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<div class="SECT1">
<h1 class="SECT1"><a id="EMACS-MODES" name="EMACS-MODES">17.3 Modes</a></h1>

<p>Every buffer in Emacs has an associated mode. This mode is very different from the
idea of modes in <tt class="COMMAND">vi</tt>: a mode tells you what kind of buffer you
are in. For example, there is text-mode for normal text files, but there are also modes
such as c-mode for editing C programs, sh-mode for editing shell scripts, latex-mode for
editing <b class="APPLICATION">LaTeX</b> files, mail-mode for editing email and news
messages, etc. A mode provides special customizations and functionality that is useful
for the kind of file you are editing. It is even possible for a mode to redefine keys and
key commands. For example, in Text mode, the Tab key simply jumps to the next tab stop,
but in many programming language modes, the <b class="KEYCAP">Tab</b> key indents the
current line according to the depth of the block that line is in.</p>

<p>The modes mentioned above are called major modes. Each buffer has exactly one major
mode. Additionally, a buffer can have one or more minor modes. A minor mode provides
additional features that may be useful for certain editing tasks. For example, if you hit
the <b class="KEYCAP">INSERT</b> key, you invoke overwrite-mode, which does what you'd
expect. There is also an auto-fill-mode, which is handy in combination with text-mode or
latex-mode: it causes each line that you type to be automatically wrapped once the line
reaches a certain number of characters. Without auto-fill-mode, you have to type <b
class="KEYCAP">M</b>-<b class="KEYCAP">q</b> to fill out a paragraph. (Which you can also
use to reformat a paragraph after you've edited some text in it and it is no longer
nicely filled out.)</p>

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<h2 class="SECT2"><a id="EMACS-OPENING-FILES" name="EMACS-OPENING-FILES">17.3.1 Opening
files</a></h2>

<p>To open a file in Emacs, type</p>

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<kbd class="USERINPUT">C-x C-f</kbd>
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<p>Emacs will ask you for the name of the file, filling in some default path for you
(which is usually <tt class="FILENAME">~/</tt> ). After you type the filename (you can
use <b class="KEYCAP">Tab</b> completion) and hit <b class="KEYCAP">ENTER</b> , Emacs
will open the file in a new buffer and display that buffer on the screen.</p>

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<p>In order to create a new file in emacs, you cannot just go typing right away. You
first have to create a buffer for it, and come up with a filename. You do this by typing
<b class="KEYCAP">C</b>-<b class="KEYCAP">x</b> <b class="KEYCAP">C</b>-<b
class="KEYCAP">f</b> and typing a filename, just as if you were opening an existing file.
Emacs will notice that the file you typed doesn't exist, and will create a new buffer and
report &#8220;(New file)&#8221; in the minibuffer.</p>

<p>When you type <b class="KEYCAP">C</b>-<b class="KEYCAP">x</b> <b
class="KEYCAP">C</b>-<b class="KEYCAP">f</b> and then enter a directory name instead of a
filename, Emacs will create a new buffer in which you will find a list of all the files
in that directory. You can move the cursor to the file that you are looking for and type
, and Emacs will open it. (There are in fact a lot more actions you can perform here,
such as deleting, renaming and moving files, etc. Emacs is now in dired-mode, which is
basically a simple file manager.)</p>

<p>When you have typed <b class="KEYCAP">C</b>-<b class="KEYCAP">x</b> <b
class="KEYCAP">C</b>-<b class="KEYCAP">f</b> and suddenly change your mind, you can type
<b class="KEYCAP">C</b>-<b class="KEYCAP">g</b> to cancel the action. <b
class="KEYCAP">C</b>-<b class="KEYCAP">g</b> works almost everywhere where you want to
cancel an action or command that you've started but don't want to finish.</p>
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