Re: Coding Systems Different from ISO 2022

From: Markus Kuhn (
Date: Tue Oct 13 1998 - 06:58:05 EDT

John Cowan wrote on 1998-10-13 06:49 UTC:
> Frank da Cruz scripsit:
> > Can anybody tell me where to find out what ISO means when it assigns an ISO
> > 2022 escape sequence for a "coding system different from ISO 2022" (such as,
> > for example, NAPLPS, or UCS-4, or UTF-8)? Is the intention to identify the
> > coding system to the recipient, so it can switch to it, and also disable
> > ISO-2022 character-set designation and invocation from that moment onwards,
> > since we have now switched to a new coding system in which we will not
> > necessarily be able to recognize escape sequences for further switching?
> Just so. There's no way back.

That is not entirely correct. There are several ISO 2022 ESC sequences for
UTF-8 registered on <>

ESC %G means: UTF-8 with no level specified, standard return by ESC %@
                 is possible (this is the one the Linux console driver
                 has supported for several years and which is already
                 being used by some applications).

ESC %/G means: UTF-8 with level 1 implementation, no standard return
                 (so a return to ISO 2022 would be via other means such
                 as a terminal reset if ISO 2022 is the default power-on

and there are also ESC %/H and ESC %/I for level 2 and level 3 with no

I expect just plain ESC %G to to become the most widely used sequence
in terminal emulators, but it won't hurt to support all variants.


Markus G. Kuhn, Security Group, Computer Lab, Cambridge University, UK
email: mkuhn at,  home page: <>

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