Commit 3af970a0 authored by Kenichi Handa's avatar Kenichi Handa
Browse files

(Charsets): Update the description for the new charset.

(list-character-sets): New findex.
parent 7f1faf1c
......@@ -1620,30 +1620,48 @@ Use @kbd{C-x 8 C-h} to list all the available @kbd{C-x 8} translations.
@section Charsets
@cindex charsets
Emacs groups all supported characters into disjoint @dfn{charsets}.
Each character code belongs to one and only one charset. For
historical reasons, Emacs typically divides an 8-bit character code
for an extended version of @acronym{ASCII} into two charsets:
@acronym{ASCII}, which covers the codes 0 through 127, plus another
charset which covers the ``right-hand part'' (the codes 128 and up).
For instance, the characters of Latin-1 include the Emacs charset
@code{ascii} plus the Emacs charset @code{latin-iso8859-1}.
Emacs characters belonging to different charsets may look the same,
but they are still different characters. For example, the letter
@samp{o} with acute accent in charset @code{latin-iso8859-1}, used for
Latin-1, is different from the letter @samp{o} with acute accent in
charset @code{latin-iso8859-2}, used for Latin-2.
Emacs defines most of popular character sets (e.g. ascii,
iso-8859-1, cp1250, big5, unicode) as @dfn{charsets} and a few of its
own charsets (e.g. emacs, unicode-bmp, eight-bit). All supported
characters belong to one or more charsets. Usually you don't have to
take care of ``charset'', but knowing about it may help understanding
the behavior of Emacs in some cases.
One example is a font selection. In each language environment,
charsets have different priorities. Emacs, at first, tries to use a
font that matches with charsets of higher priority. For instance, in
Japanese language environment, the charset @code{japanese-jisx0208}
has the highest priority (@xref{describe-language-environment}). So,
Emacs tries to use a font whose @code{registry} property is
``JISX0208.1983-0'' for characters belonging to that charset.
Another example is a use of @code{charset} text property. When
Emacs reads a file encoded in a coding systems that uses escape
sequences to switch charsets (e.g. iso-2022-int-1), the buffer text
keep the information of the original charset by @code{charset} text
property. By using this information, Emacs can write the file with
the same byte sequence as the original.
@findex list-charset-chars
@cindex characters in a certain charset
@findex describe-character-set
There are two commands for obtaining information about Emacs
charsets. The command @kbd{M-x list-charset-chars} prompts for a name
of a character set, and displays all the characters in that character
set. The command @kbd{M-x describe-character-set} prompts for a
charset name and displays information about that charset, including
its internal representation within Emacs.
charsets. The command @kbd{M-x list-charset-chars} prompts for a
charset name, and displays all the characters in that character set.
The command @kbd{M-x describe-character-set} prompts for a charset
name and displays information about that charset, including its
internal representation within Emacs.
@findex list-character-sets
To display a list of all the supported charsets, type @kbd{M-x
list-character-sets}. The list gives the names of charsets and
additional information to identity each charset (see ISO/IEC's this
page <http://www.itscj.ipsj.or.jp/ISO-IR/> for the detail). In the
list, charsets are categorized into two; the normal charsets are
listed first, and the supplementary charsets are listed last. A
charset in the latter category is used for defining another charset
(as a parent or a subset), or was used only in Emacs of the older
versions.
To find out which charset a character in the buffer belongs to,
put point before it and type @kbd{C-u C-x =}.
......
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