@c This is part of the Emacs manual.
@c Copyright (C) 1985, 1986, 1987, 1993, 1994, 1995 Free Software Foundation, Inc.
@c See file emacs.texi for copying conditions.
@node Entering Emacs, Exiting, Text Characters, Top
@chapter Entering and Exiting Emacs
@cindex entering Emacs
@cindex starting Emacs 

  The usual way to invoke Emacs is with the shell command @command{emacs}.
Emacs clears the screen and then displays an initial help message and
copyright notice.  Some operating systems discard all type-ahead when
Emacs starts up; they give Emacs no way to prevent this.  Therefore, it
is advisable to wait until Emacs clears the screen before typing your
first editing command.

  If you run Emacs from a shell window under the X Window System, run it
in the background with @command{emacs&}.  This way, Emacs does not tie up
the shell window, so you can use that to run other shell commands while
Emacs operates its own X windows.  You can begin typing Emacs commands
as soon as you direct your keyboard input to the Emacs frame.

@vindex initial-major-mode
  When Emacs starts up, it creates a buffer named @samp{*scratch*}.
That's the buffer you start out in.  The @samp{*scratch*} buffer uses Lisp
Interaction mode; you can use it to type Lisp expressions and evaluate
them, or you can ignore that capability and simply doodle.  (You can
specify a different major mode for this buffer by setting the variable
@code{initial-major-mode} in your init file.  @xref{Init File}.)

  It is possible to specify files to be visited, Lisp files to be
loaded, and functions to be called, by giving Emacs arguments in the
shell command line.  @xref{Command Arguments}.  But we don't recommend
doing this.  The feature exists mainly for compatibility with other
editors.

  Many other editors are designed to be started afresh each time you
want to edit.  You edit one file and then exit the editor.  The next
time you want to edit either another file or the same one, you must run
the editor again.  With these editors, it makes sense to use a
command-line argument to say which file to edit.

  But starting a new Emacs each time you want to edit a different file
does not make sense.  For one thing, this would be annoyingly slow.
For another, this would fail to take advantage of Emacs's ability to
visit more than one file in a single editing session.  And it would
lose the other accumulated context, such as the kill ring, registers,
undo history, and mark ring.

  The recommended way to use GNU Emacs is to start it only once, just
after you log in, and do all your editing in the same Emacs session.
Each time you want to edit a different file, you visit it with the
existing Emacs, which eventually comes to have many files in it ready
for editing.  Usually you do not kill the Emacs until you are about to
log out.  @xref{Files}, for more information on visiting more than one
file.

@node Exiting, Basic, Entering Emacs, Top
@section Exiting Emacs
@cindex exiting
@cindex killing Emacs
@cindex suspending
@cindex leaving Emacs
@cindex quitting Emacs

  There are two commands for exiting Emacs because there are two kinds
of exiting: @dfn{suspending} Emacs and @dfn{killing} Emacs.

  @dfn{Suspending} means stopping Emacs temporarily and returning
control to its parent process (usually a shell), allowing you to resume
editing later in the same Emacs job, with the same buffers, same kill
ring, same undo history, and so on.  This is the usual way to exit.

  @dfn{Killing} Emacs means destroying the Emacs job.  You can run Emacs
again later, but you will get a fresh Emacs; there is no way to resume
the same editing session after it has been killed.

@table @kbd
@item C-z
Suspend Emacs (@code{suspend-emacs}) or iconify a frame
(@code{iconify-or-deiconify-frame}).
@item C-x C-c
Kill Emacs (@code{save-buffers-kill-emacs}).
@end table

@kindex C-z
@findex suspend-emacs
  To suspend Emacs, type @kbd{C-z} (@code{suspend-emacs}).  This takes
you back to the shell from which you invoked Emacs.  You can resume
Emacs with the shell command @command{%emacs} in most common shells.

  On systems that do not support suspending programs, @kbd{C-z} starts
an inferior shell that communicates directly with the terminal.
Emacs waits until you exit the subshell.  (The way to do that is
probably with @kbd{C-d} or @command{exit}, but it depends on which shell
you use.)  The only way on these systems to get back to the shell from
which Emacs was run (to log out, for example) is to kill Emacs.

  Suspending also fails if you run Emacs under a shell that doesn't
support suspending programs, even if the system itself does support it.
In such a case, you can set the variable @code{cannot-suspend} to a
non-@code{nil} value to force @kbd{C-z} to start an inferior shell.
(One might also describe Emacs's parent shell as ``inferior'' for
failing to support job control properly, but that is a matter of taste.)

  When Emacs communicates directly with an X server and creates its own
dedicated X windows, @kbd{C-z} has a different meaning.  Suspending an
application that uses its own X windows is not meaningful or useful.
Instead, @kbd{C-z} runs the command @code{iconify-or-deiconify-frame},
which temporarily iconifies (or ``minimizes'') the selected Emacs
frame (@pxref{Frames}).  Then you can use the window manager to get
back to a shell window.

@kindex C-x C-c
@findex save-buffers-kill-emacs
  To exit and kill Emacs, type @kbd{C-x C-c}
(@code{save-buffers-kill-emacs}).  A two-character key is used for
this to make it harder to type by accident.  This command first offers
to save any modified file-visiting buffers.  If you do not save them
all, it asks for reconfirmation with @kbd{yes} before killing Emacs,
since any changes not saved will be lost forever.  Also, if any
subprocesses are still running, @kbd{C-x C-c} asks for confirmation
about them, since killing Emacs will also kill the subprocesses.

@vindex confirm-kill-emacs
  If the value of the variable @code{confirm-kill-emacs} is
non-@code{nil}, @kbd{C-x C-c} assumes that its value is a predicate
function, and calls that function.  If the result is non-@code{nil}, the
session is killed, otherwise Emacs continues to run.  One convenient
function to use as the value of @code{confirm-kill-emacs} is the
function @code{yes-or-no-p}.  The default value of
@code{confirm-kill-emacs} is @code{nil}.

  There is no way to resume an Emacs session once you have killed it.
You can, however, arrange for Emacs to record certain session
information when you kill it, such as which files are visited, so that
the next time you start Emacs it will try to visit the same files and
so on.  @xref{Saving Emacs Sessions}.

  The operating system usually listens for certain special characters
whose meaning is to kill or suspend the program you are running.
@b{This operating system feature is turned off while you are in Emacs.}
The meanings of @kbd{C-z} and @kbd{C-x C-c} as keys in Emacs were
inspired by the use of @kbd{C-z} and @kbd{C-c} on several operating
systems as the characters for stopping or killing a program, but that is
their only relationship with the operating system.  You can customize
these keys to run any commands of your choice (@pxref{Keymaps}).
