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6bf7aab6 | 1 | @c This is part of the Emacs manual. |
98c271eb | 2 | @c Copyright (C) 1997, 1999, 2000 Free Software Foundation, Inc. |
6bf7aab6 DL |
3 | @c See file emacs.texi for copying conditions. |
4 | @node International, Major Modes, Frames, Top | |
5 | @chapter International Character Set Support | |
6 | @cindex MULE | |
7 | @cindex international scripts | |
8 | @cindex multibyte characters | |
9 | @cindex encoding of characters | |
10 | ||
cca7bf28 | 11 | @cindex Celtic |
6bf7aab6 | 12 | @cindex Chinese |
fbc164de | 13 | @cindex Cyrillic |
cca7bf28 | 14 | @cindex Czech |
6bf7aab6 DL |
15 | @cindex Devanagari |
16 | @cindex Hindi | |
17 | @cindex Marathi | |
fbc164de | 18 | @cindex Ethiopic |
cca7bf28 | 19 | @cindex German |
6bf7aab6 | 20 | @cindex Greek |
fbc164de | 21 | @cindex Hebrew |
6bf7aab6 DL |
22 | @cindex IPA |
23 | @cindex Japanese | |
24 | @cindex Korean | |
25 | @cindex Lao | |
cca7bf28 EZ |
26 | @cindex Latin |
27 | @cindex Polish | |
28 | @cindex Romanian | |
29 | @cindex Slovak | |
30 | @cindex Slovenian | |
6bf7aab6 DL |
31 | @cindex Thai |
32 | @cindex Tibetan | |
cca7bf28 | 33 | @cindex Turkish |
6bf7aab6 | 34 | @cindex Vietnamese |
732b9cdd GM |
35 | @cindex Dutch |
36 | @cindex Spanish | |
6bf7aab6 DL |
37 | Emacs supports a wide variety of international character sets, |
38 | including European variants of the Latin alphabet, as well as Chinese, | |
fbc164de PE |
39 | Cyrillic, Devanagari (Hindi and Marathi), Ethiopic, Greek, Hebrew, IPA, |
40 | Japanese, Korean, Lao, Thai, Tibetan, and Vietnamese scripts. These features | |
6bf7aab6 DL |
41 | have been merged from the modified version of Emacs known as MULE (for |
42 | ``MULti-lingual Enhancement to GNU Emacs'') | |
43 | ||
9d9c2e39 | 44 | Emacs also supports various encodings of these characters used by |
4b40407a | 45 | other internationalized software, such as word processors and mailers. |
9d9c2e39 | 46 | |
6bf7aab6 DL |
47 | @menu |
48 | * International Intro:: Basic concepts of multibyte characters. | |
49 | * Enabling Multibyte:: Controlling whether to use multibyte characters. | |
50 | * Language Environments:: Setting things up for the language you use. | |
51 | * Input Methods:: Entering text characters not on your keyboard. | |
52 | * Select Input Method:: Specifying your choice of input methods. | |
53 | * Multibyte Conversion:: How single-byte characters convert to multibyte. | |
54 | * Coding Systems:: Character set conversion when you read and | |
55 | write files, and so on. | |
56 | * Recognize Coding:: How Emacs figures out which conversion to use. | |
57 | * Specify Coding:: Various ways to choose which conversion to use. | |
58 | * Fontsets:: Fontsets are collections of fonts | |
59 | that cover the whole spectrum of characters. | |
60 | * Defining Fontsets:: Defining a new fontset. | |
60245086 | 61 | * Undisplayable Characters:: When characters don't display. |
521ab838 | 62 | * Single-Byte Character Support:: |
6bf7aab6 DL |
63 | You can pick one European character set |
64 | to use without multibyte characters. | |
65 | @end menu | |
66 | ||
67 | @node International Intro | |
68 | @section Introduction to International Character Sets | |
69 | ||
2565a55e EZ |
70 | The users of international character sets and scripts have established |
71 | many more-or-less standard coding systems for storing files. Emacs | |
72 | internally uses a single multibyte character encoding, so that it can | |
73 | intermix characters from all these scripts in a single buffer or string. | |
74 | This encoding represents each non-ASCII character as a sequence of bytes | |
75 | in the range 0200 through 0377. Emacs translates between the multibyte | |
76 | character encoding and various other coding systems when reading and | |
77 | writing files, when exchanging data with subprocesses, and (in some | |
78 | cases) in the @kbd{C-q} command (@pxref{Multibyte Conversion}). | |
6bf7aab6 DL |
79 | |
80 | @kindex C-h h | |
81 | @findex view-hello-file | |
457b792c | 82 | @cindex undisplayable characters |
4b40407a | 83 | @cindex @samp{?} in display |
6bf7aab6 DL |
84 | The command @kbd{C-h h} (@code{view-hello-file}) displays the file |
85 | @file{etc/HELLO}, which shows how to say ``hello'' in many languages. | |
4b40407a RS |
86 | This illustrates various scripts. If some characters can't be |
87 | displayed on your terminal, they appear as @samp{?} or as hollow boxes | |
88 | (@pxref{Undisplayable Characters}). | |
89 | ||
90 | Keyboards, even in the countries where these character sets are used, | |
91 | generally don't have keys for all the characters in them. So Emacs | |
92 | supports various @dfn{input methods}, typically one for each script or | |
93 | language, to make it convenient to type them. | |
94 | ||
95 | @kindex C-x RET | |
96 | The prefix key @kbd{C-x @key{RET}} is used for commands that pertain | |
97 | to multibyte characters, coding systems, and input methods. | |
98 | ||
99 | @ignore | |
100 | @c This is commented out because it doesn't fit here, or anywhere. | |
101 | @c This manual does not discuss "character sets" as they | |
102 | @c are used in Mule, and it makes no sense to mention these commands | |
103 | @c except as part of a larger discussion of the topic. | |
104 | @c But it is not clear that topic is worth mentioning here, | |
105 | @c since that is more of an implementation concept | |
106 | @c than a user-level concept. And when we switch to Unicode, | |
107 | @c character sets in the current sense may not even exist. | |
6bf7aab6 | 108 | |
2565a55e EZ |
109 | @findex list-charset-chars |
110 | @cindex characters in a certain charset | |
111 | The command @kbd{M-x list-charset-chars} prompts for a name of a | |
112 | character set, and displays all the characters in that character set. | |
113 | ||
f5fac081 EZ |
114 | @findex describe-character-set |
115 | @cindex character set, description | |
116 | The command @kbd{M-x describe-character-set} prompts for a character | |
117 | set name and displays information about that character set, including | |
118 | its internal representation within Emacs. | |
4b40407a | 119 | @end ignore |
6bf7aab6 DL |
120 | |
121 | @node Enabling Multibyte | |
122 | @section Enabling Multibyte Characters | |
123 | ||
124 | You can enable or disable multibyte character support, either for | |
125 | Emacs as a whole, or for a single buffer. When multibyte characters are | |
126 | disabled in a buffer, then each byte in that buffer represents a | |
127 | character, even codes 0200 through 0377. The old features for | |
128 | supporting the European character sets, ISO Latin-1 and ISO Latin-2, | |
129 | work as they did in Emacs 19 and also work for the other ISO 8859 | |
130 | character sets. | |
131 | ||
132 | However, there is no need to turn off multibyte character support to | |
133 | use ISO Latin; the Emacs multibyte character set includes all the | |
134 | characters in these character sets, and Emacs can translate | |
135 | automatically to and from the ISO codes. | |
136 | ||
137 | To edit a particular file in unibyte representation, visit it using | |
138 | @code{find-file-literally}. @xref{Visiting}. To convert a buffer in | |
139 | multibyte representation into a single-byte representation of the same | |
140 | characters, the easiest way is to save the contents in a file, kill the | |
141 | buffer, and find the file again with @code{find-file-literally}. You | |
142 | can also use @kbd{C-x @key{RET} c} | |
143 | (@code{universal-coding-system-argument}) and specify @samp{raw-text} as | |
144 | the coding system with which to find or save a file. @xref{Specify | |
145 | Coding}. Finding a file as @samp{raw-text} doesn't disable format | |
146 | conversion, uncompression and auto mode selection as | |
147 | @code{find-file-literally} does. | |
148 | ||
149 | @vindex enable-multibyte-characters | |
150 | @vindex default-enable-multibyte-characters | |
151 | To turn off multibyte character support by default, start Emacs with | |
152 | the @samp{--unibyte} option (@pxref{Initial Options}), or set the | |
60a96371 | 153 | environment variable @env{EMACS_UNIBYTE}. You can also customize |
6bf7aab6 DL |
154 | @code{enable-multibyte-characters} or, equivalently, directly set the |
155 | variable @code{default-enable-multibyte-characters} in your init file to | |
156 | have basically the same effect as @samp{--unibyte}. | |
157 | ||
576f17ff EZ |
158 | @cindex Lisp files, and multibyte operation |
159 | @cindex multibyte operation, and Lisp files | |
160 | @cindex unibyte operation, and Lisp files | |
161 | @cindex init file, and non-ASCII characters | |
162 | @cindex environment variables, and non-ASCII characters | |
4b40407a RS |
163 | With @samp{--unibyte}, multibyte strings are not created during |
164 | initialization from the values of environment variables, | |
165 | @file{/etc/passwd} entries etc.@: that contain non-ASCII 8-bit | |
166 | characters. | |
167 | ||
168 | Emacs normally loads Lisp files as multibyte, regardless of whether | |
169 | you used @samp{--unibyte}. This includes the Emacs initialization | |
170 | file, @file{.emacs}, and the initialization files of Emacs packages | |
171 | such as Gnus. However, you can specify unibyte loading for a | |
172 | particular Lisp file, by putting @samp{-*-unibyte: t;-*-} in a comment | |
173 | on the first line. Then that file is always loaded as unibyte text, | |
174 | even if you did not start Emacs with @samp{--unibyte}. The motivation | |
175 | for these conventions is that it is more reliable to always load any | |
176 | particular Lisp file in the same way. However, you can load a Lisp | |
177 | file as unibyte, on any one occasion, by typing @kbd{C-x @key{RET} c | |
178 | raw-text @key{RET}} immediately before loading it. | |
6bf7aab6 DL |
179 | |
180 | The mode line indicates whether multibyte character support is enabled | |
181 | in the current buffer. If it is, there are two or more characters (most | |
182 | often two dashes) before the colon near the beginning of the mode line. | |
183 | When multibyte characters are not enabled, just one dash precedes the | |
184 | colon. | |
185 | ||
186 | @node Language Environments | |
187 | @section Language Environments | |
188 | @cindex language environments | |
189 | ||
190 | All supported character sets are supported in Emacs buffers whenever | |
191 | multibyte characters are enabled; there is no need to select a | |
192 | particular language in order to display its characters in an Emacs | |
193 | buffer. However, it is important to select a @dfn{language environment} | |
194 | in order to set various defaults. The language environment really | |
195 | represents a choice of preferred script (more or less) rather than a | |
196 | choice of language. | |
197 | ||
198 | The language environment controls which coding systems to recognize | |
199 | when reading text (@pxref{Recognize Coding}). This applies to files, | |
200 | incoming mail, netnews, and any other text you read into Emacs. It may | |
201 | also specify the default coding system to use when you create a file. | |
202 | Each language environment also specifies a default input method. | |
203 | ||
204 | @findex set-language-environment | |
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205 | @vindex current-language-environment |
206 | To select a language environment, customize the option | |
207 | @code{current-language-environment} or use the command @kbd{M-x | |
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208 | set-language-environment}. It makes no difference which buffer is |
209 | current when you use this command, because the effects apply globally to | |
210 | the Emacs session. The supported language environments include: | |
211 | ||
60245086 | 212 | @cindex Euro sign |
6bf7aab6 | 213 | @quotation |
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214 | Chinese-BIG5, Chinese-CNS, Chinese-GB, Cyrillic-ALT, Cyrillic-ISO, |
215 | Cyrillic-KOI8, Czech, Devanagari, English, Ethiopic, German, Greek, | |
cca7bf28 EZ |
216 | Hebrew, IPA, Japanese, Korean, Lao, Latin-1, Latin-2, Latin-3, Latin-4, |
217 | Latin-5, Latin-8 (Celtic), Latin-9 (updated Latin-1, with the Euro | |
732b9cdd GM |
218 | sign), Polish, Romanian, Slovak, Slovenian, Thai, Tibetan, Turkish, |
219 | Dutch, Spanish, and Vietnamese. | |
6bf7aab6 DL |
220 | @end quotation |
221 | ||
4b40407a RS |
222 | @cindex fonts for various scripts |
223 | To display the script(s) used by your language environment on a | |
224 | graphical display, you need to have a suitable font. If some of the | |
225 | characters appear as empty boxes, you should install the GNU Intlfonts | |
226 | package, which includes fonts for all supported scripts. | |
227 | @xref{Fontsets}, for more details about setting up your fonts. | |
9aeaea42 | 228 | |
fbc164de PE |
229 | @findex set-locale-environment |
230 | @vindex locale-language-names | |
231 | @vindex locale-charset-language-names | |
60245086 | 232 | @cindex locales |
6bf7aab6 | 233 | Some operating systems let you specify the language you are using by |
fbc164de | 234 | setting the locale environment variables @env{LC_ALL}, @env{LC_CTYPE}, |
4b40407a RS |
235 | or @env{LANG}.@footnote{If more than one of these is set, the first |
236 | one that is nonempty specifies your locale for this purpose.} Emacs | |
237 | handles this during startup by matching your locale against entries in | |
238 | the value of the variables @code{locale-charset-language-names} and | |
fbc164de | 239 | @code{locale-language-names} and selects the corresponding language |
4b40407a RS |
240 | environment if a match is found. (The former variable overrides the |
241 | latter.) It also adjusts the display table and terminal coding | |
242 | system, the locale coding system, and the preferred coding system as | |
243 | needed for the locale. | |
244 | ||
245 | If you modify the @env{LC_ALL}, @env{LC_CTYPE}, or @env{LANG} | |
246 | environment variables while running Emacs, you may want to invoke the | |
247 | @code{set-locale-environment} function afterwards to readjust the | |
248 | language environment from the new locale. | |
fa71a532 | 249 | |
fbc164de PE |
250 | @vindex locale-preferred-coding-systems |
251 | The @code{set-locale-environment} function normally uses the preferred | |
252 | coding system established by the language environment to decode system | |
253 | messages. But if your locale matches an entry in the variable | |
254 | @code{locale-preferred-coding-systems}, Emacs uses the corresponding | |
255 | coding system instead. For example, if the locale @samp{ja_JP.PCK} | |
256 | matches @code{japanese-shift-jis} in | |
257 | @code{locale-preferred-coding-systems}, Emacs uses that encoding even | |
258 | though it might normally use @code{japanese-iso-8bit}. | |
259 | ||
4b40407a RS |
260 | You can override the language environment chosen at startup with |
261 | explicit use of the command @code{set-language-environment}, or with | |
262 | customization of @code{current-language-environment} in your init | |
263 | file. | |
6bf7aab6 DL |
264 | |
265 | @kindex C-h L | |
266 | @findex describe-language-environment | |
267 | To display information about the effects of a certain language | |
268 | environment @var{lang-env}, use the command @kbd{C-h L @var{lang-env} | |
269 | @key{RET}} (@code{describe-language-environment}). This tells you which | |
270 | languages this language environment is useful for, and lists the | |
271 | character sets, coding systems, and input methods that go with it. It | |
272 | also shows some sample text to illustrate scripts used in this language | |
273 | environment. By default, this command describes the chosen language | |
274 | environment. | |
275 | ||
276 | @vindex set-language-environment-hook | |
277 | You can customize any language environment with the normal hook | |
278 | @code{set-language-environment-hook}. The command | |
279 | @code{set-language-environment} runs that hook after setting up the new | |
280 | language environment. The hook functions can test for a specific | |
281 | language environment by checking the variable | |
282 | @code{current-language-environment}. | |
283 | ||
284 | @vindex exit-language-environment-hook | |
285 | Before it starts to set up the new language environment, | |
286 | @code{set-language-environment} first runs the hook | |
287 | @code{exit-language-environment-hook}. This hook is useful for undoing | |
288 | customizations that were made with @code{set-language-environment-hook}. | |
289 | For instance, if you set up a special key binding in a specific language | |
290 | environment using @code{set-language-environment-hook}, you should set | |
291 | up @code{exit-language-environment-hook} to restore the normal binding | |
292 | for that key. | |
293 | ||
294 | @node Input Methods | |
295 | @section Input Methods | |
296 | ||
297 | @cindex input methods | |
298 | An @dfn{input method} is a kind of character conversion designed | |
299 | specifically for interactive input. In Emacs, typically each language | |
300 | has its own input method; sometimes several languages which use the same | |
301 | characters can share one input method. A few languages support several | |
302 | input methods. | |
303 | ||
304 | The simplest kind of input method works by mapping ASCII letters into | |
305 | another alphabet. This is how the Greek and Russian input methods work. | |
306 | ||
307 | A more powerful technique is composition: converting sequences of | |
308 | characters into one letter. Many European input methods use composition | |
309 | to produce a single non-ASCII letter from a sequence that consists of a | |
310 | letter followed by accent characters (or vice versa). For example, some | |
311 | methods convert the sequence @kbd{a'} into a single accented letter. | |
312 | These input methods have no special commands of their own; all they do | |
313 | is compose sequences of printing characters. | |
314 | ||
315 | The input methods for syllabic scripts typically use mapping followed | |
316 | by composition. The input methods for Thai and Korean work this way. | |
317 | First, letters are mapped into symbols for particular sounds or tone | |
318 | marks; then, sequences of these which make up a whole syllable are | |
319 | mapped into one syllable sign. | |
320 | ||
321 | Chinese and Japanese require more complex methods. In Chinese input | |
322 | methods, first you enter the phonetic spelling of a Chinese word (in | |
323 | input method @code{chinese-py}, among others), or a sequence of portions | |
324 | of the character (input methods @code{chinese-4corner} and | |
325 | @code{chinese-sw}, and others). Since one phonetic spelling typically | |
326 | corresponds to many different Chinese characters, you must select one of | |
327 | the alternatives using special Emacs commands. Keys such as @kbd{C-f}, | |
328 | @kbd{C-b}, @kbd{C-n}, @kbd{C-p}, and digits have special definitions in | |
329 | this situation, used for selecting among the alternatives. @key{TAB} | |
330 | displays a buffer showing all the possibilities. | |
331 | ||
332 | In Japanese input methods, first you input a whole word using | |
333 | phonetic spelling; then, after the word is in the buffer, Emacs converts | |
334 | it into one or more characters using a large dictionary. One phonetic | |
335 | spelling corresponds to many differently written Japanese words, so you | |
336 | must select one of them; use @kbd{C-n} and @kbd{C-p} to cycle through | |
337 | the alternatives. | |
338 | ||
339 | Sometimes it is useful to cut off input method processing so that the | |
340 | characters you have just entered will not combine with subsequent | |
341 | characters. For example, in input method @code{latin-1-postfix}, the | |
342 | sequence @kbd{e '} combines to form an @samp{e} with an accent. What if | |
343 | you want to enter them as separate characters? | |
344 | ||
345 | One way is to type the accent twice; that is a special feature for | |
346 | entering the separate letter and accent. For example, @kbd{e ' '} gives | |
347 | you the two characters @samp{e'}. Another way is to type another letter | |
348 | after the @kbd{e}---something that won't combine with that---and | |
349 | immediately delete it. For example, you could type @kbd{e e @key{DEL} | |
350 | '} to get separate @samp{e} and @samp{'}. | |
351 | ||
352 | Another method, more general but not quite as easy to type, is to use | |
353 | @kbd{C-\ C-\} between two characters to stop them from combining. This | |
354 | is the command @kbd{C-\} (@code{toggle-input-method}) used twice. | |
355 | @ifinfo | |
356 | @xref{Select Input Method}. | |
357 | @end ifinfo | |
358 | ||
359 | @kbd{C-\ C-\} is especially useful inside an incremental search, | |
360 | because it stops waiting for more characters to combine, and starts | |
361 | searching for what you have already entered. | |
362 | ||
363 | @vindex input-method-verbose-flag | |
364 | @vindex input-method-highlight-flag | |
365 | The variables @code{input-method-highlight-flag} and | |
366 | @code{input-method-verbose-flag} control how input methods explain what | |
367 | is happening. If @code{input-method-highlight-flag} is non-@code{nil}, | |
368 | the partial sequence is highlighted in the buffer. If | |
369 | @code{input-method-verbose-flag} is non-@code{nil}, the list of possible | |
370 | characters to type next is displayed in the echo area (but not when you | |
371 | are in the minibuffer). | |
372 | ||
98c271eb | 373 | @cindex Leim package |
4b40407a RS |
374 | Input methods are implemented in the separate Leim package: they are |
375 | available only if the system administrator used Leim when building | |
376 | Emacs. If Emacs was built without Leim, you will find that no input | |
377 | methods are defined. | |
98c271eb | 378 | |
6bf7aab6 DL |
379 | @node Select Input Method |
380 | @section Selecting an Input Method | |
381 | ||
382 | @table @kbd | |
383 | @item C-\ | |
384 | Enable or disable use of the selected input method. | |
385 | ||
386 | @item C-x @key{RET} C-\ @var{method} @key{RET} | |
387 | Select a new input method for the current buffer. | |
388 | ||
389 | @item C-h I @var{method} @key{RET} | |
390 | @itemx C-h C-\ @var{method} @key{RET} | |
391 | @findex describe-input-method | |
392 | @kindex C-h I | |
393 | @kindex C-h C-\ | |
394 | Describe the input method @var{method} (@code{describe-input-method}). | |
67320f8d DL |
395 | By default, it describes the current input method (if any). This |
396 | description should give you the full details of how to use any | |
a39fb83d | 397 | particular input method. |
6bf7aab6 DL |
398 | |
399 | @item M-x list-input-methods | |
400 | Display a list of all the supported input methods. | |
401 | @end table | |
402 | ||
403 | @findex set-input-method | |
404 | @vindex current-input-method | |
405 | @kindex C-x RET C-\ | |
406 | To choose an input method for the current buffer, use @kbd{C-x | |
407 | @key{RET} C-\} (@code{set-input-method}). This command reads the | |
408 | input method name with the minibuffer; the name normally starts with the | |
409 | language environment that it is meant to be used with. The variable | |
410 | @code{current-input-method} records which input method is selected. | |
411 | ||
412 | @findex toggle-input-method | |
413 | @kindex C-\ | |
414 | Input methods use various sequences of ASCII characters to stand for | |
415 | non-ASCII characters. Sometimes it is useful to turn off the input | |
416 | method temporarily. To do this, type @kbd{C-\} | |
417 | (@code{toggle-input-method}). To reenable the input method, type | |
418 | @kbd{C-\} again. | |
419 | ||
420 | If you type @kbd{C-\} and you have not yet selected an input method, | |
421 | it prompts for you to specify one. This has the same effect as using | |
422 | @kbd{C-x @key{RET} C-\} to specify an input method. | |
423 | ||
424 | @vindex default-input-method | |
425 | Selecting a language environment specifies a default input method for | |
426 | use in various buffers. When you have a default input method, you can | |
427 | select it in the current buffer by typing @kbd{C-\}. The variable | |
428 | @code{default-input-method} specifies the default input method | |
429 | (@code{nil} means there is none). | |
430 | ||
431 | @findex quail-set-keyboard-layout | |
432 | Some input methods for alphabetic scripts work by (in effect) | |
433 | remapping the keyboard to emulate various keyboard layouts commonly used | |
434 | for those scripts. How to do this remapping properly depends on your | |
435 | actual keyboard layout. To specify which layout your keyboard has, use | |
436 | the command @kbd{M-x quail-set-keyboard-layout}. | |
437 | ||
438 | @findex list-input-methods | |
439 | To display a list of all the supported input methods, type @kbd{M-x | |
440 | list-input-methods}. The list gives information about each input | |
441 | method, including the string that stands for it in the mode line. | |
442 | ||
443 | @node Multibyte Conversion | |
444 | @section Unibyte and Multibyte Non-ASCII characters | |
445 | ||
446 | When multibyte characters are enabled, character codes 0240 (octal) | |
447 | through 0377 (octal) are not really legitimate in the buffer. The valid | |
448 | non-ASCII printing characters have codes that start from 0400. | |
449 | ||
4b40407a RS |
450 | If you type a self-inserting character in the range 0240 through |
451 | 0377, or if you use @kbd{C-q} to insert one, Emacs assumes you | |
452 | intended to use one of the ISO Latin-@var{n} character sets, and | |
453 | converts it to the Emacs code representing that Latin-@var{n} | |
454 | character. You select @emph{which} ISO Latin character set to use | |
455 | through your choice of language environment | |
6bf7aab6 DL |
456 | @iftex |
457 | (see above). | |
458 | @end iftex | |
459 | @ifinfo | |
460 | (@pxref{Language Environments}). | |
461 | @end ifinfo | |
462 | If you do not specify a choice, the default is Latin-1. | |
463 | ||
4b40407a RS |
464 | If you insert a character in the range 0200 through 0237, which |
465 | forms the @code{eight-bit-control} character set, it is inserted | |
60245086 DL |
466 | literally. You should normally avoid doing this since buffers |
467 | containing such characters have to be written out in either the | |
4b40407a RS |
468 | @code{emacs-mule} or @code{raw-text} coding system, which is usually |
469 | not what you want. | |
6bf7aab6 DL |
470 | |
471 | @node Coding Systems | |
472 | @section Coding Systems | |
473 | @cindex coding systems | |
474 | ||
475 | Users of various languages have established many more-or-less standard | |
476 | coding systems for representing them. Emacs does not use these coding | |
477 | systems internally; instead, it converts from various coding systems to | |
478 | its own system when reading data, and converts the internal coding | |
479 | system to other coding systems when writing data. Conversion is | |
480 | possible in reading or writing files, in sending or receiving from the | |
481 | terminal, and in exchanging data with subprocesses. | |
482 | ||
483 | Emacs assigns a name to each coding system. Most coding systems are | |
484 | used for one language, and the name of the coding system starts with the | |
485 | language name. Some coding systems are used for several languages; | |
486 | their names usually start with @samp{iso}. There are also special | |
487 | coding systems @code{no-conversion}, @code{raw-text} and | |
488 | @code{emacs-mule} which do not convert printing characters at all. | |
489 | ||
9d9c2e39 EZ |
490 | A special class of coding systems, collectively known as |
491 | @dfn{codepages}, is designed to support text encoded by MS-Windows and | |
492 | MS-DOS software. To use any of these systems, you need to create it | |
493 | with @kbd{M-x codepage-setup}. @xref{MS-DOS and MULE}. | |
494 | ||
6bf7aab6 DL |
495 | In addition to converting various representations of non-ASCII |
496 | characters, a coding system can perform end-of-line conversion. Emacs | |
497 | handles three different conventions for how to separate lines in a file: | |
498 | newline, carriage-return linefeed, and just carriage-return. | |
499 | ||
500 | @table @kbd | |
501 | @item C-h C @var{coding} @key{RET} | |
502 | Describe coding system @var{coding}. | |
503 | ||
504 | @item C-h C @key{RET} | |
505 | Describe the coding systems currently in use. | |
506 | ||
507 | @item M-x list-coding-systems | |
508 | Display a list of all the supported coding systems. | |
509 | @end table | |
510 | ||
511 | @kindex C-h C | |
512 | @findex describe-coding-system | |
513 | The command @kbd{C-h C} (@code{describe-coding-system}) displays | |
514 | information about particular coding systems. You can specify a coding | |
515 | system name as argument; alternatively, with an empty argument, it | |
516 | describes the coding systems currently selected for various purposes, | |
517 | both in the current buffer and as the defaults, and the priority list | |
518 | for recognizing coding systems (@pxref{Recognize Coding}). | |
519 | ||
520 | @findex list-coding-systems | |
521 | To display a list of all the supported coding systems, type @kbd{M-x | |
522 | list-coding-systems}. The list gives information about each coding | |
523 | system, including the letter that stands for it in the mode line | |
524 | (@pxref{Mode Line}). | |
525 | ||
526 | @cindex end-of-line conversion | |
527 | @cindex MS-DOS end-of-line conversion | |
528 | @cindex Macintosh end-of-line conversion | |
529 | Each of the coding systems that appear in this list---except for | |
530 | @code{no-conversion}, which means no conversion of any kind---specifies | |
531 | how and whether to convert printing characters, but leaves the choice of | |
532 | end-of-line conversion to be decided based on the contents of each file. | |
533 | For example, if the file appears to use the sequence carriage-return | |
534 | linefeed to separate lines, DOS end-of-line conversion will be used. | |
535 | ||
536 | Each of the listed coding systems has three variants which specify | |
537 | exactly what to do for end-of-line conversion: | |
538 | ||
539 | @table @code | |
540 | @item @dots{}-unix | |
541 | Don't do any end-of-line conversion; assume the file uses | |
542 | newline to separate lines. (This is the convention normally used | |
543 | on Unix and GNU systems.) | |
544 | ||
545 | @item @dots{}-dos | |
546 | Assume the file uses carriage-return linefeed to separate lines, and do | |
547 | the appropriate conversion. (This is the convention normally used on | |
2684ed46 | 548 | Microsoft systems.@footnote{It is also specified for MIME @samp{text/*} |
6bf7aab6 DL |
549 | bodies and in other network transport contexts. It is different |
550 | from the SGML reference syntax record-start/record-end format which | |
551 | Emacs doesn't support directly.}) | |
552 | ||
553 | @item @dots{}-mac | |
554 | Assume the file uses carriage-return to separate lines, and do the | |
555 | appropriate conversion. (This is the convention normally used on the | |
556 | Macintosh system.) | |
557 | @end table | |
558 | ||
559 | These variant coding systems are omitted from the | |
560 | @code{list-coding-systems} display for brevity, since they are entirely | |
561 | predictable. For example, the coding system @code{iso-latin-1} has | |
562 | variants @code{iso-latin-1-unix}, @code{iso-latin-1-dos} and | |
563 | @code{iso-latin-1-mac}. | |
564 | ||
565 | The coding system @code{raw-text} is good for a file which is mainly | |
566 | ASCII text, but may contain byte values above 127 which are not meant to | |
567 | encode non-ASCII characters. With @code{raw-text}, Emacs copies those | |
568 | byte values unchanged, and sets @code{enable-multibyte-characters} to | |
569 | @code{nil} in the current buffer so that they will be interpreted | |
570 | properly. @code{raw-text} handles end-of-line conversion in the usual | |
571 | way, based on the data encountered, and has the usual three variants to | |
572 | specify the kind of end-of-line conversion to use. | |
573 | ||
574 | In contrast, the coding system @code{no-conversion} specifies no | |
575 | character code conversion at all---none for non-ASCII byte values and | |
576 | none for end of line. This is useful for reading or writing binary | |
577 | files, tar files, and other files that must be examined verbatim. It, | |
578 | too, sets @code{enable-multibyte-characters} to @code{nil}. | |
579 | ||
580 | The easiest way to edit a file with no conversion of any kind is with | |
581 | the @kbd{M-x find-file-literally} command. This uses | |
582 | @code{no-conversion}, and also suppresses other Emacs features that | |
583 | might convert the file contents before you see them. @xref{Visiting}. | |
584 | ||
585 | The coding system @code{emacs-mule} means that the file contains | |
586 | non-ASCII characters stored with the internal Emacs encoding. It | |
587 | handles end-of-line conversion based on the data encountered, and has | |
588 | the usual three variants to specify the kind of end-of-line conversion. | |
589 | ||
590 | @node Recognize Coding | |
591 | @section Recognizing Coding Systems | |
592 | ||
593 | Most of the time, Emacs can recognize which coding system to use for | |
594 | any given file---once you have specified your preferences. | |
595 | ||
596 | Some coding systems can be recognized or distinguished by which byte | |
597 | sequences appear in the data. However, there are coding systems that | |
598 | cannot be distinguished, not even potentially. For example, there is no | |
599 | way to distinguish between Latin-1 and Latin-2; they use the same byte | |
600 | values with different meanings. | |
601 | ||
602 | Emacs handles this situation by means of a priority list of coding | |
603 | systems. Whenever Emacs reads a file, if you do not specify the coding | |
604 | system to use, Emacs checks the data against each coding system, | |
605 | starting with the first in priority and working down the list, until it | |
606 | finds a coding system that fits the data. Then it converts the file | |
607 | contents assuming that they are represented in this coding system. | |
608 | ||
609 | The priority list of coding systems depends on the selected language | |
610 | environment (@pxref{Language Environments}). For example, if you use | |
611 | French, you probably want Emacs to prefer Latin-1 to Latin-2; if you use | |
612 | Czech, you probably want Latin-2 to be preferred. This is one of the | |
613 | reasons to specify a language environment. | |
614 | ||
615 | @findex prefer-coding-system | |
616 | However, you can alter the priority list in detail with the command | |
617 | @kbd{M-x prefer-coding-system}. This command reads the name of a coding | |
618 | system from the minibuffer, and adds it to the front of the priority | |
619 | list, so that it is preferred to all others. If you use this command | |
620 | several times, each use adds one element to the front of the priority | |
621 | list. | |
622 | ||
623 | If you use a coding system that specifies the end-of-line conversion | |
624 | type, such as @code{iso-8859-1-dos}, what that means is that Emacs | |
625 | should attempt to recognize @code{iso-8859-1} with priority, and should | |
626 | use DOS end-of-line conversion in case it recognizes @code{iso-8859-1}. | |
627 | ||
628 | @vindex file-coding-system-alist | |
629 | Sometimes a file name indicates which coding system to use for the | |
630 | file. The variable @code{file-coding-system-alist} specifies this | |
631 | correspondence. There is a special function | |
632 | @code{modify-coding-system-alist} for adding elements to this list. For | |
633 | example, to read and write all @samp{.txt} files using the coding system | |
634 | @code{china-iso-8bit}, you can execute this Lisp expression: | |
635 | ||
636 | @smallexample | |
637 | (modify-coding-system-alist 'file "\\.txt\\'" 'china-iso-8bit) | |
638 | @end smallexample | |
639 | ||
640 | @noindent | |
641 | The first argument should be @code{file}, the second argument should be | |
642 | a regular expression that determines which files this applies to, and | |
643 | the third argument says which coding system to use for these files. | |
644 | ||
645 | @vindex inhibit-eol-conversion | |
5be757c3 | 646 | @cindex DOS-style end-of-line display |
6bf7aab6 DL |
647 | Emacs recognizes which kind of end-of-line conversion to use based on |
648 | the contents of the file: if it sees only carriage-returns, or only | |
649 | carriage-return linefeed sequences, then it chooses the end-of-line | |
650 | conversion accordingly. You can inhibit the automatic use of | |
651 | end-of-line conversion by setting the variable @code{inhibit-eol-conversion} | |
652 | to non-@code{nil}. | |
653 | ||
5be757c3 EZ |
654 | @vindex inhibit-iso-escape-detection |
655 | @cindex escape sequences in files | |
656 | By default, the automatic detection of coding system is sensitive to | |
657 | escape sequences. If Emacs sees a sequence of characters that begin | |
4b40407a RS |
658 | with an escape character, and the sequence is valid as an ISO-2022 |
659 | code, that tells Emacs to use one of the ISO-2022 encodings to decode | |
660 | the file. | |
5be757c3 | 661 | |
4b40407a RS |
662 | However, there may be cases that you want to read escape sequences |
663 | in a file as is. In such a case, you can set the variable | |
5be757c3 | 664 | @code{inhibit-iso-escape-detection} to non-@code{nil}. Then the code |
4b40407a RS |
665 | detection ignores any escape sequences, and never uses an ISO-2022 |
666 | encoding. The result is that all escape sequences become visible in | |
667 | the buffer. | |
5be757c3 EZ |
668 | |
669 | The default value of @code{inhibit-iso-escape-detection} is | |
4b40407a RS |
670 | @code{nil}. We recommend that you not change it permanently, only for |
671 | one specific operation. That's because many Emacs Lisp source files | |
672 | that contain non-ASCII characters are encoded in the coding system | |
673 | @code{iso-2022-7bit} in the Emacs distribution, and they won't be | |
674 | decoded correctly when you visit those files if you suppress the | |
675 | escape sequence detection. | |
5be757c3 | 676 | |
6bf7aab6 DL |
677 | @vindex coding |
678 | You can specify the coding system for a particular file using the | |
679 | @samp{-*-@dots{}-*-} construct at the beginning of a file, or a local | |
680 | variables list at the end (@pxref{File Variables}). You do this by | |
681 | defining a value for the ``variable'' named @code{coding}. Emacs does | |
682 | not really have a variable @code{coding}; instead of setting a variable, | |
683 | it uses the specified coding system for the file. For example, | |
684 | @samp{-*-mode: C; coding: latin-1;-*-} specifies use of the Latin-1 | |
685 | coding system, as well as C mode. If you specify the coding explicitly | |
686 | in the file, that overrides @code{file-coding-system-alist}. | |
687 | ||
688 | @vindex auto-coding-alist | |
689 | The variable @code{auto-coding-alist} is the strongest way to specify | |
690 | the coding system for certain patterns of file names; this variable even | |
691 | overrides @samp{-*-coding:-*-} tags in the file itself. Emacs uses this | |
692 | feature for tar and archive files, to prevent Emacs from being confused | |
693 | by a @samp{-*-coding:-*-} tag in a member of the archive and thinking it | |
694 | applies to the archive file as a whole. | |
695 | ||
696 | @vindex buffer-file-coding-system | |
697 | Once Emacs has chosen a coding system for a buffer, it stores that | |
698 | coding system in @code{buffer-file-coding-system} and uses that coding | |
699 | system, by default, for operations that write from this buffer into a | |
700 | file. This includes the commands @code{save-buffer} and | |
701 | @code{write-region}. If you want to write files from this buffer using | |
702 | a different coding system, you can specify a different coding system for | |
703 | the buffer using @code{set-buffer-file-coding-system} (@pxref{Specify | |
704 | Coding}). | |
705 | ||
4b40407a RS |
706 | You can insert any possible character into any Emacs buffer, but |
707 | most coding systems can only handle some of the possible characters. | |
708 | This means that you can insert characters that cannot be encoded with | |
709 | the coding system that will be used to save the buffer. For example, | |
710 | you could start with an ASCII file and insert a few Latin-1 characters | |
22f515a9 | 711 | into it, or you could edit a text file in Polish encoded in |
4b40407a RS |
712 | @code{iso-8859-2} and add to it translations of several Polish words |
713 | into Russian. When you save the buffer, Emacs cannot use the current | |
714 | value of @code{buffer-file-coding-system}, because the characters you | |
715 | added cannot be encoded by that coding system. | |
2a886892 EZ |
716 | |
717 | When that happens, Emacs tries the most-preferred coding system (set | |
718 | by @kbd{M-x prefer-coding-system} or @kbd{M-x | |
4b40407a RS |
719 | set-language-environment}), and if that coding system can safely |
720 | encode all of the characters in the buffer, Emacs uses it, and stores | |
721 | its value in @code{buffer-file-coding-system}. Otherwise, Emacs | |
722 | displays a list of coding systems suitable for encoding the buffer's | |
723 | contents, and asks to choose one of those coding systems. | |
724 | ||
725 | If you insert the unsuitable characters in a mail message, Emacs | |
726 | behaves a bit differently. It additionally checks whether the | |
727 | most-preferred coding system is recommended for use in MIME messages; | |
728 | if it isn't, Emacs tells you that the most-preferred coding system is | |
729 | not recommended and prompts you for another coding system. This is so | |
730 | you won't inadvertently send a message encoded in a way that your | |
731 | recipient's mail software will have difficulty decoding. (If you do | |
732 | want to use the most-preferred coding system, you can type its name to | |
733 | Emacs prompt anyway.) | |
2a886892 | 734 | |
6bf7aab6 DL |
735 | @vindex sendmail-coding-system |
736 | When you send a message with Mail mode (@pxref{Sending Mail}), Emacs has | |
737 | four different ways to determine the coding system to use for encoding | |
738 | the message text. It tries the buffer's own value of | |
739 | @code{buffer-file-coding-system}, if that is non-@code{nil}. Otherwise, | |
740 | it uses the value of @code{sendmail-coding-system}, if that is | |
741 | non-@code{nil}. The third way is to use the default coding system for | |
742 | new files, which is controlled by your choice of language environment, | |
743 | if that is non-@code{nil}. If all of these three values are @code{nil}, | |
744 | Emacs encodes outgoing mail using the Latin-1 coding system. | |
745 | ||
746 | @vindex rmail-decode-mime-charset | |
747 | When you get new mail in Rmail, each message is translated | |
748 | automatically from the coding system it is written in---as if it were a | |
749 | separate file. This uses the priority list of coding systems that you | |
750 | have specified. If a MIME message specifies a character set, Rmail | |
751 | obeys that specification, unless @code{rmail-decode-mime-charset} is | |
752 | @code{nil}. | |
753 | ||
754 | @vindex rmail-file-coding-system | |
755 | For reading and saving Rmail files themselves, Emacs uses the coding | |
756 | system specified by the variable @code{rmail-file-coding-system}. The | |
757 | default value is @code{nil}, which means that Rmail files are not | |
758 | translated (they are read and written in the Emacs internal character | |
759 | code). | |
760 | ||
761 | @node Specify Coding | |
762 | @section Specifying a Coding System | |
763 | ||
764 | In cases where Emacs does not automatically choose the right coding | |
765 | system, you can use these commands to specify one: | |
766 | ||
767 | @table @kbd | |
768 | @item C-x @key{RET} f @var{coding} @key{RET} | |
769 | Use coding system @var{coding} for the visited file | |
770 | in the current buffer. | |
771 | ||
772 | @item C-x @key{RET} c @var{coding} @key{RET} | |
773 | Specify coding system @var{coding} for the immediately following | |
774 | command. | |
775 | ||
776 | @item C-x @key{RET} k @var{coding} @key{RET} | |
777 | Use coding system @var{coding} for keyboard input. | |
778 | ||
779 | @item C-x @key{RET} t @var{coding} @key{RET} | |
780 | Use coding system @var{coding} for terminal output. | |
781 | ||
782 | @item C-x @key{RET} p @var{input-coding} @key{RET} @var{output-coding} @key{RET} | |
783 | Use coding systems @var{input-coding} and @var{output-coding} for | |
784 | subprocess input and output in the current buffer. | |
785 | ||
786 | @item C-x @key{RET} x @var{coding} @key{RET} | |
787 | Use coding system @var{coding} for transferring selections to and from | |
788 | other programs through the window system. | |
789 | ||
790 | @item C-x @key{RET} X @var{coding} @key{RET} | |
791 | Use coding system @var{coding} for transferring @emph{one} | |
792 | selection---the next one---to or from the window system. | |
793 | @end table | |
794 | ||
795 | @kindex C-x RET f | |
796 | @findex set-buffer-file-coding-system | |
797 | The command @kbd{C-x @key{RET} f} (@code{set-buffer-file-coding-system}) | |
798 | specifies the file coding system for the current buffer---in other | |
799 | words, which coding system to use when saving or rereading the visited | |
800 | file. You specify which coding system using the minibuffer. Since this | |
801 | command applies to a file you have already visited, it affects only the | |
802 | way the file is saved. | |
803 | ||
804 | @kindex C-x RET c | |
805 | @findex universal-coding-system-argument | |
806 | Another way to specify the coding system for a file is when you visit | |
807 | the file. First use the command @kbd{C-x @key{RET} c} | |
808 | (@code{universal-coding-system-argument}); this command uses the | |
809 | minibuffer to read a coding system name. After you exit the minibuffer, | |
810 | the specified coding system is used for @emph{the immediately following | |
811 | command}. | |
812 | ||
813 | So if the immediately following command is @kbd{C-x C-f}, for example, | |
814 | it reads the file using that coding system (and records the coding | |
815 | system for when the file is saved). Or if the immediately following | |
816 | command is @kbd{C-x C-w}, it writes the file using that coding system. | |
817 | Other file commands affected by a specified coding system include | |
818 | @kbd{C-x C-i} and @kbd{C-x C-v}, as well as the other-window variants of | |
819 | @kbd{C-x C-f}. | |
820 | ||
821 | @kbd{C-x @key{RET} c} also affects commands that start subprocesses, | |
822 | including @kbd{M-x shell} (@pxref{Shell}). | |
823 | ||
824 | However, if the immediately following command does not use the coding | |
825 | system, then @kbd{C-x @key{RET} c} ultimately has no effect. | |
826 | ||
827 | An easy way to visit a file with no conversion is with the @kbd{M-x | |
828 | find-file-literally} command. @xref{Visiting}. | |
829 | ||
830 | @vindex default-buffer-file-coding-system | |
831 | The variable @code{default-buffer-file-coding-system} specifies the | |
832 | choice of coding system to use when you create a new file. It applies | |
833 | when you find a new file, and when you create a buffer and then save it | |
834 | in a file. Selecting a language environment typically sets this | |
835 | variable to a good choice of default coding system for that language | |
836 | environment. | |
837 | ||
838 | @kindex C-x RET t | |
839 | @findex set-terminal-coding-system | |
840 | The command @kbd{C-x @key{RET} t} (@code{set-terminal-coding-system}) | |
841 | specifies the coding system for terminal output. If you specify a | |
842 | character code for terminal output, all characters output to the | |
843 | terminal are translated into that coding system. | |
844 | ||
845 | This feature is useful for certain character-only terminals built to | |
846 | support specific languages or character sets---for example, European | |
847 | terminals that support one of the ISO Latin character sets. You need to | |
848 | specify the terminal coding system when using multibyte text, so that | |
849 | Emacs knows which characters the terminal can actually handle. | |
850 | ||
851 | By default, output to the terminal is not translated at all, unless | |
60245086 DL |
852 | Emacs can deduce the proper coding system from your terminal type or |
853 | your locale specification (@pxref{Language Environments}). | |
6bf7aab6 DL |
854 | |
855 | @kindex C-x RET k | |
856 | @findex set-keyboard-coding-system | |
aa120288 | 857 | @vindex keyboard-coding-system |
6bf7aab6 | 858 | The command @kbd{C-x @key{RET} k} (@code{set-keyboard-coding-system}) |
aa120288 | 859 | or the Custom option @code{keyboard-coding-system} |
6bf7aab6 DL |
860 | specifies the coding system for keyboard input. Character-code |
861 | translation of keyboard input is useful for terminals with keys that | |
862 | send non-ASCII graphic characters---for example, some terminals designed | |
863 | for ISO Latin-1 or subsets of it. | |
864 | ||
865 | By default, keyboard input is not translated at all. | |
866 | ||
867 | There is a similarity between using a coding system translation for | |
868 | keyboard input, and using an input method: both define sequences of | |
869 | keyboard input that translate into single characters. However, input | |
870 | methods are designed to be convenient for interactive use by humans, and | |
871 | the sequences that are translated are typically sequences of ASCII | |
872 | printing characters. Coding systems typically translate sequences of | |
873 | non-graphic characters. | |
874 | ||
875 | @kindex C-x RET x | |
876 | @kindex C-x RET X | |
877 | @findex set-selection-coding-system | |
878 | @findex set-next-selection-coding-system | |
879 | The command @kbd{C-x @key{RET} x} (@code{set-selection-coding-system}) | |
880 | specifies the coding system for sending selected text to the window | |
881 | system, and for receiving the text of selections made in other | |
882 | applications. This command applies to all subsequent selections, until | |
883 | you override it by using the command again. The command @kbd{C-x | |
884 | @key{RET} X} (@code{set-next-selection-coding-system}) specifies the | |
885 | coding system for the next selection made in Emacs or read by Emacs. | |
886 | ||
887 | @kindex C-x RET p | |
888 | @findex set-buffer-process-coding-system | |
889 | The command @kbd{C-x @key{RET} p} (@code{set-buffer-process-coding-system}) | |
890 | specifies the coding system for input and output to a subprocess. This | |
891 | command applies to the current buffer; normally, each subprocess has its | |
892 | own buffer, and thus you can use this command to specify translation to | |
893 | and from a particular subprocess by giving the command in the | |
894 | corresponding buffer. | |
895 | ||
a895a5a5 KH |
896 | The default for translation of process input and output depends on the |
897 | current language environment. | |
6bf7aab6 DL |
898 | |
899 | @vindex file-name-coding-system | |
900 | The variable @code{file-name-coding-system} specifies a coding system | |
901 | to use for encoding file names. If you set the variable to a coding | |
902 | system name (as a Lisp symbol or a string), Emacs encodes file names | |
903 | using that coding system for all file operations. This makes it | |
904 | possible to use non-ASCII characters in file names---or, at least, those | |
905 | non-ASCII characters which the specified coding system can encode. | |
906 | ||
907 | If @code{file-name-coding-system} is @code{nil}, Emacs uses a default | |
908 | coding system determined by the selected language environment. In the | |
909 | default language environment, any non-ASCII characters in file names are | |
910 | not encoded specially; they appear in the file system using the internal | |
911 | Emacs representation. | |
912 | ||
913 | @strong{Warning:} if you change @code{file-name-coding-system} (or the | |
914 | language environment) in the middle of an Emacs session, problems can | |
915 | result if you have already visited files whose names were encoded using | |
916 | the earlier coding system and cannot be encoded (or are encoded | |
917 | differently) under the new coding system. If you try to save one of | |
918 | these buffers under the visited file name, saving may use the wrong file | |
919 | name, or it may get an error. If such a problem happens, use @kbd{C-x | |
920 | C-w} to specify a new file name for that buffer. | |
921 | ||
fbc164de | 922 | @vindex locale-coding-system |
4b40407a RS |
923 | The variable @code{locale-coding-system} specifies a coding system |
924 | to use when encoding and decoding system strings such as system error | |
925 | messages and @code{format-time-string} formats and time stamps. You | |
926 | should choose a coding system that is compatible with the underlying | |
927 | system's text representation, which is normally specified by one of | |
928 | the environment variables @env{LC_ALL}, @env{LC_CTYPE}, and | |
929 | @env{LANG}. (The first one whose value is nonempty is the one that | |
930 | determines the text representation.) | |
fbc164de | 931 | |
6bf7aab6 DL |
932 | @node Fontsets |
933 | @section Fontsets | |
934 | @cindex fontsets | |
935 | ||
97878c08 EZ |
936 | A font for X typically defines shapes for one alphabet or script. |
937 | Therefore, displaying the entire range of scripts that Emacs supports | |
938 | requires a collection of many fonts. In Emacs, such a collection is | |
939 | called a @dfn{fontset}. A fontset is defined by a list of fonts, each | |
940 | assigned to handle a range of character codes. | |
6bf7aab6 DL |
941 | |
942 | Each fontset has a name, like a font. The available X fonts are | |
943 | defined by the X server; fontsets, however, are defined within Emacs | |
944 | itself. Once you have defined a fontset, you can use it within Emacs by | |
945 | specifying its name, anywhere that you could use a single font. Of | |
946 | course, Emacs fontsets can use only the fonts that the X server | |
947 | supports; if certain characters appear on the screen as hollow boxes, | |
948 | this means that the fontset in use for them has no font for those | |
4b40407a | 949 | characters.@footnote{The Emacs installation instructions have information on |
60245086 | 950 | additional font support.} |
6bf7aab6 DL |
951 | |
952 | Emacs creates two fontsets automatically: the @dfn{standard fontset} | |
953 | and the @dfn{startup fontset}. The standard fontset is most likely to | |
954 | have fonts for a wide variety of non-ASCII characters; however, this is | |
955 | not the default for Emacs to use. (By default, Emacs tries to find a | |
956 | font which has bold and italic variants.) You can specify use of the | |
957 | standard fontset with the @samp{-fn} option, or with the @samp{Font} X | |
958 | resource (@pxref{Font X}). For example, | |
959 | ||
960 | @example | |
961 | emacs -fn fontset-standard | |
962 | @end example | |
963 | ||
964 | A fontset does not necessarily specify a font for every character | |
965 | code. If a fontset specifies no font for a certain character, or if it | |
966 | specifies a font that does not exist on your system, then it cannot | |
967 | display that character properly. It will display that character as an | |
968 | empty box instead. | |
969 | ||
970 | @vindex highlight-wrong-size-font | |
971 | The fontset height and width are determined by the ASCII characters | |
972 | (that is, by the font used for ASCII characters in that fontset). If | |
973 | another font in the fontset has a different height, or a different | |
974 | width, then characters assigned to that font are clipped to the | |
975 | fontset's size. If @code{highlight-wrong-size-font} is non-@code{nil}, | |
976 | a box is displayed around these wrong-size characters as well. | |
977 | ||
978 | @node Defining Fontsets | |
979 | @section Defining fontsets | |
980 | ||
981 | @vindex standard-fontset-spec | |
982 | @cindex standard fontset | |
983 | Emacs creates a standard fontset automatically according to the value | |
984 | of @code{standard-fontset-spec}. This fontset's name is | |
985 | ||
986 | @example | |
987 | -*-fixed-medium-r-normal-*-16-*-*-*-*-*-fontset-standard | |
988 | @end example | |
989 | ||
990 | @noindent | |
991 | or just @samp{fontset-standard} for short. | |
992 | ||
993 | Bold, italic, and bold-italic variants of the standard fontset are | |
994 | created automatically. Their names have @samp{bold} instead of | |
995 | @samp{medium}, or @samp{i} instead of @samp{r}, or both. | |
996 | ||
997 | @cindex startup fontset | |
998 | If you specify a default ASCII font with the @samp{Font} resource or | |
999 | the @samp{-fn} argument, Emacs generates a fontset from it | |
1000 | automatically. This is the @dfn{startup fontset} and its name is | |
1001 | @code{fontset-startup}. It does this by replacing the @var{foundry}, | |
1002 | @var{family}, @var{add_style}, and @var{average_width} fields of the | |
1003 | font name with @samp{*}, replacing @var{charset_registry} field with | |
1004 | @samp{fontset}, and replacing @var{charset_encoding} field with | |
1005 | @samp{startup}, then using the resulting string to specify a fontset. | |
1006 | ||
1007 | For instance, if you start Emacs this way, | |
1008 | ||
1009 | @example | |
1010 | emacs -fn "*courier-medium-r-normal--14-140-*-iso8859-1" | |
1011 | @end example | |
1012 | ||
1013 | @noindent | |
1014 | Emacs generates the following fontset and uses it for the initial X | |
1015 | window frame: | |
1016 | ||
1017 | @example | |
1018 | -*-*-medium-r-normal-*-14-140-*-*-*-*-fontset-startup | |
1019 | @end example | |
1020 | ||
1021 | With the X resource @samp{Emacs.Font}, you can specify a fontset name | |
1022 | just like an actual font name. But be careful not to specify a fontset | |
1023 | name in a wildcard resource like @samp{Emacs*Font}---that wildcard | |
1024 | specification applies to various other purposes, such as menus, and | |
1025 | menus cannot handle fontsets. | |
1026 | ||
1027 | You can specify additional fontsets using X resources named | |
1028 | @samp{Fontset-@var{n}}, where @var{n} is an integer starting from 0. | |
1029 | The resource value should have this form: | |
1030 | ||
1031 | @smallexample | |
1032 | @var{fontpattern}, @r{[}@var{charsetname}:@var{fontname}@r{]@dots{}} | |
1033 | @end smallexample | |
1034 | ||
1035 | @noindent | |
1036 | @var{fontpattern} should have the form of a standard X font name, except | |
1037 | for the last two fields. They should have the form | |
1038 | @samp{fontset-@var{alias}}. | |
1039 | ||
1040 | The fontset has two names, one long and one short. The long name is | |
1041 | @var{fontpattern}. The short name is @samp{fontset-@var{alias}}. You | |
1042 | can refer to the fontset by either name. | |
1043 | ||
1044 | The construct @samp{@var{charset}:@var{font}} specifies which font to | |
1045 | use (in this fontset) for one particular character set. Here, | |
1046 | @var{charset} is the name of a character set, and @var{font} is the | |
1047 | font to use for that character set. You can use this construct any | |
1048 | number of times in defining one fontset. | |
1049 | ||
1050 | For the other character sets, Emacs chooses a font based on | |
1051 | @var{fontpattern}. It replaces @samp{fontset-@var{alias}} with values | |
1052 | that describe the character set. For the ASCII character font, | |
1053 | @samp{fontset-@var{alias}} is replaced with @samp{ISO8859-1}. | |
1054 | ||
1055 | In addition, when several consecutive fields are wildcards, Emacs | |
1056 | collapses them into a single wildcard. This is to prevent use of | |
1057 | auto-scaled fonts. Fonts made by scaling larger fonts are not usable | |
1058 | for editing, and scaling a smaller font is not useful because it is | |
1059 | better to use the smaller font in its own size, which Emacs does. | |
1060 | ||
1061 | Thus if @var{fontpattern} is this, | |
1062 | ||
1063 | @example | |
1064 | -*-fixed-medium-r-normal-*-24-*-*-*-*-*-fontset-24 | |
1065 | @end example | |
1066 | ||
1067 | @noindent | |
1068 | the font specification for ASCII characters would be this: | |
1069 | ||
1070 | @example | |
1071 | -*-fixed-medium-r-normal-*-24-*-ISO8859-1 | |
1072 | @end example | |
1073 | ||
1074 | @noindent | |
1075 | and the font specification for Chinese GB2312 characters would be this: | |
1076 | ||
1077 | @example | |
1078 | -*-fixed-medium-r-normal-*-24-*-gb2312*-* | |
1079 | @end example | |
1080 | ||
1081 | You may not have any Chinese font matching the above font | |
1082 | specification. Most X distributions include only Chinese fonts that | |
1083 | have @samp{song ti} or @samp{fangsong ti} in @var{family} field. In | |
1084 | such a case, @samp{Fontset-@var{n}} can be specified as below: | |
1085 | ||
1086 | @smallexample | |
1087 | Emacs.Fontset-0: -*-fixed-medium-r-normal-*-24-*-*-*-*-*-fontset-24,\ | |
1088 | chinese-gb2312:-*-*-medium-r-normal-*-24-*-gb2312*-* | |
1089 | @end smallexample | |
1090 | ||
1091 | @noindent | |
1092 | Then, the font specifications for all but Chinese GB2312 characters have | |
1093 | @samp{fixed} in the @var{family} field, and the font specification for | |
1094 | Chinese GB2312 characters has a wild card @samp{*} in the @var{family} | |
1095 | field. | |
1096 | ||
1097 | @findex create-fontset-from-fontset-spec | |
1098 | The function that processes the fontset resource value to create the | |
1099 | fontset is called @code{create-fontset-from-fontset-spec}. You can also | |
1100 | call this function explicitly to create a fontset. | |
1101 | ||
1102 | @xref{Font X}, for more information about font naming in X. | |
1103 | ||
60245086 DL |
1104 | @node Undisplayable Characters |
1105 | @section Undisplayable Characters | |
1106 | ||
4b40407a RS |
1107 | Your terminal may be unable to display some non-@sc{ascii} |
1108 | characters. Most non-windowing terminals can only use a single | |
1109 | character set (use the variable @code{default-terminal-coding-system} | |
1110 | (@pxref{Specify Coding}) to tell Emacs which one); characters which | |
1111 | can't be encoded in that coding system are displayed as @samp{?} by | |
1112 | default. | |
1113 | ||
1114 | Windowing terminals can display a broader range of characters, but | |
1115 | you may not have fonts installed for all of them; characters that have | |
1116 | no font appear as a hollow box. | |
60245086 | 1117 | |
4b40407a RS |
1118 | If you use Latin-1 characters but your terminal can't display |
1119 | Latin-1, you can arrange to display mnemonic @sc{ascii} sequences | |
1120 | instead, e.g.@: @samp{"o} for o-umlaut. Load the library | |
1121 | @file{iso-ascii} to do this. | |
60245086 | 1122 | |
4b40407a RS |
1123 | If your terminal can display Latin-1, you can display characters |
1124 | from other European character sets using a mixture of equivalent | |
1125 | Latin-1 characters and @sc{ascii} mnemonics. Use the Custom option | |
1126 | @code{latin1-display} to enable this. The mnemonic @sc{ascii} | |
1127 | sequences mostly correspond to those of the prefix input methods. | |
60245086 | 1128 | |
521ab838 DL |
1129 | @node Single-Byte Character Support |
1130 | @section Single-byte Character Set Support | |
6bf7aab6 DL |
1131 | |
1132 | @cindex European character sets | |
1133 | @cindex accented characters | |
1134 | @cindex ISO Latin character sets | |
1135 | @cindex Unibyte operation | |
6bf7aab6 DL |
1136 | The ISO 8859 Latin-@var{n} character sets define character codes in |
1137 | the range 160 to 255 to handle the accented letters and punctuation | |
521ab838 DL |
1138 | needed by various European languages (and some non-European ones). |
1139 | If you disable multibyte | |
6bf7aab6 DL |
1140 | characters, Emacs can still handle @emph{one} of these character codes |
1141 | at a time. To specify @emph{which} of these codes to use, invoke | |
1142 | @kbd{M-x set-language-environment} and specify a suitable language | |
1143 | environment such as @samp{Latin-@var{n}}. | |
1144 | ||
1145 | For more information about unibyte operation, see @ref{Enabling | |
1146 | Multibyte}. Note particularly that you probably want to ensure that | |
1147 | your initialization files are read as unibyte if they contain non-ASCII | |
1148 | characters. | |
1149 | ||
1150 | @vindex unibyte-display-via-language-environment | |
1151 | Emacs can also display those characters, provided the terminal or font | |
1152 | in use supports them. This works automatically. Alternatively, if you | |
1153 | are using a window system, Emacs can also display single-byte characters | |
1154 | through fontsets, in effect by displaying the equivalent multibyte | |
1155 | characters according to the current language environment. To request | |
1156 | this, set the variable @code{unibyte-display-via-language-environment} | |
1157 | to a non-@code{nil} value. | |
1158 | ||
1159 | @cindex @code{iso-ascii} library | |
1160 | If your terminal does not support display of the Latin-1 character | |
1161 | set, Emacs can display these characters as ASCII sequences which at | |
1162 | least give you a clear idea of what the characters are. To do this, | |
1163 | load the library @code{iso-ascii}. Similar libraries for other | |
1164 | Latin-@var{n} character sets could be implemented, but we don't have | |
1165 | them yet. | |
1166 | ||
1167 | @findex standard-display-8bit | |
1168 | @cindex 8-bit display | |
1169 | Normally non-ISO-8859 characters (between characters 128 and 159 | |
1170 | inclusive) are displayed as octal escapes. You can change this for | |
2684ed46 | 1171 | non-standard ``extended'' versions of ISO-8859 character sets by using the |
6bf7aab6 DL |
1172 | function @code{standard-display-8bit} in the @code{disp-table} library. |
1173 | ||
133f8c71 | 1174 | There are several ways you can input single-byte non-ASCII |
6bf7aab6 DL |
1175 | characters: |
1176 | ||
1177 | @itemize @bullet | |
521ab838 | 1178 | @cindex 8-bit input |
6bf7aab6 DL |
1179 | @item |
1180 | If your keyboard can generate character codes 128 and up, representing | |
4b40407a RS |
1181 | non-ASCII you can type those character codes directly. |
1182 | ||
1183 | On a windowing terminal, you should not need to do anything special to | |
1184 | use these keys; they should simply work. On a text-only terminal, you | |
1185 | should use the command @code{M-x set-keyboard-coding-system} or the | |
1186 | Custom option @code{keyboard-coding-system} to specify which coding | |
1187 | system your keyboard uses (@pxref{Specify Coding}). Enabling this | |
1188 | feature will probably require you to use @kbd{ESC} to type Meta | |
1189 | characters; however, on a Linux console or in @code{xterm}, you can | |
1190 | arrange for Meta to be converted to @kbd{ESC} and still be able type | |
1191 | 8-bit characters present directly on the keyboard or using | |
1192 | @kbd{Compose} or @kbd{AltGr} keys. @xref{User Input}. | |
521ab838 | 1193 | |
6bf7aab6 DL |
1194 | @item |
1195 | You can use an input method for the selected language environment. | |
1196 | @xref{Input Methods}. When you use an input method in a unibyte buffer, | |
1197 | the non-ASCII character you specify with it is converted to unibyte. | |
1198 | ||
1199 | @kindex C-x 8 | |
1200 | @cindex @code{iso-transl} library | |
98c271eb DL |
1201 | @cindex compose character |
1202 | @cindex dead character | |
6bf7aab6 DL |
1203 | @item |
1204 | For Latin-1 only, you can use the | |
1205 | key @kbd{C-x 8} as a ``compose character'' prefix for entry of | |
1206 | non-ASCII Latin-1 printing characters. @kbd{C-x 8} is good for | |
1207 | insertion (in the minibuffer as well as other buffers), for searching, | |
1208 | and in any other context where a key sequence is allowed. | |
1209 | ||
1210 | @kbd{C-x 8} works by loading the @code{iso-transl} library. Once that | |
1211 | library is loaded, the @key{ALT} modifier key, if you have one, serves | |
1212 | the same purpose as @kbd{C-x 8}; use @key{ALT} together with an accent | |
1213 | character to modify the following letter. In addition, if you have keys | |
4b40407a | 1214 | for the Latin-1 ``dead accent characters,'' they too are defined to |
6bf7aab6 | 1215 | compose with the following character, once @code{iso-transl} is loaded. |
133f8c71 DL |
1216 | Use @kbd{C-x 8 C-h} to list the available translations as mnemonic |
1217 | command names. | |
1218 | ||
133f8c71 | 1219 | @item |
98c271eb DL |
1220 | @cindex @code{iso-acc} library |
1221 | @cindex ISO Accents mode | |
1222 | @findex iso-accents-mode | |
13142d70 | 1223 | @cindex Latin-1, Latin-2 and Latin-3 input mode |
4b40407a RS |
1224 | For Latin-1, Latin-2 and Latin-3, @kbd{M-x iso-accents-mode} installs |
1225 | a minor mode which works much like the @code{latin-1-prefix} input | |
1226 | method does not depend on having the input methods installed. This | |
1227 | mode is buffer-local. It can be customized for various languages with | |
1228 | @kbd{M-x iso-accents-customize}. | |
6bf7aab6 | 1229 | @end itemize |