The bindings between characters and command functions are recorded in
data structures called "keymaps". Emacs has many of these. One, the
"global" keymap, defines the meanings of the single-character keys that
are defined regardless of major mode. It is the value of the variable
Each major mode has another keymap, its "local keymap", which
contains overriding definitions for the single-character keys that are
redefined in that mode. Each buffer records which local keymap is
installed for it at any time, and the current buffer's local keymap is
the only one that directly affects command execution. The local keymaps
for Lisp mode, C mode, and many other major modes always exist even when
not in use. They are the values of the variables `lisp-mode-map',
`c-mode-map', and so on. For less frequently used major modes, the
local keymap is sometimes constructed only when the mode is used for the
first time in a session, to save space.
There are local keymaps for the minibuffer, too; they contain various
completion and exit commands.
* `minibuffer-local-map' is used for ordinary input (no completion).
* `minibuffer-local-ns-map' is similar, except that <SPC> exits just
like <RET>. This is used mainly for Mocklisp compatibility.
* `minibuffer-local-completion-map' is for permissive completion.
* `minibuffer-local-must-match-map' is for strict completion and for
* `repeat-complex-command-map' is for use in `C-x <ESC> <ESC>'.
* `isearch-mode-map' contains the bindings of the special keys which
are bound in the pseudo-mode entered with `C-s' and `C-r'.
Finally, each prefix key has a keymap which defines the key sequences
that start with it. For example, `ctl-x-map' is the keymap used for
characters following a `C-x'.
* `ctl-x-map' is the variable name for the map used for characters
that follow `C-x'.
* `help-map' is used for characters that follow `C-h'.
* `esc-map' is for characters that follow <ESC>. All Meta characters
are actually defined by this map.
* `ctl-x-4-map' is for characters that follow `C-x 4'.
* `mode-specific-map' is for characters that follow `C-c'.
The definition of a prefix key is the keymap to use for looking up
the following character. Sometimes the definition is actually a Lisp
symbol whose function definition is the following character keymap. The
effect is the same, but it provides a command name for the prefix key
that you can use as a description of what the prefix key is for. Thus
the binding of `C-x' is the symbol `Ctl-X-Prefix', whose function
definition is the keymap for `C-x' commands, the value of `ctl-x-map'.
Prefix key definitions can appear in either the global map or a
local map. The definitions of `C-c', `C-x', `C-h', and <ESC> as prefix
keys appear in the global map, so these prefix keys are always
available. Major modes can locally redefine a key as a prefix by
putting a prefix key definition for it in the local map.
A mode can also put a prefix definition of a global prefix character
such as `C-x' into its local map. This is how major modes override the
definitions of certain keys that start with `C-x'. This case is
special, because the local definition does not entirely replace the
global one. When both the global and local definitions of a key are
other keymaps, the next character is looked up in both keymaps, with
the local definition overriding the global one. The character after the
`C-x' is looked up in both the major mode's own keymap for redefined
`C-x' commands and in `ctl-x-map'. If the major mode's own keymap for
`C-x' commands contains `nil', the definition from the global keymap
for `C-x' commands is used.
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