VM (CMS) follows the same 3270 data stream protocols as does
"MVS". So the 3270 emulation is where the code pages have to be
effected for the "workstation".
I say this because I used two different 3270 emulators for CMS
(QWS3270 & HOD) and one gets the same issues with "NOT" and the
like. Throw in a VTAM session manager, and you get some funny
things happening there too. But it has been over 10 years since I
did that with other than HOD.
HOD in my opinion has other issues being written with Java(?) and
the developers/support people apparently not having access to
z/OS, and apparently not understanding they are emulating a 3270
device.... sigh.
Steve Thompson
On 10/10/2023 3:23 PM, Seymour J Metz wrote:
It depends on the software that you're using. I'll addres ISPF on z/OS because
I'm more familiar with that than, e.g., z/VM.
Worst case the data stream is subject to translation on the MVS side by both
ISPF and VTIOC (TSO/VTAM IOC), both allowing the user to control the
translation. On the PC side you also have page table issues; the details depend
on which TN3270 code page you're using.
For upper case A it's pretty easy; the common code pages share code points
'20'X through '7F'X with ASCII. But for Logical Not (¬, '5F'X) the client might
use either 'AA'X or 'AC'X even if UTF-8 isn't in play.
Peter: does ISPF bypass VTIOC translation?
________________________________________
From: IBM Mainframe Discussion List <IBM-MAIN@LISTSERV.UA.EDU> on behalf of
jgmauta...@yahoo.com.ar <000001f9499d67db-dmarc-requ...@listserv.ua.edu>
Sent: Tuesday, October 10, 2023 12:18 PM
To: IBM-MAIN@LISTSERV.UA.EDU
Subject: TN3270, EBCDIC and ASCII
Hi!
I want to understand how TN3270 emulation works regarding convertion of
characters (between EBCDIC and ASCII, and viceversa).
This is how I think it works (more or less), but I am not sure at all. So
please let me know about any mistakes.
Let suppose that you use a TN3270 emulator program to access the ISPF browser to display a dataset.
Let also assume, to simplify, that it contains just a single character, an "A".In DASD,
what is indeed stored is X'C1' or, to be more accurate, BINARY'1100 0001'. When you BROWSE the
dataset, then the Mainframe sends to the TN3270 PC client exactly X'C1' (BIN'1100 0001'). No
convertion is done at the Mainframe side. Then, when the TN3270 client receives X'C1', because it
knows that this is a TN3270 session and that its configured CODEPAGE is say 500, it realizes that
X'C1' corresponds to an "A" displayable character. And, before sending the instruction to
display it on the PC screen, it converts X'C1' to X'41'.
Is this more or less how this works?
Thanks in advnace for your help,
Juan Mautalen
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