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<!DOCTYPE concept

  PUBLIC "-//OASIS//DTD DITA Concept//EN" "concept.dtd">

<concept id="GUID-6D1A830E-F0F1-5C0F-8EEB-70922C0EF6B8" xml:lang="en"><title>Length,

maximum length and size</title><shortdesc>Describes the length of 8-bit and 16-bit descriptors.</shortdesc><prolog><metadata><keywords/></metadata></prolog><conbody>

<p>A descriptor characterises the data it represents by the length of that

data. The length of a descriptor is the number of data items it represents:</p>

<ul>

<li id="GUID-3AF8F237-CA2A-5AAF-A56E-ECC7C95907B7"><p>for 8 bit variant

descriptors, the length is the number of single-bytes of data. When the descriptor

represents non-Unicode strings, the length is the number of characters in

the string.</p> </li>

<li id="GUID-7610BC67-31CD-57DA-A72C-B1F4348C8FAC"><p>for 16 bit variant

descriptors, the length is the number of double-bytes of data. When the descriptor

represents Unicode strings, the length is the number of characters in the

string.</p> </li>

</ul>

<p>The length of a descriptor cannot be greater than 2<sup>28</sup>.</p>

<p>The size of a descriptor is the number of bytes occupied by the data represented

by that descriptor:</p>

<ul>

<li id="GUID-830C6F31-EE2D-5C30-91D4-AB15FE4D2BA5"><p>for the 8 bit variant

descriptors, the size is the same as the length.</p> </li>

<li id="GUID-C7AF88D8-5836-53B9-A991-EA97B539C7CF"><p>for the 16 bit

variant descriptors, the size is twice the length.</p> </li>

</ul>

<p>The descriptors which allow their data to be modified are also characterised

by a maximum length. This represents an upper limit on the length of data

the descriptor can represent, i.e.the length of data represented by the descriptor

can vary can vary from zero up to, and including, this maximum value.</p>

</conbody></concept>