Commit a85cdd1f authored by Richard M. Stallman's avatar Richard M. Stallman
Browse files

Minor cleanups. Refer to "graphical" terminals, rather than X.

parent 0939d23b
......@@ -39,8 +39,7 @@ holding down the @key{CTRL} key while pressing @kbd{a}.
have special keys you can type them with: for example, @key{RET},
@key{TAB}, @key{DEL} and @key{ESC}. The space character is usually
referred to below as @key{SPC}, even though strictly speaking it is a
graphic character whose graphic happens to be blank. Some keyboards
have a key labeled ``linefeed'' which is an alias for @kbd{C-j}.
graphic character whose graphic happens to be blank.
Emacs extends the @acronym{ASCII} character set with thousands more printing
characters (@pxref{International}), additional control characters, and a
......@@ -54,31 +53,28 @@ distinguish them.
But the Emacs character set has room for control variants of all
printing characters, and for distinguishing between @kbd{C-a} and
@kbd{C-A}. The X Window System makes it possible to enter all these
characters. For example, @kbd{C--} (that's Control-Minus) and @kbd{C-5}
are meaningful Emacs commands under X.
@kbd{C-A}. Graphical terminals make it possible to enter all these
characters. For example, @kbd{C--} (that's Control-Minus) and
@kbd{C-5} are meaningful Emacs commands on a graphical terminal.
Another Emacs character-set extension is additional modifier bits.
Only one modifier bit is commonly used; it is called Meta. Every
character has a Meta variant; examples include @kbd{Meta-a} (normally
written @kbd{M-a}, for short), @kbd{M-A} (not the same character as
@kbd{M-a}, but those two characters normally have the same meaning in
Emacs), @kbd{M-@key{RET}}, and @kbd{M-C-a}. For reasons of tradition,
we usually write @kbd{C-M-a} rather than @kbd{M-C-a}; logically
speaking, the order in which the modifier keys @key{CTRL} and @key{META}
are mentioned does not matter.
written @kbd{M-a}, for short), @kbd{M-A} (different from @kbd{M-a},
but they are normally equivalent in Emacs), @kbd{M-@key{RET}}, and
@kbd{M-C-a}. That last means @kbd{a} with both the @key{CTRL} and
@key{META} modifiers. We usually write it as @kbd{C-M-a} rather than
@kbd{M-C-a}, for reasons of tradition.
@cindex Meta
@cindex M-
@cindex @key{ESC} replacing @key{META} key
Some terminals have a @key{META} key, and allow you to type Meta
characters by holding this key down. Thus, @kbd{Meta-a} is typed by
holding down @key{META} and pressing @kbd{a}. The @key{META} key
works much like the @key{SHIFT} key. Such a key is not always labeled
@key{META}, however, as this function is often a special option for a
key with some other primary purpose. Sometimes it is labeled
@key{ALT} or @key{EDIT}; on a Sun keyboard, it may have a diamond on
it.
characters by holding this key down. Thus, you can type @kbd{Meta-a}
by holding down @key{META} and pressing @kbd{a}. The @key{META} key
works much like the @key{SHIFT} key. In fact, this key is more often
labeled @key{ALT} or @key{EDIT}, instead of @key{META}; on a Sun
keyboard, it may have a diamond on it.
If there is no @key{META} key, you can still type Meta characters
using two-character sequences starting with @key{ESC}. Thus, you can
......@@ -90,16 +86,16 @@ you press it and release it, then you enter the next character.
@key{ESC} is allowed on terminals with @key{META} keys, too, in case
you have formed a habit of using it.
The X Window System provides several other modifier keys that can be
applied to any input character. These are called @key{SUPER},
@key{HYPER} and @key{ALT}. We write @samp{s-}, @samp{H-} and @samp{A-}
to say that a character uses these modifiers. Thus, @kbd{s-H-C-x} is
short for @kbd{Super-Hyper-Control-x}. Not all X terminals actually
Emacs defines several other modifier keys that can be applied to any
input character. These are called @key{SUPER}, @key{HYPER} and
@key{ALT}. We write @samp{s-}, @samp{H-} and @samp{A-} to say that a
character uses these modifiers. Thus, @kbd{s-H-C-x} is short for
@kbd{Super-Hyper-Control-x}. Not all graphical terminals actually
provide keys for these modifier flags---in fact, many terminals have a
key labeled @key{ALT} which is really a @key{META} key. The standard
key bindings of Emacs do not include any characters with these
modifiers. But you can assign them meanings of your own by customizing
Emacs.
modifiers. But you can assign them meanings of your own by
customizing Emacs.
If your keyboard lacks one of these modifier keys, you can enter it
using @kbd{C-x @@}: @kbd{C-x @@ h} adds the ``hyper'' flag to the next
......@@ -109,18 +105,18 @@ enter @kbd{Hyper-Control-a}. (Unfortunately there is no way to add
two modifiers by using @kbd{C-x @@} twice for the same character,
because the first one goes to work on the @kbd{C-x}.)
Keyboard input includes keyboard keys that are not characters at all:
for example function keys and arrow keys. Mouse buttons are also
outside the gamut of characters. You can modify these events with the
modifier keys @key{CTRL}, @key{META}, @key{SUPER}, @key{HYPER} and
@key{ALT}, just like keyboard characters.
Keyboard input includes keyboard keys that are not characters at
all: for example function keys and arrow keys. Mouse buttons are also
outside the gamut of characters. However, you can modify these events
with the modifier keys @key{CTRL}, @key{META}, @key{SUPER},
@key{HYPER} and @key{ALT}, just as you can modify keyboard characters.
@cindex input event
Input characters and non-character inputs are collectively called
@dfn{input events}. @xref{Input Events,,, elisp, The Emacs Lisp
Reference Manual}, for more information. If you are not doing Lisp
programming, but simply want to redefine the meaning of some characters
or non-character events, see @ref{Customization}.
Reference Manual}, for the full Lisp-level details. If you are not
doing Lisp programming, but simply want to redefine the meaning of
some characters or non-character events, see @ref{Customization}.
@acronym{ASCII} terminals cannot really send anything to the computer except
@acronym{ASCII} characters. These terminals use a sequence of characters to
......@@ -170,12 +166,12 @@ key sequences, not one.@refill
All told, the prefix keys in Emacs are @kbd{C-c}, @kbd{C-h},
@kbd{C-x}, @kbd{C-x @key{RET}}, @kbd{C-x @@}, @kbd{C-x a}, @kbd{C-x
n}, @w{@kbd{C-x r}}, @kbd{C-x v}, @kbd{C-x 4}, @kbd{C-x 5}, @kbd{C-x 6},
@key{ESC}, @kbd{M-o} and @kbd{M-g}. (@key{F1} and @key{F2} are aliases for
@kbd{C-h} and @kbd{C-x 6}.) But this list is not cast in concrete; it
is just a matter of Emacs's standard key bindings. If you customize
Emacs, you can make new prefix keys, or eliminate these. @xref{Key
Bindings}.
n}, @w{@kbd{C-x r}}, @kbd{C-x v}, @kbd{C-x 4}, @kbd{C-x 5}, @kbd{C-x
6}, @key{ESC}, @kbd{M-g}, and @kbd{M-o}. (@key{F1} and @key{F2} are
aliases for @kbd{C-h} and @kbd{C-x 6}.) But this list is not cast in
concrete; it is just a matter of Emacs's standard key bindings. If
you customize Emacs, you can make new prefix keys, or eliminate some
of the standard ones. @xref{Key Bindings}.
If you do make or eliminate prefix keys, that changes the set of
possible key sequences. For example, if you redefine @kbd{C-f} as a
......@@ -184,12 +180,11 @@ define that too as a prefix). Conversely, if you remove the prefix
definition of @kbd{C-x 4}, then @kbd{C-x 4 f} (or @kbd{C-x 4
@var{anything}}) is no longer a key.
Typing the help character (@kbd{C-h} or @key{F1}) after a prefix
key displays a list of the commands starting with that prefix.
There are a few prefix keys for which @kbd{C-h} does not
work---for historical reasons, they have other meanings for @kbd{C-h}
which are not easy to change. But @key{F1} should work for all prefix
keys.
Typing the help character (@kbd{C-h} or @key{F1}) after a prefix key
displays a list of the commands starting with that prefix. There are
a few prefix keys for which @kbd{C-h} does not work---for historical
reasons, they define other meanings for @kbd{C-h} which are painful to
change. But @key{F1} should work for all prefix keys.
@node Commands, Text Characters, Keys, Top
@section Keys and Commands
......
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