Entering and Exiting Emacs
**************************

The usual way to invoke Emacs is with the shell command emacs.  Emacs clears the screen, then displays an initial help message and copyright notice.  Some operating systems discard your type-ahead when Emacs starts up; they give Emacs no way to prevent this.  On those systems, wait for Emacs to clear the screen before you start typing.

From a shell window under the X Window System, run Emacs in the background with emacs&.  This way, Emacs won't tie up the shell window, so you can use it to run other shell commands while Emacs is running.  You can type Emacs commands as soon as you direct your keyboard input to an Emacs frame.

When Emacs starts up, it creates a buffer named *scratch*. That's the buffer you start out in.  The *scratch* buffer uses Lisp Interaction mode; you can use it to type Lisp expressions and evaluate them.  You can also ignore that capability and just write notes there.  You can specify a different major mode for this buffer by setting the variable initial-major-mode in your init file. See Init File.

It is possible to specify files to be visited, Lisp files to be loaded, and functions to be called through Emacs command-line arguments.  See Emacs Invocation.  The feature exists mainly for compatibility with other editors, and for scripts.

Many editors are designed to edit one file.  When done with that file, you exit the editor.  The next time you want to edit a file, you must start the editor again.  Working this way, it is convenient to use a command-line argument to say which file to edit.

However, killing Emacs after editing one each and starting it afresh for the next file is both unnecessary and harmful, since it denies you the full power of Emacs.  Emacs can visit more than one file in a single editing session, and that is the right way to use it.  Exiting the Emacs session loses valuable accumulated context, such as the kill ring, registers, undo history, and mark ring.  These features are useful for operating on multiple files, or even continuing to edit one file.  If you kill Emacs after each file, you don't take advantage of them.

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 edit a file, you visit it with the existing Emacs, which eventually has many files in it ready for editing.  Usually you do not kill Emacs until you are about to log out.  See Files, for more information on visiting more than one file.

To edit a file from another program while Emacs is running, you can use the emacsclient helper program to open a file in the already running Emacs.  See Emacs Server.

Exiting Emacs
=============

There are two commands for exiting Emacs, and three kinds of exiting: iconifying Emacs, suspending Emacs, and killing Emacs.

Iconifying means replacing the Emacs frame with a small box or ``icon'' on the screen.  This is the usual way to exit Emacs when you're using a graphical display---if you bother to ``exit'' at all. (Just switching to another application is usually sufficient.)

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.  This is the usual way to exit Emacs when running it on a text terminal.

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.

C-z
     Suspend Emacs (suspend-emacs) or iconify a frame (iconify-or-deiconify-frame).

C-x C-c
     Kill Emacs (save-buffers-kill-emacs).

On graphical displays, C-z runs the command iconify-or-deiconify-frame, which temporarily iconifies (or ``minimizes'') the selected Emacs frame (see Frames).  You can then use the window manager to select some other application.  (You could select another application without iconifying Emacs first, but getting the Emacs frame out of the way can make it more convenient to find the other application.)

On a text terminal, C-z runs the command suspend-emacs. Suspending Emacs takes you back to the shell from which you invoked Emacs.  You can resume Emacs with the shell command %emacs in most common shells.  On systems that don't support suspending programs, C-z starts an inferior shell that communicates directly with the terminal, and Emacs waits until you exit the subshell.  (The way to do that is probably with C-d or exit, but it depends on which shell you use.)  On these systems, you can only get back to the shell from which Emacs was run (to log out, for example) when you kill Emacs.

Suspending can fail if you run Emacs under a shell that doesn't support suspendion of its subjobs, even if the system itself does support it.  In such a case, you can set the variable cannot-suspend to a non-nil value to force C-z to start an inferior shell.

To exit and kill Emacs, type C-x C-c (save-buffers-kill-emacs).  A two-character key is used 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 confirmation with yes before killing Emacs, since any changes not saved now will be lost forever.  Also, if any subprocesses are still running, C-x C-c asks for confirmation about them, since killing Emacs will also kill the subprocesses.

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

You can't resume an Emacs session after killing it.  Emacs can, however, record certain session information when you kill it, such as which files you visited, so the next time you start Emacs it will try to visit the same files.  See Saving Emacs Sessions.

The operating system usually listens for certain special characters whose meaning is to kill or suspend the program you are running. This operating system feature is turned off while you are in Emacs. The meanings of C-z and C-x C-c as keys in Emacs were inspired by the use of C-z and 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 (see Keymaps).