Re: switching ISO 2022 <-> Unicode

From: Martin J. Duerst (
Date: Fri Jan 17 1997 - 12:06:44 EST

On Thu, 16 Jan 1997 John Plaice wrote:

> > Werner LEMBERG wrote:
> >
> > > ISO 2022 has a mechanism to change to other encoding schemes. It would be
> > > nice to have a certain control character in Unicode which do a similar
> > > thing.
> > > Comments?

> Rick wrote:

> > And the CNS issue is something that the CJK IRG is working on, certainly,
> > and eventually there will (likely) be a solution that satisfies the
> > community which needs the said CNS characters.

Specifically, in addition to the ~21000 CJKV ideographs in Unicode 2.0,
around ~7000 have been approved as extension A. They will go either into
the base plane or into plane 2, which is a plane completely reserved
for ideographs. More extensions are being worked on, as well as a
more general "composition" mechanism for ideographs.

> >I wouldn't look upon
> > this as a permanent disability of Unicode. If you have specific character
> > requirements, you could forward those. I'm under the impression that
> > Unicode's CNS coverage is already adequate for all but the most obscure
> > situations.
> Be serious, Rick, there will ALWAYS be characters that are not encoded
> in Unicode, for various reasons. The fact that Unicode does not provide
> for other means for encoding other character sets ensures that people
> who are forced to deal with such characters will have to come up with
> ad hoc means for setting up character set changes.

There are ~6000 private positions in the BMP, and ~130,000 in UTF-16.
For quite some time, until work is completed on rare, historical, and
obscure scripts in ISO 10646/Unicode, there will be a need to encode
characters that are not yet defined.
But the need for character set changes such as switching changes does
not follow from the need to encode not-yet-defined characters for
some specific purpose.

Regards, Martin.

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