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(elisp)Keyboard Events

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Keyboard Events
---------------

   There are two kinds of input you can get from the keyboard: ordinary
keys, and function keys.  Ordinary keys correspond to characters; the
events they generate are represented in Lisp as characters.  The event
type of a character event is the character itself (an integer); see
Note: Classifying Events.

   An input character event consists of a "basic code" between 0 and
524287, plus any or all of these "modifier bits":

meta
     The 2**27 bit in the character code indicates a character typed
     with the meta key held down.

control
     The 2**26 bit in the character code indicates a non-ASCII control
     character.

     ASCII control characters such as `C-a' have special basic codes of
     their own, so Emacs needs no special bit to indicate them.  Thus,
     the code for `C-a' is just 1.

     But if you type a control combination not in ASCII, such as `%'
     with the control key, the numeric value you get is the code for
     `%' plus 2**26 (assuming the terminal supports non-ASCII control
     characters).

shift
     The 2**25 bit in the character code indicates an ASCII control
     character typed with the shift key held down.

     For letters, the basic code itself indicates upper versus lower
     case; for digits and punctuation, the shift key selects an
     entirely different character with a different basic code.  In
     order to keep within the ASCII character set whenever possible,
     Emacs avoids using the 2**25 bit for those characters.

     However, ASCII provides no way to distinguish `C-A' from `C-a', so
     Emacs uses the 2**25 bit in `C-A' and not in `C-a'.

hyper
     The 2**24 bit in the character code indicates a character typed
     with the hyper key held down.

super
     The 2**23 bit in the character code indicates a character typed
     with the super key held down.

alt
     The 2**22 bit in the character code indicates a character typed
     with the alt key held down.  (On some terminals, the key labeled
     <ALT> is actually the meta key.)

   It is best to avoid mentioning specific bit numbers in your program.
To test the modifier bits of a character, use the function
`event-modifiers' (Note: Classifying Events).  When making key
bindings, you can use the read syntax for characters with modifier bits
(`\C-', `\M-', and so on).  For making key bindings with `define-key',
you can use lists such as `(control hyper ?x)' to specify the
characters (Note: Changing Key Bindings).  The function
`event-convert-list' converts such a list into an event type (Note:
Classifying Events).