Re: "Coding system"? Eh?

[Lars Magne Ingebrigtsen <larsi@gnus.org>]

Michael Welsh Duggan <md5i@cs.cmu.edu> writes:

> No, not really.  A character set is merely a set of characters.
> latin-1, etc, are often called character sets because they use the
> same number of characters as extended ASCII, etc.  A coding-system is
> just that: a coding-system.  The characters could be encoded any which
> way (including encrypted!).  For example, old-jis uses escapes around
> sequences of 7-bit characters.  This is an encoding, which you can
> display using a character set, but not a character set in and of
> itself.

All texts consists of characters (from some character set) encoded
(using some coding system).  iso-8859-1, for instance, represents the
character LATIN-LETTER-A-WITH-UMLAUT ("ä") with one byte that contains
the number 0xe4.  The same letter encoded in a different charset (say,
Unicode) would occupy two bytes.  Other character sets use multiple
bytes to represent characters, like iso-2022-jp.

When one talks about character sets (in, say, MIME) one talks about
encoded character sets.  Abstract character sets aren't all that
interesting when fiddling with data.  iso-8859-1, which MULE calls a
coding system, is something everyone else calls a character set.  The
same with old-jis and iso-2022-jp.

Or something.  

-- 
(domestic pets only, the antidote for overdose, milk.)
  larsi@gnus.org * Lars Magne Ingebrigtsen