On Thu, 23 Oct 1997, John Cowan wrote:
> Martin J. Dürst wrote:
> Thanks for your comments, Martin.
> > There can also be triple-byte (and quadruple-byte,...) sets, together
> > with double-byte sets called multibyte sets. And these can also be
> > 96 x 96 (x 96...).
> Are these used in practice?
Not that I know. But there could be private uses.
> > Some can have two bytes for designation, or more, in the future.
> But not now used in practice, correct?
Yes. But you should either label your document as "features of
ISO 2022 currently (widely) used", or do something else to avoid
that people think that what you describe is all of ISO 2022.
> > To use ISO 2022, you always need a common agreement, or some
> > additional introductory ESC sequences.
> Are these introductory sequences used in practice?
Not that I have seen them. But that doesn't mean much.
> > > ISO 2022 decoding affects input bytes in the ranges 33 to 126 and 160 to 255,
> > > known as "the left half" and "the right half" respectively. All other bytes,
> > > unless they belong to a control sequence shown in this document, remain
> > > unchanged.
> > No. There is a quite similar, although somewhat simpler, system,
> > for control character blocks.
> I didn't know about this part.
Have you ever read the standard? If not, you should do that if you
want to write an explanation or a summary.
> > Also, please note that
> > ISO-2022-JP is not in fact conformant to ISO 2022, despite its name,
> > because it uses designations only, anew on each line, whereas
> > the basic idea of ISO 2022 is to use designations once, or once on
> > each line, and then only invocations. This is clearly stated in
> > the new version of JIS 208, namely JIS X 0208:1997, Appendix 2
> > (normative), Note to item 1.
> ISO-2022-JP swaps different character sets in and out of G0.
> While this may not be the best practice in some sense, it seems
> unlikely to me that it's actually forbidden.
The swapping of different character sets in and out of G0 is
not at all forbidden. It is one of the core features of ISO
2022, called designation. But some other details of ISO-2022-JP
are wrong, at least as far as JIS X 0208:1997 goes. I would
have to find out what these details are.
> > I still think that for understanding ISO 2022, it's best to look
> > at the standard itself.
> Until today (special thanks to Werner Lemberg), I didn't know where
> ISO 2022 could be obtained except by shelling out $$$$.
Yes, you have to pay some $$$. But 2022 is rather thin, and
I guess it would be around 10 Pounds or so in the UK. Of course,
getting it from ECMA for free is even better :-).
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