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6f585e44 | 1 | @c This is part of the Emacs manual. |
acaf905b | 2 | @c Copyright (C) 2004-2012 Free Software Foundation, Inc. |
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3 | @c See file emacs.texi for copying conditions. |
4 | @c | |
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5 | @c This file is included either in emacs-xtra.texi (when producing the |
6 | @c printed version) or in the main Emacs manual (for the on-line version). | |
7 | @node MS-DOS | |
8 | @section Emacs and MS-DOS | |
9 | @cindex MS-DOG | |
10 | @cindex MS-DOS peculiarities | |
11 | ||
12 | This section briefly describes the peculiarities of using Emacs on | |
13 | the MS-DOS ``operating system'' (also known as ``MS-DOG''). | |
234c95a9 | 14 | @iftex |
c5184807 | 15 | Information about Emacs and Microsoft's current operating system |
17577183 | 16 | Windows (also known as ``Losedows'') is in the main Emacs manual |
375e8351 | 17 | (@pxref{Microsoft Windows,,, emacs, the Emacs Manual}). |
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18 | @end iftex |
19 | @ifnottex | |
20 | Information about peculiarities common to MS-DOS and Microsoft's | |
17577183 | 21 | current operating systems Windows (also known as ``Losedows'') is in |
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22 | @ref{Microsoft Windows}. |
23 | @end ifnottex | |
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24 | |
25 | If you build Emacs for MS-DOS, the binary will also run on Windows | |
41155aef | 26 | 3.X, Windows NT, Windows 9X/ME, Windows 2000/XP, or OS/2 as a DOS |
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27 | application; all of this chapter applies for all of those systems, if |
28 | you use an Emacs that was built for MS-DOS. | |
29 | ||
234c95a9 | 30 | @iftex |
c5184807 | 31 | @xref{Text and Binary,,,emacs, the Emacs Manual}, for information |
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32 | @end iftex |
33 | @ifnottex | |
34 | @xref{Text and Binary}, for information | |
35 | @end ifnottex | |
44e97401 | 36 | about Emacs's special handling of text files under MS-DOS (and Windows). |
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37 | |
38 | @menu | |
39 | * Keyboard: MS-DOS Keyboard. Keyboard conventions on MS-DOS. | |
40 | * Mouse: MS-DOS Mouse. Mouse conventions on MS-DOS. | |
41 | * Display: MS-DOS Display. Fonts, frames and display size on MS-DOS. | |
42 | * Files: MS-DOS File Names. File name conventions on MS-DOS. | |
43 | * Printing: MS-DOS Printing. Printing specifics on MS-DOS. | |
44 | * I18N: MS-DOS and MULE. Support for internationalization on MS-DOS. | |
45 | * Processes: MS-DOS Processes. Running subprocesses on MS-DOS. | |
46 | @end menu | |
47 | ||
48 | @node MS-DOS Keyboard | |
49 | @subsection Keyboard Usage on MS-DOS | |
50 | ||
51 | @kindex DEL @r{(MS-DOS)} | |
52 | @kindex BS @r{(MS-DOS)} | |
53 | The key that is called @key{DEL} in Emacs (because that's how it is | |
54 | designated on most workstations) is known as @key{BS} (backspace) on a | |
55 | PC. That is why the PC-specific terminal initialization remaps the | |
56 | @key{BS} key to act as @key{DEL}; the @key{DELETE} key is remapped to act | |
57 | as @kbd{C-d} for the same reasons. | |
58 | ||
59 | @kindex C-g @r{(MS-DOS)} | |
60 | @kindex C-BREAK @r{(MS-DOS)} | |
61 | @cindex quitting on MS-DOS | |
62 | Emacs built for MS-DOS recognizes @kbd{C-@key{BREAK}} as a quit | |
63 | character, just like @kbd{C-g}. This is because Emacs cannot detect | |
64 | that you have typed @kbd{C-g} until it is ready for more input. As a | |
65 | consequence, you cannot use @kbd{C-g} to stop a running command | |
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66 | @iftex |
67 | (@pxref{Quitting,,,emacs, the Emacs Manual}). | |
68 | @end iftex | |
69 | @ifnottex | |
70 | (@pxref{Quitting}). | |
71 | @end ifnottex | |
72 | By contrast, @kbd{C-@key{BREAK}} @emph{is} detected as soon as you | |
73 | type it (as @kbd{C-g} is on other systems), so it can be used to stop | |
74 | a running command and for emergency escape | |
75 | @iftex | |
76 | (@pxref{Emergency Escape,,,emacs, the Emacs Manual}). | |
77 | @end iftex | |
78 | @ifnottex | |
79 | (@pxref{Emergency Escape}). | |
80 | @end ifnottex | |
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81 | |
82 | @cindex Meta (under MS-DOS) | |
83 | @cindex Hyper (under MS-DOS) | |
84 | @cindex Super (under MS-DOS) | |
85 | @vindex dos-super-key | |
86 | @vindex dos-hyper-key | |
87 | The PC keyboard maps use the left @key{ALT} key as the @key{META} key. | |
88 | You have two choices for emulating the @key{SUPER} and @key{HYPER} keys: | |
89 | choose either the right @key{CTRL} key or the right @key{ALT} key by | |
90 | setting the variables @code{dos-hyper-key} and @code{dos-super-key} to 1 | |
91 | or 2 respectively. If neither @code{dos-super-key} nor | |
92 | @code{dos-hyper-key} is 1, then by default the right @key{ALT} key is | |
93 | also mapped to the @key{META} key. However, if the MS-DOS international | |
94 | keyboard support program @file{KEYB.COM} is installed, Emacs will | |
95 | @emph{not} map the right @key{ALT} to @key{META}, since it is used for | |
96 | accessing characters like @kbd{~} and @kbd{@@} on non-US keyboard | |
97 | layouts; in this case, you may only use the left @key{ALT} as @key{META} | |
98 | key. | |
99 | ||
100 | @kindex C-j @r{(MS-DOS)} | |
101 | @vindex dos-keypad-mode | |
102 | The variable @code{dos-keypad-mode} is a flag variable that controls | |
103 | what key codes are returned by keys in the numeric keypad. You can also | |
104 | define the keypad @key{ENTER} key to act like @kbd{C-j}, by putting the | |
105 | following line into your @file{_emacs} file: | |
106 | ||
107 | @smallexample | |
108 | ;; @r{Make the @key{ENTER} key from the numeric keypad act as @kbd{C-j}.} | |
109 | (define-key function-key-map [kp-enter] [?\C-j]) | |
110 | @end smallexample | |
111 | ||
112 | @node MS-DOS Mouse | |
113 | @subsection Mouse Usage on MS-DOS | |
114 | ||
115 | @cindex mouse support under MS-DOS | |
116 | Emacs on MS-DOS supports a mouse (on the default terminal only). | |
117 | The mouse commands work as documented, including those that use menus | |
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118 | and the menu bar |
119 | @iftex | |
120 | (@pxref{Menu Bar,,,emacs, the Emacs Manual}). | |
121 | @end iftex | |
122 | @ifnottex | |
123 | (@pxref{Menu Bar}). | |
124 | @end ifnottex | |
125 | Scroll bars don't work in MS-DOS Emacs. PC mice usually have only | |
126 | two buttons; these act as @kbd{Mouse-1} and @kbd{Mouse-2}, but if you | |
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127 | press both of them together, that has the effect of @kbd{Mouse-3}. If |
128 | the mouse does have 3 buttons, Emacs detects that at startup, and all | |
129 | the 3 buttons function normally, as on X. | |
130 | ||
131 | Help strings for menu-bar and pop-up menus are displayed in the echo | |
132 | area when the mouse pointer moves across the menu items. Highlighting | |
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133 | of mouse-sensitive text |
134 | @iftex | |
135 | (@pxref{Mouse References,,,emacs, the Emacs Manual}) | |
136 | @end iftex | |
137 | @ifnottex | |
138 | (@pxref{Mouse References}) | |
139 | @end ifnottex | |
140 | is also supported. | |
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141 | |
142 | @cindex mouse, set number of buttons | |
143 | @findex msdos-set-mouse-buttons | |
144 | Some versions of mouse drivers don't report the number of mouse | |
145 | buttons correctly. For example, mice with a wheel report that they | |
146 | have 3 buttons, but only 2 of them are passed to Emacs; the clicks on | |
147 | the wheel, which serves as the middle button, are not passed. In | |
148 | these cases, you can use the @kbd{M-x msdos-set-mouse-buttons} command | |
149 | to tell Emacs how many mouse buttons to expect. You could make such a | |
150 | setting permanent by adding this fragment to your @file{_emacs} init | |
151 | file: | |
152 | ||
153 | @example | |
154 | ;; @r{Treat the mouse like a 2-button mouse.} | |
155 | (msdos-set-mouse-buttons 2) | |
156 | @end example | |
157 | ||
158 | @cindex Windows clipboard support | |
159 | Emacs built for MS-DOS supports clipboard operations when it runs on | |
160 | Windows. Commands that put text on the kill ring, or yank text from | |
161 | the ring, check the Windows clipboard first, just as Emacs does on the | |
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162 | X Window System |
163 | @iftex | |
164 | (@pxref{Mouse Commands,,,emacs, the Emacs Manual}). | |
165 | @end iftex | |
166 | @ifnottex | |
167 | (@pxref{Mouse Commands}). | |
168 | @end ifnottex | |
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169 | Only the primary selection and the cut buffer are supported by MS-DOS |
170 | Emacs on Windows; the secondary selection always appears as empty. | |
171 | ||
172 | Due to the way clipboard access is implemented by Windows, the | |
173 | length of text you can put into the clipboard is limited by the amount | |
174 | of free DOS memory that is available to Emacs. Usually, up to 620KB of | |
175 | text can be put into the clipboard, but this limit depends on the system | |
176 | configuration and is lower if you run Emacs as a subprocess of | |
177 | another program. If the killed text does not fit, Emacs outputs a | |
178 | message saying so, and does not put the text into the clipboard. | |
179 | ||
180 | Null characters also cannot be put into the Windows clipboard. If the | |
181 | killed text includes null characters, Emacs does not put such text into | |
182 | the clipboard, and displays in the echo area a message to that effect. | |
183 | ||
184 | @vindex dos-display-scancodes | |
185 | The variable @code{dos-display-scancodes}, when non-@code{nil}, | |
186 | directs Emacs to display the @acronym{ASCII} value and the keyboard scan code of | |
187 | each keystroke; this feature serves as a complement to the | |
188 | @code{view-lossage} command, for debugging. | |
189 | ||
190 | @node MS-DOS Display | |
191 | @subsection Display on MS-DOS | |
192 | @cindex faces under MS-DOS | |
193 | @cindex fonts, emulating under MS-DOS | |
194 | ||
195 | Display on MS-DOS cannot use font variants, like bold or italic, but | |
196 | it does support multiple faces, each of which can specify a foreground | |
197 | and a background color. Therefore, you can get the full functionality | |
198 | of Emacs packages that use fonts (such as @code{font-lock}, Enriched | |
199 | Text mode, and others) by defining the relevant faces to use different | |
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200 | colors. Use the @code{list-colors-display} command |
201 | @iftex | |
371fb833 | 202 | (@pxref{Colors,,,emacs, the Emacs Manual}) |
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203 | @end iftex |
204 | @ifnottex | |
371fb833 | 205 | (@pxref{Colors}) |
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206 | @end ifnottex |
207 | and the @code{list-faces-display} command | |
208 | @iftex | |
209 | (@pxref{Faces,,,emacs, the Emacs Manual}) | |
210 | @end iftex | |
211 | @ifnottex | |
212 | (@pxref{Faces}) | |
213 | @end ifnottex | |
214 | to see what colors and faces are available and what they look like. | |
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215 | |
216 | @xref{MS-DOS and MULE}, later in this chapter, for information on | |
217 | how Emacs displays glyphs and characters that aren't supported by the | |
218 | native font built into the DOS display. | |
219 | ||
220 | @cindex cursor shape on MS-DOS | |
221 | When Emacs starts, it changes the cursor shape to a solid box. This | |
222 | is for compatibility with other systems, where the box cursor is the | |
223 | default in Emacs. This default shape can be changed to a bar by | |
224 | specifying the @code{cursor-type} parameter in the variable | |
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225 | @code{default-frame-alist} |
226 | @iftex | |
227 | (@pxref{Creating Frames,,,emacs, the Emacs Manual}). | |
228 | @end iftex | |
229 | @ifnottex | |
230 | (@pxref{Creating Frames}). | |
231 | @end ifnottex | |
232 | The MS-DOS terminal doesn't support a vertical-bar cursor, | |
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233 | so the bar cursor is horizontal, and the @code{@var{width}} parameter, |
234 | if specified by the frame parameters, actually determines its height. | |
235 | For this reason, the @code{bar} and @code{hbar} cursor types produce | |
236 | the same effect on MS-DOS. As an extension, the bar cursor | |
237 | specification can include the starting scan line of the cursor as well | |
238 | as its width, like this: | |
239 | ||
240 | @example | |
241 | '(cursor-type bar @var{width} . @var{start}) | |
242 | @end example | |
243 | ||
244 | @noindent | |
245 | In addition, if the @var{width} parameter is negative, the cursor bar | |
246 | begins at the top of the character cell. | |
247 | ||
248 | @cindex frames on MS-DOS | |
249 | The MS-DOS terminal can only display a single frame at a time. The | |
0be641c0 | 250 | Emacs frame facilities work on MS-DOS much as they do on text |
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251 | terminals |
252 | @iftex | |
253 | (@pxref{Frames,,,emacs, the Emacs Manual}). | |
254 | @end iftex | |
255 | @ifnottex | |
256 | (@pxref{Frames}). | |
257 | @end ifnottex | |
258 | When you run Emacs from a DOS window on MS-Windows, you can make the | |
259 | visible frame smaller than the full screen, but Emacs still cannot | |
260 | display more than a single frame at a time. | |
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261 | |
262 | @cindex frame size under MS-DOS | |
371fb833 GM |
263 | @findex dos-mode4350 |
264 | @findex dos-mode25 | |
265 | The @code{dos-mode4350} command switches the display to 43 or 50 | |
266 | lines, depending on your hardware; the @code{dos-mode25} command switches | |
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267 | to the default 80x25 screen size. |
268 | ||
269 | By default, Emacs only knows how to set screen sizes of 80 columns by | |
270 | 25, 28, 35, 40, 43 or 50 rows. However, if your video adapter has | |
271 | special video modes that will switch the display to other sizes, you can | |
272 | have Emacs support those too. When you ask Emacs to switch the frame to | |
273 | @var{n} rows by @var{m} columns dimensions, it checks if there is a | |
274 | variable called @code{screen-dimensions-@var{n}x@var{m}}, and if so, | |
275 | uses its value (which must be an integer) as the video mode to switch | |
276 | to. (Emacs switches to that video mode by calling the BIOS @code{Set | |
277 | Video Mode} function with the value of | |
278 | @code{screen-dimensions-@var{n}x@var{m}} in the @code{AL} register.) | |
279 | For example, suppose your adapter will switch to 66x80 dimensions when | |
280 | put into video mode 85. Then you can make Emacs support this screen | |
281 | size by putting the following into your @file{_emacs} file: | |
282 | ||
283 | @example | |
284 | (setq screen-dimensions-66x80 85) | |
285 | @end example | |
286 | ||
287 | Since Emacs on MS-DOS can only set the frame size to specific | |
288 | supported dimensions, it cannot honor every possible frame resizing | |
289 | request. When an unsupported size is requested, Emacs chooses the next | |
290 | larger supported size beyond the specified size. For example, if you | |
291 | ask for 36x80 frame, you will get 40x80 instead. | |
292 | ||
293 | The variables @code{screen-dimensions-@var{n}x@var{m}} are used only | |
294 | when they exactly match the specified size; the search for the next | |
295 | larger supported size ignores them. In the above example, even if your | |
296 | VGA supports 38x80 dimensions and you define a variable | |
297 | @code{screen-dimensions-38x80} with a suitable value, you will still get | |
298 | 40x80 screen when you ask for a 36x80 frame. If you want to get the | |
299 | 38x80 size in this case, you can do it by setting the variable named | |
300 | @code{screen-dimensions-36x80} with the same video mode value as | |
301 | @code{screen-dimensions-38x80}. | |
302 | ||
303 | Changing frame dimensions on MS-DOS has the effect of changing all the | |
304 | other frames to the new dimensions. | |
305 | ||
306 | @node MS-DOS File Names | |
307 | @subsection File Names on MS-DOS | |
308 | @cindex file names under MS-DOS | |
309 | @cindex init file, default name under MS-DOS | |
310 | ||
311 | On MS-DOS, file names are case-insensitive and limited to eight | |
312 | characters, plus optionally a period and three more characters. Emacs | |
313 | knows enough about these limitations to handle file names that were | |
314 | meant for other operating systems. For instance, leading dots | |
315 | @samp{.} in file names are invalid in MS-DOS, so Emacs transparently | |
316 | converts them to underscores @samp{_}; thus your default init file | |
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317 | @iftex |
318 | (@pxref{Init File,,,emacs, the Emacs Manual}) | |
319 | @end iftex | |
320 | @ifnottex | |
321 | (@pxref{Init File}) | |
322 | @end ifnottex | |
323 | is called @file{_emacs} on MS-DOS. Excess characters before or after | |
324 | the period are generally ignored by MS-DOS itself; thus, if you visit | |
325 | the file @file{LongFileName.EvenLongerExtension}, you will silently | |
326 | get @file{longfile.eve}, but Emacs will still display the long file | |
327 | name on the mode line. Other than that, it's up to you to specify | |
328 | file names which are valid under MS-DOS; the transparent conversion as | |
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329 | described above only works on file names built into Emacs. |
330 | ||
331 | @cindex backup file names on MS-DOS | |
332 | The above restrictions on the file names on MS-DOS make it almost | |
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333 | impossible to construct the name of a backup file |
334 | @iftex | |
335 | (@pxref{Backup Names,,,emacs, the Emacs Manual}) | |
336 | @end iftex | |
337 | @ifnottex | |
338 | (@pxref{Backup Names}) | |
339 | @end ifnottex | |
340 | without losing some of the original file name characters. For | |
341 | example, the name of a backup file for @file{docs.txt} is | |
342 | @file{docs.tx~} even if single backup is used. | |
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343 | |
344 | @cindex file names under Windows 95/NT | |
345 | @cindex long file names in DOS box under Windows 95/NT | |
346 | If you run Emacs as a DOS application under Windows 9X, Windows ME, or | |
41155aef | 347 | Windows 2000/XP, you can turn on support for long file names. If you do |
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348 | that, Emacs doesn't truncate file names or convert them to lower case; |
349 | instead, it uses the file names that you specify, verbatim. To enable | |
350 | long file name support, set the environment variable @env{LFN} to | |
351 | @samp{y} before starting Emacs. Unfortunately, Windows NT doesn't allow | |
352 | DOS programs to access long file names, so Emacs built for MS-DOS will | |
353 | only see their short 8+3 aliases. | |
354 | ||
355 | @cindex @env{HOME} directory under MS-DOS | |
356 | MS-DOS has no notion of home directory, so Emacs on MS-DOS pretends | |
357 | that the directory where it is installed is the value of the @env{HOME} | |
358 | environment variable. That is, if your Emacs binary, | |
359 | @file{emacs.exe}, is in the directory @file{c:/utils/emacs/bin}, then | |
360 | Emacs acts as if @env{HOME} were set to @samp{c:/utils/emacs}. In | |
361 | particular, that is where Emacs looks for the init file @file{_emacs}. | |
362 | With this in mind, you can use @samp{~} in file names as an alias for | |
363 | the home directory, as you would on GNU or Unix. You can also set | |
364 | @env{HOME} variable in the environment before starting Emacs; its | |
365 | value will then override the above default behavior. | |
366 | ||
367 | Emacs on MS-DOS handles the directory name @file{/dev} specially, | |
368 | because of a feature in the emulator libraries of DJGPP that pretends | |
369 | I/O devices have names in that directory. We recommend that you avoid | |
370 | using an actual directory named @file{/dev} on any disk. | |
371 | ||
372 | @node MS-DOS Printing | |
373 | @subsection Printing and MS-DOS | |
374 | ||
375 | Printing commands, such as @code{lpr-buffer} | |
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376 | @iftex |
377 | (@pxref{Printing,,,emacs, the Emacs Manual}) and @code{ps-print-buffer} | |
378 | (@pxref{PostScript,,,emacs, the Emacs Manual}) | |
379 | @end iftex | |
380 | @ifnottex | |
381 | (@pxref{Printing}) and @code{ps-print-buffer} (@pxref{PostScript}) | |
382 | @end ifnottex | |
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383 | can work on MS-DOS by sending the output to one of the printer ports, |
384 | if a Posix-style @code{lpr} program is unavailable. The same Emacs | |
385 | variables control printing on all systems, but in some cases they have | |
386 | different default values on MS-DOS. | |
387 | ||
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388 | @iftex |
389 | @xref{Windows Printing,,,emacs, the Emacs Manual}, | |
390 | @end iftex | |
391 | @ifnottex | |
392 | @xref{Windows Printing}, | |
393 | @end ifnottex | |
394 | for details about setting up printing to a networked printer. | |
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395 | |
396 | Some printers expect DOS codepage encoding of non-@acronym{ASCII} text, even | |
371fb833 | 397 | though they are connected to a Windows machine that uses a different |
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398 | encoding for the same locale. For example, in the Latin-1 locale, DOS |
399 | uses codepage 850 whereas Windows uses codepage 1252. @xref{MS-DOS and | |
400 | MULE}. When you print to such printers from Windows, you can use the | |
401 | @kbd{C-x RET c} (@code{universal-coding-system-argument}) command before | |
402 | @kbd{M-x lpr-buffer}; Emacs will then convert the text to the DOS | |
403 | codepage that you specify. For example, @kbd{C-x RET c cp850-dos RET | |
404 | M-x lpr-region RET} will print the region while converting it to the | |
d073c1eb | 405 | codepage 850 encoding. |
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406 | |
407 | @vindex dos-printer | |
408 | @vindex dos-ps-printer | |
409 | For backwards compatibility, the value of @code{dos-printer} | |
410 | (@code{dos-ps-printer}), if it has a value, overrides the value of | |
411 | @code{printer-name} (@code{ps-printer-name}), on MS-DOS. | |
412 | ||
413 | ||
414 | @node MS-DOS and MULE | |
415 | @subsection International Support on MS-DOS | |
416 | @cindex international support @r{(MS-DOS)} | |
417 | ||
418 | Emacs on MS-DOS supports the same international character sets as it | |
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419 | does on GNU, Unix and other platforms |
420 | @iftex | |
421 | (@pxref{International,,,emacs, the Emacs Manual}), | |
422 | @end iftex | |
423 | @ifnottex | |
424 | (@pxref{International}), | |
425 | @end ifnottex | |
426 | including coding systems for converting between the different | |
427 | character sets. However, due to incompatibilities between | |
428 | MS-DOS/MS-Windows and other systems, there are several DOS-specific | |
429 | aspects of this support that you should be aware of. This section | |
430 | describes these aspects. | |
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431 | |
432 | The description below is largely specific to the MS-DOS port of | |
433 | Emacs, especially where it talks about practical implications for | |
d073c1eb | 434 | Emacs users. |
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435 | |
436 | @table @kbd | |
437 | @item M-x dos-codepage-setup | |
438 | Set up Emacs display and coding systems as appropriate for the current | |
439 | DOS codepage. | |
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440 | @end table |
441 | ||
442 | @cindex codepage, MS-DOS | |
443 | @cindex DOS codepages | |
444 | MS-DOS is designed to support one character set of 256 characters at | |
445 | any given time, but gives you a variety of character sets to choose | |
446 | from. The alternative character sets are known as @dfn{DOS codepages}. | |
447 | Each codepage includes all 128 @acronym{ASCII} characters, but the other 128 | |
448 | characters (codes 128 through 255) vary from one codepage to another. | |
449 | Each DOS codepage is identified by a 3-digit number, such as 850, 862, | |
450 | etc. | |
451 | ||
452 | In contrast to X, which lets you use several fonts at the same time, | |
453 | MS-DOS normally doesn't allow use of several codepages in a single | |
454 | session. MS-DOS was designed to load a single codepage at system | |
455 | startup, and require you to reboot in order to change | |
456 | it@footnote{Normally, one particular codepage is burnt into the | |
457 | display memory, while other codepages can be installed by modifying | |
458 | system configuration files, such as @file{CONFIG.SYS}, and rebooting. | |
459 | While there is third-party software that allows changing the codepage | |
460 | without rebooting, we describe here how a stock MS-DOS system | |
461 | behaves.}. Much the same limitation applies when you run DOS | |
462 | executables on other systems such as MS-Windows. | |
463 | ||
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464 | @vindex dos-codepage |
465 | For multibyte operation on MS-DOS, Emacs needs to know which | |
466 | characters the chosen DOS codepage can display. So it queries the | |
467 | system shortly after startup to get the chosen codepage number, and | |
468 | stores the number in the variable @code{dos-codepage}. Some systems | |
469 | return the default value 437 for the current codepage, even though the | |
470 | actual codepage is different. (This typically happens when you use the | |
471 | codepage built into the display hardware.) You can specify a different | |
472 | codepage for Emacs to use by setting the variable @code{dos-codepage} in | |
473 | your init file. | |
474 | ||
475 | @cindex language environment, automatic selection on @r{MS-DOS} | |
476 | Multibyte Emacs supports only certain DOS codepages: those which can | |
477 | display Far-Eastern scripts, like the Japanese codepage 932, and those | |
478 | that encode a single ISO 8859 character set. | |
479 | ||
480 | The Far-Eastern codepages can directly display one of the MULE | |
481 | character sets for these countries, so Emacs simply sets up to use the | |
482 | appropriate terminal coding system that is supported by the codepage. | |
483 | The special features described in the rest of this section mostly | |
484 | pertain to codepages that encode ISO 8859 character sets. | |
485 | ||
371fb833 | 486 | For the codepages that correspond to one of the ISO character sets, |
d073c1eb | 487 | Emacs knows the character set based on the codepage number. Emacs |
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488 | automatically creates a coding system to support reading and writing |
489 | files that use the current codepage, and uses this coding system by | |
490 | default. The name of this coding system is @code{cp@var{nnn}}, where | |
491 | @var{nnn} is the codepage number.@footnote{The standard Emacs coding | |
492 | systems for ISO 8859 are not quite right for the purpose, because | |
493 | typically the DOS codepage does not match the standard ISO character | |
494 | codes. For example, the letter @samp{@,{c}} (@samp{c} with cedilla) has | |
495 | code 231 in the standard Latin-1 character set, but the corresponding | |
496 | DOS codepage 850 uses code 135 for this glyph.} | |
497 | ||
498 | @cindex mode line @r{(MS-DOS)} | |
499 | All the @code{cp@var{nnn}} coding systems use the letter @samp{D} | |
500 | (for ``DOS'') as their mode-line mnemonic. Since both the terminal | |
501 | coding system and the default coding system for file I/O are set to | |
502 | the proper @code{cp@var{nnn}} coding system at startup, it is normal | |
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503 | for the mode line on MS-DOS to begin with @samp{-DD\-}. |
504 | @iftex | |
505 | @xref{Mode Line,,,emacs, the Emacs Manual}. | |
506 | @end iftex | |
507 | @ifnottex | |
508 | @xref{Mode Line}. | |
509 | @end ifnottex | |
510 | Far-Eastern DOS terminals do not use the @code{cp@var{nnn}} coding | |
511 | systems, and thus their initial mode line looks like the Emacs | |
512 | default. | |
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513 | |
514 | Since the codepage number also indicates which script you are using, | |
515 | Emacs automatically runs @code{set-language-environment} to select the | |
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516 | language environment for that script |
517 | @iftex | |
518 | (@pxref{Language Environments,,,emacs, the Emacs Manual}). | |
519 | @end iftex | |
520 | @ifnottex | |
521 | (@pxref{Language Environments}). | |
522 | @end ifnottex | |
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523 | |
524 | If a buffer contains a character belonging to some other ISO 8859 | |
525 | character set, not the one that the chosen DOS codepage supports, Emacs | |
526 | displays it using a sequence of @acronym{ASCII} characters. For example, if the | |
527 | current codepage doesn't have a glyph for the letter @samp{@`o} (small | |
528 | @samp{o} with a grave accent), it is displayed as @samp{@{`o@}}, where | |
529 | the braces serve as a visual indication that this is a single character. | |
530 | (This may look awkward for some non-Latin characters, such as those from | |
531 | Greek or Hebrew alphabets, but it is still readable by a person who | |
532 | knows the language.) Even though the character may occupy several | |
533 | columns on the screen, it is really still just a single character, and | |
534 | all Emacs commands treat it as one. | |
535 | ||
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536 | @cindex MS-Windows codepages |
537 | MS-Windows provides its own codepages, which are different from the | |
538 | DOS codepages for the same locale. For example, DOS codepage 850 | |
539 | supports the same character set as Windows codepage 1252; DOS codepage | |
540 | 855 supports the same character set as Windows codepage 1251, etc. | |
541 | The MS-Windows version of Emacs uses the current codepage for display | |
d073c1eb | 542 | when invoked with the @samp{-nw} option. |
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543 | |
544 | @node MS-DOS Processes | |
545 | @subsection Subprocesses on MS-DOS | |
546 | ||
547 | @cindex compilation under MS-DOS | |
548 | @cindex inferior processes under MS-DOS | |
549 | @findex compile @r{(MS-DOS)} | |
550 | @findex grep @r{(MS-DOS)} | |
16152b76 | 551 | Because MS-DOS is a single-process ``operating system'', |
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552 | asynchronous subprocesses are not available. In particular, Shell |
553 | mode and its variants do not work. Most Emacs features that use | |
554 | asynchronous subprocesses also don't work on MS-DOS, including | |
555 | Shell mode and GUD. When in doubt, try and see; commands that | |
556 | don't work output an error message saying that asynchronous processes | |
557 | aren't supported. | |
558 | ||
559 | Compilation under Emacs with @kbd{M-x compile}, searching files with | |
560 | @kbd{M-x grep} and displaying differences between files with @kbd{M-x | |
561 | diff} do work, by running the inferior processes synchronously. This | |
562 | means you cannot do any more editing until the inferior process | |
563 | finishes. | |
564 | ||
565 | Spell checking also works, by means of special support for synchronous | |
566 | invocation of the @code{ispell} program. This is slower than the | |
567 | asynchronous invocation on other platforms | |
568 | ||
569 | Instead of the Shell mode, which doesn't work on MS-DOS, you can use | |
570 | the @kbd{M-x eshell} command. This invokes the Eshell package that | |
571 | implements a Posix-like shell entirely in Emacs Lisp. | |
572 | ||
573 | By contrast, Emacs compiled as a native Windows application | |
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574 | @strong{does} support asynchronous subprocesses. |
575 | @iftex | |
576 | @xref{Windows Processes,,,emacs, the Emacs Manual}. | |
577 | @end iftex | |
578 | @ifnottex | |
579 | @xref{Windows Processes}. | |
580 | @end ifnottex | |
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581 | |
582 | @cindex printing under MS-DOS | |
583 | Printing commands, such as @code{lpr-buffer} | |
234c95a9 | 584 | @iftex |
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585 | (@pxref{Printing,,,emacs, the Emacs Manual}) and |
586 | @code{ps-print-buffer} (@pxref{PostScript,,,emacs, the Emacs Manual}), | |
587 | work in MS-DOS by sending the output to one of the printer ports. | |
588 | @xref{MS-DOS Printing,,,emacs, the Emacs Manual}. | |
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589 | @end iftex |
590 | @ifnottex | |
591 | (@pxref{Printing}) and @code{ps-print-buffer} (@pxref{PostScript}), | |
592 | work in MS-DOS by sending the output to one of the printer ports. | |
593 | @xref{MS-DOS Printing}. | |
594 | @end ifnottex | |
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595 | |
596 | When you run a subprocess synchronously on MS-DOS, make sure the | |
597 | program terminates and does not try to read keyboard input. If the | |
598 | program does not terminate on its own, you will be unable to terminate | |
599 | it, because MS-DOS provides no general way to terminate a process. | |
600 | Pressing @kbd{C-c} or @kbd{C-@key{BREAK}} might sometimes help in these | |
601 | cases. | |
602 | ||
603 | Accessing files on other machines is not supported on MS-DOS. Other | |
604 | network-oriented commands such as sending mail, Web browsing, remote | |
605 | login, etc., don't work either, unless network access is built into | |
606 | MS-DOS with some network redirector. | |
607 | ||
608 | @cindex directory listing on MS-DOS | |
609 | @vindex dired-listing-switches @r{(MS-DOS)} | |
371fb833 GM |
610 | Dired on MS-DOS uses the @code{ls-lisp} package |
611 | @iftex | |
612 | (@pxref{ls in Lisp,,,emacs, the Emacs Manual}). | |
613 | @end iftex | |
614 | @ifnottex | |
615 | (@pxref{ls in Lisp}). | |
616 | @end ifnottex | |
617 | Therefore, Dired on MS-DOS supports only some of the possible options | |
618 | you can mention in the @code{dired-listing-switches} variable. The | |
619 | options that work are @samp{-A}, @samp{-a}, @samp{-c}, @samp{-i}, | |
620 | @samp{-r}, @samp{-S}, @samp{-s}, @samp{-t}, and @samp{-u}. |