer.  I think it
would be a similar effect.

-----Original Message-----
From: Ravi Prasanna Annasagara Nagarajan
[mailto:ravi.annasagara@wipro.com]
Sent: Tuesday, August 13, 2002 7:25 AM
To: cobol400-l@midrange.com
Subject: RE: Need for separate Input and Output Areas in Display File



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Terry,

Thanks for the reply. I know it is not necessary to define separate
Input and Output areas. I refer to the case that is shown below.

WORKING-STORAGE SECTION.
01  HEADER-OUTPUT.
    COPY DDS-HEADER-O   OF PAD0137NW.
01  HEADER-INPUT.
    COPY DDS-HEADER-I   OF PAD0137NW.

In this case, the HEADER record format has  seperate as Input and Output
Areas. What is the need for this?

As you said it is easier to code without seperating the two areas and
also eliminates the need for qualification. But what do you think is the
purpose of seperating the I-O area? I have been blinding doing this from
a long time, but have not understood the reason for seperating the I-O
area, hence the question.

I would be grateful for any inputs on this issue.


Thanks and Regards,
Ravi Prasanna A.N.
mailto:ravi.annasagara@wipro.com


-----Original Message-----
From: cobol400-l-admin@midrange.com
[mailto:cobol400-l-admin@midrange.com] On Behalf Of Winchester Terry
Sent: Tuesday, August 13, 2002 4:37 PM
To: 'cobol400-l@midrange.com'
Subject: RE: Need for separate Input and Output Areas in Display File


Ravi,

You're not required to have separate I-O areas in your program for a
display file.  There may be a slight performance advantage for sending a
smaller amount of data to the display but I have never noticed it.

Generally, I code all of my fields as B (input/output) and then use the
DSPATR(PR) and CHGINPDFT keywords on those fields that are only required
for output.  This allows you to copy only the *output* (-O) records into
your program. This eliminates the need for qualification and allows a
single record structure to work with.  I believe it makes the code
easier to understand.

Its also easier on my brain :)

Terry

> -----Original Message-----
> From: Ravi Prasanna Annasagara Nagarajan
> [mailto:ravi.annasagara@wipro.com]
> Sent: Tuesday, August 13, 2002 6:13 AM
> To: cobol400-l@midrange.com
> Subject: Need for separate Input and Output Areas in Display File
>
>
> This is a multi-part message in MIME format.
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> --
> [ Picked text/plain from multipart/alternative ]
> Hello
>
> This is a pretty basic question. Why do we need to separate Input and
> Output Areas in display file? Is there any advantage in that? The
> reason I am asking this question is because we do not do any such
> thing in RPG programs. So why is it required in Cobol programs? Does
> it provide any performance enhancements?
>
> Many thanks in advance.
>
> Regards,
> Ravi Prasanna A.N.
> mailto:ravi.annasagara@wipro.com
>
> --
>
>
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