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<chapter>
  <header>
    <copyright>
      <year>2003</year><year>2013</year>
      <holder>Ericsson AB. All Rights Reserved.</holder>
    </copyright>
    <legalnotice>
      The contents of this file are subject to the Erlang Public License,
      Version 1.1, (the "License"); you may not use this file except in
      compliance with the License. You should have received a copy of the
      Erlang Public License along with this software. If not, it can be
      retrieved online at http://www.erlang.org/.
    
      Software distributed under the License is distributed on an "AS IS"
      basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See
      the License for the specific language governing rights and limitations
      under the License.
    
    </legalnotice>

    <title>Introduction</title>
    <prepared></prepared>
    <docno></docno>
    <date></date>
    <rev></rev>
    <file>introduction.xml</file>
  </header>

  <section>
    <title>Purpose</title>
    <p>This reference manual describes the Erlang programming
      language. The focus is on the language itself, not
      the implementation. The language constructs are described in
      text and with examples rather than formally specified, with
      the intention to make the manual more readable.
      The manual is not intended as a tutorial.</p>
    <p>Information about this implementation of Erlang can be found, for
      example, in <em>System Principles</em> (starting and stopping,
      boot scripts, code loading, error logging, creating target
      systems), <em>Efficiency Guide</em> (memory consumption, system
      limits) and <em>ERTS User's Guide</em> (crash dumps, drivers).</p>
  </section>

  <section>
    <title>Prerequisites</title>
    <p>It is assumed that the reader has done some programming and
      is familiar with concepts such as data types and programming
      language syntax.</p>
  </section>

  <section>
    <title>Document Conventions</title>
    <p>In the document, the following terminology is used:</p>
    <list type="bulleted">
      <item>A <em>sequence</em> is one or more items. For example, a
       clause body consists of a sequence of expressions. This
       means that there must be at least one expression.</item>
      <item>A <em>list</em> is any number of items. For example,
       an argument list can consist of zero, one or more arguments.</item>
    </list>
    <p>If a feature has been added recently, in Erlang 5.0/OTP R7 or
      later, this is mentioned in the text.</p>
  </section>

  <section>
    <title>Complete List of BIFs</title>
    <p>For a complete list of BIFs, their arguments and return values,
      refer to <c>erlang(3)</c>.</p>
  </section>

  <section>
    <title>Reserved Words</title>
    <p>The following are reserved words in Erlang:</p>
    <p>after and andalso band begin bnot bor bsl bsr bxor case catch
      cond div end fun if let not of or orelse receive rem try
      when xor</p>
  </section>

  <section>
    <title>Character Set</title>
    <p>In Erlang 4.8/OTP R5A the syntax of Erlang tokens was extended to
      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 R16 the syntax of Erlang tokens was extended to
       handle Unicode. To begin with the support is limited to strings,
       but Erlang/OTP R18 is expected to handle Unicode atoms as well.
       More about the usage of Unicode in Erlang source files can be
       found in <seealso
       marker="stdlib:unicode_usage#unicode_in_erlang">STDLIB's User'S
       Guide</seealso>. The default encoding for Erlang source files
       is still Latin-1, but in Erlang/OTP R17 the default encoding
       will be UTF-8. The details on how to state the encoding of an
       Erlang source file can be found in <seealso
       marker="stdlib:epp#encoding">epp(3)</seealso>.</p>
  </section>
</chapter>

