Re: switching ISO 2022 <-> Unicode

From: Kenneth Whistler (
Date: Thu Jan 16 1997 - 18:16:13 EST

> 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?

^G^G^G^G^G, as in ding! ding! ding! ding! ding!

The Unicode architecture has explicitly foresworn such escapes (within
Unicode) to other encoding schemes.

An ISO 2022 implementation which makes use of ISO 10646 can use the
announcement mechanism to break out of 10646, if it so desires.

The revised language of 10646, Clause 17.5 states:

"When the escape sequences from ISO/IEC 2022 are used, the identification
of a return, or transfer, from UCS to the coding system of ISO/IEC 2022
shall be by the escape sequence ESC 02/05 04/00. If such an escape
sequence appears within a CC-data-element conforming to ISO/IEC 10646,
it shall be padded in accordance with clause 16."

> The very reason for this is the fact that some CJK encodings (e.g. CNS)
> can't be covered with Unicode, but Western languages are most easily
> implemented in Unicode.

The Unicode (as opposed to 2022+10646) approach is to get as much of
CNS covered via standard codes as possible, and if the rest is required
for representation in Unicode, to use user space (including the 131,000+
codepoints accessible via UTF-16).

--Ken Whistler

> Werner

This archive was generated by hypermail 2.1.2 : Tue Jul 10 2001 - 17:20:33 EDT