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+<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"><html><head><title>Character encoding</title><meta http-equiv="content-type" content="text/html; charset=ISO-8859-1"></head><body>
+<h1 align="center">Character encoding</h1>
+<br>
+<h2>Index</h2>
+<ul>
+ <li><a href="#The_character_encoding_problem">The character encoding problem</a></li>
+ <li><a href="#Unicode">Unicode</a><br>
+ </li>
+</ul>
+<br>
+<hr width="100%" size="2">
+<h2><a name="The_character_encoding_problem"></a>The character encoding problem</h2>
+
+Developers are usually familiar with the ASCII character set. This
+is a character set that assigns a unique number to some characters, e.g.
+an "A" has ASCII code 65 (or 0x41 in hex), and an "a" has ASCII code 97 (or
+0x61 in hex). Some people may also have used ASCII codes for several
+drawing characters (such as a horizontal bar, a vertical bar, or a top-right
+corner) in the old DOS days, to be able to draw nice windows in text mode.<br>
+<br>
+
+However, these last characters are strictly spoken not part of the ASCII
+set. The standard ASCII set contains only the character positions from
+0 to 127 (i.e. anything that fits into an integer that is 7 bits wide). An
+example of this table can be found <a href="http://web.cs.mun.ca/%7Emichael/c/ascii-table.html">here</a>. Anything that has an ASCII code between 128 and 255 is in principle undefined.<br>
+<br>
+
+Now, several systems (including the old DOS) have defined those character
+positions anyway, but usually in totally different ways. Some well
+known extensions are:<br>
+<ul>
+<li>the <a href="http://czyborra.com/charsets/cp437.gif">DOS</a>
+ character set, nowadays usually known as Code Page 437, but sometimes also
+named LatinUS, ECS (Extended Character Set) or PC-8; note that the table
+displayed in the link also contains the standard ASCII part</li><li>the <a href="http://czyborra.com/charsets/cp1252.gif">ANSI</a> character set, also known as Code Page 1252, and usually the default on Windows</li><li>the <a href="http://czyborra.com/charsets/iso8859-1.gif">ISO-8859-1</a> character set (also called Latin-1), which is an ISO standard for Western European languages, mostly used on various Unices</li><li>the <a href="http://czyborra.com/charsets/adobe-stdenc.gif">Adobe Standard Encoding</a>, which is by default used in Postscript, unless overridden</li>
+</ul>
+
+And these are only examples of character sets used in West-European languages.
+ For Japanese, Chinese, Korean, Vietnamese, ... there are separate character
+sets in which one byte's meaning can even be influenced by what the previous
+byte was, i.e. these are multi-byte character sets. This is because
+even 256 characters (the maximum for 8 bits) is totally inadequate to represent all characters in
+such languages.<br>
+<br>
+
+So, summarizing, if a text file contains a byte that has a value 65, it is
+pretty safe to assume that this byte represents an "A", if we ignore the
+multi-byte character sets spoken of before. However, a value 233 cannot
+be interpreted without knowing in which character set the text file is written.
+ In Latin-1, it happens to be the character "é", but in another
+character set it can be something totally different (e.g. in the DOS character
+set it is the Greek letter theta).<br>
+<br>
+
+Vice versa, if you need to write a character "é" to a file, it depends
+on the character set you will use what the numerical value will be in the
+file: in Latin-1 it will be 233, but if you use the DOS character set it
+will be 130.<br>
+<hr width="100%" size="2">
+<h2><a name="Unicode"></a>Unicode</h2>
+
+Enter the Unicode standard...<br>
+<hr width="100%" size="2">
+<pre><font size="-1">$Id$<br>$Name$</font><br></pre>
+<br>
+</body></html>
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