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000295_news@columbia.edu_Tue May 2 14:44:20 1995.msg
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From: fdc@watsun.cc.columbia.edu (Frank da Cruz)
Newsgroups: comp.protocols.kermit.misc,comp.os.os2.apps
Subject: Re: OS/2 C-Kermit 191 and character set problem
Date: 2 May 1995 14:44:20 GMT
Organization: Columbia University
Lines: 95
Message-Id: <3o5gg4$88k@apakabar.cc.columbia.edu>
References: <1995May1.172104.121387@daniel>
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In article <1995May1.172104.121387@daniel>,
Paul Coen <pcoen@daniel.drew.edu> wrote:
: I've noticed a tendency for C-Kermit for OS/2 191 (final release) to have
: special character problems after you exit from any utility based on TPU
: (edit/tpu, DEC Notes, etc.).
:
: My character set is latin-1.
:
: Before entering Notes, for example, if I press the compose character key
: (alt-c) and then enter -: I get the w division sign without any problem.
:
: After I enter Notes and exit, the above sequence gives me a / instead of
: the line with two dots above and below. Other characters give me a ?
: instead of the proper character. For instance, I get a ? instead of
: the Icelandic eth character. Not that I use that, in all honesty,
: it was just an example.
:
: If I reset my terminal (alt-=) the problem goes away.
:
: Before entering Notes or TPU, my character set is:
:
: Terminal character-sets:
: Local: cp850
: Remote: GL->G0: ascii (94 chars)
: G1: latin1-iso (96 chars)
: GR->G2: latin1-iso (96 chars)
: G3: latin1-iso (96 chars)
:
: After exiting DEC Notes or TPU, we've got:
:
: Terminal character-sets:
: Local: cp850
: Remote: GL->G0: ascii (94 chars)
: G1: dec-special (96 chars)
: GR->G2: dec-multinational (96 chars)
: G3: latin1-iso (96 chars)
:
It seems you've answered your own question. The DEC Multinational
Character Set (DEC MCS) is similar to, but not identical with, Latin-1.
The differences are pretty much as noted -- DEC MCS has "undefined" cells
where Latin-1 has Icelandic letters (and a couple others), and MCS has
OE/oe "ligature" in place of multiply and divide.
: I would assume that this change is the root of the problem, since the
: reset puts it back. I guess my question is whether TPU-based programs
: don't clean up after themselves, or if C-Kermit should be resetting
: itself and isn't. This problem does not occur in MS-Kermit 3.14, but
: for all I know, MS-Kermit may not implement host-directed character set
: changes the same way.
:
The session log (that Paul sent under separate cover to illustrate this
report) contains the following mysterious control sequences:
ESC [ 1 ; 2 ' z
ESC [ 1 ; 3 ' {
ESC [ 0 ' z
I can't find these in the VT220 Programmer Reference Manual or VT220
Programmer Pocket Guide, nor can I find them the VT320 or VT420 manual.
However, if the apostrophe (') were changed to dollar-sign ($), they would
be VT420 "rectangular area" functions. Prior to VT420, I don't think
there were any control sequences whose final characters were "z" or "{".
And since the sequences listed above are not valid for the VT420 itself,
I can only speculate that either (a) your VMS session was set for an even
higher VT level (e.g. 520), (b) TPU is malfunctioning, (c) TPU is using
undocumented escape sequences, or (c) there is something wrong with your
session log. A further piece of evidence is that your log contains some
stray 8-bit ST (String Terminator) C1 controls, which are not terminating
any string (such as would be introduced by DCS, APC, etc).
In any case, OS/2 C-Kermit is emulating a VT220. A real VT220 does not
support the Latin-1 character set, and so there is no way the host
application can "save and restore" it. Once it switches your terminal to
DEC MCS (as it does, by sending:
ESC * <
which designates DEC MCS to G2) it has no way of restoring Latin-1. For
example, if it sent the proper ISO escape sequence for this, which would be:
ESC * A
the VT220 would not understand it.
One might argue that CSI ! p (DECSTR, Soft Reset), which is supposed to
restore the VT200 startup default character sets (G0..G3, GL, GR) should
be interpreted by C-Kermit to restore the user's character-set
configuration, as specified in the most recent SET TERMINAL CHARACTER-SET
commands, but VAX Notes is not sending this sequence.
So in summary, yes, it is not surprising that one needs to push the
\Kreset button to get the character sets back to normal after a session
like the one that you recorded.
- Frank