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000303_news@columbia.edu_Wed Jan 25 04:40:36 1995.msg
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From: jrd@cc.usu.edu (Joe Doupnik)
Newsgroups: comp.protocols.kermit.misc
Subject: Re: Need help.
Message-Id: <1995Jan25.104036.39192@cc.usu.edu>
Date: 25 Jan 95 10:40:36 MDT
References: <8j9IFUu00iWP859O8s@andrew.cmu.edu>
Organization: Utah State University
Lines: 137
Apparently-To: kermit.misc@watsun.cc.columbia.edu
In article <8j9IFUu00iWP859O8s@andrew.cmu.edu>, Mark Kuang Luo <luo+@CMU.EDU> writes:
> Hi:
> I need to find out for my networks class how Kermit allows all bytes
> to be displayed in 7-bit ASCII format. Is there a FAQ for Kermit, or a
> www page? Or if anyone has a short explanation, it would be appreciated.
-------------
Far be it from me to do your homework (I'm a Prof too, and my grad
networks class is slaving away on my IP packet fragment reassembly techniques
without many hints from me).
Your question is a little mysterious. Kermit does not display all
bytes as ASCII because not all byte values (code points in the jargon)
are displayable (printable in the jargon). Control codes aren't, for example.
Only one character set is ASCII, ASCII itself. Yet Kermit deals with many
different character sets.
In general, there isn't a way of answering adequately in a News
message, but I'll indicate the tip of the iceberg in a few sentences.
Display devices have one or two display "pages", named Graphics Left
(GLeft) and Graphics Right (GRight). GLeft is without a high bit set
in its code points and is often ASCII; GRight is for code points with
the high bit set and is a variety of character sets. VT100 terminals
have only GLeft and use control codes SO and SI to change to/from (Shift
Out / In, respectively) a replacement character set. VT200 and above
have GLeft and GRight, and they support ISO 2022 control sequences to
map character sets to either GR or GL. ISO 2022 says behind the GR/GL
display pair exists four pages named G0..G3 ready to move into GR/GL
upon command. Commands exist to load G0..G3 with character sets of
choice drawn from a secondary storage of many possible sets.
If you review cryptic doc msvibm.vt located on kermit.columbia.edu
in directory kermit/a you will see the command sequences to load GR/GL
from G0..G3, to shift in/out, and so on. That's hard to understand without
also reading the ISO 2022 doc, but we can't reproduce the latter item
(copyright, etc). A cutout of some interesting pieces of msvibm.vt are
appended below. If you have access to DEC VT200/300/400 technical manuals
then they have good pictures and discussion of the ISO 2022 mechanisms.
Joe D.
---------------
ESC ( <ident> SCS Designates 94 byte character set <ident> to G0
ESC ) <ident> SCS Designates 94 byte character set <ident> to G1
ESC * <ident> SCS Designates 94 byte character set <ident> to G2
ESC + <ident> SCS Designates 94 byte character set <ident> to G3
ESC - <ident> SCS Designates 96 byte character set <ident> to G1
ESC . <ident> SCS Designates 96 byte character set <ident> to G2
ESC / <ident> SCS Designates 96 byte character set <ident> to G3
<ident> size character set
A 94 UK-ASCII (ASCII, sharp sign 2/3 replaced by
Sterling sign), strictly only when a VT102
but permitted by Kermit also for VT220/VT320
A 96 ISO Latin-1 (default in G2, G3)
B 94 ASCII (default in G0, G1)
0 94 DEC Special Graphics (line drawing)
1 94/96 Kermit, ALT-ROM
2 94 DEC Special Graphics (line drawing)
%5 94 DEC Supplemental Graphics
< 94/96 User Preferred Supplemental Set*
> 94 DEC Technical set (from VT340's)
H 96 Hebrew-ISO (ISO 8859-8)
"4 94 Hebrew-7
* VT300 terminals give choice of ISO Latin-1 (96) or DEC Supplemental
Graphics (94) determined by a Setup menu selection or host command. VT420
Hebrew terminals add choices of Hebrew-ISO and Hebrew-7. MS-DOS Kermit has
DEC Supplemental Graphics as the startup UPSS character set.
If the size of the character set does not match the <ident> nothing happens.
Startup defaults are ASCII in G0 and G1, ISO Latin-1 in G2 and G3, GL points
to G0, GR points to G2. Activating DEC National Replacement Characters maps
the NRC set selected by SET TERMINAL CHARACTER-SET <country> into G0..G3.
Single and Locking shifts, SS2, SS3, LS0 (SI), LS1 (SO), LS1R, LS2, LS2R, LS3,
LS3R determine which set is mapped to the GLeft or GRight area.
ESC n LS2 Map character set in G2 to GL, locking shift
ESC o LS3 Map character set in G3 to GL, locking shift
ESC | LS3R Map character set in G3 to GR, locking shift
ESC } LS2R Map character set in G2 to GR, locking shift
ESC ~ LS1R Map character set in G1 to GR, locking shift
Control Codes in C0 (no high bit) Area:
Name ASCII value
chart hex keyboard operation
SO/LS1 0/14 0eh ^N Map character set in G1 to GL, locking shift
SI/LS0 0/15 0fh ^O Map character set in G0 to GL, locking shift
Control codes in C1 (high bit set) Area:
Name ASCII value
chart 8-bit 7-bit operation
SS2 8/14 8eh ESC N Map G2 to GL for next char only, single shift
SS3 8/15 8fh ESC O Map G3 to GL for next char only, single shift
Character sets:
VT320 Character set storage areas
G0 G1, G2, and G3
------------------------------- --------------------------------
Any 94 char set Any 94 or 96 char set
ASCII ("B"/94) default G1 default is ASCII ("B"/94),
G2 and G3 defaults are
ISO Latin-1 ("A"/96)
Special Graphics ("0"/94, "2"/94)
Alt-Rom ("1"/94) (MS-DOS Kermit only)
Supplementary Graphics ("%5"/94)
Technical (">"/94) (from VT340)
User Preferred, UPSS, if Suppl Gr. UPSS if ISO Latin-1 or Suppl Gr.
DEC-Hebrew or Hebrew-ISO
National Replacement Characters are forced into all sets when activated
by CSI ? 42 h but only if a <country> has been previously selected by
SET TERMINAL CHARACTER-SET <country>
VT102 Character set storage areas
G0 and G1 G2 and G3
-------------------------------- ----------------------------------
ASCII ("B"/94) Default ASCII ("B"/94) Default
Special Graphics ("0"/94, "2"/94)
Alt-Rom ("1"/94) (MS Kermit only)
Supplementary Graphics ("%5"/94)
Technical (">"/94) (from VT340)
National Replacement Characters Always ASCII ("B"/94)
are selected and activated by
SET TERMINAL CHARACTER-SET <country>
and affect only G0 and G1.
Request CSI ? 26 n keyboard dialect
Response CSI ? 27; Ps n in MS Kermit this is controlled by
command SET TERMINAL CHARACTER-SET <country>
Ps Country Ps Country
1 North American/ASCII 9 Italian
2 British 13 Norwegian/Danish
8 Dutch 16 Portugese
6 Finnish 15 Spanish
14 French 12 Swedish
4 French Canadian 11 Swiss (German)
7 German 14 Hebrew