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<h4 class="subsection">16.6.2 Host Addresses</h4>

<p>Each computer on the Internet has one or more <dfn>Internet addresses</dfn>,
numbers which identify that computer among all those on the Internet. 
Users typically write IPv4 numeric host addresses as sequences of four
numbers, separated by periods, as in &lsquo;<samp><span class="samp">128.52.46.32</span></samp>&rsquo;, and IPv6
numeric host addresses as sequences of up to eight numbers separated by
colons, as in &lsquo;<samp><span class="samp">5f03:1200:836f:c100::1</span></samp>&rsquo;.

   <p>Each computer also has one or more <dfn>host names</dfn>, which are strings
of words separated by periods, as in &lsquo;<samp><span class="samp">mescaline.gnu.org</span></samp>&rsquo;.

   <p>Programs that let the user specify a host typically accept both numeric
addresses and host names.  To open a connection a program needs a
numeric address, and so must convert a host name to the numeric address
it stands for.

<ul class="menu">
<li><a accesskey="1" href="Abstract-Host-Addresses.html#Abstract-Host-Addresses">Abstract Host Addresses</a>: 	What a host number consists of. 
<li><a accesskey="2" href="Host-Address-Data-Type.html#Host-Address-Data-Type">Data type</a>: 	Data type for a host number. 
<li><a accesskey="3" href="Host-Address-Functions.html#Host-Address-Functions">Functions</a>: 	Functions to operate on them. 
<li><a accesskey="4" href="Host-Names.html#Host-Names">Names</a>: 		Translating host names to host numbers. 
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