Entering and Exiting Emacs
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The usual way to invoke Emacs is with the shell 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.  If you ever use those systems, learn the habit of waiting for Emacs to clear 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 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.

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, or you can ignore that capability and just write notes in it.  (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, by giving Emacs arguments in the shell command line.  See Emacs Invocation.  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.  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, that are useful for operating on multiple files or even one.

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.  See Files, for more information on visiting more than one file.

If you want to edit a file from another program and already have Emacs running, you can use the emacsclient program to open a file in the already running Emacs.  See Emacs Server, for more information on editing files with Emacs from other programs.

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

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

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 Emacs when running on a text terminal.

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

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).

To suspend or iconify Emacs, type C-z (suspend-emacs). On text terminals, this suspends Emacs.  On graphical displays, it iconifies the Emacs frame.

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.)  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 can fail 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 cannot-suspend to a non-nil value to force 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.)

On graphical displays, C-z has a different meaning: it runs the command iconify-or-deiconify-frame, which temporarily iconifies (or ``minimizes'') the selected Emacs frame (see Frames).  Then you can use the window manager to get back to a shell window.

To exit and kill Emacs, type C-x C-c (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 yes before killing Emacs, since any changes not saved 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.

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.  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).