devdocs/elisp/meta_002dchar-syntax.html


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 <h4 class="subsubsection">Meta-Character Syntax</h4>  <p>A <em>meta character</em> is a character typed with the <tt class="key">META</tt> modifier key. The integer that represents such a character has the 2**27 bit set. We use high bits for this and other modifiers to make possible a wide range of basic character codes. </p> <p>In a string, the 2**7 bit attached to an <acronym>ASCII</acronym> character indicates a meta character; thus, the meta characters that can fit in a string have codes in the range from 128 to 255, and are the meta versions of the ordinary <acronym>ASCII</acronym> characters. See <a href="strings-of-events">Strings of Events</a>, for details about <tt class="key">META</tt>-handling in strings. </p> <p>The read syntax for meta characters uses ‘<samp>\M-</samp>’. For example, ‘<samp>?\M-A</samp>’ stands for <kbd>M-A</kbd>. You can use ‘<samp>\M-</samp>’ together with octal character codes (see below), with ‘<samp>\C-</samp>’, or with any other syntax for a character. Thus, you can write <kbd>M-A</kbd> as ‘<samp>?\M-A</samp>’, or as ‘<samp>?\M-\101</samp>’. Likewise, you can write <kbd>C-M-b</kbd> as ‘<samp>?\M-\C-b</samp>’, ‘<samp>?\C-\M-b</samp>’, or ‘<samp>?\M-\002</samp>’. </p><div class="_attribution">
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    Copyright &copy; 1990-1996, 1998-2022 Free Software Foundation, Inc. <br>Licensed under the GNU GPL license.<br>
    <a href="https://www.gnu.org/software/emacs/manual/html_node/elisp/Meta_002dChar-Syntax.html" class="_attribution-link">https://www.gnu.org/software/emacs/manual/html_node/elisp/Meta_002dChar-Syntax.html</a>
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