[Emacs-diffs] Changes to emacs/man/emacs-xtra.texi

[Karl Berry]

Index: emacs/man/emacs-xtra.texi
diff -u emacs/man/emacs-xtra.texi:1.16 emacs/man/emacs-xtra.texi:1.17
--- emacs/man/emacs-xtra.texi:1.16      Sat Mar 25 23:13:20 2006
+++ emacs/man/emacs-xtra.texi   Sun Apr  9 22:40:34 2006
@@ -64,6 +64,7 @@
 * Picture Mode::                  Editing pictures made up of characters
                                     using the quarter-plane screen model.
 * Fortran::                       Fortran mode and its special features.
+* MS-DOG::                        
 * Index::
 @end menu
 
@@ -2406,6 +2407,687 @@
   Type @samp{;?} or @samp{;C-h} to display a list of all the built-in
 Fortran abbrevs and what they stand for.
 
+
address@hidden MS-DOG
address@hidden Emacs and MS-DOS
address@hidden MS-DOG
address@hidden MS-DOS peculiarities
+
+  This section briefly describes the peculiarities of using Emacs on
+the MS-DOS ``operating system'' (also known as ``MS-DOG'').
+Information about Emacs and Microsoft's current operating system
+Windows (also known as ``Losedows) is in the main Emacs manual
+(@pxref{Emacs and Microsoft Systems,,, emacs, the Emacs Manual}).
+
+  If you build Emacs for MS-DOS, the binary will also run on Windows
+3.X, Windows NT, Windows 9X/ME, Windows 2000, or OS/2 as a DOS
+application; all of this chapter applies for all of those systems, if
+you use an Emacs that was built for MS-DOS.
+
+  @xref{Text and Binary,,,emacs, the Emacs Manual}, for information
+about Emacs' special handling of text files under MS-DOS (and
+Windows).
+
address@hidden
+* Keyboard: MS-DOS Keyboard.   Keyboard conventions on MS-DOS.
+* Mouse: MS-DOS Mouse.         Mouse conventions on MS-DOS.
+* Display: MS-DOS Display.     Fonts, frames and display size on MS-DOS.
+* Files: MS-DOS File Names.    File name conventions on MS-DOS.
+* Printing: MS-DOS Printing.   How to specify the printer on MS-DOS.
+* I18N: MS-DOS and MULE.       Support for internationalization on MS-DOS.
+* Processes: MS-DOS Processes. Running subprocesses on MS-DOS.
address@hidden menu
+
address@hidden MS-DOS Keyboard
address@hidden Keyboard Usage on MS-DOS
+
address@hidden DEL @r{(MS-DOS)}
address@hidden BS @r{(MS-DOS)}
+  The key that is called @key{DEL} in Emacs (because that's how it is
+designated on most workstations) is known as @key{BS} (backspace) on a
+PC.  That is why the PC-specific terminal initialization remaps the
address@hidden key to act as @key{DEL}; the @key{DELETE} key is remapped to act
+as @kbd{C-d} for the same reasons.
+
address@hidden C-g @r{(MS-DOS)}
address@hidden C-BREAK @r{(MS-DOS)}
address@hidden quitting on MS-DOS
+  Emacs built for MS-DOS recognizes @address@hidden as a quit
+character, just like @kbd{C-g}.  This is because Emacs cannot detect
+that you have typed @kbd{C-g} until it is ready for more input.  As a
+consequence, you cannot use @kbd{C-g} to stop a running command
+(@pxref{Quitting,,,emacs, the Emacs Manual}).  By contrast,
address@hidden@key{BREAK}} @emph{is} detected as soon as you type it (as
address@hidden is on other systems), so it can be used to stop a running
+command and for emergency escape (@pxref{Emergency Escape,,,emacs, the
+Emacs Manual}).
+
address@hidden Meta (under MS-DOS)
address@hidden Hyper (under MS-DOS)
address@hidden Super (under MS-DOS)
address@hidden dos-super-key
address@hidden dos-hyper-key
+  The PC keyboard maps use the left @key{ALT} key as the @key{META} key.
+You have two choices for emulating the @key{SUPER} and @key{HYPER} keys:
+choose either the right @key{CTRL} key or the right @key{ALT} key by
+setting the variables @code{dos-hyper-key} and @code{dos-super-key} to 1
+or 2 respectively.  If neither @code{dos-super-key} nor
address@hidden is 1, then by default the right @key{ALT} key is
+also mapped to the @key{META} key.  However, if the MS-DOS international
+keyboard support program @file{KEYB.COM} is installed, Emacs will
address@hidden map the right @key{ALT} to @key{META}, since it is used for
+accessing characters like @kbd{~} and @kbd{@@} on non-US keyboard
+layouts; in this case, you may only use the left @key{ALT} as @key{META}
+key.
+
address@hidden C-j @r{(MS-DOS)}
address@hidden dos-keypad-mode
+  The variable @code{dos-keypad-mode} is a flag variable that controls
+what key codes are returned by keys in the numeric keypad.  You can also
+define the keypad @key{ENTER} key to act like @kbd{C-j}, by putting the
+following line into your @file{_emacs} file:
+
address@hidden
+;; @r{Make the @key{ENTER} key from the numeric keypad act as @kbd{C-j}.}
+(define-key function-key-map [kp-enter] [?\C-j])
address@hidden smallexample
+
address@hidden MS-DOS Mouse
address@hidden Mouse Usage on MS-DOS
+
address@hidden mouse support under MS-DOS
+  Emacs on MS-DOS supports a mouse (on the default terminal only).
+The mouse commands work as documented, including those that use menus
+and the menu bar (@pxref{Menu Bar,,,emacs, the Emacs Manual}).  Scroll
+bars don't work in MS-DOS Emacs.  PC mice usually have only two
+buttons; these act as @kbd{Mouse-1} and @kbd{Mouse-2}, but if you
+press both of them together, that has the effect of @kbd{Mouse-3}.  If
+the mouse does have 3 buttons, Emacs detects that at startup, and all
+the 3 buttons function normally, as on X.
+
+  Help strings for menu-bar and pop-up menus are displayed in the echo
+area when the mouse pointer moves across the menu items.  Highlighting
+of mouse-sensitive text (@pxref{Mouse References,,,emacs, the Emacs
+Manual}) is also supported.
+
address@hidden mouse, set number of buttons
address@hidden msdos-set-mouse-buttons
+  Some versions of mouse drivers don't report the number of mouse
+buttons correctly.  For example, mice with a wheel report that they
+have 3 buttons, but only 2 of them are passed to Emacs; the clicks on
+the wheel, which serves as the middle button, are not passed.  In
+these cases, you can use the @kbd{M-x msdos-set-mouse-buttons} command
+to tell Emacs how many mouse buttons to expect.  You could make such a
+setting permanent by adding this fragment to your @file{_emacs} init
+file:
+
address@hidden
+;; @r{Treat the mouse like a 2-button mouse.}
+(msdos-set-mouse-buttons 2)
address@hidden example
+
address@hidden Windows clipboard support
+  Emacs built for MS-DOS supports clipboard operations when it runs on
+Windows.  Commands that put text on the kill ring, or yank text from
+the ring, check the Windows clipboard first, just as Emacs does on the
+X Window System (@pxref{Mouse Commands,,,emacs, the Emacs Manual}).
+Only the primary selection and the cut buffer are supported by MS-DOS
+Emacs on Windows; the secondary selection always appears as empty.
+
+  Due to the way clipboard access is implemented by Windows, the
+length of text you can put into the clipboard is limited by the amount
+of free DOS memory that is available to Emacs.  Usually, up to 620KB of
+text can be put into the clipboard, but this limit depends on the system
+configuration and is lower if you run Emacs as a subprocess of
+another program.  If the killed text does not fit, Emacs outputs a
+message saying so, and does not put the text into the clipboard.
+
+  Null characters also cannot be put into the Windows clipboard.  If the
+killed text includes null characters, Emacs does not put such text into
+the clipboard, and displays in the echo area a message to that effect.
+
address@hidden dos-display-scancodes
+  The variable @code{dos-display-scancodes}, when address@hidden,
+directs Emacs to display the @acronym{ASCII} value and the keyboard scan code 
of
+each keystroke; this feature serves as a complement to the
address@hidden command, for debugging.
+
address@hidden MS-DOS Display
address@hidden Display on MS-DOS
address@hidden faces under MS-DOS
address@hidden fonts, emulating under MS-DOS
+
+  Display on MS-DOS cannot use font variants, like bold or italic, but
+it does support multiple faces, each of which can specify a foreground
+and a background color.  Therefore, you can get the full functionality
+of Emacs packages that use fonts (such as @code{font-lock}, Enriched
+Text mode, and others) by defining the relevant faces to use different
+colors.  Use the @code{list-colors-display} command (@pxref{Frame
+Parameters,,,emacs, the Emacs Manual}) and the
address@hidden command (@pxref{Faces,,,emacs, the Emacs
+Manual}) to see what colors and faces are available and what they look
+like.
+
+  @xref{MS-DOS and MULE}, later in this chapter, for information on
+how Emacs displays glyphs and characters that aren't supported by the
+native font built into the DOS display.
+
address@hidden cursor shape on MS-DOS
+  When Emacs starts, it changes the cursor shape to a solid box.  This
+is for compatibility with other systems, where the box cursor is the
+default in Emacs.  This default shape can be changed to a bar by
+specifying the @code{cursor-type} parameter in the variable
address@hidden (@pxref{Creating Frames,,,emacs, the Emacs
+Manual}).  The MS-DOS terminal doesn't support a vertical-bar cursor,
+so the bar cursor is horizontal, and the @address@hidden parameter,
+if specified by the frame parameters, actually determines its height.
+For this reason, the @code{bar} and @code{hbar} cursor types produce
+the same effect on MS-DOS.  As an extension, the bar cursor
+specification can include the starting scan line of the cursor as well
+as its width, like this:
+
address@hidden
+ '(cursor-type bar @var{width} . @var{start})
address@hidden example
+
address@hidden
+In addition, if the @var{width} parameter is negative, the cursor bar
+begins at the top of the character cell.
+
address@hidden frames on MS-DOS
+  The MS-DOS terminal can only display a single frame at a time.  The
+Emacs frame facilities work on MS-DOS much as they do on text-only
+terminals (@pxref{Frames,,,emacs, the Emacs Manual}).  When you run
+Emacs from a DOS window on MS-Windows, you can make the visible frame
+smaller than the full screen, but Emacs still cannot display more than
+a single frame at a time.
+
address@hidden frame size under MS-DOS
address@hidden mode4350
address@hidden mode25
+  The @code{mode4350} command switches the display to 43 or 50
+lines, depending on your hardware; the @code{mode25} command switches
+to the default 80x25 screen size.
+
+  By default, Emacs only knows how to set screen sizes of 80 columns by
+25, 28, 35, 40, 43 or 50 rows.  However, if your video adapter has
+special video modes that will switch the display to other sizes, you can
+have Emacs support those too.  When you ask Emacs to switch the frame to
address@hidden rows by @var{m} columns dimensions, it checks if there is a
+variable called @address@hidden@var{m}}, and if so,
+uses its value (which must be an integer) as the video mode to switch
+to.  (Emacs switches to that video mode by calling the BIOS @code{Set
+Video Mode} function with the value of
address@hidden@address@hidden in the @code{AL} register.)
+For example, suppose your adapter will switch to 66x80 dimensions when
+put into video mode 85.  Then you can make Emacs support this screen
+size by putting the following into your @file{_emacs} file:
+
address@hidden
+(setq screen-dimensions-66x80 85)
address@hidden example
+
+  Since Emacs on MS-DOS can only set the frame size to specific
+supported dimensions, it cannot honor every possible frame resizing
+request.  When an unsupported size is requested, Emacs chooses the next
+larger supported size beyond the specified size.  For example, if you
+ask for 36x80 frame, you will get 40x80 instead.
+
+  The variables @address@hidden@var{m}} are used only
+when they exactly match the specified size; the search for the next
+larger supported size ignores them.  In the above example, even if your
+VGA supports 38x80 dimensions and you define a variable
address@hidden with a suitable value, you will still get
+40x80 screen when you ask for a 36x80 frame.  If you want to get the
+38x80 size in this case, you can do it by setting the variable named
address@hidden with the same video mode value as
address@hidden
+
+  Changing frame dimensions on MS-DOS has the effect of changing all the
+other frames to the new dimensions.
+
address@hidden MS-DOS File Names
address@hidden File Names on MS-DOS
address@hidden file names under MS-DOS
address@hidden init file, default name under MS-DOS
+
+  MS-DOS normally uses a backslash, @samp{\}, to separate name units
+within a file name, instead of the slash used on other systems.  Emacs
+on MS-DOS permits use of either slash or backslash, and also knows
+about drive letters in file names.
+
+  On MS-DOS, file names are case-insensitive and limited to eight
+characters, plus optionally a period and three more characters.  Emacs
+knows enough about these limitations to handle file names that were
+meant for other operating systems.  For instance, leading dots
address@hidden  in file names are invalid in MS-DOS, so Emacs transparently
+converts them to underscores @samp{_}; thus your default init file
+(@pxref{Init File,,,emacs, the Emacs Manual}) is called @file{_emacs}
+on MS-DOS.  Excess characters before or after the period are generally
+ignored by MS-DOS itself; thus, if you visit the file
address@hidden, you will silently get
address@hidden, but Emacs will still display the long file name
+on the mode line.  Other than that, it's up to you to specify file
+names which are valid under MS-DOS; the transparent conversion as
+described above only works on file names built into Emacs.
+
address@hidden backup file names on MS-DOS
+  The above restrictions on the file names on MS-DOS make it almost
+impossible to construct the name of a backup file (@pxref{Backup
+Names,,,emacs, the Emacs Manual}) without losing some of the original
+file name characters.  For example, the name of a backup file for
address@hidden is @file{docs.tx~} even if single backup is used.
+
address@hidden file names under Windows 95/NT
address@hidden long file names in DOS box under Windows 95/NT
+  If you run Emacs as a DOS application under Windows 9X, Windows ME, or
+Windows 2000, you can turn on support for long file names.  If you do
+that, Emacs doesn't truncate file names or convert them to lower case;
+instead, it uses the file names that you specify, verbatim.  To enable
+long file name support, set the environment variable @env{LFN} to
address@hidden before starting Emacs.  Unfortunately, Windows NT doesn't allow
+DOS programs to access long file names, so Emacs built for MS-DOS will
+only see their short 8+3 aliases.
+
address@hidden @env{HOME} directory under MS-DOS
+  MS-DOS has no notion of home directory, so Emacs on MS-DOS pretends
+that the directory where it is installed is the value of the @env{HOME}
+environment variable.  That is, if your Emacs binary,
address@hidden, is in the directory @file{c:/utils/emacs/bin}, then
+Emacs acts as if @env{HOME} were set to @samp{c:/utils/emacs}.  In
+particular, that is where Emacs looks for the init file @file{_emacs}.
+With this in mind, you can use @samp{~} in file names as an alias for
+the home directory, as you would on GNU or Unix.  You can also set
address@hidden variable in the environment before starting Emacs; its
+value will then override the above default behavior.
+
+  Emacs on MS-DOS handles the directory name @file{/dev} specially,
+because of a feature in the emulator libraries of DJGPP that pretends
+I/O devices have names in that directory.  We recommend that you avoid
+using an actual directory named @file{/dev} on any disk.
+
address@hidden MS-DOS Printing
address@hidden Printing and MS-DOS
+
+  Printing commands, such as @code{lpr-buffer}
+(@pxref{Printing,,,emacs, the Emacs Manual }) and
address@hidden (@pxref{PostScript,,,emacs, the Emacs Manual})
+can work in MS-DOS and MS-Windows by sending the output to one of the
+printer ports, if a Posix-style @code{lpr} program is unavailable.
+The same Emacs variables control printing on all systems, but in some
+cases they have different default values on MS-DOS and MS-Windows.
+
address@hidden printer-name @r{(MS-DOS)}
+  If you want to use your local printer, printing on it in the usual DOS
+manner, then set the Lisp variable @code{lpr-command} to @code{""} (its
+default value) and @code{printer-name} to the name of the printer
+port---for example, @code{"PRN"}, the usual local printer port (that's
+the default), or @code{"LPT2"}, or @code{"COM1"} for a serial printer.
+You can also set @code{printer-name} to a file name, in which case
+``printed'' output is actually appended to that file.  If you set
address@hidden to @code{"NUL"}, printed output is silently
+discarded (sent to the system null device).
+
+  On MS-Windows, when the Windows network software is installed, you can
+also use a printer shared by another machine by setting
address@hidden to the UNC share name for that printer---for example,
address@hidden"//joes_pc/hp4si"}.  (It doesn't matter whether you use forward
+slashes or backslashes here.)  To find out the names of shared printers,
+run the command @samp{net view} at a DOS command prompt to obtain a list
+of servers, and @samp{net view @var{server-name}} to see the names of printers
+(and directories) shared by that server.  Alternatively, click the
address@hidden Neighborhood} icon on your desktop, and look for machines
+which share their printers via the network.
+
address@hidden @samp{net use}, and printing on MS-Windows
address@hidden networked printers (MS-Windows)
+  If the printer doesn't appear in the output of @samp{net view}, or
+if setting @code{printer-name} to the UNC share name doesn't produce a
+hardcopy on that printer, you can use the @samp{net use} command to
+connect a local print port such as @code{"LPT2"} to the networked
+printer.  For example, typing @kbd{net use LPT2:
address@hidden
+Note that the @samp{net use} command requires the UNC share name to be
+typed with the Windows-style backslashes, while the value of
address@hidden can be set with either forward- or backslashes.}
+causes Windows to @dfn{capture} the LPT2 port and redirect the printed
+material to the printer connected to the machine @code{joes_pc}.
+After this command, setting @code{printer-name} to @code{"LPT2"}
+should produce the hardcopy on the networked printer.
+
+  With some varieties of Windows network software, you can instruct
+Windows to capture a specific printer port such as @code{"LPT2"}, and
+redirect it to a networked printer via the @address@hidden
+Panel->Printers}} applet instead of @samp{net use}.
+
+  Some printers expect DOS codepage encoding of address@hidden text, even
+though they are connected to a Windows machine which uses a different
+encoding for the same locale.  For example, in the Latin-1 locale, DOS
+uses codepage 850 whereas Windows uses codepage 1252.  @xref{MS-DOS and
+MULE}.  When you print to such printers from Windows, you can use the
address@hidden RET c} (@code{universal-coding-system-argument}) command before
address@hidden lpr-buffer}; Emacs will then convert the text to the DOS
+codepage that you specify.  For example, @kbd{C-x RET c cp850-dos RET
+M-x lpr-region RET} will print the region while converting it to the
+codepage 850 encoding.  You may need to create the @address@hidden
+coding system with @kbd{M-x codepage-setup}.
+
+  If you set @code{printer-name} to a file name, it's best to use an
+absolute file name.  Emacs changes the working directory according to
+the default directory of the current buffer, so if the file name in
address@hidden is relative, you will end up with several such
+files, each one in the directory of the buffer from which the printing
+was done.
+
address@hidden print-buffer @r{(MS-DOS)}
address@hidden print-region @r{(MS-DOS)}
address@hidden lpr-headers-switches @r{(MS-DOS)}
+  The commands @code{print-buffer} and @code{print-region} call the
address@hidden program, or use special switches to the @code{lpr} program, to
+produce headers on each printed page.  MS-DOS and MS-Windows don't
+normally have these programs, so by default, the variable
address@hidden is set so that the requests to print page
+headers are silently ignored.  Thus, @code{print-buffer} and
address@hidden produce the same output as @code{lpr-buffer} and
address@hidden, respectively.  If you do have a suitable @code{pr}
+program (for example, from GNU Textutils), set
address@hidden to @code{nil}; Emacs will then call
address@hidden to produce the page headers, and print the resulting output as
+specified by @code{printer-name}.
+
address@hidden print-region-function @r{(MS-DOS)}
address@hidden lpr usage under MS-DOS
address@hidden lpr-command @r{(MS-DOS)}
address@hidden lpr-switches @r{(MS-DOS)}
+  Finally, if you do have an @code{lpr} work-alike, you can set the
+variable @code{lpr-command} to @code{"lpr"}.  Then Emacs will use
address@hidden for printing, as on other systems.  (If the name of the
+program isn't @code{lpr}, set @code{lpr-command} to specify where to
+find it.)  The variable @code{lpr-switches} has its standard meaning
+when @code{lpr-command} is not @code{""}.  If the variable
address@hidden has a string value, it is used as the value for the
address@hidden option to @code{lpr}, as on Unix.
+
address@hidden ps-print-buffer @r{(MS-DOS)}
address@hidden ps-spool-buffer @r{(MS-DOS)}
address@hidden ps-printer-name @r{(MS-DOS)}
address@hidden ps-lpr-command @r{(MS-DOS)}
address@hidden ps-lpr-switches @r{(MS-DOS)}
+  A parallel set of variables, @code{ps-lpr-command},
address@hidden, and @code{ps-printer-name} (@pxref{PostScript
+Variables,,,emacs, the Emacs Manual}), defines how PostScript files
+should be printed.  These variables are used in the same way as the
+corresponding variables described above for non-PostScript printing.
+Thus, the value of @code{ps-printer-name} is used as the name of the
+device (or file) to which PostScript output is sent, just as
address@hidden is used for non-PostScript printing.  (There are
+two distinct sets of variables in case you have two printers attached
+to two different ports, and only one of them is a PostScript printer.)
+
+  The default value of the variable @code{ps-lpr-command} is @code{""},
+which causes PostScript output to be sent to the printer port specified
+by @code{ps-printer-name}, but @code{ps-lpr-command} can also be set to
+the name of a program which will accept PostScript files.  Thus, if you
+have a non-PostScript printer, you can set this variable to the name of
+a PostScript interpreter program (such as Ghostscript).  Any switches
+that need to be passed to the interpreter program are specified using
address@hidden  (If the value of @code{ps-printer-name} is a
+string, it will be added to the list of switches as the value for the
address@hidden option.  This is probably only useful if you are using
address@hidden, so when using an interpreter typically you would set
address@hidden to something other than a string so it is
+ignored.)
+
+  For example, to use Ghostscript for printing on an Epson printer
+connected to the @samp{LPT2} port, put this in your @file{_emacs} file:
+
address@hidden
+(setq ps-printer-name t)  ; Ghostscript doesn't understand -P
+(setq ps-lpr-command "c:/gs/gs386")
+(setq ps-lpr-switches '("-q" "-dNOPAUSE"
+                       "-sDEVICE=epson"
+                       "-r240x72"
+                       "-sOutputFile=LPT2"
+                       "-Ic:/gs"))
address@hidden example
+
address@hidden
+(This assumes that Ghostscript is installed in the @file{"c:/gs"}
+directory.)
+
address@hidden dos-printer
address@hidden dos-ps-printer
+  For backwards compatibility, the value of @code{dos-printer}
+(@code{dos-ps-printer}), if it has a value, overrides the value of
address@hidden (@code{ps-printer-name}), on MS-DOS and MS-Windows
+only.
+
+
address@hidden MS-DOS and MULE
address@hidden International Support on MS-DOS
address@hidden international support @r{(MS-DOS)}
+
+  Emacs on MS-DOS supports the same international character sets as it
+does on GNU, Unix and other platforms (@pxref{International,,,emacs,
+the Emacs Manual}), including coding systems for converting between
+the different character sets.  However, due to incompatibilities
+between MS-DOS/MS-Windows and other systems, there are several
+DOS-specific aspects of this support that you should be aware of.
+This section describes these aspects.
+
+  The description below is largely specific to the MS-DOS port of
+Emacs, especially where it talks about practical implications for
+Emacs users.  For other operating systems, see the @file{code-pages.el}
+package, which implements support for MS-DOS- and MS-Windows-specific
+encodings for all platforms other than MS-DOS.
+
address@hidden @kbd
address@hidden M-x dos-codepage-setup
+Set up Emacs display and coding systems as appropriate for the current
+DOS codepage.
+
address@hidden M-x codepage-setup
+Create a coding system for a certain DOS codepage.
address@hidden table
+
address@hidden codepage, MS-DOS
address@hidden DOS codepages
+  MS-DOS is designed to support one character set of 256 characters at
+any given time, but gives you a variety of character sets to choose
+from.  The alternative character sets are known as @dfn{DOS codepages}.
+Each codepage includes all 128 @acronym{ASCII} characters, but the other 128
+characters (codes 128 through 255) vary from one codepage to another.
+Each DOS codepage is identified by a 3-digit number, such as 850, 862,
+etc.
+
+  In contrast to X, which lets you use several fonts at the same time,
+MS-DOS normally doesn't allow use of several codepages in a single
+session.  MS-DOS was designed to load a single codepage at system
+startup, and require you to reboot in order to change
address@hidden, one particular codepage is burnt into the
+display memory, while other codepages can be installed by modifying
+system configuration files, such as @file{CONFIG.SYS}, and rebooting.
+While there is third-party software that allows changing the codepage
+without rebooting, we describe here how a stock MS-DOS system
+behaves.}.  Much the same limitation applies when you run DOS
+executables on other systems such as MS-Windows.
+
address@hidden unibyte operation @r{(MS-DOS)}
+  If you invoke Emacs on MS-DOS with the @samp{--unibyte} option
+(@pxref{Initial Options,,,emacs, the Emacs Manual}), Emacs does not
+perform any conversion of address@hidden characters.  Instead, it
+reads and writes any address@hidden characters verbatim, and
+sends their 8-bit codes to the display verbatim.  Thus, unibyte Emacs
+on MS-DOS supports the current codepage, whatever it may be, but
+cannot even represent any other characters.
+
address@hidden dos-codepage
+  For multibyte operation on MS-DOS, Emacs needs to know which
+characters the chosen DOS codepage can display.  So it queries the
+system shortly after startup to get the chosen codepage number, and
+stores the number in the variable @code{dos-codepage}.  Some systems
+return the default value 437 for the current codepage, even though the
+actual codepage is different.  (This typically happens when you use the
+codepage built into the display hardware.)  You can specify a different
+codepage for Emacs to use by setting the variable @code{dos-codepage} in
+your init file.
+
address@hidden language environment, automatic selection on @r{MS-DOS}
+  Multibyte Emacs supports only certain DOS codepages: those which can
+display Far-Eastern scripts, like the Japanese codepage 932, and those
+that encode a single ISO 8859 character set.
+
+  The Far-Eastern codepages can directly display one of the MULE
+character sets for these countries, so Emacs simply sets up to use the
+appropriate terminal coding system that is supported by the codepage.
+The special features described in the rest of this section mostly
+pertain to codepages that encode ISO 8859 character sets.
+
+  For the codepages which correspond to one of the ISO character sets,
+Emacs knows the character set name based on the codepage number.  Emacs
+automatically creates a coding system to support reading and writing
+files that use the current codepage, and uses this coding system by
+default.  The name of this coding system is @address@hidden, where
address@hidden is the codepage address@hidden standard Emacs coding
+systems for ISO 8859 are not quite right for the purpose, because
+typically the DOS codepage does not match the standard ISO character
+codes.  For example, the letter @samp{@,{c}} (@samp{c} with cedilla) has
+code 231 in the standard Latin-1 character set, but the corresponding
+DOS codepage 850 uses code 135 for this glyph.}
+
address@hidden mode line @r{(MS-DOS)}
+  All the @address@hidden coding systems use the letter @samp{D}
+(for ``DOS'') as their mode-line mnemonic.  Since both the terminal
+coding system and the default coding system for file I/O are set to
+the proper @address@hidden coding system at startup, it is normal
+for the mode line on MS-DOS to begin with @samp{-DD\-}.  @xref{Mode
+Line,,,emacs, the Emacs Manual}.  Far-Eastern DOS terminals do not use
+the @address@hidden coding systems, and thus their initial mode
+line looks like the Emacs default.
+
+  Since the codepage number also indicates which script you are using,
+Emacs automatically runs @code{set-language-environment} to select the
+language environment for that script (@pxref{Language
+Environments,,,emacs, the Emacs Manual}).
+
+  If a buffer contains a character belonging to some other ISO 8859
+character set, not the one that the chosen DOS codepage supports, Emacs
+displays it using a sequence of @acronym{ASCII} characters.  For example, if 
the
+current codepage doesn't have a glyph for the letter @address@hidden (small
address@hidden with a grave accent), it is displayed as @address@hidden@}}, 
where
+the braces serve as a visual indication that this is a single character.
+(This may look awkward for some non-Latin characters, such as those from
+Greek or Hebrew alphabets, but it is still readable by a person who
+knows the language.)  Even though the character may occupy several
+columns on the screen, it is really still just a single character, and
+all Emacs commands treat it as one.
+
address@hidden IBM graphics characters (MS-DOS)
address@hidden box-drawing characters (MS-DOS)
address@hidden line-drawing characters (MS-DOS)
+  Not all characters in DOS codepages correspond to ISO 8859
+characters---some are used for other purposes, such as box-drawing
+characters and other graphics.  Emacs maps these characters to two
+special character sets called @code{eight-bit-control} and
address@hidden, and displays them as their IBM glyphs.
+However, you should be aware that other systems might display these
+characters differently, so you should avoid them in text that might be
+copied to a different operating system, or even to another DOS machine
+that uses a different codepage.
+
address@hidden dos-unsupported-character-glyph
+  Emacs supports many other characters sets aside from ISO 8859, but it
+cannot display them on MS-DOS.  So if one of these multibyte characters
+appears in a buffer, Emacs on MS-DOS displays them as specified by the
address@hidden variable; by default, this glyph
+is an empty triangle.  Use the @kbd{C-u C-x =} command to display the
+actual code and character set of such characters.  @xref{Position
+Info,,,emacs, the Emacs Manual}.
+
address@hidden codepage-setup
+  By default, Emacs defines a coding system to support the current
+codepage.  To define a coding system for some other codepage (e.g., to
+visit a file written on a DOS machine in another country), use the
address@hidden codepage-setup} command.  It prompts for the 3-digit code of
+the codepage, with completion, then creates the coding system for the
+specified codepage.  You can then use the new coding system to read and
+write files, but you must specify it explicitly for the file command
+when you want to use it (@pxref{Text Coding,,,emacs, the Emacs Manual}).
+
+  These coding systems are also useful for visiting a file encoded using
+a DOS codepage, using Emacs running on some other operating system.
+
address@hidden MS-Windows codepages
+  MS-Windows provides its own codepages, which are different from the
+DOS codepages for the same locale.  For example, DOS codepage 850
+supports the same character set as Windows codepage 1252; DOS codepage
+855 supports the same character set as Windows codepage 1251, etc.
+The MS-Windows version of Emacs uses the current codepage for display
+when invoked with the @samp{-nw} option.  Support for codepages in the
+Windows port of Emacs is part of the @file{code-pages.el} package.
+
address@hidden MS-DOS Processes
address@hidden Subprocesses on MS-DOS
+
address@hidden compilation under MS-DOS
address@hidden inferior processes under MS-DOS
address@hidden compile @r{(MS-DOS)}
address@hidden grep @r{(MS-DOS)}
+  Because MS-DOS is a single-process ``operating system,''
+asynchronous subprocesses are not available.  In particular, Shell
+mode and its variants do not work.  Most Emacs features that use
+asynchronous subprocesses also don't work on MS-DOS, including
+Shell mode and GUD.  When in doubt, try and see; commands that
+don't work output an error message saying that asynchronous processes
+aren't supported.
+
+  Compilation under Emacs with @kbd{M-x compile}, searching files with
address@hidden grep} and displaying differences between files with @kbd{M-x
+diff} do work, by running the inferior processes synchronously.  This
+means you cannot do any more editing until the inferior process
+finishes.
+
+  Spell checking also works, by means of special support for synchronous
+invocation of the @code{ispell} program.  This is slower than the
+asynchronous invocation on other platforms
+
+  Instead of the Shell mode, which doesn't work on MS-DOS, you can use
+the @kbd{M-x eshell} command.  This invokes the Eshell package that
+implements a Posix-like shell entirely in Emacs Lisp.
+
+  By contrast, Emacs compiled as a native Windows application
address@hidden support asynchronous subprocesses.  @xref{Windows
+Processes,,,emacs, the Emacs Manual}.
+
address@hidden printing under MS-DOS
+  Printing commands, such as @code{lpr-buffer}
+(@pxref{Printing,,,emacs, the Emacs Manual}) and
address@hidden (@pxref{PostScript,,,emacs, the Emacs Manual}),
+work in MS-DOS by sending the output to one of the printer ports.
address@hidden Printing,,,emacs, the Emacs Manual}.
+
+  When you run a subprocess synchronously on MS-DOS, make sure the
+program terminates and does not try to read keyboard input.  If the
+program does not terminate on its own, you will be unable to terminate
+it, because MS-DOS provides no general way to terminate a process.
+Pressing @kbd{C-c} or @address@hidden might sometimes help in these
+cases.
+
+  Accessing files on other machines is not supported on MS-DOS.  Other
+network-oriented commands such as sending mail, Web browsing, remote
+login, etc., don't work either, unless network access is built into
+MS-DOS with some network redirector.
+
address@hidden directory listing on MS-DOS
address@hidden dired-listing-switches @r{(MS-DOS)}
+  Dired on MS-DOS uses the @code{ls-lisp} package where other
+platforms use the system @code{ls} command.  Therefore, Dired on
+MS-DOS supports only some of the possible options you can mention in
+the @code{dired-listing-switches} variable.  The options that work are
address@hidden, @samp{-a}, @samp{-c}, @samp{-i}, @samp{-r}, @samp{-S},
address@hidden, @samp{-t}, and @samp{-u}.
+
+
 @node Index
 @unnumbered Index