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    12 <concept id="GUID-261ADCEC-C8C8-46E3-A7DC-804AC868C233" xml:lang="en"><title>Descriptors</title><prolog><metadata><keywords/></metadata></prolog><conbody>

    13 <p>Descriptors are self-describing strings that can be used to store binary

    14 data and text. Each descriptor object holds the length of the string as well

    15 as its type which identifies the underlying memory layout of the data it holds.

    16 For more information on different descriptor classes, see <xref href="GUID-11EEFB3D-0414-5BEB-9D78-56A4B9154008.dita">Using

    17 Descriptors</xref>.</p>

    18 <p>There are modifiable and non-modifiable descriptors, the latter type

    19 is identified by a "C" suffix in the class name. The length of a non-modifiable

    20 descriptor is defined when compiling an application, and the length of a modifiable

    21 descriptor can vary within the limits set by <codeph>iMaxLength</codeph>.

    22 Nonmodifiable descriptors are more secure, as their length is checked during

    23 compilation. The following figure shows the differences between these types.</p>

    24 <fig id="GUID-A8F9937F-25A6-4E80-845F-35994B7E13E5"><title>Differences between modifiable, nonmodifiable, and pointer descriptors</title><image href="GUID-40619192-8C2F-4267-BFCA-F53E10BF5A31_d0e11254_href.png"/></fig>

    25 <p>When designing applications, avoid using fixed-length buffers as parameters

    26 and use base classes (preferably constant base type <codeph><xref href="jar:GUID-35228542-8C95-4849-A73F-2B4F082F0C44.jar!/sdk/doc_source/reference/reference-cpp/Kernel_Architecture_2/e32cmn.hGlobals.html#%3a%3aTDesC" format="application/java-archive">TDesC</xref></codeph>)

    27 instead. Descriptor objects provide a flexible interface for manipulating

    28 the contained string, including size and length checks. Take advantage of

    29 these when possible.</p>

    30 <p>For more information and examples, see the <xref href="GUID-0817AD1D-58CF-5108-ACBF-26DFD4BA395E.dita">Descriptors

    31 Overview</xref> topic.</p>

    32 </conbody></concept>