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<!DOCTYPE concept
  PUBLIC "-//OASIS//DTD DITA Concept//EN" "concept.dtd">
<concept id="GUID-591552AB-D708-5CB5-9597-A0AF3D303178" xml:lang="en"><title>Headers</title><shortdesc>This document describes the concept of headers as regards to doubly
linked lists.</shortdesc><prolog><metadata><keywords/></metadata></prolog><conbody>
<p>A header forms the anchor point for a doubly linked list. In common with
the elements of the list, the header includes a <i>link</i> object as a component.</p>
<p>The header includes the following functionality:</p>
<ul>
<li id="GUID-A713D790-2003-5788-889F-E3B3D9669B0D"><p>allows elements to be
added to the start and end of a doubly linked list, but <i>not</i> to the
middle.</p> </li>
<li id="GUID-84EB986A-7501-57FF-BFD0-DB67182A3050"><p>tests if an element
is at the start or end of a list.</p> </li>
<li id="GUID-94683FD4-C576-520D-8CEC-D1D7A8978D0C"><p>returns pointers to
elements at the start or the end of a list.</p> </li>
</ul>
<p>A header is an instance of the templated class <codeph>TDblQue&lt;class
        T&gt;</codeph>.</p>
</conbody></concept>