@c This is part of the Emacs manual.
-@c Copyright (C) 1997, 1999, 2000, 2001, 2005 Free Software Foundation, Inc.
+@c Copyright (C) 1997, 1999, 2000, 2001, 2002, 2003, 2004,
+@c 2005, 2006, 2007 Free Software Foundation, Inc.
@c See file emacs.texi for copying conditions.
@node International, Major Modes, Frames, Top
@chapter International Character Set Support
well as Cyrillic, Devanagari (for Hindi and Marathi), Ethiopic, Greek,
Han (for Chinese and Japanese), Hangul (for Korean), Hebrew, IPA,
Kannada, Lao, Malayalam, Tamil, Thai, Tibetan, and Vietnamese scripts.
-These features have been merged from the modified version of Emacs
-known as MULE (for ``MULti-lingual Enhancement to GNU Emacs'')
-
- Emacs also supports various encodings of these characters used by
+Emacs also supports various encodings of these characters used by
other internationalized software, such as word processors and mailers.
Emacs allows editing text with international characters by supporting
environment (@pxref{Language Environments}) takes care of setting up the
coding systems and other options for a specific language or culture.
Alternatively, you can specify how Emacs should encode or decode text
-for each command; see @ref{Specify Coding}.
+for each command; see @ref{Text Coding}.
@item
-You can display non-@acronym{ASCII} characters encoded by the various scripts.
-This works by using appropriate fonts on X and similar graphics
-displays (@pxref{Defining Fontsets}), and by sending special codes to
-text-only displays (@pxref{Specify Coding}). If some characters are
-displayed incorrectly, refer to @ref{Undisplayable Characters}, which
-describes possible problems and explains how to solve them.
+You can display non-@acronym{ASCII} characters encoded by the various
+scripts. This works by using appropriate fonts on graphics displays
+(@pxref{Defining Fontsets}), and by sending special codes to text-only
+displays (@pxref{Terminal Coding}). If some characters are displayed
+incorrectly, refer to @ref{Undisplayable Characters}, which describes
+possible problems and explains how to solve them.
@item
You can insert non-@acronym{ASCII} characters or search for them. To do that,
for your language, or use the default input method set up when you set
your language environment. If
your keyboard can produce non-@acronym{ASCII} characters, you can select an
-appropriate keyboard coding system (@pxref{Specify Coding}), and Emacs
+appropriate keyboard coding system (@pxref{Terminal 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}. 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}.
+using the @kbd{C-x 8} prefix, see @ref{Unibyte Mode}.
+
+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.
* Coding Systems:: Character set conversion when you read and
write files, and so on.
* Recognize Coding:: How Emacs figures out which conversion to use.
-* Specify Coding:: Various ways to choose which conversion to use.
+* Specify Coding:: Specifying a file's coding system explicitly.
+* Output Coding:: Choosing coding systems for output.
+* Text Coding:: Choosing conversion to use for file text.
+* Communication Coding:: Coding systems for interprocess communication.
+* File Name Coding:: Coding systems for file @emph{names}.
+* Terminal Coding:: Specifying coding systems for converting
+ terminal input and output.
* Fontsets:: Fontsets are collections of fonts
that cover the whole spectrum of characters.
* Defining Fontsets:: Defining a new fontset.
* Undisplayable Characters:: When characters don't display.
-* Single-Byte Character Support:: You can pick one European character set
+* Unibyte Mode:: 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
@section Introduction to International Character Sets
- The users of international character sets and scripts have established
-many more-or-less standard coding systems for storing files. Emacs
-internally uses a single multibyte character encoding, so that it can
-intermix characters from all these scripts in a single buffer or string.
-This encoding represents each non-@acronym{ASCII} character as a sequence of bytes
-in the range 0200 through 0377. Emacs translates between the multibyte
-character encoding and various other coding systems when reading and
-writing files, when exchanging data with subprocesses, and (in some
-cases) in the @kbd{C-q} command (@pxref{Multibyte Conversion}).
+ The users of international character sets and scripts have
+established many more-or-less standard coding systems for storing
+files. Emacs internally uses a single multibyte character encoding,
+so that it can intermix characters from all these scripts in a single
+buffer or string. This encoding represents each non-@acronym{ASCII}
+character as a sequence of bytes in the range 0200 through 0377.
+Emacs translates between the multibyte character encoding and various
+other coding systems when reading and writing files, when exchanging
+data with subprocesses, and (in some cases) in the @kbd{C-q} command
+(@pxref{Multibyte Conversion}).
@kindex C-h h
@findex view-hello-file
@node Enabling Multibyte
@section Enabling Multibyte Characters
-@cindex turn multibyte support on or off
- You can enable or disable multibyte character support, either for
-Emacs as a whole, or for a single buffer. When multibyte characters are
-disabled in a buffer, then each byte in that buffer represents a
-character, even codes 0200 through 0377. The old features for
-supporting the European character sets, ISO Latin-1 and ISO Latin-2,
-work as they did in Emacs 19 and also work for the other ISO 8859
-character sets.
-
- However, there is no need to turn off multibyte character support to
-use ISO Latin; the Emacs multibyte character set includes all the
-characters in these character sets, and Emacs can translate
-automatically to and from the ISO codes.
-
By default, Emacs starts in multibyte mode, because that allows you to
use all the supported languages and scripts without limitations.
+@cindex turn multibyte support on or off
+ You can enable or disable multibyte character support, either for
+Emacs as a whole, or for a single buffer. When multibyte characters
+are disabled in a buffer, we call that @dfn{unibyte mode}. Then each
+byte in that buffer represents a character, even codes 0200 through
+0377.
+
+ The old features for supporting the European character sets, ISO
+Latin-1 and ISO Latin-2, work in unibyte mode as they did in Emacs 19
+and also work for the other ISO 8859 character sets. However, there
+is no need to turn off multibyte character support to use ISO Latin;
+the Emacs multibyte character set includes all the characters in these
+character sets, and Emacs can translate automatically to and from the
+ISO codes.
+
To edit a particular file in unibyte representation, visit it using
@code{find-file-literally}. @xref{Visiting}. To convert a buffer in
multibyte representation into a single-byte representation of the same
buffer, and find the file again with @code{find-file-literally}. You
can also use @kbd{C-x @key{RET} c}
(@code{universal-coding-system-argument}) and specify @samp{raw-text} as
-the coding system with which to find or save a file. @xref{Specify
+the coding system with which to find or save a file. @xref{Text
Coding}. Finding a file as @samp{raw-text} doesn't disable format
conversion, uncompression and auto mode selection as
@code{find-file-literally} does.
load a Lisp file as unibyte, on any one occasion, by typing @kbd{C-x
@key{RET} c raw-text @key{RET}} immediately before loading it.
- The mode line indicates whether multibyte character support is enabled
-in the current buffer. If it is, there are two or more characters (most
-often two dashes) before the colon near the beginning of the mode line.
-When multibyte characters are not enabled, just one dash precedes the
-colon.
+ The mode line indicates whether multibyte character support is
+enabled in the current buffer. If it is, there are two or more
+characters (most often two dashes) near the beginning of the mode
+line, before the indication of the visited file's end-of-line
+convention (colon, backslash, etc.). When multibyte characters
+are not enabled, nothing precedes the colon except a single dash.
+@xref{Mode Line}, for more details about this.
@node Language Environments
@section Language Environments
@findex describe-language-environment
To display information about the effects of a certain language
environment @var{lang-env}, use the command @kbd{C-h L @var{lang-env}
-@key{RET}} (@code{describe-language-environment}). This tells you which
-languages this language environment is useful for, and lists the
+@key{RET}} (@code{describe-language-environment}). This tells you
+which languages this language environment is useful for, and lists the
character sets, coding systems, and input methods that go with it. It
-also shows some sample text to illustrate scripts used in this language
-environment. By default, this command describes the chosen language
-environment.
+also shows some sample text to illustrate scripts used in this
+language environment. If you give an empty input for @var{lang-env},
+this command describes the chosen language environment.
@vindex set-language-environment-hook
You can customize any language environment with the normal hook
Another method, more general but not quite as easy to type, is to use
@kbd{C-\ C-\} between two characters to stop them from combining. This
is the command @kbd{C-\} (@code{toggle-input-method}) used twice.
-@ifinfo
+@ifnottex
@xref{Select Input Method}.
-@end ifinfo
+@end ifnottex
@cindex incremental search, input method interference
@kbd{C-\ C-\} is especially useful inside an incremental search,
@findex toggle-input-method
@kindex C-\
- Input methods use various sequences of @acronym{ASCII} characters to stand for
-non-@acronym{ASCII} characters. Sometimes it is useful to turn off the input
-method temporarily. To do this, type @kbd{C-\}
+ Input methods use various sequences of @acronym{ASCII} characters to
+stand for non-@acronym{ASCII} characters. Sometimes it is useful to
+turn off the input method temporarily. To do this, type @kbd{C-\}
(@code{toggle-input-method}). To reenable the input method, type
@kbd{C-\} again.
character.
@findex list-input-methods
- To display a list of all the supported input methods, type @kbd{M-x
+ To see a list of all the supported input methods, type @kbd{M-x
list-input-methods}. The list gives information about each input
method, including the string that stands for it in the mode line.
@iftex
(see above).
@end iftex
-@ifinfo
+@ifnottex
(@pxref{Language Environments}).
-@end ifinfo
+@end ifnottex
If you do not specify a choice, the default is Latin-1.
If you insert a character in the range 0200 through 0237, which
@key{RET}}@footnote{
In the MS-DOS port of Emacs, you need to create a @code{cp@var{nnn}}
coding system with @kbd{M-x codepage-setup}, before you can use it.
-@xref{MS-DOS and MULE}.}.
+@iftex
+@xref{MS-DOS and MULE,,,emacs-extra,Specialized Emacs Features}.
+@end iftex
+@ifnottex
+@xref{MS-DOS and MULE}.
+@end ifnottex
+}.
In addition to converting various representations of non-@acronym{ASCII}
characters, a coding system can perform end-of-line conversion. Emacs
@kindex C-h C
@findex describe-coding-system
The command @kbd{C-h C} (@code{describe-coding-system}) displays
-information about particular coding systems. You can specify a coding
+information about particular coding systems, including the end-of-line
+conversion specified by those coding systems. You can specify a coding
system name as the argument; alternatively, with an empty argument, it
describes the coding systems currently selected for various purposes,
both in the current buffer and as the defaults, and the priority list
(@pxref{Mode Line}).
@cindex end-of-line conversion
+@cindex line endings
@cindex MS-DOS end-of-line conversion
@cindex Macintosh end-of-line conversion
Each of the coding systems that appear in this list---except for
variants @code{iso-latin-1-unix}, @code{iso-latin-1-dos} and
@code{iso-latin-1-mac}.
+@cindex @code{undecided}, coding system
+ The coding systems @code{unix}, @code{dos}, and @code{mac} are
+aliases for @code{undecided-unix}, @code{undecided-dos}, and
+@code{undecided-mac}, respectively. These coding systems specify only
+the end-of-line conversion, and leave the character code conversion to
+be deduced from the text itself.
+
The coding system @code{raw-text} is good for a file which is mainly
-@acronym{ASCII} text, but may contain byte values above 127 which are not meant to
-encode non-@acronym{ASCII} characters. With @code{raw-text}, Emacs copies those
-byte values unchanged, and sets @code{enable-multibyte-characters} to
-@code{nil} in the current buffer so that they will be interpreted
-properly. @code{raw-text} handles end-of-line conversion in the usual
-way, based on the data encountered, and has the usual three variants to
-specify the kind of end-of-line conversion to use.
+@acronym{ASCII} text, but may contain byte values above 127 which are
+not meant to encode non-@acronym{ASCII} characters. With
+@code{raw-text}, Emacs copies those byte values unchanged, and sets
+@code{enable-multibyte-characters} to @code{nil} in the current buffer
+so that they will be interpreted properly. @code{raw-text} handles
+end-of-line conversion in the usual way, based on the data
+encountered, and has the usual three variants to specify the kind of
+end-of-line conversion to use.
In contrast, the coding system @code{no-conversion} specifies no
character code conversion at all---none for non-@acronym{ASCII} byte values and
handles end-of-line conversion based on the data encountered, and has
the usual three variants to specify the kind of end-of-line conversion.
+@findex unify-8859-on-decoding-mode
+@anchor{Character Translation}
+ The @dfn{character translation} feature can modify the effect of
+various coding systems, by changing the internal Emacs codes that
+decoding produces. For instance, 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-@acronym{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 enable-character-translation
+ If you set the variable @code{enable-character-translation} to
+@code{nil}, that disables all character translation (including
+@code{unify-8859-on-decoding-mode}).
+
@node Recognize Coding
@section Recognizing Coding Systems
correspondence. There is a special function
@code{modify-coding-system-alist} for adding elements to this list. For
example, to read and write all @samp{.txt} files using the coding system
-@code{china-iso-8bit}, you can execute this Lisp expression:
+@code{chinese-iso-8bit}, you can execute this Lisp expression:
@smallexample
(modify-coding-system-alist 'file "\\.txt\\'" 'chinese-iso-8bit)
decoded correctly when you visit those files if you suppress the
escape sequence detection.
-@vindex coding
- You can specify the coding system for a particular file using the
-@w{@samp{-*-@dots{}-*-}} construct at the beginning of a file, or a
-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, 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. 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
@vindex auto-coding-functions
pattern, are decoded correctly. One of the builtin
@code{auto-coding-functions} detects the encoding for XML files.
+@vindex rmail-decode-mime-charset
+ When you get new mail in Rmail, each message is translated
+automatically from the coding system it is written in, as if it were a
+separate file. This uses the priority list of coding systems that you
+have specified. If a MIME message specifies a character set, Rmail
+obeys that specification, unless @code{rmail-decode-mime-charset} is
+@code{nil}.
+
+@vindex rmail-file-coding-system
+ For reading and saving Rmail files themselves, Emacs uses the coding
+system specified by the variable @code{rmail-file-coding-system}. The
+default value is @code{nil}, which means that Rmail files are not
+translated (they are read and written in the Emacs internal character
+code).
+
+@node Specify Coding
+@section Specifying a File's Coding System
+
If Emacs recognizes the encoding of a file incorrectly, you can
reread the file using the correct coding system by typing @kbd{C-x
-@key{RET} r @var{coding-system}
-@key{RET}}. To see what coding system Emacs actually used to decode
-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}}.
+@key{RET} r @var{coding-system} @key{RET}}. To see what coding system
+Emacs actually used to decode 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-@acronym{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 coding
+ You can specify the coding system for a particular file in the file
+itself, using the @w{@samp{-*-@dots{}-*-}} construct at the beginning,
+or a 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, 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. When you specify
+the coding explicitly in the file, that overrides
+@code{file-coding-system-alist}.
+
+ If you add the character @samp{!} at the end of the coding system
+name in @code{coding}, it disables any character translation
+(@pxref{Character Translation}) while decoding the file. This is
+useful when you need to make sure that the character codes in the
+Emacs buffer will not vary due to changes in user settings; for
+instance, for the sake of strings in Emacs Lisp source files.
+
+@node Output Coding
+@section Choosing Coding Systems for Output
@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
-system, by default, for operations that write from this buffer into a
-file. This includes the commands @code{save-buffer} and
-@code{write-region}. If you want to write files from this buffer using
-a different coding system, you can specify a different coding system for
-the buffer using @code{set-buffer-file-coding-system} (@pxref{Specify
-Coding}).
-
- You can insert any possible character into any Emacs buffer, but
-most coding systems can only handle some of the possible characters.
-This means that it is possible for you to insert characters that
-cannot be encoded with the coding system that will be used to save the
-buffer. For example, you could start with an @acronym{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 some Russian words to it.
-When you save the buffer, Emacs cannot use the current value of
+coding system in @code{buffer-file-coding-system}. That makes it the
+default for operations that write from this buffer into a file, such
+as @code{save-buffer} and @code{write-region}. You can specify a
+different coding system for further file output from the buffer using
+@code{set-buffer-file-coding-system} (@pxref{Text Coding}).
+
+ You can insert any character Emacs supports into any Emacs buffer,
+but most coding systems can only handle a subset of these characters.
+Therefore, you can insert characters that cannot be encoded with the
+coding system that will be used to save the buffer. For example, you
+could start with an @acronym{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 some Russian words to it. When you save
+that 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.
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 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
-want to use the most-preferred coding system, you can still type its
-name in response to the question.)
+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. (You can
+still use an unsuitable coding system if you type its name in response
+to the question.)
@vindex sendmail-coding-system
When you send a message with Mail mode (@pxref{Sending Mail}), Emacs has
if that is non-@code{nil}. If all of these three values are @code{nil},
Emacs encodes outgoing mail using the Latin-1 coding system.
-@vindex rmail-decode-mime-charset
- When you get new mail in Rmail, each message is translated
-automatically from the coding system it is written in, as if it were a
-separate file. This uses the priority list of coding systems that you
-have specified. If a MIME message specifies a character set, Rmail
-obeys that specification, unless @code{rmail-decode-mime-charset} is
-@code{nil}.
-
-@vindex rmail-file-coding-system
- For reading and saving Rmail files themselves, Emacs uses the coding
-system specified by the variable @code{rmail-file-coding-system}. The
-default value is @code{nil}, which means that Rmail files are not
-translated (they are read and written in the Emacs internal character
-code).
-
-@node Specify Coding
-@section Specifying a Coding System
+@node Text Coding
+@section Specifying a Coding System for File Text
In cases where Emacs does not automatically choose the right coding
-system, you can use these commands to specify one:
+system for a file's contents, you can use these commands to specify
+one:
@table @kbd
@item C-x @key{RET} f @var{coding} @key{RET}
@item C-x @key{RET} r @var{coding} @key{RET}
Revisit the current file using the coding system @var{coding}.
-@item C-x @key{RET} k @var{coding} @key{RET}
-Use coding system @var{coding} for keyboard input.
-
-@item C-x @key{RET} t @var{coding} @key{RET}
-Use coding system @var{coding} for terminal output.
-
-@item C-x @key{RET} p @var{input-coding} @key{RET} @var{output-coding} @key{RET}
-Use coding systems @var{input-coding} and @var{output-coding} for
-subprocess input and output in the current buffer.
-
-@item C-x @key{RET} x @var{coding} @key{RET}
-Use coding system @var{coding} for transferring selections to and from
-other programs through the window system.
-
-@item C-x @key{RET} F @var{coding} @key{RET}
-Use coding system @var{coding} for encoding and decoding file
-@emph{names}. This affects the use of non-ASCII characters in file
-names. It has no effect on reading and writing the @emph{contents} of
-files.
-
-@item C-x @key{RET} X @var{coding} @key{RET}
-Use coding system @var{coding} for transferring @emph{one}
-selection---the next one---to or from the window system.
-
-@item M-x recode-region
-Convert the region from a previous coding system to a new one.
+@item M-x recode-region @key{RET} @var{right} @key{RET} @var{wrong} @key{RET}
+Convert a region that was decoded using coding system @var{wrong},
+decoding it using coding system @var{right} instead.
@end table
@kindex C-x RET f
you about the troublesome characters when you actually save the
buffer.
+@cindex specify end-of-line conversion
+ You can also use this command to specify the end-of-line conversion
+(@pxref{Coding Systems, end-of-line conversion}) for encoding the
+current buffer. For example, @kbd{C-x @key{RET} f dos @key{RET}} will
+cause Emacs to save the current buffer's text with DOS-style CRLF line
+endings.
+
@kindex C-x RET c
@findex universal-coding-system-argument
Another way to specify the coding system for a file is when you visit
contains characters that the coding system cannot handle.
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
+@kbd{C-x 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}).
-
- If the immediately following command does not use the coding system,
-then @kbd{C-x @key{RET} c} ultimately has no effect.
+start subprocesses, including @kbd{M-x shell} (@pxref{Shell}). 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}.
with @kbd{C-x @key{RET} r} (@code{revert-buffer-with-coding-system}).
This visits the current file again, using a coding system you specify.
-@kindex C-x RET t
-@findex set-terminal-coding-system
- The command @kbd{C-x @key{RET} t} (@code{set-terminal-coding-system})
-specifies the coding system for terminal output. If you specify a
-character code for terminal output, all characters output to the
-terminal are translated into that coding system.
-
- This feature is useful for certain character-only terminals built to
-support specific languages or character sets---for example, European
-terminals that support one of the ISO Latin character sets. You need to
-specify the terminal coding system when using multibyte text, so that
-Emacs knows which characters the terminal can actually handle.
+@findex recode-region
+ If a piece of text has already been inserted into a buffer using the
+wrong coding system, you can redo the decoding of it using @kbd{M-x
+recode-region}. This prompts you for the proper coding system, then
+for the wrong coding system that was actually used, and does the
+conversion. It first encodes the region using the wrong coding system,
+then decodes it again using the proper coding system.
- By default, output to the terminal is not translated at all, unless
-Emacs can deduce the proper coding system from your terminal type or
-your locale specification (@pxref{Language Environments}).
+@node Communication Coding
+@section Coding Systems for Interprocess Communication
-@kindex C-x RET k
-@findex set-keyboard-coding-system
-@vindex keyboard-coding-system
- The command @kbd{C-x @key{RET} k} (@code{set-keyboard-coding-system})
-or the variable @code{keyboard-coding-system} specifies the coding
-system for keyboard input. Character-code translation of keyboard
-input is useful for terminals with keys that send non-@acronym{ASCII}
-graphic characters---for example, some terminals designed for ISO
-Latin-1 or subsets of it.
+ This section explains how to specify coding systems for use
+in communication with other processes.
- 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-@acronym{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
+@table @kbd
+@item C-x @key{RET} x @var{coding} @key{RET}
+Use coding system @var{coding} for transferring selections to and from
+other window-based applications.
-@lisp
-(set-keyboard-coding-system nil)
-@end lisp
+@item C-x @key{RET} X @var{coding} @key{RET}
+Use coding system @var{coding} for transferring @emph{one}
+selection---the next one---to or from another window-based application.
-@noindent
-in your @file{~/.emacs} file.
+@item C-x @key{RET} p @var{input-coding} @key{RET} @var{output-coding} @key{RET}
+Use coding systems @var{input-coding} and @var{output-coding} for
+subprocess input and output in the current buffer.
- There is a similarity between using a coding system translation for
-keyboard input, and using an input method: both define sequences of
-keyboard input that translate into single characters. However, input
-methods are designed to be convenient for interactive use by humans, and
-the sequences that are translated are typically sequences of @acronym{ASCII}
-printing characters. Coding systems typically translate sequences of
-non-graphic characters.
+@item C-x @key{RET} c @var{coding} @key{RET}
+Specify coding system @var{coding} for the immediately following
+command.
+@end table
@kindex C-x RET x
@kindex C-x RET X
@findex set-selection-coding-system
@findex set-next-selection-coding-system
The command @kbd{C-x @key{RET} x} (@code{set-selection-coding-system})
-specifies the coding system for sending selected text to the window
-system, and for receiving the text of selections made in other
+specifies the coding system for sending selected text to other windowing
+applications, and for receiving the text of selections made in other
applications. This command applies to all subsequent selections, until
you override it by using the command again. The command @kbd{C-x
@key{RET} X} (@code{set-next-selection-coding-system}) specifies the
and from a particular subprocess by giving the command in the
corresponding buffer.
+ You can also use @kbd{C-x @key{RET} c} just before the command that
+runs or starts a subprocess, to specify the coding system to use for
+communication with that subprocess.
+
The default for translation of process input and output depends on the
current language environment.
-@findex recode-region
- If a piece of text has already been inserted into a buffer using the
-wrong coding system, you can decode it again using @kbd{M-x
-recode-region}. This prompts you for the old coding system and the
-desired coding system, and acts on the text in the region.
+@vindex locale-coding-system
+@cindex decoding non-@acronym{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. That
+coding system is also used for decoding non-@acronym{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 File Name Coding
+@section Coding Systems for File Names
+
+@table @kbd
+@item C-x @key{RET} F @var{coding} @key{RET}
+Use coding system @var{coding} for encoding and decoding file
+@emph{names}.
+@end table
@vindex file-name-coding-system
@cindex file names with non-@acronym{ASCII} characters
+ The variable @code{file-name-coding-system} specifies a coding
+system to use for encoding file names. It has no effect on reading
+and writing the @emph{contents} of files.
+
@findex set-file-name-coding-system
@kindex C-x @key{RET} F
- The variable @code{file-name-coding-system} specifies a coding
-system to use for encoding file names. If you set the variable to a
-coding system name (as a Lisp symbol or a string), Emacs encodes file
-names using that coding system for all file operations. This makes it
-possible to use non-@acronym{ASCII} characters in file names---or, at
-least, those non-@acronym{ASCII} characters which the specified coding
-system can encode. Use @kbd{C-x @key{RET} F}
-(@code{set-file-name-coding-system}) to specify this interactively.
-
- If @code{file-name-coding-system} is @code{nil}, Emacs uses a default
-coding system determined by the selected language environment. In the
-default language environment, any non-@acronym{ASCII} characters in file names are
-not encoded specially; they appear in the file system using the internal
-Emacs representation.
+ If you set the variable to a coding system name (as a Lisp symbol or
+a string), Emacs encodes file names using that coding system for all
+file operations. This makes it possible to use non-@acronym{ASCII}
+characters in file names---or, at least, those non-@acronym{ASCII}
+characters which the specified coding system can encode. Use @kbd{C-x
+@key{RET} F} (@code{set-file-name-coding-system}) to specify this
+interactively.
+
+ If @code{file-name-coding-system} is @code{nil}, Emacs uses a
+default coding system determined by the selected language environment.
+In the default language environment, any non-@acronym{ASCII}
+characters in file names are not encoded specially; they appear in the
+file system using the internal Emacs representation.
@strong{Warning:} if you change @code{file-name-coding-system} (or the
language environment) in the middle of an Emacs session, problems can
system. This prompts for an existing file name, its old coding
system, and the coding system to which you wish to convert.
-@vindex locale-coding-system
-@cindex decoding non-@acronym{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. That
-coding system is also used for decoding non-@acronym{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 Terminal Coding
+@section Coding Systems for Terminal I/O
+
+@table @kbd
+@item C-x @key{RET} k @var{coding} @key{RET}
+Use coding system @var{coding} for keyboard input.
+
+@item C-x @key{RET} t @var{coding} @key{RET}
+Use coding system @var{coding} for terminal output.
+@end table
+
+@kindex C-x RET t
+@findex set-terminal-coding-system
+ The command @kbd{C-x @key{RET} t} (@code{set-terminal-coding-system})
+specifies the coding system for terminal output. If you specify a
+character code for terminal output, all characters output to the
+terminal are translated into that coding system.
+
+ This feature is useful for certain character-only terminals built to
+support specific languages or character sets---for example, European
+terminals that support one of the ISO Latin character sets. You need to
+specify the terminal coding system when using multibyte text, so that
+Emacs knows which characters the terminal can actually handle.
+
+ By default, output to the terminal is not translated at all, unless
+Emacs can deduce the proper coding system from your terminal type or
+your locale specification (@pxref{Language Environments}).
+
+@kindex C-x RET k
+@findex set-keyboard-coding-system
+@vindex keyboard-coding-system
+ The command @kbd{C-x @key{RET} k} (@code{set-keyboard-coding-system})
+or the variable @code{keyboard-coding-system} specifies the coding
+system for keyboard input. Character-code translation of keyboard
+input is useful for terminals with keys that send non-@acronym{ASCII}
+graphic characters---for example, some terminals designed for ISO
+Latin-1 or subsets of it.
+
+ 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-@acronym{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
+keyboard input that translate into single characters. However, input
+methods are designed to be convenient for interactive use by humans, and
+the sequences that are translated are typically sequences of @acronym{ASCII}
+printing characters. Coding systems typically translate sequences of
+non-graphic characters.
@node Fontsets
@section Fontsets
@cindex fontsets
- A font for X typically defines shapes for a single alphabet or script.
+ A font typically defines shapes for a single alphabet or script.
Therefore, displaying the entire range of scripts that Emacs supports
requires a collection of many fonts. In Emacs, such a collection is
called a @dfn{fontset}. A fontset is defined by a list of fonts, each
assigned to handle a range of character codes.
- Each fontset has a name, like a font. The available X fonts are
-defined by the X server; fontsets, however, are defined within Emacs
-itself. Once you have defined a fontset, you can use it within Emacs by
-specifying its name, anywhere that you could use a single font. Of
-course, Emacs fontsets can use only the fonts that the X server
-supports; if certain characters appear on the screen as hollow boxes,
-this means that the fontset in use for them has no font for those
-characters.@footnote{The Emacs installation instructions have information on
-additional font support.}
+ Each fontset has a name, like a font. However, while fonts are
+stored in the system and the available font names are defined by the
+system, fontsets are defined within Emacs itself. Once you have
+defined a fontset, you can use it within Emacs by specifying its name,
+anywhere that you could use a single font. Of course, Emacs fontsets
+can use only the fonts that the system supports; if certain characters
+appear on the screen as hollow boxes, this means that the fontset in
+use for them has no font for those characters.@footnote{The Emacs
+installation instructions have information on additional font
+support.}
Emacs creates two fontsets automatically: the @dfn{standard fontset}
and the @dfn{startup fontset}. The standard fontset is most likely to
-have fonts for a wide variety of non-@acronym{ASCII} characters; however, this is
-not the default for Emacs to use. (By default, Emacs tries to find a
-font that has bold and italic variants.) You can specify use of the
-standard fontset with the @samp{-fn} option, or with the @samp{Font} X
-resource (@pxref{Font X}). For example,
+have fonts for a wide variety of non-@acronym{ASCII} characters;
+however, this is not the default for Emacs to use. (By default, Emacs
+tries to find a font that has bold and italic variants.) You can
+specify use of the standard fontset with the @samp{-fn} option. For
+example,
@example
emacs -fn fontset-standard
@end example
+@noindent
+You can also specify a fontset with the @samp{Font} resource (@pxref{X
+Resources}).
+
A fontset does not necessarily specify a font for every character
code. If a fontset specifies no font for a certain character, or if it
specifies a font that does not exist on your system, then it cannot
The resource value should have this form:
@smallexample
-@var{fontpattern}, @r{[}@var{charsetname}:@var{fontname}@r{]@dots{}}
+@var{fontpattern}, @r{[}@var{charset}:@var{font}@r{]@dots{}}
@end smallexample
@noindent
@section Undisplayable Characters
There may be a some non-@acronym{ASCII} characters that your terminal cannot
-display. Most non-windowing terminals support just a single character
+display. Most text-only 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
+(@pxref{Terminal Coding}) to tell Emacs which one); characters which
can't be encoded in that coding system are displayed as @samp{?} by
default.
- Windowing terminals can display a broader range of characters, but
+ Graphical displays can display a broader range of characters, but
you may not have fonts installed for all of them; characters that have
no font appear as a hollow box.
@code{latin1-display} to enable this. The mnemonic @acronym{ASCII}
sequences mostly correspond to those of the prefix input methods.
-@node Single-Byte Character Support
-@section Single-byte Character Set Support
+@node Unibyte Mode
+@section Unibyte Editing Mode
@cindex European character sets
@cindex accented characters
For more information about unibyte operation, see @ref{Enabling
Multibyte}. Note particularly that you probably want to ensure that
-your initialization files are read as unibyte if they contain non-@acronym{ASCII}
-characters.
+your initialization files are read as unibyte if they contain
+non-@acronym{ASCII} characters.
@vindex unibyte-display-via-language-environment
Emacs can also display those characters, provided the terminal or font
-in use supports them. This works automatically. Alternatively, if you
-are using a window system, Emacs can also display single-byte characters
+in use supports them. This works automatically. Alternatively, on a
+graphical display, Emacs can also display single-byte characters
through fontsets, in effect by displaying the equivalent multibyte
characters according to the current language environment. To request
this, set the variable @code{unibyte-display-via-language-environment}
representing non-@acronym{ASCII} characters, you can type those character codes
directly.
-On a window system, you should not need to do anything special to use
+On a graphical display, you should not need to do anything special to use
these keys; they should simply work. On a text-only terminal, you
should use the command @code{M-x set-keyboard-coding-system} or the
variable @code{keyboard-coding-system} to specify which coding system
-your keyboard uses (@pxref{Specify Coding}). Enabling this feature
+your keyboard uses (@pxref{Terminal Coding}). Enabling this feature
will probably require you to use @kbd{ESC} to type Meta characters;
however, on a console terminal or in @code{xterm}, you can arrange for
Meta to be converted to @kbd{ESC} and still be able type 8-bit
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}.
+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