@c This is part of the Emacs manual.
@c Copyright (C) 1985, 1986, 1987, 1993 Free Software Foundation, Inc.
@c See file emacs.texi for copying conditions.
@node Mark, Killing, Help, Top
@chapter The Mark and the Region
@cindex mark
@cindex region

  There are many Emacs commands which operate on an arbitrary contiguous
part of the current buffer.  To specify the text for such a command to
operate on, you set @dfn{the mark} at one end of it, and move point to the
other end.  The text between point and the mark is called @dfn{the region}.
You can move point or the mark to adjust the boundaries of the region.  It
doesn't matter which one is set first chronologically, or which one comes
earlier in the text.

  Once the mark has been set, it remains where you put it until it is
set again at another place.  The mark remains fixed with respect to the
preceding character if text is inserted or deleted in the buffer.  Each
Emacs buffer has its own mark, so that when you return to a buffer that
had been selected previously, it has the same mark it had before.

  Many commands that insert text, such as @kbd{C-y} (@code{yank}) and
@kbd{M-x insert-buffer}, position point and the mark at opposite ends of
the inserted text, so that the region contains the text just inserted.

  Aside from delimiting the region, the mark is also useful for
remembering a spot that you may want to go back to.  To make this
feature more useful, each buffer remembers 16 previous locations of the
mark in the @dfn{mark ring}.

@menu
* Setting Mark::	Commands to set the mark.
* Transient Mark::	How to make Emacs highlight the region--
			  when there is one.
* Using Region::	Summary of ways to operate on contents of the region.
* Marking Objects::	Commands to put region around textual units.
* Mark Ring::   Previous mark positions saved so you can go back there.
@end menu

@node Setting Mark
@section Setting the Mark

  Here are some commands for setting the mark:

@c WideCommands
@table @kbd
@item C-@key{SPC}
Set the mark where point is (@code{set-mark-command}).
@item C-@@
The same.
@item C-x C-x
Interchange mark and point (@code{exchange-point-and-mark}).
@end table

  For example, suppose you wish to convert part of the buffer to all
upper-case, using the @kbd{C-x C-u} (@code{upcase-region}) command
which operates on the text in the region.  You can first go to the
beginning of the text to be capitalized, type @kbd{C-@key{SPC}} to put
the mark there, move to the end, and then type @kbd{C-x C-u}.  Or, you
can set the mark at the end of the text, move to the beginning, and then
type @kbd{C-x C-u}.

@kindex C-SPC
@findex set-mark-command
  The most common way to set the mark is with the @kbd{C-@key{SPC}} command
(@code{set-mark-command}).  This sets the mark where point is.  Then you
can move point away, leaving the mark behind.

@kindex C-x C-x
@findex exchange-point-and-mark
  Ordinary terminals have only one cursor, so there is no way for Emacs
to show you where the mark is located.  You have to remember.  The usual
solution to this problem is to set the mark and then use it soon, before
you forget where it is.  Alternatively, you can see where the mark is
with the command @kbd{C-x C-x} (@code{exchange-point-and-mark}) which
puts the mark where point was and point where the mark was.  The extent
of the region is unchanged, but the cursor and point are now at the
previous position of the mark.

  @kbd{C-x C-x} is also useful when you are satisfied with the position
of point but want to move the mark; do @kbd{C-x C-x} to put point at
that end of the region, and then move it.  A second use of @kbd{C-x
C-x}, if necessary, puts the mark at the new position with point back at
its original position.

@kindex C-@@
  There is no such character as @kbd{C-@key{SPC}} in ASCII; when you
type @key{SPC} while holding down @key{CTRL}, what you get on most
ordinary terminals is the character @kbd{C-@@}.  This key is actually
bound to @code{set-mark-command}.  But unless you are unlucky enough to
have a terminal where typing @kbd{C-@key{SPC}} does not produce
@kbd{C-@@}, you might as well think of this character as
@kbd{C-@key{SPC}}.  Under X, @kbd{C-@key{SPC}} is actually a distinct
character, but its binding is still @code{set-mark-command}.

@node Transient Mark
@section Transient Mark Mode
@cindex mode, Transient Mark
@cindex Transient Mark mode

  Many Emacs commands move the mark and invisibly set new regions.
This means that there is almost always some region that you can act
on.  This is convenient, provided you get used to keeping track of the
mark's position.

  Some people prefer a more rigid mode of operation in which you must
set up a region for each command that uses one---in which the region
``lasts'' only temporarily.  This is called Transient Mark mode.  It
is particularly well-suited to window systems such as X, since Emacs
can highlight the region when it is active.

@findex transient-mark-mode
  To enable Transient Mark mode, type @kbd{M-x transient-mark-mode}.
This command toggles the mode, so you can issue it again to return to
the normal Emacs way of handling the mark and the region.

  Here are the details of Transient Mark mode:

@itemize @bullet
@item
To set the mark, type @kbd{C-@key{SPC}} (@code{set-mark-command}).
This makes the mark active; as you move point, you will see the region
highlighting change in extent.

@item
On a window system, an easy way to select a region is to press the
button @key{Mouse-1} (normally the left button) at one end of it, drag
the mouse to the other end, and then release the button.

@item
When the mark is active, you can execute any commands you want on the
region, such as killing, indentation, or writing to a file.

@item
Any change to the buffer, such as inserting or deleting a character,
deactivates the mark.  This means any subsequent command that operates
on a region will get an error and refuse to operate.  You can make the
region active again by typing @kbd{C-x C-x}.

@item
Commands like @kbd{M->} that ``leave the mark behind'' do not activate
the new mark.  it.  You can activate the new region by executing
@kbd{C-x C-x} (@code{exchange-point-and-mark}).

@item
Quitting with @kbd{C-g} deactivates the mark.
@end itemize

  Transient Mark mode is also sometimes known as ``Zmacs mode''
because the Zmacs editor on the MIT Lisp Machine handled the mark in a
similar way.

  When multiple windows show the same buffer, they can have different
regions, because they can have different values of point.  In Transient
Mark mode, each window highlights its own region.  The part that is
highlighted in the selected window is the region that editing commands
use.  @xref{Windows}.

@node Using Region
@section Operating on the Region

  Once you have set up a region and the mark is active, you can do many
things to the text in it:

@itemize @bullet
@item
Kill it with @kbd{C-w} (@pxref{Killing}).
@item
Save it in a register with @kbd{C-x r s} (@pxref{Registers}).
@item
Save it in a buffer or a file (@pxref{Accumulating Text}).
@item
Convert case with @kbd{C-x C-l} or @kbd{C-x C-u} (@pxref{Case}).
@item
Indent it with @kbd{C-x @key{TAB}} or @kbd{C-M-\} (@pxref{Indentation}).
@item
Fill it as text with @kbd{M-x fill-region} (@pxref{Filling}).
@item
Print hardcopy with @kbd{M-x print-region} (@pxref{Hardcopy}).
@item
Evaluate it as Lisp code with @kbd{M-x eval-region} (@pxref{Lisp Eval}).
@end itemize

  Most commands that operate on the text in the
region have the word @code{region} in their names.

@node Marking Objects
@section Commands to Mark Textual Objects

  Here are the commands for placing point and the mark around a textual
object such as a word, list, paragraph or page.

@table @kbd
@item M-@@
Set mark after end of next word (@code{mark-word}).  This command and
the following one do not move point.
@item C-M-@@
Set mark after end of next Lisp expression (@code{mark-sexp}).
@item M-h
Put region around current paragraph (@code{mark-paragraph}).
@item C-M-h
Put region around current Lisp defun (@code{mark-defun}).
@item C-x h
Put region around entire buffer (@code{mark-whole-buffer}).
@item C-x C-p
Put region around current page (@code{mark-page}).
@end table

@kbd{M-@@} (@code{mark-word}) puts the mark at the end of the next word,
while @kbd{C-M-@@} (@code{mark-sexp}) puts it at the end of the next Lisp
expression.  These commands handle arguments just like @kbd{M-f} and
@kbd{C-M-f}.

@kindex C-x h
@findex mark-whole-buffer
   Other commands set both point and mark, to delimit an object in the
buffer.  For example, @kbd{M-h} (@code{mark-paragraph}) moves point to
the beginning of the paragraph that surrounds or follows point, and puts
the mark at the end of that paragraph (@pxref{Paragraphs}).  It prepares
the region so you can indent, case-convert, or kill a whole paragraph.

  @kbd{C-M-h} (@code{mark-defun}) similarly puts point before and the
mark after the current or following defun (@pxref{Defuns}).  @kbd{C-x
C-p} (@code{mark-page}) puts point before the current page, and mark at
the end (@pxref{Pages}).  The mark goes after the terminating page
delimiter (to include it), while point goes after the preceding page
delimiter (to exclude it).  A numeric argument specifies a later page
(if positive) or an earlier page (if negative) instead of the current
page.

  Finally, @kbd{C-x h} (@code{mark-whole-buffer}) sets up the entire
buffer as the region, by putting point at the beginning and the mark at
the end.

@node Mark Ring
@section The Mark Ring

@kindex C-u C-SPC
@cindex mark ring
@kindex C-u C-@@
  Aside from delimiting the region, the mark is also useful for
remembering a spot that you may want to go back to.  To make this
feature more useful, each buffer remembers 16 previous locations of the
mark, in the @dfn{mark ring}.  Commands that set the mark also push the
old mark onto this ring.  To return to a marked location, use @kbd{C-u
C-@key{SPC}} (or @kbd{C-u C-@@}); this is the command
@code{set-mark-command} given a numeric argument.  It moves point to
where the mark was, and restores the mark from the ring of former
marks.  Thus, repeated use of this command moves point to all of the old
marks on the ring, one by one.  The mark positions you move through in
this way are not lost; they go to the end of the ring.

  Each buffer has its own mark ring.  All editing commands use the current
buffer's mark ring.  In particular, @kbd{C-u C-@key{SPC}} always stays in
the same buffer.

  Many commands that can move long distances, such as @kbd{M-<}
(@code{beginning-of-buffer}), start by setting the mark and saving the
old mark on the mark ring.  This is to make it easier for you to move
back later.  Searches set the mark if they move point.  You can tell
when a command sets the mark because it displays @samp{Mark Set} in the
echo area.

  If you want to move back to the same place over and over, the mark
ring may not be convenient enough.  If so, you can record the position
in a register for later retrieval (@pxref{RegPos}).

@vindex mark-ring-max
  The variable @code{mark-ring-max} specifies the maximum number of
entries to keep in the mark ring.  If that many entries exist and
another one is pushed, the last one in the list is discarded.  Repeating
@kbd{C-u C-@key{SPC}} circulates through the positions currently in the
ring.

@vindex mark-ring
  The variable @code{mark-ring} holds the mark ring itself, as a list of
marker objects in the order most recent first.  This variable is local
in every buffer.


