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+++ b/Symbian3/SDK/Source/GUID-547CF71C-6A62-57C0-A9BE-E76B4286C6D6.dita	Wed Mar 31 11:11:55 2010 +0100
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+<?xml version="1.0" encoding="utf-8"?>
+<!-- Copyright (c) 2007-2010 Nokia Corporation and/or its subsidiary(-ies) All rights reserved. -->
+<!-- This component and the accompanying materials are made available under the terms of the License 
+"Eclipse Public License v1.0" which accompanies this distribution, 
+and is available at the URL "http://www.eclipse.org/legal/epl-v10.html". -->
+<!-- Initial Contributors:
+    Nokia Corporation - initial contribution.
+Contributors: 
+-->
+<!DOCTYPE concept
+  PUBLIC "-//OASIS//DTD DITA Concept//EN" "concept.dtd">
+<concept id="GUID-547CF71C-6A62-57C0-A9BE-E76B4286C6D6" xml:lang="en"><title>Threads
+And Processes Overview</title><shortdesc>This document provides an overview of threads and processes.</shortdesc><prolog><metadata><keywords/></metadata></prolog><conbody>
+<section id="GUID-D894C473-2BCF-4988-BF07-435C7A779BAF"><title>Purpose</title> <p>Provides
+access to processes, threads, and thread-local storage.</p> <p>Processes are
+usually only manipulated directly by system programs. Threads can be directly
+manipulated by multi-threaded programs. Note however that the active objects
+framework provided by the Asynchronous Services API is usually preferred to
+multi-threading in Symbian platform programming.</p> </section>
+<section id="GUID-90EBDA3E-A7E1-4460-9A63-CDEC922AC58A"><title>Description</title> <p>The
+API has three key concepts: process, thread, and thread-local storage. </p> <p><b>Process</b> </p> <p>A program running in Symbian platform is a process,
+which can contains one or more conceptually concurrent threads of execution.
+Each user process has its own private address space. A process can create
+another process. </p> <p>Processes are Kernel objects and so are accessed
+by user programs through handles. </p> <p>The process handle interface is
+provided by <xref href="GUID-9DD1EA2B-DC59-315C-8E9C-CE6D9461B695.dita"><apiname>RProcess</apiname></xref>.</p> <p><xref href="GUID-71AF2BC3-5CCD-3561-8807-7B8CDC1A64E9.dita"><apiname>TFindProcess</apiname></xref> is
+used for finding another process.</p> <p><b>Thread</b> </p> <p>A thread is the unit of execution within a process. The scheduling
+of threads is pre-emptive, i.e. a currently executing thread may be suspended
+at any time to allow another thread to run.</p> <p>Note the following properties
+of threads:</p> <ul>
+<li id="GUID-7FA506FD-3F36-51AB-87C6-0A4415ED4257"><p>every process has a
+primary thread that is created when the process is initialised </p> </li>
+<li id="GUID-3C2107B8-2979-5835-8985-AC289C75AAA6"><p>a thread can create,
+suspend, resume, panic and kill other threads, subject to protection</p> </li>
+<li id="GUID-D4298E05-F3C7-59E9-9E05-EA43BAE51D93"><p>data can be passed between
+threads whether those threads are in different processes or the same process</p> </li>
+<li id="GUID-8EF7BA10-3BBA-568B-A0BE-00A6F4B58D6C"><p>each thread has a priority:
+the scheduler runs the highest-priority thread that is ready to run </p> </li>
+</ul> <p>Threads are Kernel objects and so are accessed by user programs through
+handles. </p> <p>The thread handle interface is provided by <xref href="GUID-B0E661BC-4058-3256-B9C3-5A4FD52F6DE5.dita"><apiname>RThread</apiname></xref>. </p> <p><xref href="GUID-29F27759-CC53-36DF-AE92-623F061D6C96.dita"><apiname>TFindThread</apiname></xref> is
+used for finding another thread.</p> <p>The System Static Functions API <xref href="GUID-C197C9A7-EA05-3F24-9854-542E984C612D.dita"><apiname>User</apiname></xref> class
+provides a number of functions that operate on the current thread.</p> <p><b>Thread-local storage</b> </p> <p>Thread-local storage in Symbian platform
+supports one machine word of static data per DLL per thread. The scope of
+the word is the thread and is only accessible to DLL code. DLL code running
+on behalf of one thread does not see the same word when running on behalf
+of another thread.</p> <p>The thread-local storage interface is provided by <xref href="GUID-6085A635-1664-323E-997A-EA11F75FBAC3.dita"><apiname>Dll</apiname></xref>.</p> </section>
+<section id="GUID-33582F5A-3ADA-434C-BDD2-503AA667BAE0"><title>See also</title> <p><xref href="GUID-1294F540-FDA7-5050-BAFB-3C9888491B98.dita">Asynchronous Services Overview</xref> </p> <p><xref href="GUID-FF8F5D97-7D37-5F6B-84A3-C064E2FD53E0.dita">System Static Functions Overview</xref> </p> </section>
+</conbody></concept>
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