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<chapter>
  <header>
    <copyright>
      <year>2014</year><year>2021</year>
      <holder>Ericsson AB. All Rights Reserved.</holder>
    </copyright>
    <legalnotice>
      Licensed under the Apache License, Version 2.0 (the "License");
      you may not use this file except in compliance with the License.
      You may obtain a copy of the License at
 
          http://www.apache.org/licenses/LICENSE-2.0

      Unless required by applicable law or agreed to in writing, software
      distributed under the License is distributed on an "AS IS" BASIS,
      WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
      See the License for the specific language governing permissions and
      limitations under the License.

    </legalnotice>

    <title>Character Set and Source File Encoding</title>
    <prepared></prepared>
    <docno></docno>
    <date></date>
    <rev></rev>
    <file>character_set.xml</file>
  </header>

  <section>
    <title>Character Set</title>
    <p>The syntax of Erlang tokens allow the use of the full
    ISO-8859-1 (Latin-1) character set. This is noticeable in the
    following ways:</p>
    <list type="bulleted">
      <item>
        <p>All the Latin-1 printable characters can be used and are
          shown without the escape backslash convention.</p>
      </item>
      <item>
        <p>Atoms and variables can use all Latin-1 letters.</p>
      </item>
    </list>
    <table>
      <row>
        <cell align="left" valign="middle"><em>Octal</em></cell>
        <cell align="left" valign="middle"><em>Decimal</em></cell>
        <cell align="left" valign="middle">&nbsp;</cell>
        <cell align="left" valign="middle"><em>Class</em></cell>
      </row>
      <row>
        <cell align="left" valign="middle">200 - 237</cell>
        <cell align="left" valign="middle">128 - 159</cell>
        <cell align="left" valign="middle">&nbsp;</cell>
        <cell align="left" valign="middle">Control characters</cell>
      </row>
      <row>
        <cell align="left" valign="middle">240 - 277</cell>
        <cell align="left" valign="middle">160 - 191</cell>
        <cell align="right" valign="middle">- &iquest;</cell>
        <cell align="left" valign="middle">Punctuation characters</cell>
      </row>
      <row>
        <cell align="left" valign="middle">300 - 326</cell>
        <cell align="left" valign="middle">192 - 214</cell>
        <cell align="center" valign="middle">&Agrave; - &Ouml;</cell>
        <cell align="left" valign="middle">Uppercase letters</cell>
      </row>
      <row>
        <cell align="center" valign="middle">327</cell>
        <cell align="center" valign="middle">215</cell>
        <cell align="center" valign="middle">&times;</cell>
        <cell align="left" valign="middle">Punctuation character</cell>
      </row>
      <row>
        <cell align="left" valign="middle">330 - 336</cell>
        <cell align="left" valign="middle">216 - 222</cell>
        <cell align="center" valign="middle">&Oslash; - &THORN;</cell>
        <cell align="left" valign="middle">Uppercase letters</cell>
      </row>
      <row>
        <cell align="left" valign="middle">337 - 366</cell>
        <cell align="left" valign="middle">223 - 246</cell>
        <cell align="center" valign="middle">&szlig; - &ouml;</cell>
        <cell align="left" valign="middle">Lowercase letters</cell>
      </row>
      <row>
        <cell align="center" valign="middle">367</cell>
        <cell align="center" valign="middle">247</cell>
        <cell align="center" valign="middle">&divide;</cell>
        <cell align="left" valign="middle">Punctuation character</cell>
      </row>
      <row>
        <cell align="left" valign="middle">370 - 377</cell>
        <cell align="left" valign="middle">248 - 255</cell>
        <cell align="center" valign="middle">&oslash; - &yuml;</cell>
        <cell align="left" valign="middle">Lowercase letters</cell>
      </row>
      <tcaption>Character Classes</tcaption>
    </table>
    <p>In Erlang/OTP R16B the syntax of Erlang tokens was extended to
       handle Unicode. The support was limited to
       string literals and comments.
       More about the usage of Unicode in Erlang source files
       can be found in <seeguide
       marker="stdlib:unicode_usage#unicode_in_erlang">STDLIB's User's
       Guide</seeguide>.</p>
       <p>From Erlang/OTP 20, atoms and function names are also allowed
       to contain Unicode characters outside the ISO-Latin-1 range.
       Module names, application names, and node names are still
       restricted to the ISO-Latin-1 range.</p>
  </section>
  <section>
    <title>Source File Encoding</title>
    <marker id="encoding"></marker>
    <p>The Erlang source file <c>encoding</c> is selected by a
      comment in one of the first two lines of the source file. The
      first string that matches the regular expression
      <c>coding\s*[:=]\s*([-a-zA-Z0-9])+</c> selects the encoding. If
      the matching string is an invalid encoding, it is ignored. The
      valid encodings are <c>Latin-1</c> and <c>UTF-8</c>, where the
      case of the characters can be chosen freely.</p>
    <p>The following example selects UTF-8 as default encoding:</p>
      <pre>
%% coding: utf-8</pre>
    <p>Two more examples, both selecting Latin-1 as default encoding:</p>
      <pre>
%% For this file we have chosen encoding = Latin-1</pre>
      <pre>
%% -*- coding: latin-1 -*-</pre>
    <p>The default encoding for Erlang source files is changed from
      Latin-1 to UTF-8 since Erlang/OTP 17.0.</p>
  </section>
</chapter>
