Emacs can split a frame into two or many windows. Multiple windows can display parts of different buffers, or different parts of one buffer. Multiple frames always imply multiple windows, because each frame has its own set of windows. Each window belongs to one and only one frame.
Each Emacs window displays one Emacs buffer at any time. A single buffer may appear in more than one window; if it does, any changes in its text are displayed in all the windows where it appears. But the windows showing the same buffer can show different parts of it, because each window has its own value of point.
At any time, one of the windows is the selected window; the buffer this window is displaying is the current buffer. The terminal's cursor shows the location of point in this window. Each other window has a location of point as well, but since the terminal has only one cursor there is no way to show where those locations are. When multiple frames are visible in X Windows, each frame has a cursor which appears in the frame's selected window. The cursor in the selected frame is solid; the cursor in other frames is a hollow box.
Commands to move point affect the value of point for the selected Emacs
window only. They do not change the value of point in any other Emacs
window, even one showing the same buffer. The same is true for commands
such as C-x b to change the selected buffer in the selected window;
they do not affect other windows at all. However, there are other commands
such as C-x 4 b that select a different window and switch buffers in
it. Also, all commands that display information in a window, including
(for example) C-h f (describe-function) and C-x C-b
(list-buffers), work by switching buffers in a nonselected window
without affecting the selected window.
When multiple windows show the same buffer, they can have different regions, because they can have different values of point. However, they all have the same value for the mark, because each buffer has only one mark position.
Each window has its own mode line, which displays the buffer name, modification status and major and minor modes of the buffer that is displayed in the window. See section The Mode Line, for full details on the mode line.
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split-window-vertically).
split-window-horizontally).
The command C-x 2 (split-window-vertically) breaks the
selected window into two windows, one above the other. Both windows start
out displaying the same buffer, with the same value of point. By default
the two windows each get half the height of the window that was split; a
numeric argument specifies how many lines to give to the top window.
C-x 3 (split-window-horizontally) breaks the selected
window into two side-by-side windows. A numeric argument specifies how
many columns to give the one on the left. A line of vertical bars
separates the two windows. Windows that are not the full width of the
screen have mode lines, but they are truncated. On terminals where
Emacs does not support highlighting, truncated mode lines sometimes do
not appear in inverse video.
You can split a window horizontally or vertically by clicking C-Mouse-2 in the mode line or the scroll bar. The line of splitting goes through the place where you click: if you click on the mode line, the new scroll bar goes above the spot; if you click in the scroll bar, the mode line of the split window is side by side with your click.
When a window is less than the full width, text lines too long to fit are
frequent. Continuing all those lines might be confusing. The variable
truncate-partial-width-windows can be set non-nil to force
truncation in all windows less than the full width of the screen,
independent of the buffer being displayed and its value for
truncate-lines. See section Continuation Lines.
Horizontal scrolling is often used in side-by-side windows. See section Controlling the Display.
If split-window-keep-point is non-nil, the default, both
of the windows resulting from C-x 2 inherit the value of point
from the window that was split. This means that scrolling is
inevitable. If this variable is nil, then C-x 2 tries to
avoid shifting any text the screen, by putting point in each window at a
position already visible in the window. It also selects whichever
window contain the screen line that the cursor was previously on. Some
users prefer the latter mode slow terminals.
other-window). That is o, not zero.
scroll-other-window).
mouse-select-window).
To select a different window, click with Mouse-1 on its mode
line. With the keyboard, you can switch windows by typing C-x o
(other-window). That is an o, for `other', not a zero.
When there are more than two windows, this command moves through all the
windows in a cyclic order, generally top to bottom and left to right.
After the rightmost and bottommost window, it goes back to the one at
the upper left corner. A numeric argument means to move several steps
in the cyclic order of windows. A negative argument moves around the
cycle in the opposite order. When the minibuffer is active, the
minibuffer is the last window in the cycle; you can switch from the
minibuffer window to one of the other windows, and later switch back and
finish supplying the minibuffer argument that is requested.
See section Editing in the Minibuffer.
The usual scrolling commands (see section Controlling the Display) apply to the selected
window only, but there is one command to scroll the next window.
C-M-v (scroll-other-window) scrolls the window that
C-x o would select. It takes arguments, positive and negative,
like C-v. (In the minibuffer, C-M-v scrolls the window
that contains the minibuffer help display, if any, rather than the
next window in the standard cyclic order.)
The command M-x compare-windows lets you compare two files or
buffers visible in two windows, by moving through them to the next
mismatch. See section Comparing Files, for details.
C-x 4 is a prefix key for commands that select another window (splitting the window if there is only one) and select a buffer in that window. Different C-x 4 commands have different ways of finding the buffer to select.
switch-to-buffer-other-window.
display-buffer.
find-file-other-window. See section Visiting Files.
dired-other-window. See section Dired, the Directory Editor.
mail-other-window; its same-window analogue is C-x m
(see section Sending Mail).
find-tag-other-window, the multiple-window variant of M-.
(see section Tags Tables).
find-file-read-only-other-window.
See section Visiting Files.
Certain Emacs commands switch to a specific buffer with special contents. For example, M-x shell switches to a buffer named `*Shell*'. By convention, all these commands are written to pop up the buffer in a separate window. But you can specify that certain of these buffers should appear in the selected window.
If you add a buffer name to the list same-window-buffer-names,
the effect is that such commands display that particular buffer by
switching to it in the selected window. For example, if you add the
element "*grep*" to the list, the grep command will
display its output buffer in the selected window.
The default value of same-window-buffer-names is not
nil: it specifies buffer names `*info*', `*mail*' and
`*shell*' (as well as others used by more obscure Emacs packages).
This is why M-x shell normally switches to the `*shell*'
buffer in the selected window. If you delete this element from the
value of same-window-buffer-names, the behavior of M-x
shell will change--it will pop up the buffer in another window
instead.
You can specify these buffers more generally with the variable
same-window-regexps. Set it to a list of regular expressions;
then any buffer whose name matches one of those regular expressions is
displayed by switching to it in the selected window. (Once again, this
applies only to buffers that normally get displayed for you in a
separate window.) The default value of this variable specifies Telnet
and rlogin buffers.
An analogous feature lets you specify buffers which should be displayed in their own individual frames. See section Special Buffer Frames.
delete-window). The last character
in this key sequence is a zero.
delete-other-windows).
kill-buffer-and-window). The last character in this key
sequence is a zero.
enlarge-window).
enlarge-window-horizontally).
shrink-window-horizontally).
shrink-window-if-larger-than-buffer).
balance-windows).
mouse-delete-other-windows).
mouse-delete-window).
To delete a window, type C-x 0 (delete-window). (That is
a zero.) The space occupied by the deleted window is given to an
adjacent window (but not the minibuffer window, even if that is active
at the time). Once a window is deleted, its attributes are forgotten;
only restoring a window configuration can bring it back. Deleting the
window has no effect on the buffer it used to display; the buffer
continues to exist, and you can select it in any window with C-x
b.
C-x 4 0 (kill-buffer-and-window) is a stronger command
than C-x 0; it kills the current buffer and then deletes the
selected window.
C-x 1 (delete-other-windows) is more powerful in a
different way; it deletes all the windows except the selected one (and
the minibuffer); the selected window expands to use the whole frame
except for the echo area.
You can also delete a window by clicking on its mode line with Mouse-2, and delete all the windows in a frame except one window by clicking on that window's mode line with Mouse-3.
The easiest way to adjust window heights is with a mouse. If you press Mouse-1 on a mode line, you can drag that mode line up or down, changing the heights of the windows above and below it.
To readjust the division of space among vertically adjacent windows,
use C-x ^ (enlarge-window). It makes the currently
selected window get one line bigger, or as many lines as is specified
with a numeric argument. With a negative argument, it makes the
selected window smaller. C-x }
(enlarge-window-horizontally) makes the selected window wider by
the specified number of columns. C-x {
(shrink-window-horizontally) makes the selected window narrower
by the specified number of columns.
When you make a window bigger, the space comes from one of its
neighbors. If this makes any window too small, it is deleted and its
space is given to an adjacent window. The minimum size is specified by
the variables window-min-height and window-min-width.
The command C-x - (shrink-window-if-larger-than-buffer)
reduces the height of the selected window, if it is taller than
necessary to show the whole text of the buffer it is displaying. It
gives the extra lines to other windows in the frame.
You can also use C-x + (balance-windows) to even out the
heights of all the windows in the selected frame.
See section Editing in the Minibuffer, for information about the Resize-Minibuffer mode, which automatically changes the size of the minibuffer window to fit the text in the minibuffer.