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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>