appropriate keyboard coding system (@pxref{Specify Coding}), and Emacs
will accept those characters. Latin-1 characters can also be input by
using the @kbd{C-x 8} prefix, see @ref{Single-Byte Character Support,
-C-x 8}.
+C-x 8}. On X Window systems, your locale should be set to an
+appropriate value to make sure Emacs interprets keyboard input
+correctly; see @ref{Language Environments, locales}.
@end itemize
The rest of this chapter describes these issues in detail.
* Single-Byte Character Support::
You can pick one European character set
to use without multibyte characters.
+* Charsets:: How Emacs groups its internal character codes.
@end menu
@node International Chars
The prefix key @kbd{C-x @key{RET}} is used for commands that pertain
to multibyte characters, coding systems, and input methods.
-@ignore
-@c This is commented out because it doesn't fit here, or anywhere.
-@c This manual does not discuss "character sets" as they
-@c are used in Mule, and it makes no sense to mention these commands
-@c except as part of a larger discussion of the topic.
-@c But it is not clear that topic is worth mentioning here,
-@c since that is more of an implementation concept
-@c than a user-level concept. And when we switch to Unicode,
-@c character sets in the current sense may not even exist.
-
-@findex list-charset-chars
-@cindex characters in a certain charset
- 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.
-
-@findex describe-character-set
-@cindex character set, description
- The command @kbd{M-x describe-character-set} prompts for a character
-set name and displays information about that character set, including
-its internal representation within Emacs.
-@end ignore
-
@node Enabling Multibyte
@section Enabling Multibyte Characters
@findex set-language-environment
@vindex current-language-environment
- To select a language environment, customize the option
+ To select a language environment, you can customize the variable
@code{current-language-environment} or use the command @kbd{M-x
set-language-environment}. It makes no difference which buffer is
current when you use this command, because the effects apply globally to
the Emacs session. The supported language environments include:
@cindex Euro sign
+@cindex UTF-8
@quotation
Chinese-BIG5, Chinese-CNS, Chinese-GB, Cyrillic-ALT, Cyrillic-ISO,
Cyrillic-KOI8, Czech, Devanagari, Dutch, English, Ethiopic, German,
Greek, Hebrew, IPA, Japanese, Korean, Lao, Latin-1, Latin-2, Latin-3,
Latin-4, Latin-5, Latin-8 (Celtic), Latin-9 (updated Latin-1, with the
-Euro sign), Polish, Romanian, Slovak, Slovenian, Spanish, Thai,
-Tibetan, Turkish, and Vietnamese.
+Euro sign), Polish, Romanian, Slovak, Slovenian, Spanish, Thai, Tibetan,
+Turkish, UTF-8 (for a setup which prefers Unicode characters and files
+encoded in UTF-8), and Vietnamese.
@end quotation
@cindex fonts for various scripts
@code{locale-charset-language-names} and @code{locale-language-names},
and selects the corresponding language environment if a match is found.
(The former variable overrides the latter.) It also adjusts the display
-table and terminal coding system, the locale coding system, and the
-preferred coding system as needed for the locale.
+table and terminal coding system, the locale coding system, the
+preferred coding system as needed for the locale, and---last but not
+least---the way Emacs decodes non-ASCII characters sent by your keyboard.
If you modify the @env{LC_ALL}, @env{LC_CTYPE}, or @env{LANG}
environment variables while running Emacs, you may want to invoke the
-@code{set-locale-environment} function afterwards to re-adjust the
+@code{set-locale-environment} function afterwards to readjust the
language environment from the new locale.
@vindex locale-preferred-coding-systems
input methods.
The simplest kind of input method works by mapping ASCII letters
-into another alphabet; this allows you to type characters that your
-keyboard doesn't support directly. This is how the Greek and Russian
-input methods work.
+into another alphabet; this allows you to use one other alphabet
+instead of ASCII. The Greek and Russian input methods
+work this way.
A more powerful technique is composition: converting sequences of
characters into one letter. Many European input methods use composition
methods, first you enter the phonetic spelling of a Chinese word (in
input method @code{chinese-py}, among others), or a sequence of
portions of the character (input methods @code{chinese-4corner} and
-@code{chinese-sw}, and others). One phonetic spelling typically
-corresponds to many different Chinese characters. You select the one
+@code{chinese-sw}, and others). One input sequence typically
+corresponds to many possible Chinese characters. You select the one
you mean using keys such as @kbd{C-f}, @kbd{C-b}, @kbd{C-n},
@kbd{C-p}, and digits, which have special meanings in this situation.
@key{TAB} in these Chinese input methods displays a buffer showing
all the possible characters at once; then clicking @kbd{Mouse-2} on
one of them selects that alternative. The keys @kbd{C-f}, @kbd{C-b},
-@kbd{C-n}, @kbd{C-p}, and digits continue to work also. When this
-buffer is visible, @kbd{C-n} and @kbd{C-p} move the current
-alternative to a different row.
+@kbd{C-n}, @kbd{C-p}, and digits continue to work as usual, but they
+do the highlighting in the buffer showing the possible characters,
+rather than in the echo area.
In Japanese input methods, first you input a whole word using
phonetic spelling; then, after the word is in the buffer, Emacs
input method name from the minibuffer; the name normally starts with the
language environment that it is meant to be used with. The variable
@code{current-input-method} records which input method is selected.
-
+
@findex toggle-input-method
@kindex C-\
Input methods use various sequences of ASCII characters to stand for
reasons to specify a language environment.
@findex prefer-coding-system
- However, you can alter the priority list in detail with the command
-@kbd{M-x prefer-coding-system}. This command reads the name of a coding
-system from the minibuffer, and adds it to the front of the priority
-list, so that it is preferred to all others. If you use this command
-several times, each use adds one element to the front of the priority
-list.
+ However, you can alter the coding system priority list in detail
+with the command @kbd{M-x prefer-coding-system}. This command reads
+the name of a coding system from the minibuffer, and adds it to the
+front of the priority list, so that it is preferred to all others. If
+you use this command several times, each use adds one element to the
+front of the priority list.
If you use a coding system that specifies the end-of-line conversion
type, such as @code{iso-8859-1-dos}, what this means is that Emacs
should attempt to recognize @code{iso-8859-1} with priority, and should
-use DOS end-of-line conversion if it recognizes @code{iso-8859-1}.
+use DOS end-of-line conversion when it does recognize @code{iso-8859-1}.
@vindex file-coding-system-alist
Sometimes a file name indicates which coding system to use for the
local variables list at the end (@pxref{File Variables}). You do this
by defining a value for the ``variable'' named @code{coding}. Emacs
does not really have a variable @code{coding}; instead of setting a
-variable, it uses the specified coding system for the file. For
+variable, this uses the specified coding system for the file. For
example, @samp{-*-mode: C; coding: latin-1;-*-} specifies use of the
-Latin-1 coding system, as well as C mode. If you specify the coding
+Latin-1 coding system, as well as C mode. When you specify the coding
explicitly in the file, that overrides
@code{file-coding-system-alist}.
@vindex auto-coding-alist
@vindex auto-coding-regexp-alist
- The variables @code{auto-coding-alist} and
-@code{auto-coding-regexp-alist} are the strongest way to specify the
-coding system for certain patterns of file names, or for files
-containing certain patterns; these variables even override
-@samp{-*-coding:-*-} tags in the file itself. Emacs uses
-@code{auto-coding-alist} for tar and archive files, to prevent it
+@vindex auto-coding-functions
+ The variables @code{auto-coding-alist},
+@code{auto-coding-regexp-alist} and @code{auto-coding-functions} are
+the strongest way to specify the coding system for certain patterns of
+file names, or for files containing certain patterns; these variables
+even override @samp{-*-coding:-*-} tags in the file itself. Emacs
+uses @code{auto-coding-alist} for tar and archive files, to prevent it
from being confused by a @samp{-*-coding:-*-} tag in a member of the
archive and thinking it applies to the archive file as a whole.
Likewise, Emacs uses @code{auto-coding-regexp-alist} to ensure that
-RMAIL files, whose names in general don't match any particular pattern,
-are decoded correctly.
+RMAIL files, whose names in general don't match any particular
+pattern, are decoded correctly. One of the builtin
+@code{auto-coding-functions} detects the encoding for XML files.
If Emacs recognizes the encoding of a file incorrectly, you can
reread the file using the correct coding system by typing @kbd{C-x
the file, look at the coding system mnemonic letter near the left edge
of the mode line (@pxref{Mode Line}), or type @kbd{C-h C @key{RET}}.
+@findex unify-8859-on-decoding-mode
+ The command @code{unify-8859-on-decoding-mode} enables a mode that
+``unifies'' the Latin alphabets when decoding text. This works by
+converting all non-ASCII Latin-@var{n} characters to either Latin-1 or
+Unicode characters. This way it is easier to use various
+Latin-@var{n} alphabets together. In a future Emacs version we hope
+to move towards full Unicode support and complete unification of
+character sets.
+
@vindex buffer-file-coding-system
Once Emacs has chosen a coding system for a buffer, it stores that
coding system in @code{buffer-file-coding-system} and uses that coding
cannot be encoded with the coding system that will be used to save the
buffer. For example, you could start with an ASCII file and insert a
few Latin-1 characters into it, or you could edit a text file in
-Polish encoded in @code{iso-8859-2} and add to it translations of
-several Polish words into Russian. When you save the buffer, Emacs
-cannot use the current value of @code{buffer-file-coding-system},
-because the characters you added cannot be encoded by that coding
-system.
+Polish encoded in @code{iso-8859-2} and add some Russian words to it.
+When you save the buffer, Emacs cannot use the current value of
+@code{buffer-file-coding-system}, because the characters you added
+cannot be encoded by that coding system.
When that happens, Emacs tries the most-preferred coding system (set
by @kbd{M-x prefer-coding-system} or @kbd{M-x
If you insert the unsuitable characters in a mail message, Emacs
behaves a bit differently. It additionally checks whether the
most-preferred coding system is recommended for use in MIME messages;
-if it isn't, Emacs tells you that the most-preferred coding system is
+if not, Emacs tells you that the most-preferred coding system is
not recommended and prompts you for another coding system. This is so
you won't inadvertently send a message encoded in a way that your
recipient's mail software will have difficulty decoding. (If you do
@table @kbd
@item C-x @key{RET} f @var{coding} @key{RET}
-Use coding system @var{coding} for the visited file
-in the current buffer.
+Use coding system @var{coding} for saving or revisiting the visited
+file in the current buffer.
@item C-x @key{RET} c @var{coding} @key{RET}
Specify coding system @var{coding} for the immediately following
@kindex C-x RET f
@findex set-buffer-file-coding-system
- The command @kbd{C-x @key{RET} f} (@code{set-buffer-file-coding-system})
-specifies the file coding system for the current buffer---in other
-words, which coding system to use when saving or rereading the visited
-file. You specify which coding system using the minibuffer. Since this
-command applies to a file you have already visited, it affects only the
-way the file is saved.
+ The command @kbd{C-x @key{RET} f}
+(@code{set-buffer-file-coding-system}) sets the file coding system for
+the current buffer---in other words, it says which coding system to
+use when saving or reverting the visited file. You specify which
+coding system using the minibuffer. If you specify a coding system
+that cannot handle all of the characters in the buffer, Emacs warns
+you about the troublesome characters when you actually save the
+buffer.
@kindex C-x RET c
@findex universal-coding-system-argument
So if the immediately following command is @kbd{C-x C-f}, for example,
it reads the file using that coding system (and records the coding
-system for when the file is saved). Or if the immediately following
+system for when you later save the file). Or if the immediately following
command is @kbd{C-x C-w}, it writes the file using that coding system.
-Other file commands affected by a specified coding system include
-@kbd{C-x C-i} and @kbd{C-x C-v}, as well as the other-window variants of
-@kbd{C-x C-f}.
+When you specify the coding system for saving in this way, instead
+of with @kbd{C-x @key{RET} f}, there is no warning if the buffer
+contains characters that the coding system cannot handle.
- @kbd{C-x @key{RET} c} also affects commands that start subprocesses,
-including @kbd{M-x shell} (@pxref{Shell}).
+ Other file commands affected by a specified coding system include
+@kbd{C-x C-i} and @kbd{C-x C-v}, as well as the other-window variants
+of @kbd{C-x C-f}. @kbd{C-x @key{RET} c} also affects commands that
+start subprocesses, including @kbd{M-x shell} (@pxref{Shell}).
- However, if the immediately following command does not use the coding
-system, then @kbd{C-x @key{RET} c} ultimately has no effect.
+ If the immediately following command does not use the coding system,
+then @kbd{C-x @key{RET} c} ultimately has no effect.
An easy way to visit a file with no conversion is with the @kbd{M-x
find-file-literally} command. @xref{Visiting}.
send non-ASCII graphic characters---for example, some terminals designed
for ISO Latin-1 or subsets of it.
- By default, keyboard input is not translated at all.
+ By default, keyboard input is translated based on your system locale
+setting. If your terminal does not really support the encoding
+implied by your locale (for example, if you find it inserts a
+non-ASCII character if you type @kbd{M-i}), you will need to set
+@code{keyboard-coding-system} to @code{nil} to turn off encoding.
+You can do this by putting
+
+@lisp
+(set-keyboard-coding-system nil)
+@end lisp
+
+@noindent
+in your @file{~/.emacs} file.
There is a similarity between using a coding system translation for
keyboard input, and using an input method: both define sequences of
C-w} to specify a new file name for that buffer.
@vindex locale-coding-system
+@cindex decoding non-ASCII keyboard input on X
The variable @code{locale-coding-system} specifies a coding system
to use when encoding and decoding system strings such as system error
-messages and @code{format-time-string} formats and time stamps. You
-should choose a coding system that is compatible with the underlying
-system's text representation, which is normally specified by one of
-the environment variables @env{LC_ALL}, @env{LC_CTYPE}, and
-@env{LANG}. (The first one, in the order specified above, whose value
-is nonempty is the one that determines the text representation.)
+messages and @code{format-time-string} formats and time stamps. That
+coding system is also used for decoding non-ASCII keyboard input on X
+Window systems. You should choose a coding system that is compatible
+with the underlying system's text representation, which is normally
+specified by one of the environment variables @env{LC_ALL},
+@env{LC_CTYPE}, and @env{LANG}. (The first one, in the order
+specified above, whose value is nonempty is the one that determines
+the text representation.)
@node Fontsets
@section Fontsets
display that character properly. It will display that character as an
empty box instead.
-@vindex highlight-wrong-size-font
- The fontset height and width are determined by the ASCII characters
-(that is, by the font used for ASCII characters in that fontset). If
-another font in the fontset has a different height, or a different
-width, then characters assigned to that font are clipped to the
-fontset's size. If @code{highlight-wrong-size-font} is non-@code{nil},
-a box is displayed around these wrong-size characters as well.
-
@node Defining Fontsets
@section Defining fontsets
@node Undisplayable Characters
@section Undisplayable Characters
- Your terminal may be unable to display some non-@sc{ascii}
-characters. Most non-windowing terminals can only use a single
-character set (use the variable @code{default-terminal-coding-system}
+ There may be a some non-ASCII characters that your terminal cannot
+display. Most non-windowing terminals support just a single character
+set (use the variable @code{default-terminal-coding-system}
(@pxref{Specify Coding}) to tell Emacs which one); characters which
can't be encoded in that coding system are displayed as @samp{?} by
default.
no font appear as a hollow box.
If you use Latin-1 characters but your terminal can't display
-Latin-1, you can arrange to display mnemonic @sc{ascii} sequences
+Latin-1, you can arrange to display mnemonic ASCII sequences
instead, e.g.@: @samp{"o} for o-umlaut. Load the library
@file{iso-ascii} to do this.
@vindex latin1-display
If your terminal can display Latin-1, you can display characters
from other European character sets using a mixture of equivalent
-Latin-1 characters and @sc{ascii} mnemonics. Use the Custom option
-@code{latin1-display} to enable this. The mnemonic @sc{ascii}
+Latin-1 characters and ASCII mnemonics. Use the Custom option
+@code{latin1-display} to enable this. The mnemonic ASCII
sequences mostly correspond to those of the prefix input methods.
@node Single-Byte Character Support
mode is buffer-local. It can be customized for various languages with
@kbd{M-x iso-accents-customize}.
@end itemize
+
+@node Charsets
+@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 ASCII into two charsets: 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.
+
+@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.
+
+ To find out which charset a character in the buffer belongs to,
+put point before it and type @kbd{C-u C-x =}.