Re: Terminal Graphics Draft 2

From: Frank da Cruz (
Date: Thu Oct 08 1998 - 17:33:12 EDT

John Cowan wrote:

> I agree with Rick: don't propose characters that someone might need
> someday. There are quite enough characters, and indeed whole
> scripts, that are not yet available!
> > 2421 7F DEL DT Symbol for Delete (3)
> [...]
> > (3) Not, strictly speaking, a control character, but not a visible
> > one either.
> DEL is a control character in every sense, despite its position at 7F.
It depends who you ask. ISO 6429, 3rd Edition, 1992, says (in Annex F,
section 8.1) "The character DELETE..., not being a control function in the
strict sense, has been removed from the body of this International Standard."

DELETE and SPACE are special to ISO 4873 and ISO 2022, in which "character
sets" (as we think of them, monolithically) are actually composed of a control
portion (C0 or C1), SPACE (or not), a graphics portion, and DELETE (or not).

SPACE is a character set unto itself, and so is DELETE. If one is present,
the other must be too, in which case the graphics set is a 94-byte character
set (with a little "byte" taken out of the northwest and southeast corner),
and this is crucial to its identification. When SPACE and DELETE are not
present, it is a 96-byte set (such as "the right half of ISO-8859 Latin
Alphabet 1").

> > 5.3. EBCDIC Control Pictures
> Note: the EBCDIC/Unicode mapping tables at the Unicode FTP site
> map the EBCDIC-specific controls onto the C1 space, but the mapping
> seems to make no sense. For example, EBCDIC 09 (Superscript)
> is mapped to Unicode 008D (Reverse Line Feed). Why?
IBM provides its own EBCDIC / ASCII control-character mapping in the CDRA.
Of course it is inadequate as there are 64 EBCDIC control characters (three
undefined), but there are only 32 in ASCII.

In any case, we don't care about ASCII/EBCDIC mapping here. The need is
for glyphs for visual representation of each EBCDIC control character,
by name so people who live in the EBCDIC / 3270 world who must debug EBCDIC
and/or 3270 data streams using Unicode-based software will be able to see
these control characters represented by the names they are known by in
the EBCDIC/3270 world.

- Frank

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