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#### 20.7.1 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 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. (The key labeled `Alt` on most keyboards is actually treated as the meta key, not this.)

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` (see 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 (see Changing Key Bindings). The function `event-convert-list` converts such a list into an event type (see Classifying Events).

Next: Function Keys, Up: Input Events [Contents][Index]