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<concept id="GUID-B01EDE29-0861-52B0-97BE-8B41E580817F" xml:lang="en"><title>Identifying

Optional Features</title><shortdesc>This document details how to identify optional features for querying

with the Feature Registry. </shortdesc><prolog><metadata><keywords/></metadata></prolog><conbody>

<section id="GUID-EA8C9852-C613-51DC-8027-866FEE91EB39"><title>Feature UIDs</title> <p>Each

optional or managed feature on Symbian platform is given a 32-bit unique identifier

and represented by a <xref href="GUID-530281E6-29FC-33F2-BC9B-610FBA389444.dita"><apiname>TUid</apiname></xref>. The names of Symbian platform

features and their UID assignments are defined in the <filepath>featureUIDs.h</filepath> header

file. </p> <p>These names or UIDs are the argument values for the Feature

Registry query functions. The <i>granularity</i> of features is generally

quite coarse. Seldom will a feature correspond to a single API method or aspect

of its behaviour. Other approaches (beyond what is provided by the Feature

Registry) are generally required to detect these minor variations. Strong

guarantees of backward compatibility mean that existing functionality associated

with a feature or identifier may not change or be removed, though it may grow

in later releases. Functionality is only removed when the entire feature is

removed. </p> </section>

<example id="GUID-970828DC-81E0-506F-B96B-74DE79B38F1B"><title>Feature UIDs

example</title> <p>This code is an example of UIDs assigned to features to

be queried using the Feature Registry. </p> <codeblock id="GUID-71DAFE3B-381D-5F97-9449-CFF04DA91FCB" xml:space="preserve">namespace NFeature

    {

    const TUid KFax = {0x10279806};         // Sample only! Refer to true

    const TUid KPrint = {0x10279807};       // featureUIDs.h header file for

    const TUid KBluetooth = {0x10279808};   // actual names and UIDs (plus

    const TUid KInfrared = {0x10279809};    // proper in-code documentation

    const TUid KMmc = {0x1027980a};         // about each feature).

    const TUid KUsb = {0x1027980b};

    // . . .

    }</codeblock> </example>

</conbody><related-links>

<link href="GUID-747869DD-ECD1-5515-B876-0D7D753B1CD9.dita"><linktext>Optional

Features Query                 API</linktext></link>

<link href="GUID-9F9D6764-D86E-5665-B51A-04A4D3949FB4.dita"><linktext>Optional

Features                 Notification API</linktext></link>

<link href="GUID-F55EAA3A-5D30-5983-9053-7C3935D99802.dita"><linktext>Feature Registry

                Overview</linktext></link>