1 @c This is part of the Emacs manual.
2 @c Copyright (C) 1997, 1999, 2000, 2001 Free Software Foundation, Inc.
3 @c See file emacs.texi for copying conditions.
4 @node International, Major Modes, Frames, Top
5 @chapter International Character Set Support
7 @cindex international scripts
8 @cindex multibyte characters
9 @cindex encoding of characters
37 Emacs supports a wide variety of international character sets,
38 including European variants of the Latin alphabet, as well as Chinese,
39 Cyrillic, Devanagari (Hindi and Marathi), Ethiopic, Greek, Hebrew, IPA,
40 Japanese, Korean, Lao, Thai, Tibetan, and Vietnamese scripts. These features
41 have been merged from the modified version of Emacs known as MULE (for
42 ``MULti-lingual Enhancement to GNU Emacs'')
44 Emacs also supports various encodings of these characters used by
45 other internationalized software, such as word processors and mailers.
47 Emacs allows editing text with international characters by supporting
48 all the related activities:
52 You can visit files with non-ASCII characters, save non-ASCII text, and
53 pass non-ASCII text between Emacs and programs it invokes (such as
54 compilers, spell-checkers, and mailers). Setting your language
55 environment (@pxref{Language Environments}) takes care of setting up the
56 coding systems and other options for a specific language or culture.
57 Alternatively, you can specify how Emacs should encode or decode text
58 for each command; see @ref{Specify Coding}.
61 You can display non-ASCII characters encoded by the various scripts.
62 This works by using appropriate fonts on X and similar graphics
63 displays (@pxref{Defining Fontsets}), and by sending special codes to
64 text-only displays (@pxref{Specify Coding}). If some characters are
65 displayed incorrectly, refer to @ref{Undisplayable Characters}, which
66 describes possible problems and explains how to solve them.
69 You can insert non-ASCII characters or search for them. To do that,
70 you can specify an input method (@pxref{Select Input Method}) suitable
71 for your language, or use the default input method set up when you set
72 your language environment. (Emacs input methods are part of the Leim
73 package, which must be installed for you to be able to use them.) If
74 your keyboard can produce non-ASCII characters, you can select an
75 appropriate keyboard coding system (@pxref{Specify Coding}), and Emacs
76 will accept those characters. Latin-1 characters can also be input by
77 using the @kbd{C-x 8} prefix, see @ref{Single-Byte Character Support,
78 C-x 8}. On X Window systems, your locale should be set to an
79 appropriate value to make sure Emacs interprets keyboard input
80 correctly, see @ref{Language Environments, locales}.
83 The rest of this chapter describes these issues in detail.
86 * International Chars:: Basic concepts of multibyte characters.
87 * Enabling Multibyte:: Controlling whether to use multibyte characters.
88 * Language Environments:: Setting things up for the language you use.
89 * Input Methods:: Entering text characters not on your keyboard.
90 * Select Input Method:: Specifying your choice of input methods.
91 * Multibyte Conversion:: How single-byte characters convert to multibyte.
92 * Coding Systems:: Character set conversion when you read and
93 write files, and so on.
94 * Recognize Coding:: How Emacs figures out which conversion to use.
95 * Specify Coding:: Various ways to choose which conversion to use.
96 * Fontsets:: Fontsets are collections of fonts
97 that cover the whole spectrum of characters.
98 * Defining Fontsets:: Defining a new fontset.
99 * Undisplayable Characters:: When characters don't display.
100 * Single-Byte Character Support::
101 You can pick one European character set
102 to use without multibyte characters.
105 @node International Chars
106 @section Introduction to International Character Sets
108 The users of international character sets and scripts have established
109 many more-or-less standard coding systems for storing files. Emacs
110 internally uses a single multibyte character encoding, so that it can
111 intermix characters from all these scripts in a single buffer or string.
112 This encoding represents each non-ASCII character as a sequence of bytes
113 in the range 0200 through 0377. Emacs translates between the multibyte
114 character encoding and various other coding systems when reading and
115 writing files, when exchanging data with subprocesses, and (in some
116 cases) in the @kbd{C-q} command (@pxref{Multibyte Conversion}).
119 @findex view-hello-file
120 @cindex undisplayable characters
121 @cindex @samp{?} in display
122 The command @kbd{C-h h} (@code{view-hello-file}) displays the file
123 @file{etc/HELLO}, which shows how to say ``hello'' in many languages.
124 This illustrates various scripts. If some characters can't be
125 displayed on your terminal, they appear as @samp{?} or as hollow boxes
126 (@pxref{Undisplayable Characters}).
128 Keyboards, even in the countries where these character sets are used,
129 generally don't have keys for all the characters in them. So Emacs
130 supports various @dfn{input methods}, typically one for each script or
131 language, to make it convenient to type them.
134 The prefix key @kbd{C-x @key{RET}} is used for commands that pertain
135 to multibyte characters, coding systems, and input methods.
138 @c This is commented out because it doesn't fit here, or anywhere.
139 @c This manual does not discuss "character sets" as they
140 @c are used in Mule, and it makes no sense to mention these commands
141 @c except as part of a larger discussion of the topic.
142 @c But it is not clear that topic is worth mentioning here,
143 @c since that is more of an implementation concept
144 @c than a user-level concept. And when we switch to Unicode,
145 @c character sets in the current sense may not even exist.
147 @findex list-charset-chars
148 @cindex characters in a certain charset
149 The command @kbd{M-x list-charset-chars} prompts for a name of a
150 character set, and displays all the characters in that character set.
152 @findex describe-character-set
153 @cindex character set, description
154 The command @kbd{M-x describe-character-set} prompts for a character
155 set name and displays information about that character set, including
156 its internal representation within Emacs.
159 @node Enabling Multibyte
160 @section Enabling Multibyte Characters
162 @cindex turn multibyte support on or off
163 You can enable or disable multibyte character support, either for
164 Emacs as a whole, or for a single buffer. When multibyte characters are
165 disabled in a buffer, then each byte in that buffer represents a
166 character, even codes 0200 through 0377. The old features for
167 supporting the European character sets, ISO Latin-1 and ISO Latin-2,
168 work as they did in Emacs 19 and also work for the other ISO 8859
171 However, there is no need to turn off multibyte character support to
172 use ISO Latin; the Emacs multibyte character set includes all the
173 characters in these character sets, and Emacs can translate
174 automatically to and from the ISO codes.
176 By default, Emacs starts in multibyte mode, because that allows you to
177 use all the supported languages and scripts without limitations.
179 To edit a particular file in unibyte representation, visit it using
180 @code{find-file-literally}. @xref{Visiting}. To convert a buffer in
181 multibyte representation into a single-byte representation of the same
182 characters, the easiest way is to save the contents in a file, kill the
183 buffer, and find the file again with @code{find-file-literally}. You
184 can also use @kbd{C-x @key{RET} c}
185 (@code{universal-coding-system-argument}) and specify @samp{raw-text} as
186 the coding system with which to find or save a file. @xref{Specify
187 Coding}. Finding a file as @samp{raw-text} doesn't disable format
188 conversion, uncompression and auto mode selection as
189 @code{find-file-literally} does.
191 @vindex enable-multibyte-characters
192 @vindex default-enable-multibyte-characters
193 To turn off multibyte character support by default, start Emacs with
194 the @samp{--unibyte} option (@pxref{Initial Options}), or set the
195 environment variable @env{EMACS_UNIBYTE}. You can also customize
196 @code{enable-multibyte-characters} or, equivalently, directly set the
197 variable @code{default-enable-multibyte-characters} to @code{nil} in
198 your init file to have basically the same effect as @samp{--unibyte}.
200 @findex toggle-enable-multibyte-characters
201 To convert a unibyte session to a multibyte session, set
202 @code{default-enable-multibyte-characters} to @code{t}. Buffers which
203 were created in the unibyte session before you turn on multibyte support
204 will stay unibyte. You can turn on multibyte support in a specific
205 buffer by invoking the command @code{toggle-enable-multibyte-characters}
208 @cindex Lisp files, and multibyte operation
209 @cindex multibyte operation, and Lisp files
210 @cindex unibyte operation, and Lisp files
211 @cindex init file, and non-ASCII characters
212 @cindex environment variables, and non-ASCII characters
213 With @samp{--unibyte}, multibyte strings are not created during
214 initialization from the values of environment variables,
215 @file{/etc/passwd} entries etc.@: that contain non-ASCII 8-bit
218 Emacs normally loads Lisp files as multibyte, regardless of whether
219 you used @samp{--unibyte}. This includes the Emacs initialization
220 file, @file{.emacs}, and the initialization files of Emacs packages
221 such as Gnus. However, you can specify unibyte loading for a
222 particular Lisp file, by putting @w{@samp{-*-unibyte: t;-*-}} in a
223 comment on the first line. Then that file is always loaded as unibyte
224 text, even if you did not start Emacs with @samp{--unibyte}. The
225 motivation for these conventions is that it is more reliable to always
226 load any particular Lisp file in the same way. However, you can load
227 a Lisp file as unibyte, on any one occasion, by typing @kbd{C-x
228 @key{RET} c raw-text @key{RET}} immediately before loading it.
230 The mode line indicates whether multibyte character support is enabled
231 in the current buffer. If it is, there are two or more characters (most
232 often two dashes) before the colon near the beginning of the mode line.
233 When multibyte characters are not enabled, just one dash precedes the
236 @node Language Environments
237 @section Language Environments
238 @cindex language environments
240 All supported character sets are supported in Emacs buffers whenever
241 multibyte characters are enabled; there is no need to select a
242 particular language in order to display its characters in an Emacs
243 buffer. However, it is important to select a @dfn{language environment}
244 in order to set various defaults. The language environment really
245 represents a choice of preferred script (more or less) rather than a
248 The language environment controls which coding systems to recognize
249 when reading text (@pxref{Recognize Coding}). This applies to files,
250 incoming mail, netnews, and any other text you read into Emacs. It may
251 also specify the default coding system to use when you create a file.
252 Each language environment also specifies a default input method.
254 @findex set-language-environment
255 @vindex current-language-environment
256 To select a language environment, customize the option
257 @code{current-language-environment} or use the command @kbd{M-x
258 set-language-environment}. It makes no difference which buffer is
259 current when you use this command, because the effects apply globally to
260 the Emacs session. The supported language environments include:
264 Chinese-BIG5, Chinese-CNS, Chinese-GB, Cyrillic-ALT, Cyrillic-ISO,
265 Cyrillic-KOI8, Czech, Devanagari, Dutch, English, Ethiopic, German,
266 Greek, Hebrew, IPA, Japanese, Korean, Lao, Latin-1, Latin-2, Latin-3,
267 Latin-4, Latin-5, Latin-8 (Celtic), Latin-9 (updated Latin-1, with the
268 Euro sign), Polish, Romanian, Slovak, Slovenian, Spanish, Thai,
269 Tibetan, Turkish, and Vietnamese.
272 @cindex fonts for various scripts
273 @cindex Intlfonts package, installation
274 To display the script(s) used by your language environment on a
275 graphical display, you need to have a suitable font. If some of the
276 characters appear as empty boxes, you should install the GNU Intlfonts
277 package, which includes fonts for all supported scripts.@footnote{If
278 you run Emacs on X, you need to inform the X server about the location
279 of the newly installed fonts with the following commands:
282 xset fp+ /usr/local/share/emacs/fonts
286 @xref{Fontsets}, for more details about setting up your fonts.
288 @findex set-locale-environment
289 @vindex locale-language-names
290 @vindex locale-charset-language-names
292 Some operating systems let you specify the character-set locale you
293 are using by setting the locale environment variables @env{LC_ALL},
294 @env{LC_CTYPE}, or @env{LANG}.@footnote{If more than one of these is
295 set, the first one that is nonempty specifies your locale for this
296 purpose.} During startup, Emacs looks up your character-set locale's
297 name in the system locale alias table, matches its canonical name
298 against entries in the value of the variables
299 @code{locale-charset-language-names} and @code{locale-language-names},
300 and selects the corresponding language environment if a match is found.
301 (The former variable overrides the latter.) It also adjusts the display
302 table and terminal coding system, the locale coding system, the
303 preferred coding system as needed for the locale, and---last but not
304 least---the way Emacs decodes non-ASCII characters sent by your keyboard.
306 If you modify the @env{LC_ALL}, @env{LC_CTYPE}, or @env{LANG}
307 environment variables while running Emacs, you may want to invoke the
308 @code{set-locale-environment} function afterwards to readjust the
309 language environment from the new locale.
311 @vindex locale-preferred-coding-systems
312 The @code{set-locale-environment} function normally uses the preferred
313 coding system established by the language environment to decode system
314 messages. But if your locale matches an entry in the variable
315 @code{locale-preferred-coding-systems}, Emacs uses the corresponding
316 coding system instead. For example, if the locale @samp{ja_JP.PCK}
317 matches @code{japanese-shift-jis} in
318 @code{locale-preferred-coding-systems}, Emacs uses that encoding even
319 though it might normally use @code{japanese-iso-8bit}.
321 You can override the language environment chosen at startup with
322 explicit use of the command @code{set-language-environment}, or with
323 customization of @code{current-language-environment} in your init
327 @findex describe-language-environment
328 To display information about the effects of a certain language
329 environment @var{lang-env}, use the command @kbd{C-h L @var{lang-env}
330 @key{RET}} (@code{describe-language-environment}). This tells you which
331 languages this language environment is useful for, and lists the
332 character sets, coding systems, and input methods that go with it. It
333 also shows some sample text to illustrate scripts used in this language
334 environment. By default, this command describes the chosen language
337 @vindex set-language-environment-hook
338 You can customize any language environment with the normal hook
339 @code{set-language-environment-hook}. The command
340 @code{set-language-environment} runs that hook after setting up the new
341 language environment. The hook functions can test for a specific
342 language environment by checking the variable
343 @code{current-language-environment}. This hook is where you should
344 put non-default settings for specific language environment, such as
345 coding systems for keyboard input and terminal output, the default
348 @vindex exit-language-environment-hook
349 Before it starts to set up the new language environment,
350 @code{set-language-environment} first runs the hook
351 @code{exit-language-environment-hook}. This hook is useful for undoing
352 customizations that were made with @code{set-language-environment-hook}.
353 For instance, if you set up a special key binding in a specific language
354 environment using @code{set-language-environment-hook}, you should set
355 up @code{exit-language-environment-hook} to restore the normal binding
359 @section Input Methods
361 @cindex input methods
362 An @dfn{input method} is a kind of character conversion designed
363 specifically for interactive input. In Emacs, typically each language
364 has its own input method; sometimes several languages which use the same
365 characters can share one input method. A few languages support several
368 The simplest kind of input method works by mapping ASCII letters
369 into another alphabet; this allows you to use one other alphabet
370 instead of ASCII. The Greek and Russian input methods
373 A more powerful technique is composition: converting sequences of
374 characters into one letter. Many European input methods use composition
375 to produce a single non-ASCII letter from a sequence that consists of a
376 letter followed by accent characters (or vice versa). For example, some
377 methods convert the sequence @kbd{a'} into a single accented letter.
378 These input methods have no special commands of their own; all they do
379 is compose sequences of printing characters.
381 The input methods for syllabic scripts typically use mapping followed
382 by composition. The input methods for Thai and Korean work this way.
383 First, letters are mapped into symbols for particular sounds or tone
384 marks; then, sequences of these which make up a whole syllable are
385 mapped into one syllable sign.
387 Chinese and Japanese require more complex methods. In Chinese input
388 methods, first you enter the phonetic spelling of a Chinese word (in
389 input method @code{chinese-py}, among others), or a sequence of
390 portions of the character (input methods @code{chinese-4corner} and
391 @code{chinese-sw}, and others). One input sequence typically
392 corresponds to many possible Chinese characters. You select the one
393 you mean using keys such as @kbd{C-f}, @kbd{C-b}, @kbd{C-n},
394 @kbd{C-p}, and digits, which have special meanings in this situation.
396 The possible characters are conceptually arranged in several rows,
397 with each row holding up to 10 alternatives. Normally, Emacs displays
398 just one row at a time, in the echo area; @code{(@var{i}/@var{j})}
399 appears at the beginning, to indicate that this is the @var{i}th row
400 out of a total of @var{j} rows. Type @kbd{C-n} or @kbd{C-p} to
401 display the next row or the previous row.
403 Type @kbd{C-f} and @kbd{C-b} to move forward and backward among
404 the alternatives in the current row. As you do this, Emacs highlights
405 the current alternative with a special color; type @code{C-@key{SPC}}
406 to select the current alternative and use it as input. The
407 alternatives in the row are also numbered; the number appears before
408 the alternative. Typing a digit @var{n} selects the @var{n}th
409 alternative of the current row and uses it as input.
411 @key{TAB} in these Chinese input methods displays a buffer showing
412 all the possible characters at once; then clicking @kbd{Mouse-2} on
413 one of them selects that alternative. The keys @kbd{C-f}, @kbd{C-b},
414 @kbd{C-n}, @kbd{C-p}, and digits continue to work as usual, but they
415 do the highlighting in the buffer showing the possible characters,
416 rather than in the echo area.
418 In Japanese input methods, first you input a whole word using
419 phonetic spelling; then, after the word is in the buffer, Emacs
420 converts it into one or more characters using a large dictionary. One
421 phonetic spelling corresponds to a number of different Japanese words;
422 to select one of them, use @kbd{C-n} and @kbd{C-p} to cycle through
425 Sometimes it is useful to cut off input method processing so that the
426 characters you have just entered will not combine with subsequent
427 characters. For example, in input method @code{latin-1-postfix}, the
428 sequence @kbd{e '} combines to form an @samp{e} with an accent. What if
429 you want to enter them as separate characters?
431 One way is to type the accent twice; this is a special feature for
432 entering the separate letter and accent. For example, @kbd{e ' '} gives
433 you the two characters @samp{e'}. Another way is to type another letter
434 after the @kbd{e}---something that won't combine with that---and
435 immediately delete it. For example, you could type @kbd{e e @key{DEL}
436 '} to get separate @samp{e} and @samp{'}.
438 Another method, more general but not quite as easy to type, is to use
439 @kbd{C-\ C-\} between two characters to stop them from combining. This
440 is the command @kbd{C-\} (@code{toggle-input-method}) used twice.
442 @xref{Select Input Method}.
445 @cindex incremental search, input method interference
446 @kbd{C-\ C-\} is especially useful inside an incremental search,
447 because it stops waiting for more characters to combine, and starts
448 searching for what you have already entered.
450 @vindex input-method-verbose-flag
451 @vindex input-method-highlight-flag
452 The variables @code{input-method-highlight-flag} and
453 @code{input-method-verbose-flag} control how input methods explain
454 what is happening. If @code{input-method-highlight-flag} is
455 non-@code{nil}, the partial sequence is highlighted in the buffer (for
456 most input methods---some disable this feature). If
457 @code{input-method-verbose-flag} is non-@code{nil}, the list of
458 possible characters to type next is displayed in the echo area (but
459 not when you are in the minibuffer).
462 Input methods are implemented in the separate Leim package: they are
463 available only if the system administrator used Leim when building
464 Emacs. If Emacs was built without Leim, you will find that no input
467 @node Select Input Method
468 @section Selecting an Input Method
472 Enable or disable use of the selected input method.
474 @item C-x @key{RET} C-\ @var{method} @key{RET}
475 Select a new input method for the current buffer.
477 @item C-h I @var{method} @key{RET}
478 @itemx C-h C-\ @var{method} @key{RET}
479 @findex describe-input-method
482 Describe the input method @var{method} (@code{describe-input-method}).
483 By default, it describes the current input method (if any). This
484 description should give you the full details of how to use any
485 particular input method.
487 @item M-x list-input-methods
488 Display a list of all the supported input methods.
491 @findex set-input-method
492 @vindex current-input-method
494 To choose an input method for the current buffer, use @kbd{C-x
495 @key{RET} C-\} (@code{set-input-method}). This command reads the
496 input method name from the minibuffer; the name normally starts with the
497 language environment that it is meant to be used with. The variable
498 @code{current-input-method} records which input method is selected.
500 @findex toggle-input-method
502 Input methods use various sequences of ASCII characters to stand for
503 non-ASCII characters. Sometimes it is useful to turn off the input
504 method temporarily. To do this, type @kbd{C-\}
505 (@code{toggle-input-method}). To reenable the input method, type
508 If you type @kbd{C-\} and you have not yet selected an input method,
509 it prompts for you to specify one. This has the same effect as using
510 @kbd{C-x @key{RET} C-\} to specify an input method.
512 When invoked with a numeric argument, as in @kbd{C-u C-\},
513 @code{toggle-input-method} always prompts you for an input method,
514 suggesting the most recently selected one as the default.
516 @vindex default-input-method
517 Selecting a language environment specifies a default input method for
518 use in various buffers. When you have a default input method, you can
519 select it in the current buffer by typing @kbd{C-\}. The variable
520 @code{default-input-method} specifies the default input method
521 (@code{nil} means there is none).
523 In some language environments, which support several different input
524 methods, you might want to use an input method different from the
525 default chosen by @code{set-language-environment}. You can instruct
526 Emacs to select a different default input method for a certain
527 language environment, if you wish, by using
528 @code{set-language-environment-hook} (@pxref{Language Environments,
529 set-language-environment-hook}). For example:
532 (defun my-chinese-setup ()
533 "Set up my private Chinese environment."
534 (if (equal current-language-environment "Chinese-GB")
535 (setq default-input-method "chinese-tonepy")))
536 (add-hook 'set-language-environment-hook 'my-chinese-setup)
540 This sets the default input method to be @code{chinese-tonepy}
541 whenever you choose a Chinese-GB language environment.
543 @findex quail-set-keyboard-layout
544 Some input methods for alphabetic scripts work by (in effect)
545 remapping the keyboard to emulate various keyboard layouts commonly used
546 for those scripts. How to do this remapping properly depends on your
547 actual keyboard layout. To specify which layout your keyboard has, use
548 the command @kbd{M-x quail-set-keyboard-layout}.
550 @findex list-input-methods
551 To display a list of all the supported input methods, type @kbd{M-x
552 list-input-methods}. The list gives information about each input
553 method, including the string that stands for it in the mode line.
555 @node Multibyte Conversion
556 @section Unibyte and Multibyte Non-ASCII characters
558 When multibyte characters are enabled, character codes 0240 (octal)
559 through 0377 (octal) are not really legitimate in the buffer. The valid
560 non-ASCII printing characters have codes that start from 0400.
562 If you type a self-inserting character in the range 0240 through
563 0377, or if you use @kbd{C-q} to insert one, Emacs assumes you
564 intended to use one of the ISO Latin-@var{n} character sets, and
565 converts it to the Emacs code representing that Latin-@var{n}
566 character. You select @emph{which} ISO Latin character set to use
567 through your choice of language environment
572 (@pxref{Language Environments}).
574 If you do not specify a choice, the default is Latin-1.
576 If you insert a character in the range 0200 through 0237, which
577 forms the @code{eight-bit-control} character set, it is inserted
578 literally. You should normally avoid doing this since buffers
579 containing such characters have to be written out in either the
580 @code{emacs-mule} or @code{raw-text} coding system, which is usually
584 @section Coding Systems
585 @cindex coding systems
587 Users of various languages have established many more-or-less standard
588 coding systems for representing them. Emacs does not use these coding
589 systems internally; instead, it converts from various coding systems to
590 its own system when reading data, and converts the internal coding
591 system to other coding systems when writing data. Conversion is
592 possible in reading or writing files, in sending or receiving from the
593 terminal, and in exchanging data with subprocesses.
595 Emacs assigns a name to each coding system. Most coding systems are
596 used for one language, and the name of the coding system starts with the
597 language name. Some coding systems are used for several languages;
598 their names usually start with @samp{iso}. There are also special
599 coding systems @code{no-conversion}, @code{raw-text} and
600 @code{emacs-mule} which do not convert printing characters at all.
602 @cindex international files from DOS/Windows systems
603 A special class of coding systems, collectively known as
604 @dfn{codepages}, is designed to support text encoded by MS-Windows and
605 MS-DOS software. To use any of these systems, you need to create it
606 with @kbd{M-x codepage-setup}. @xref{MS-DOS and MULE}. After
607 creating the coding system for the codepage, you can use it as any
608 other coding system. For example, to visit a file encoded in codepage
609 850, type @kbd{C-x @key{RET} c cp850 @key{RET} C-x C-f @var{filename}
612 In addition to converting various representations of non-ASCII
613 characters, a coding system can perform end-of-line conversion. Emacs
614 handles three different conventions for how to separate lines in a file:
615 newline, carriage-return linefeed, and just carriage-return.
618 @item C-h C @var{coding} @key{RET}
619 Describe coding system @var{coding}.
621 @item C-h C @key{RET}
622 Describe the coding systems currently in use.
624 @item M-x list-coding-systems
625 Display a list of all the supported coding systems.
629 @findex describe-coding-system
630 The command @kbd{C-h C} (@code{describe-coding-system}) displays
631 information about particular coding systems. You can specify a coding
632 system name as the argument; alternatively, with an empty argument, it
633 describes the coding systems currently selected for various purposes,
634 both in the current buffer and as the defaults, and the priority list
635 for recognizing coding systems (@pxref{Recognize Coding}).
637 @findex list-coding-systems
638 To display a list of all the supported coding systems, type @kbd{M-x
639 list-coding-systems}. The list gives information about each coding
640 system, including the letter that stands for it in the mode line
643 @cindex end-of-line conversion
644 @cindex MS-DOS end-of-line conversion
645 @cindex Macintosh end-of-line conversion
646 Each of the coding systems that appear in this list---except for
647 @code{no-conversion}, which means no conversion of any kind---specifies
648 how and whether to convert printing characters, but leaves the choice of
649 end-of-line conversion to be decided based on the contents of each file.
650 For example, if the file appears to use the sequence carriage-return
651 linefeed to separate lines, DOS end-of-line conversion will be used.
653 Each of the listed coding systems has three variants which specify
654 exactly what to do for end-of-line conversion:
658 Don't do any end-of-line conversion; assume the file uses
659 newline to separate lines. (This is the convention normally used
660 on Unix and GNU systems.)
663 Assume the file uses carriage-return linefeed to separate lines, and do
664 the appropriate conversion. (This is the convention normally used on
665 Microsoft systems.@footnote{It is also specified for MIME @samp{text/*}
666 bodies and in other network transport contexts. It is different
667 from the SGML reference syntax record-start/record-end format which
668 Emacs doesn't support directly.})
671 Assume the file uses carriage-return to separate lines, and do the
672 appropriate conversion. (This is the convention normally used on the
676 These variant coding systems are omitted from the
677 @code{list-coding-systems} display for brevity, since they are entirely
678 predictable. For example, the coding system @code{iso-latin-1} has
679 variants @code{iso-latin-1-unix}, @code{iso-latin-1-dos} and
680 @code{iso-latin-1-mac}.
682 The coding system @code{raw-text} is good for a file which is mainly
683 ASCII text, but may contain byte values above 127 which are not meant to
684 encode non-ASCII characters. With @code{raw-text}, Emacs copies those
685 byte values unchanged, and sets @code{enable-multibyte-characters} to
686 @code{nil} in the current buffer so that they will be interpreted
687 properly. @code{raw-text} handles end-of-line conversion in the usual
688 way, based on the data encountered, and has the usual three variants to
689 specify the kind of end-of-line conversion to use.
691 In contrast, the coding system @code{no-conversion} specifies no
692 character code conversion at all---none for non-ASCII byte values and
693 none for end of line. This is useful for reading or writing binary
694 files, tar files, and other files that must be examined verbatim. It,
695 too, sets @code{enable-multibyte-characters} to @code{nil}.
697 The easiest way to edit a file with no conversion of any kind is with
698 the @kbd{M-x find-file-literally} command. This uses
699 @code{no-conversion}, and also suppresses other Emacs features that
700 might convert the file contents before you see them. @xref{Visiting}.
702 The coding system @code{emacs-mule} means that the file contains
703 non-ASCII characters stored with the internal Emacs encoding. It
704 handles end-of-line conversion based on the data encountered, and has
705 the usual three variants to specify the kind of end-of-line conversion.
707 @node Recognize Coding
708 @section Recognizing Coding Systems
710 Emacs tries to recognize which coding system to use for a given text
711 as an integral part of reading that text. (This applies to files
712 being read, output from subprocesses, text from X selections, etc.)
713 Emacs can select the right coding system automatically most of the
714 time---once you have specified your preferences.
716 Some coding systems can be recognized or distinguished by which byte
717 sequences appear in the data. However, there are coding systems that
718 cannot be distinguished, not even potentially. For example, there is no
719 way to distinguish between Latin-1 and Latin-2; they use the same byte
720 values with different meanings.
722 Emacs handles this situation by means of a priority list of coding
723 systems. Whenever Emacs reads a file, if you do not specify the coding
724 system to use, Emacs checks the data against each coding system,
725 starting with the first in priority and working down the list, until it
726 finds a coding system that fits the data. Then it converts the file
727 contents assuming that they are represented in this coding system.
729 The priority list of coding systems depends on the selected language
730 environment (@pxref{Language Environments}). For example, if you use
731 French, you probably want Emacs to prefer Latin-1 to Latin-2; if you use
732 Czech, you probably want Latin-2 to be preferred. This is one of the
733 reasons to specify a language environment.
735 @findex prefer-coding-system
736 However, you can alter the priority list in detail with the command
737 @kbd{M-x prefer-coding-system}. This command reads the name of a coding
738 system from the minibuffer, and adds it to the front of the priority
739 list, so that it is preferred to all others. If you use this command
740 several times, each use adds one element to the front of the priority
743 If you use a coding system that specifies the end-of-line conversion
744 type, such as @code{iso-8859-1-dos}, what this means is that Emacs
745 should attempt to recognize @code{iso-8859-1} with priority, and should
746 use DOS end-of-line conversion when it does recognize @code{iso-8859-1}.
748 @vindex file-coding-system-alist
749 Sometimes a file name indicates which coding system to use for the
750 file. The variable @code{file-coding-system-alist} specifies this
751 correspondence. There is a special function
752 @code{modify-coding-system-alist} for adding elements to this list. For
753 example, to read and write all @samp{.txt} files using the coding system
754 @code{china-iso-8bit}, you can execute this Lisp expression:
757 (modify-coding-system-alist 'file "\\.txt\\'" 'china-iso-8bit)
761 The first argument should be @code{file}, the second argument should be
762 a regular expression that determines which files this applies to, and
763 the third argument says which coding system to use for these files.
765 @vindex inhibit-eol-conversion
766 @cindex DOS-style end-of-line display
767 Emacs recognizes which kind of end-of-line conversion to use based on
768 the contents of the file: if it sees only carriage-returns, or only
769 carriage-return linefeed sequences, then it chooses the end-of-line
770 conversion accordingly. You can inhibit the automatic use of
771 end-of-line conversion by setting the variable @code{inhibit-eol-conversion}
772 to non-@code{nil}. If you do that, DOS-style files will be displayed
773 with the @samp{^M} characters visible in the buffer; some people
774 prefer this to the more subtle @samp{(DOS)} end-of-line type
775 indication near the left edge of the mode line (@pxref{Mode Line,
778 @vindex inhibit-iso-escape-detection
779 @cindex escape sequences in files
780 By default, the automatic detection of coding system is sensitive to
781 escape sequences. If Emacs sees a sequence of characters that begin
782 with an escape character, and the sequence is valid as an ISO-2022
783 code, that tells Emacs to use one of the ISO-2022 encodings to decode
786 However, there may be cases that you want to read escape sequences
787 in a file as is. In such a case, you can set the variable
788 @code{inhibit-iso-escape-detection} to non-@code{nil}. Then the code
789 detection ignores any escape sequences, and never uses an ISO-2022
790 encoding. The result is that all escape sequences become visible in
793 The default value of @code{inhibit-iso-escape-detection} is
794 @code{nil}. We recommend that you not change it permanently, only for
795 one specific operation. That's because many Emacs Lisp source files
796 in the Emacs distribution contain non-ASCII characters encoded in the
797 coding system @code{iso-2022-7bit}, and they won't be
798 decoded correctly when you visit those files if you suppress the
799 escape sequence detection.
802 You can specify the coding system for a particular file using the
803 @w{@samp{-*-@dots{}-*-}} construct at the beginning of a file, or a
804 local variables list at the end (@pxref{File Variables}). You do this
805 by defining a value for the ``variable'' named @code{coding}. Emacs
806 does not really have a variable @code{coding}; instead of setting a
807 variable, this uses the specified coding system for the file. For
808 example, @samp{-*-mode: C; coding: latin-1;-*-} specifies use of the
809 Latin-1 coding system, as well as C mode. When you specify the coding
810 explicitly in the file, that overrides
811 @code{file-coding-system-alist}.
813 @vindex auto-coding-alist
814 @vindex auto-coding-regexp-alist
815 The variables @code{auto-coding-alist} and
816 @code{auto-coding-regexp-alist} are the strongest way to specify the
817 coding system for certain patterns of file names, or for files
818 containing certain patterns; these variables even override
819 @samp{-*-coding:-*-} tags in the file itself. Emacs uses
820 @code{auto-coding-alist} for tar and archive files, to prevent it
821 from being confused by a @samp{-*-coding:-*-} tag in a member of the
822 archive and thinking it applies to the archive file as a whole.
823 Likewise, Emacs uses @code{auto-coding-regexp-alist} to ensure that
824 RMAIL files, whose names in general don't match any particular pattern,
825 are decoded correctly.
827 If Emacs recognizes the encoding of a file incorrectly, you can
828 reread the file using the correct coding system by typing @kbd{C-x
829 @key{RET} c @var{coding-system} @key{RET} M-x revert-buffer
830 @key{RET}}. To see what coding system Emacs actually used to decode
831 the file, look at the coding system mnemonic letter near the left edge
832 of the mode line (@pxref{Mode Line}), or type @kbd{C-h C @key{RET}}.
834 @vindex buffer-file-coding-system
835 Once Emacs has chosen a coding system for a buffer, it stores that
836 coding system in @code{buffer-file-coding-system} and uses that coding
837 system, by default, for operations that write from this buffer into a
838 file. This includes the commands @code{save-buffer} and
839 @code{write-region}. If you want to write files from this buffer using
840 a different coding system, you can specify a different coding system for
841 the buffer using @code{set-buffer-file-coding-system} (@pxref{Specify
844 You can insert any possible character into any Emacs buffer, but
845 most coding systems can only handle some of the possible characters.
846 This means that it is possible for you to insert characters that
847 cannot be encoded with the coding system that will be used to save the
848 buffer. For example, you could start with an ASCII file and insert a
849 few Latin-1 characters into it, or you could edit a text file in
850 Polish encoded in @code{iso-8859-2} and add some Russian words to it.
851 When you save the buffer, Emacs cannot use the current value of
852 @code{buffer-file-coding-system}, because the characters you added
853 cannot be encoded by that coding system.
855 When that happens, Emacs tries the most-preferred coding system (set
856 by @kbd{M-x prefer-coding-system} or @kbd{M-x
857 set-language-environment}), and if that coding system can safely
858 encode all of the characters in the buffer, Emacs uses it, and stores
859 its value in @code{buffer-file-coding-system}. Otherwise, Emacs
860 displays a list of coding systems suitable for encoding the buffer's
861 contents, and asks you to choose one of those coding systems.
863 If you insert the unsuitable characters in a mail message, Emacs
864 behaves a bit differently. It additionally checks whether the
865 most-preferred coding system is recommended for use in MIME messages;
866 if not, Emacs tells you that the most-preferred coding system is
867 not recommended and prompts you for another coding system. This is so
868 you won't inadvertently send a message encoded in a way that your
869 recipient's mail software will have difficulty decoding. (If you do
870 want to use the most-preferred coding system, you can still type its
871 name in response to the question.)
873 @vindex sendmail-coding-system
874 When you send a message with Mail mode (@pxref{Sending Mail}), Emacs has
875 four different ways to determine the coding system to use for encoding
876 the message text. It tries the buffer's own value of
877 @code{buffer-file-coding-system}, if that is non-@code{nil}. Otherwise,
878 it uses the value of @code{sendmail-coding-system}, if that is
879 non-@code{nil}. The third way is to use the default coding system for
880 new files, which is controlled by your choice of language environment,
881 if that is non-@code{nil}. If all of these three values are @code{nil},
882 Emacs encodes outgoing mail using the Latin-1 coding system.
884 @vindex rmail-decode-mime-charset
885 When you get new mail in Rmail, each message is translated
886 automatically from the coding system it is written in, as if it were a
887 separate file. This uses the priority list of coding systems that you
888 have specified. If a MIME message specifies a character set, Rmail
889 obeys that specification, unless @code{rmail-decode-mime-charset} is
892 @vindex rmail-file-coding-system
893 For reading and saving Rmail files themselves, Emacs uses the coding
894 system specified by the variable @code{rmail-file-coding-system}. The
895 default value is @code{nil}, which means that Rmail files are not
896 translated (they are read and written in the Emacs internal character
900 @section Specifying a Coding System
902 In cases where Emacs does not automatically choose the right coding
903 system, you can use these commands to specify one:
906 @item C-x @key{RET} f @var{coding} @key{RET}
907 Use coding system @var{coding} for the visited file
908 in the current buffer.
910 @item C-x @key{RET} c @var{coding} @key{RET}
911 Specify coding system @var{coding} for the immediately following
914 @item C-x @key{RET} k @var{coding} @key{RET}
915 Use coding system @var{coding} for keyboard input.
917 @item C-x @key{RET} t @var{coding} @key{RET}
918 Use coding system @var{coding} for terminal output.
920 @item C-x @key{RET} p @var{input-coding} @key{RET} @var{output-coding} @key{RET}
921 Use coding systems @var{input-coding} and @var{output-coding} for
922 subprocess input and output in the current buffer.
924 @item C-x @key{RET} x @var{coding} @key{RET}
925 Use coding system @var{coding} for transferring selections to and from
926 other programs through the window system.
928 @item C-x @key{RET} X @var{coding} @key{RET}
929 Use coding system @var{coding} for transferring @emph{one}
930 selection---the next one---to or from the window system.
934 @findex set-buffer-file-coding-system
935 The command @kbd{C-x @key{RET} f} (@code{set-buffer-file-coding-system})
936 specifies the file coding system for the current buffer---in other
937 words, which coding system to use when saving or rereading the visited
938 file. You specify which coding system using the minibuffer. Since this
939 command applies to a file you have already visited, it affects only the
940 way the file is saved.
943 @findex universal-coding-system-argument
944 Another way to specify the coding system for a file is when you visit
945 the file. First use the command @kbd{C-x @key{RET} c}
946 (@code{universal-coding-system-argument}); this command uses the
947 minibuffer to read a coding system name. After you exit the minibuffer,
948 the specified coding system is used for @emph{the immediately following
951 So if the immediately following command is @kbd{C-x C-f}, for example,
952 it reads the file using that coding system (and records the coding
953 system for when the file is saved). Or if the immediately following
954 command is @kbd{C-x C-w}, it writes the file using that coding system.
955 Other file commands affected by a specified coding system include
956 @kbd{C-x C-i} and @kbd{C-x C-v}, as well as the other-window variants of
959 @kbd{C-x @key{RET} c} also affects commands that start subprocesses,
960 including @kbd{M-x shell} (@pxref{Shell}).
962 However, if the immediately following command does not use the coding
963 system, then @kbd{C-x @key{RET} c} ultimately has no effect.
965 An easy way to visit a file with no conversion is with the @kbd{M-x
966 find-file-literally} command. @xref{Visiting}.
968 @vindex default-buffer-file-coding-system
969 The variable @code{default-buffer-file-coding-system} specifies the
970 choice of coding system to use when you create a new file. It applies
971 when you find a new file, and when you create a buffer and then save it
972 in a file. Selecting a language environment typically sets this
973 variable to a good choice of default coding system for that language
977 @findex set-terminal-coding-system
978 The command @kbd{C-x @key{RET} t} (@code{set-terminal-coding-system})
979 specifies the coding system for terminal output. If you specify a
980 character code for terminal output, all characters output to the
981 terminal are translated into that coding system.
983 This feature is useful for certain character-only terminals built to
984 support specific languages or character sets---for example, European
985 terminals that support one of the ISO Latin character sets. You need to
986 specify the terminal coding system when using multibyte text, so that
987 Emacs knows which characters the terminal can actually handle.
989 By default, output to the terminal is not translated at all, unless
990 Emacs can deduce the proper coding system from your terminal type or
991 your locale specification (@pxref{Language Environments}).
994 @findex set-keyboard-coding-system
995 @vindex keyboard-coding-system
996 The command @kbd{C-x @key{RET} k} (@code{set-keyboard-coding-system})
997 or the Custom option @code{keyboard-coding-system}
998 specifies the coding system for keyboard input. Character-code
999 translation of keyboard input is useful for terminals with keys that
1000 send non-ASCII graphic characters---for example, some terminals designed
1001 for ISO Latin-1 or subsets of it.
1003 By default, keyboard input is not translated at all.
1005 There is a similarity between using a coding system translation for
1006 keyboard input, and using an input method: both define sequences of
1007 keyboard input that translate into single characters. However, input
1008 methods are designed to be convenient for interactive use by humans, and
1009 the sequences that are translated are typically sequences of ASCII
1010 printing characters. Coding systems typically translate sequences of
1011 non-graphic characters.
1015 @findex set-selection-coding-system
1016 @findex set-next-selection-coding-system
1017 The command @kbd{C-x @key{RET} x} (@code{set-selection-coding-system})
1018 specifies the coding system for sending selected text to the window
1019 system, and for receiving the text of selections made in other
1020 applications. This command applies to all subsequent selections, until
1021 you override it by using the command again. The command @kbd{C-x
1022 @key{RET} X} (@code{set-next-selection-coding-system}) specifies the
1023 coding system for the next selection made in Emacs or read by Emacs.
1026 @findex set-buffer-process-coding-system
1027 The command @kbd{C-x @key{RET} p} (@code{set-buffer-process-coding-system})
1028 specifies the coding system for input and output to a subprocess. This
1029 command applies to the current buffer; normally, each subprocess has its
1030 own buffer, and thus you can use this command to specify translation to
1031 and from a particular subprocess by giving the command in the
1032 corresponding buffer.
1034 The default for translation of process input and output depends on the
1035 current language environment.
1037 @vindex file-name-coding-system
1038 @cindex file names with non-ASCII characters
1039 The variable @code{file-name-coding-system} specifies a coding system
1040 to use for encoding file names. If you set the variable to a coding
1041 system name (as a Lisp symbol or a string), Emacs encodes file names
1042 using that coding system for all file operations. This makes it
1043 possible to use non-ASCII characters in file names---or, at least, those
1044 non-ASCII characters which the specified coding system can encode.
1046 If @code{file-name-coding-system} is @code{nil}, Emacs uses a default
1047 coding system determined by the selected language environment. In the
1048 default language environment, any non-ASCII characters in file names are
1049 not encoded specially; they appear in the file system using the internal
1050 Emacs representation.
1052 @strong{Warning:} if you change @code{file-name-coding-system} (or the
1053 language environment) in the middle of an Emacs session, problems can
1054 result if you have already visited files whose names were encoded using
1055 the earlier coding system and cannot be encoded (or are encoded
1056 differently) under the new coding system. If you try to save one of
1057 these buffers under the visited file name, saving may use the wrong file
1058 name, or it may get an error. If such a problem happens, use @kbd{C-x
1059 C-w} to specify a new file name for that buffer.
1061 @vindex locale-coding-system
1062 @cindex decoding non-ASCII keyboard input on X
1063 The variable @code{locale-coding-system} specifies a coding system
1064 to use when encoding and decoding system strings such as system error
1065 messages and @code{format-time-string} formats and time stamps. That
1066 coding system is also used for decoding non-ASCII keyboard input on X
1067 Window systems. You should choose a coding system that is compatible
1068 with the underlying system's text representation, which is normally
1069 specified by one of the environment variables @env{LC_ALL},
1070 @env{LC_CTYPE}, and @env{LANG}. (The first one, in the order
1071 specified above, whose value is nonempty is the one that determines
1072 the text representation.)
1078 A font for X typically defines shapes for a single alphabet or script.
1079 Therefore, displaying the entire range of scripts that Emacs supports
1080 requires a collection of many fonts. In Emacs, such a collection is
1081 called a @dfn{fontset}. A fontset is defined by a list of fonts, each
1082 assigned to handle a range of character codes.
1084 Each fontset has a name, like a font. The available X fonts are
1085 defined by the X server; fontsets, however, are defined within Emacs
1086 itself. Once you have defined a fontset, you can use it within Emacs by
1087 specifying its name, anywhere that you could use a single font. Of
1088 course, Emacs fontsets can use only the fonts that the X server
1089 supports; if certain characters appear on the screen as hollow boxes,
1090 this means that the fontset in use for them has no font for those
1091 characters.@footnote{The Emacs installation instructions have information on
1092 additional font support.}
1094 Emacs creates two fontsets automatically: the @dfn{standard fontset}
1095 and the @dfn{startup fontset}. The standard fontset is most likely to
1096 have fonts for a wide variety of non-ASCII characters; however, this is
1097 not the default for Emacs to use. (By default, Emacs tries to find a
1098 font that has bold and italic variants.) You can specify use of the
1099 standard fontset with the @samp{-fn} option, or with the @samp{Font} X
1100 resource (@pxref{Font X}). For example,
1103 emacs -fn fontset-standard
1106 A fontset does not necessarily specify a font for every character
1107 code. If a fontset specifies no font for a certain character, or if it
1108 specifies a font that does not exist on your system, then it cannot
1109 display that character properly. It will display that character as an
1112 @vindex highlight-wrong-size-font
1113 The fontset height and width are determined by the ASCII characters
1114 (that is, by the font used for ASCII characters in that fontset). If
1115 another font in the fontset has a different height, or a different
1116 width, then characters assigned to that font are clipped to the
1117 fontset's size. If @code{highlight-wrong-size-font} is non-@code{nil},
1118 a box is displayed around these wrong-size characters as well.
1120 @node Defining Fontsets
1121 @section Defining fontsets
1123 @vindex standard-fontset-spec
1124 @cindex standard fontset
1125 Emacs creates a standard fontset automatically according to the value
1126 of @code{standard-fontset-spec}. This fontset's name is
1129 -*-fixed-medium-r-normal-*-16-*-*-*-*-*-fontset-standard
1133 or just @samp{fontset-standard} for short.
1135 Bold, italic, and bold-italic variants of the standard fontset are
1136 created automatically. Their names have @samp{bold} instead of
1137 @samp{medium}, or @samp{i} instead of @samp{r}, or both.
1139 @cindex startup fontset
1140 If you specify a default ASCII font with the @samp{Font} resource or
1141 the @samp{-fn} argument, Emacs generates a fontset from it
1142 automatically. This is the @dfn{startup fontset} and its name is
1143 @code{fontset-startup}. It does this by replacing the @var{foundry},
1144 @var{family}, @var{add_style}, and @var{average_width} fields of the
1145 font name with @samp{*}, replacing @var{charset_registry} field with
1146 @samp{fontset}, and replacing @var{charset_encoding} field with
1147 @samp{startup}, then using the resulting string to specify a fontset.
1149 For instance, if you start Emacs this way,
1152 emacs -fn "*courier-medium-r-normal--14-140-*-iso8859-1"
1156 Emacs generates the following fontset and uses it for the initial X
1160 -*-*-medium-r-normal-*-14-140-*-*-*-*-fontset-startup
1163 With the X resource @samp{Emacs.Font}, you can specify a fontset name
1164 just like an actual font name. But be careful not to specify a fontset
1165 name in a wildcard resource like @samp{Emacs*Font}---that wildcard
1166 specification matches various other resources, such as for menus, and
1167 menus cannot handle fontsets.
1169 You can specify additional fontsets using X resources named
1170 @samp{Fontset-@var{n}}, where @var{n} is an integer starting from 0.
1171 The resource value should have this form:
1174 @var{fontpattern}, @r{[}@var{charsetname}:@var{fontname}@r{]@dots{}}
1178 @var{fontpattern} should have the form of a standard X font name, except
1179 for the last two fields. They should have the form
1180 @samp{fontset-@var{alias}}.
1182 The fontset has two names, one long and one short. The long name is
1183 @var{fontpattern}. The short name is @samp{fontset-@var{alias}}. You
1184 can refer to the fontset by either name.
1186 The construct @samp{@var{charset}:@var{font}} specifies which font to
1187 use (in this fontset) for one particular character set. Here,
1188 @var{charset} is the name of a character set, and @var{font} is the
1189 font to use for that character set. You can use this construct any
1190 number of times in defining one fontset.
1192 For the other character sets, Emacs chooses a font based on
1193 @var{fontpattern}. It replaces @samp{fontset-@var{alias}} with values
1194 that describe the character set. For the ASCII character font,
1195 @samp{fontset-@var{alias}} is replaced with @samp{ISO8859-1}.
1197 In addition, when several consecutive fields are wildcards, Emacs
1198 collapses them into a single wildcard. This is to prevent use of
1199 auto-scaled fonts. Fonts made by scaling larger fonts are not usable
1200 for editing, and scaling a smaller font is not useful because it is
1201 better to use the smaller font in its own size, which is what Emacs
1204 Thus if @var{fontpattern} is this,
1207 -*-fixed-medium-r-normal-*-24-*-*-*-*-*-fontset-24
1211 the font specification for ASCII characters would be this:
1214 -*-fixed-medium-r-normal-*-24-*-ISO8859-1
1218 and the font specification for Chinese GB2312 characters would be this:
1221 -*-fixed-medium-r-normal-*-24-*-gb2312*-*
1224 You may not have any Chinese font matching the above font
1225 specification. Most X distributions include only Chinese fonts that
1226 have @samp{song ti} or @samp{fangsong ti} in @var{family} field. In
1227 such a case, @samp{Fontset-@var{n}} can be specified as below:
1230 Emacs.Fontset-0: -*-fixed-medium-r-normal-*-24-*-*-*-*-*-fontset-24,\
1231 chinese-gb2312:-*-*-medium-r-normal-*-24-*-gb2312*-*
1235 Then, the font specifications for all but Chinese GB2312 characters have
1236 @samp{fixed} in the @var{family} field, and the font specification for
1237 Chinese GB2312 characters has a wild card @samp{*} in the @var{family}
1240 @findex create-fontset-from-fontset-spec
1241 The function that processes the fontset resource value to create the
1242 fontset is called @code{create-fontset-from-fontset-spec}. You can also
1243 call this function explicitly to create a fontset.
1245 @xref{Font X}, for more information about font naming in X.
1247 @node Undisplayable Characters
1248 @section Undisplayable Characters
1250 Your terminal may be unable to display some non-ASCII
1251 characters. Most non-windowing terminals can only use a single
1252 character set (use the variable @code{default-terminal-coding-system}
1253 (@pxref{Specify Coding}) to tell Emacs which one); characters which
1254 can't be encoded in that coding system are displayed as @samp{?} by
1257 Windowing terminals can display a broader range of characters, but
1258 you may not have fonts installed for all of them; characters that have
1259 no font appear as a hollow box.
1261 If you use Latin-1 characters but your terminal can't display
1262 Latin-1, you can arrange to display mnemonic ASCII sequences
1263 instead, e.g.@: @samp{"o} for o-umlaut. Load the library
1264 @file{iso-ascii} to do this.
1266 @vindex latin1-display
1267 If your terminal can display Latin-1, you can display characters
1268 from other European character sets using a mixture of equivalent
1269 Latin-1 characters and ASCII mnemonics. Use the Custom option
1270 @code{latin1-display} to enable this. The mnemonic ASCII
1271 sequences mostly correspond to those of the prefix input methods.
1273 @node Single-Byte Character Support
1274 @section Single-byte Character Set Support
1276 @cindex European character sets
1277 @cindex accented characters
1278 @cindex ISO Latin character sets
1279 @cindex Unibyte operation
1280 The ISO 8859 Latin-@var{n} character sets define character codes in
1281 the range 0240 to 0377 octal (160 to 255 decimal) to handle the
1282 accented letters and punctuation needed by various European languages
1283 (and some non-European ones). If you disable multibyte characters,
1284 Emacs can still handle @emph{one} of these character codes at a time.
1285 To specify @emph{which} of these codes to use, invoke @kbd{M-x
1286 set-language-environment} and specify a suitable language environment
1287 such as @samp{Latin-@var{n}}.
1289 For more information about unibyte operation, see @ref{Enabling
1290 Multibyte}. Note particularly that you probably want to ensure that
1291 your initialization files are read as unibyte if they contain non-ASCII
1294 @vindex unibyte-display-via-language-environment
1295 Emacs can also display those characters, provided the terminal or font
1296 in use supports them. This works automatically. Alternatively, if you
1297 are using a window system, Emacs can also display single-byte characters
1298 through fontsets, in effect by displaying the equivalent multibyte
1299 characters according to the current language environment. To request
1300 this, set the variable @code{unibyte-display-via-language-environment}
1301 to a non-@code{nil} value.
1303 @cindex @code{iso-ascii} library
1304 If your terminal does not support display of the Latin-1 character
1305 set, Emacs can display these characters as ASCII sequences which at
1306 least give you a clear idea of what the characters are. To do this,
1307 load the library @code{iso-ascii}. Similar libraries for other
1308 Latin-@var{n} character sets could be implemented, but we don't have
1311 @findex standard-display-8bit
1312 @cindex 8-bit display
1313 Normally non-ISO-8859 characters (decimal codes between 128 and 159
1314 inclusive) are displayed as octal escapes. You can change this for
1315 non-standard ``extended'' versions of ISO-8859 character sets by using the
1316 function @code{standard-display-8bit} in the @code{disp-table} library.
1318 There are several ways you can input single-byte non-ASCII
1324 If your keyboard can generate character codes 128 (decimal) and up,
1325 representing non-ASCII characters, you can type those character codes
1328 On a windowing terminal, you should not need to do anything special to
1329 use these keys; they should simply work. On a text-only terminal, you
1330 should use the command @code{M-x set-keyboard-coding-system} or the
1331 Custom option @code{keyboard-coding-system} to specify which coding
1332 system your keyboard uses (@pxref{Specify Coding}). Enabling this
1333 feature will probably require you to use @kbd{ESC} to type Meta
1334 characters; however, on a Linux console or in @code{xterm}, you can
1335 arrange for Meta to be converted to @kbd{ESC} and still be able type
1336 8-bit characters present directly on the keyboard or using
1337 @kbd{Compose} or @kbd{AltGr} keys. @xref{User Input}.
1340 You can use an input method for the selected language environment.
1341 @xref{Input Methods}. When you use an input method in a unibyte buffer,
1342 the non-ASCII character you specify with it is converted to unibyte.
1345 @cindex @code{iso-transl} library
1346 @cindex compose character
1347 @cindex dead character
1349 For Latin-1 only, you can use the
1350 key @kbd{C-x 8} as a ``compose character'' prefix for entry of
1351 non-ASCII Latin-1 printing characters. @kbd{C-x 8} is good for
1352 insertion (in the minibuffer as well as other buffers), for searching,
1353 and in any other context where a key sequence is allowed.
1355 @kbd{C-x 8} works by loading the @code{iso-transl} library. Once that
1356 library is loaded, the @key{ALT} modifier key, if you have one, serves
1357 the same purpose as @kbd{C-x 8}; use @key{ALT} together with an accent
1358 character to modify the following letter. In addition, if you have keys
1359 for the Latin-1 ``dead accent characters,'' they too are defined to
1360 compose with the following character, once @code{iso-transl} is loaded.
1361 Use @kbd{C-x 8 C-h} to list the available translations as mnemonic
1365 @cindex @code{iso-acc} library
1366 @cindex ISO Accents mode
1367 @findex iso-accents-mode
1368 @cindex Latin-1, Latin-2 and Latin-3 input mode
1369 For Latin-1, Latin-2 and Latin-3, @kbd{M-x iso-accents-mode} enables
1370 a minor mode that works much like the @code{latin-1-prefix} input
1371 method, but does not depend on having the input methods installed. This
1372 mode is buffer-local. It can be customized for various languages with
1373 @kbd{M-x iso-accents-customize}.