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(emacs)MS-DOS Input

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Keyboard and Mouse on MS-DOS
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   The PC keyboard maps use the left <ALT> key as the <META> key.  You
have two choices for emulating the <SUPER> and <HYPER> keys: choose
either the right <CTRL> key or the right <ALT> key by setting the
variables `dos-hyper-key' and `dos-super-key' to 1 or 2 respectively.
If neither `dos-super-key' nor `dos-hyper-key' is 1, then by default
the right <ALT> key is also mapped to the <META> key.  However, if the
MS-DOS international keyboard support program `KEYB.COM' is installed,
Emacs will _not_ map the right <ALT> to <META>, since it is used for
accessing characters like `~' and `@' on non-US keyboard layouts; in
this case, you may only use the left <ALT> as <META> key.

   The variable `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 <ENTER> key to act like `C-j', by putting the
following line into your `_emacs' file:

     ;; Make the <ENTER> key from the numeric keypad act as `C-j'.
     (define-key function-key-map [kp-enter] [?\C-j])

   The key that is called <DEL> in Emacs (because that's how it is
designated on most workstations) is known as <BS> (backspace) on a PC.
That is why the PC-specific terminal initialization remaps the <BS> key
to act as <DEL>; the <DEL> key is remapped to act as `C-d' for the same
reasons.

   Emacs built for MS-DOS recognizes `C-<BREAK>' as a quit character,
just like `C-g'.  This is because Emacs cannot detect that you have
typed `C-g' until it is ready for more input.  As a consequence, you
cannot use `C-g' to stop a running command (Note: Quitting).  By
contrast, `C-<BREAK>' _is_ detected as soon as you type it (as `C-g' is
on other systems), so it can be used to stop a running command and for
emergency escape (Note: Emergency Escape).

   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 (Note: Menu Bar).  Scroll bars don't work in MS-DOS
Emacs.  PC mice usually have only two buttons; these act as `Mouse-1'
and `Mouse-2', but if you press both of them together, that has the
effect of `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 (Note: Mouse References) is also supported.

   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 `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 `_emacs' init file:

     ;; Treat the mouse like a 2-button mouse.
     (msdos-set-mouse-buttons 2)

   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 (Note: Mouse Commands).  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.

   The variable `dos-display-scancodes', when non-`nil', directs Emacs
to display the ASCII value and the keyboard scan code of each
keystroke; this feature serves as a complement to the `view-lossage'
command, for debugging.