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 <head>
 <title>ReadMe for ICU 64.2</title>
 <meta name="COPYRIGHT" content=
 "Copyright (C) 2016 and later: Unicode, Inc. and others. License &amp; terms of use: http://www.unicode.org/copyright.html"/>
 
 <meta name="KEYWORDS" content=
 "ICU; International Components for Unicode; ICU4C; what's new; readme; read me; introduction; downloads; downloading; building; installation;" />
 <meta name="DESCRIPTION" content=
 "The introduction to the International Components for Unicode with instructions on building, installation, usage and other information about ICU." />
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<body>
 
 Note: This is a draft readme.

<h1>
 DRAFT
 International Components for Unicode 
 Release Candidate
 (Milestone Release)
 <abbr title="International Components for Unicode">ICU</abbr> 64.2 ReadMe
 </h1>

This is a development milestone release of ICU
 This milestone is intended for those wishing to get an early look at new features and API changes.
 It is not recommended for production use.

This is a release candidate version of ICU4C.
 It is not recommended for production use.

Last updated: 2019-Apr-04 
 Copyright &copy; 2016 and later: Unicode, Inc. and others. License &amp; terms of use:
 <a href="http://www.unicode.org/copyright.html">http://www.unicode.org/copyright.html</a> 
 Copyright &copy; 1997-2016 International Business Machines Corporation and others.
 All Rights Reserved.
 
 <hr/>

<h2 class="TOC">Table of Contents</h2>

<ul class="TOC">
 <li><a href="#Introduction">Introduction</a></li>

<li><a href="#GettingStarted">Getting Started</a></li>

<li><a href="#News">What Is New In This Release?</a></li>

<li><a href="#Download">How To Download the Source Code</a></li>

<li><a href="#SourceCode">ICU Source Code Organization</a></li>

<li>
 <a href="#HowToBuild">How To Build And Install ICU</a>

<ul >
 <li><a href="#RecBuild">Recommended Build Options</a></li>

<li><a href="#UserConfig">User-Configurable Settings</a></li>

<li><a href="#HowToBuildWindows">Windows</a></li>

<li><a href="#HowToBuildCygwin">Cygwin</a></li>

<li><a href="#HowToBuildOS400">IBM i family (IBM i, i5/OS, OS/400)</a></li>

<li><a href="#HowToCrossCompileICU">How to Cross Compile ICU</a></li>
 </ul>
 </li>

<li><a href="#HowToPackage">How To Package ICU</a></li>

<li>
 <a href="#ImportantNotes">Important Notes About Using ICU</a>

<ul >
 <li><a href="#ImportantNotesMultithreaded">Using ICU in a Multithreaded
 Environment</a></li>

<li><a href="#ImportantNotesWindows">Windows Platform</a></li>

<li><a href="#ImportantNotesUNIX">UNIX Type Platforms</a></li>
 </ul>
 </li>

<li>
 <a href="#PlatformDependencies">Platform Dependencies</a>

<ul >
 <li><a href="#PlatformDependenciesNew">Porting To A New
 Platform</a></li>

<li><a href="#PlatformDependenciesImpl">Platform Dependent
 Implementations</a></li>
 </ul>
 </li>
 </ul>
 <hr />

<h2><a name="Introduction" href="#Introduction" id=
 "Introduction">Introduction</a></h2>

Today's software market is a global one in which it is desirable to
 develop and maintain one application (single source/single binary) that
 supports a wide variety of languages. The International Components for
 Unicode (ICU) libraries provide robust and full-featured Unicode services on
 a wide variety of platforms to help this design goal. The ICU libraries
 provide support for:

<ul>
 <li>The latest version of the Unicode standard</li>

<li>Character set conversions with support for over 220 codepages</li>

<li>Locale data for more than 300 locales</li>

<li>Language sensitive text collation (sorting) and searching based on the
 Unicode Collation Algorithm (=ISO 14651)</li>

<li>Regular expression matching and Unicode sets</li>

<li>Transformations for normalization, upper/lowercase, script
 transliterations (50+ pairs)</li>

<li>Resource bundles for storing and accessing localized information</li>

<li>Date/Number/Message formatting and parsing of culture specific
 input/output formats</li>

<li>Calendar specific date and time manipulation</li>

<li>Text boundary analysis for finding characters, word and sentence
 boundaries</li>
 </ul>

ICU has a sister project ICU4J that extends the internationalization
 capabilities of Java to a level similar to ICU. The ICU C/C++ project is also
 called ICU4C when a distinction is necessary.

<h2><a name="GettingStarted" href="#GettingStarted" id=
 "GettingStarted">Getting started</a></h2>

This document describes how to build and install ICU on your machine. For
 other information about ICU please see the following table of links. 
 The ICU homepage also links to related information about writing
 internationalized software.

<table class="docTable" summary="These are some useful links regarding ICU and internationalization in general.">
 <caption>
 Here are some useful links regarding ICU and internationalization in
 general.
 </caption>

<tr>
 <td>ICU, ICU4C &amp; ICU4J Homepage</td>

<td><a href=
 "http://icu-project.org/">http://icu-project.org/</a></td>
 </tr>

<tr>
 <td>FAQ - Frequently Asked Questions about ICU</td>

<td><a href=
 "http://userguide.icu-project.org/icufaq">http://userguide.icu-project.org/icufaq</a></td>
 </tr>

<tr>
 <td>ICU User's Guide</td>

<td><a href=
 "http://userguide.icu-project.org/">http://userguide.icu-project.org/</a></td>
 </tr>

<td><a href="http://userguide.icu-project.org/howtouseicu">http://userguide.icu-project.org/howtouseicu</a></td>
 </tr>

<tr>
 <td>Download ICU Releases</td>

<td><a href=
 "http://site.icu-project.org/download">http://site.icu-project.org/download</a></td>
 </tr>

<tr>
 <td>ICU4C API Documentation Online</td>

<td><a href=
 "http://icu-project.org/apiref/icu4c/">http://icu-project.org/apiref/icu4c/</a></td>
 </tr>

<tr>
 <td>Online ICU Demos</td>

<td><a href=
 "http://demo.icu-project.org/icu-bin/icudemos">http://demo.icu-project.org/icu-bin/icudemos</a></td>
 </tr>

<tr>
 <td>Contacts and Bug Reports/Feature Requests</td>

<td><a href=
 "http://site.icu-project.org/contacts">http://site.icu-project.org/contacts</a></td>
 </tr>
 </table>

Important: Please make sure you understand the <a href=
 "http://source.icu-project.org/repos/icu/trunk/icu4c/LICENSE">Copyright and License Information</a>.

<h2><a name="News" href="#News" id="News">What Is New In This Release?</a></h2>

See the <a href="http://site.icu-project.org/download/64">ICU 64 download page</a>
 for an overview of this release, important changes, new features, bug fixes, known issues,
 changes to supported platforms and build environments,
 and migration issues for existing applications migrating from previous ICU releases.

See the <a href="APIChangeReport.html">API Change Report</a> for a complete list of
 APIs added, removed, or changed in this release.

<a name="RecentPreviousChanges" id="RecentPreviousChanges"></a>For
 changes in previous releases, see the
 main <a href="http://site.icu-project.org/download">ICU download page</a>
 with its version-specific subpages.

<h2><a name="Download" href="#Download" id="Download">How To Download the
 Source Code</a></h2>

There are two ways to download ICU releases:

<ul>
 <li>Official Release Snapshot: 
 If you want to use ICU (as opposed to developing it), you should download
 an official packaged version of the ICU source code. These versions are
 tested more thoroughly than day-to-day development builds of the system,
 and they are packaged in zip and tar files for convenient download. These
 packaged files can be found at <a href=
 "http://site.icu-project.org/download">http://site.icu-project.org/download</a>. 
 The packaged snapshots are named icu-nnnn.zip or
 icu-nnnn.tgz, where nnnn is the version number. The .zip
 file is used for Windows platforms, while the .tgz file is preferred on
 most other platforms. 
 Please unzip this file. </li>

<li>GitHub Source Repository: 
 If you are interested in developing features, patches, or bug fixes for
 ICU, you should probably be working with the latest version of the ICU
 source code. You will need to clone and checkout the code from our GitHub repository to
 ensure that you have the most recent version of all of the files. See our
 <a href="http://site.icu-project.org/repository">source
 repository</a> for details.</li>
 </ul>

<h2><a name="SourceCode" href="#SourceCode" id="SourceCode">ICU Source Code
 Organization</a></h2>

In the descriptions below, &lt;ICU&gt; is the full
 path name of the ICU directory (the top level directory from the distribution
 archives) in your file system. You can also view the <a href=
 "http://userguide.icu-project.org/design">ICU Architectural
 Design</a> section of the User's Guide to see which libraries you need for
 your software product. You need at least the data (<code>[lib]icudt</code>)
 and the common (<code>[lib]icuuc</code>) libraries in order to use ICU.

<table class="docTable" summary="The following files describe the code drop.">
 <caption>
 The following files describe the code drop.
 </caption>

<th scope="col">Description</th>
 </tr>

<tr>
 <td>readme.html</td>

<td>Describes the International Components for Unicode (this file)</td>
 </tr>

<tr>
 <td>LICENSE</td>

<td>Contains the text of the ICU license</td>
 </tr>
 </table>

<table class="docTable" summary=
 "The following directories contain source code and data files.">
 <caption>
 The following directories contain source code and data files.
 </caption>

<tr>
 <th scope="col">Directory</th>

<th scope="col">Description</th>
 </tr>

<tr>
 <td>&lt;ICU&gt;/source/common/</td>

<td>The core Unicode and support functionality, such as resource bundles,
 character properties, locales, codepage conversion, normalization,
 Unicode properties, Locale, and UnicodeString.</td>
 </tr>

<tr>
 <td>&lt;ICU&gt;/source/i18n/</td>

<td>Modules in i18n are generally the more data-driven, that is to say
 resource bundle driven, components. These deal with higher-level
 internationalization issues such as formatting, collation, text break
 analysis, and transliteration.</td>
 </tr>

<tr>
 <td>&lt;ICU&gt;/source/layoutex/</td>

<td>Contains the ICU paragraph layout engine.</td>
 </tr>

<tr>
 <td>&lt;ICU&gt;/source/io/</td>

<td>Contains the ICU I/O library.</td>
 </tr>

<tr>
 <td>&lt;ICU&gt;/source/data/</td>

<td>
 This directory contains the source data in text format, which is
 compiled into binary form during the ICU build process. It contains
 several subdirectories, in which the data files are grouped by
 function. Note that the build process must be run again after any
 changes are made to this directory.

If some of the following directories are missing, it's probably
 because you got an official download. If you need the data source files
 for customization, then please download the complete ICU source code from <a
 href="http://site.icu-project.org/repository">the ICU repository</a>.

<ul>
 <li>in/ A directory that contains a pre-built data library for
 ICU. A standard source code package will contain this file without
 several of the following directories. This is to simplify the build
 process for the majority of users and to reduce platform porting
 issues.</li>

<li>brkitr/ Data files for character, word, sentence, title
 casing and line boundary analysis.</li>

<li>coll/ Data for collation tailorings. The makefile
 colfiles.mk contains the list of resource bundle files.</li>

<li>locales/ These .txt files contain ICU language and
 culture-specific localization data. Two special bundles are
 root, which is the fallback data and parent of other bundles,
 and index, which contains a list of installed bundles. The
 makefile resfiles.mk contains the list of resource bundle
 files. Some of the locale data is split out into the type-specific
 directories curr, lang, region, unit, and zone, described below.</li>

<li>curr/ Locale data for currency symbols and names (including
 plural forms), with its own makefile resfiles.mk.</li>

<li>lang/ Locale data for names of languages, scripts, and locale
 key names and values, with its own makefile resfiles.mk.</li>

<li>region/ Locale data for names of regions, with its own
 makefile resfiles.mk.</li>

<li>unit/ Locale data for measurement unit patterns and names, 
 with its own makefile resfiles.mk.</li>

<li>zone/ Locale data for time zone names, with its own
 makefile resfiles.mk.</li>

<li>mappings/ Here are the code page converter tables. These
 .ucm files contain mappings to and from Unicode. These are compiled
 into .cnv files. convrtrs.txt is the alias mapping table from
 various converter name formats to ICU internal format and vice versa.
 It produces cnvalias.icu. The makefiles ucmfiles.mk,
 ucmcore.mk, and ucmebcdic.mk contain the list of
 converters to be built.</li>

<li>translit/ This directory contains transliterator rules as
 resource bundles, a makefile trnsfiles.mk containing the list
 of installed system translitaration files, and as well the special
 bundle translit_index which lists the system transliterator
 aliases.</li>

<li>unidata/ This directory contains the Unicode data files.
 Please see <a href=
 "http://www.unicode.org/">http://www.unicode.org/</a> for more
 information.</li>

<li>misc/ The misc directory contains other data files which
 did not fit into the above categories, including time zone
 information, region-specific data, and other data derived from CLDR
 supplemental data.</li>

<li>out/ This directory contains the assembled memory mapped
 files.</li>

<li>out/build/ This directory contains intermediate (compiled)
 files, such as .cnv, .res, etc.</li>
 </ul>

If you are creating a special ICU build, you can set the ICU_DATA
 environment variable to the out/ or the out/build/ directories, but
 this is generally discouraged because most people set it incorrectly.
 You can view the <a href=
 "http://userguide.icu-project.org/icudata">ICU Data
 Management</a> section of the ICU User's Guide for details.
 </td>
 </tr>

<tr>
 <td>&lt;ICU&gt;/source/test/intltest/</td>

<td>A test suite including all C++ APIs. For information about running
 the test suite, see the build instructions specific to your platform
 later in this document.</td>
 </tr>

<tr>
 <td>&lt;ICU&gt;/source/test/cintltst/</td>

<td>A test suite written in C, including all C APIs. For information
 about running the test suite, see the build instructions specific to your
 platform later in this document.</td>
 </tr>

<tr>
 <td>&lt;ICU&gt;/source/test/iotest/</td>

<td>A test suite written in C and C++ to test the icuio library. For
 information about running the test suite, see the build instructions
 specific to your platform later in this document.</td>
 </tr>

<tr>
 <td>&lt;ICU&gt;/source/test/testdata/</td>

<td>Source text files for data, which are read by the tests. It contains
 the subdirectories out/build/ which is used for intermediate
 files, and out/ which contains testdata.dat.</td>
 </tr>

<tr>
 <td>&lt;ICU&gt;/source/tools/</td>

<td>Tools for generating the data files. Data files are generated by
 invoking &lt;ICU&gt;/source/data/build/makedata.bat on Win32 or
 &lt;ICU&gt;/source/make on UNIX.</td>
 </tr>

<tr>
 <td>&lt;ICU&gt;/source/samples/</td>

<td>Various sample programs that use ICU</td>
 </tr>

<tr>
 <td>&lt;ICU&gt;/source/extra/</td>

<td>Non-supported API additions. Currently, it contains the 'uconv' tool
 to perform codepage conversion on files.</td>
 </tr>

<tr>
 <td>&lt;ICU&gt;/packaging/</td>

<td>This directory contain scripts and tools for packaging the final
 ICU build for various release platforms.</td>
 </tr>

<tr>
 <td>&lt;ICU&gt;/source/config/</td>

<td>Contains helper makefiles for platform specific build commands. Used
 by 'configure'.</td>
 </tr>

<tr>
 <td>&lt;ICU&gt;/source/allinone/</td>

<td>Contains top-level ICU workspace and project files, for instance to
 build all of ICU under one MSVC project.</td>
 </tr>

<tr>
 <td>&lt;ICU&gt;/include/</td>

<td>Contains the headers needed for developing software that uses ICU on
 Windows.</td>
 </tr>

<td>Contains the import libraries for linking ICU into your Windows
 application.</td>
 </tr>

<td>Contains the libraries and executables for using ICU on Windows.</td>
 </tr>
 </table>

<h2><a name="HowToBuild" href="#HowToBuild" id="HowToBuild">How To Build And
 Install ICU</a></h2>

<h3><a name="RecBuild" href="#RecBuild" id=
 "RecBuild">Recommended Build Options</a></h3>

Depending on the platform and the type of installation,
 we recommend a small number of modifications and build options.
 Note that C99 compatibility is now required.
 <ul>
 <li>Namespace (ICU 61 and later):
 Since ICU 61, call sites need to qualify ICU types explicitly,
 for example <code>icu::UnicodeString</code>,
 or do <code>using icu::UnicodeString;</code> where appropriate.
 If your code relies on the "using namespace icu;" that used to be in unicode/uversion.h,
 then you need to update your code. 
 You could temporarily (until you have more time to update your code)
 revert to the default "using"
 via <code>-DU_USING_ICU_NAMESPACE=1</code>
 or by modifying unicode/uversion.h:
<pre>Index: icu4c/source/common/unicode/uversion.h
===================================================================
--- icu4c/source/common/unicode/uversion.h (revision 40704)
+++ icu4c/source/common/unicode/uversion.h (working copy)
@@ -127,7 +127,7 @@
 defined(U_LAYOUTEX_IMPLEMENTATION) || defined(U_TOOLUTIL_IMPLEMENTATION)
 # define U_USING_ICU_NAMESPACE 0
 # else
-# define U_USING_ICU_NAMESPACE 0
+# define U_USING_ICU_NAMESPACE 1
 # endif
 # endif
 # if U_USING_ICU_NAMESPACE
</pre>
 </li>
 <li>Namespace (ICU 60 and earlier): By default, unicode/uversion.h has
 "using namespace icu;" which defeats much of the purpose of the namespace.
 (This is for historical reasons: Originally, ICU4C did not use namespaces,
 and some compilers did not support them. The default "using" statement
 preserves source code compatibility.) 
 You should turn this off
 via <code>-DU_USING_ICU_NAMESPACE=0</code>
 or by modifying unicode/uversion.h:
<pre>Index: source/common/unicode/uversion.h
===================================================================
--- source/common/unicode/uversion.h (revision 26606)
+++ source/common/unicode/uversion.h (working copy)
@@ -180,7 +180,8 @@
 # define U_NAMESPACE_QUALIFIER U_ICU_NAMESPACE::

# ifndef U_USING_ICU_NAMESPACE
-# define U_USING_ICU_NAMESPACE 1
+ // Set to 0 to force namespace declarations in ICU usage.
+# define U_USING_ICU_NAMESPACE 0
 # endif
 # if U_USING_ICU_NAMESPACE
 U_NAMESPACE_USE
</pre>
 ICU call sites then either qualify ICU types explicitly,
 for example <code>icu::UnicodeString</code>,
 or do <code>using icu::UnicodeString;</code> where appropriate.</li>
 <li>Hardcode the default charset to UTF-8: On platforms where
 the default charset is always UTF-8,
 like MacOS X and some Linux distributions,
 we recommend hardcoding ICU's default charset to UTF-8.
 This means that some implementation code becomes simpler and faster,
 and statically linked ICU libraries become smaller.
 (See the <a href="http://icu-project.org/apiref/icu4c/platform_8h.html#a0a33e1edf3cd23d9e9c972b63c9f7943">U_CHARSET_IS_UTF8</a>
 API documentation for more details.) 
 You can <code>-DU_CHARSET_IS_UTF8=1</code> or
 modify unicode/utypes.h (in ICU 4.8 and below)
 or modify unicode/platform.h (in ICU 49 and higher):
<pre>Index: source/common/unicode/utypes.h
===================================================================
--- source/common/unicode/utypes.h (revision 26606)
+++ source/common/unicode/utypes.h (working copy)
@@ -160,7 +160,7 @@
 * @see UCONFIG_NO_CONVERSION
 */
 #ifndef U_CHARSET_IS_UTF8
-# define U_CHARSET_IS_UTF8 0
+# define U_CHARSET_IS_UTF8 1
 #endif

/*===========================================================================*/
</pre></li>
 <li>UnicodeString constructors: The UnicodeString class has
 several single-argument constructors that are not marked "explicit"
 for historical reasons.
 This can lead to inadvertent construction of a <code>UnicodeString</code>
 with a single character by using an integer,
 and it can lead to inadvertent dependency on the conversion framework
 by using a C string literal. 
 Beginning with ICU 49, you should do the following:
 <ul>
 <li>Consider marking the from-<code>UChar</code>
 and from-<code>UChar32</code> constructors explicit via
 <code>-DUNISTR_FROM_CHAR_EXPLICIT=explicit</code> or similar.</li>
 <li>Consider marking the from-<code>const char*</code> and
 from-<code>const UChar*</code> constructors explicit via
 <code>-DUNISTR_FROM_STRING_EXPLICIT=explicit</code> or similar.</li>
 </ul>
 Note: The ICU test suites cannot be compiled with these settings.
 </li>
 <li>utf.h, utf8.h, utf16.h, utf_old.h:
 By default, utypes.h (and thus almost every public ICU header)
 includes all of these header files.
 Often, none of them are needed, or only one or two of them.
 All of utf_old.h is deprecated or obsolete. 
 Beginning with ICU 49,
 you should define <code>U_NO_DEFAULT_INCLUDE_UTF_HEADERS</code> to 1
 (via -D or uconfig.h, as above)
 and include those header files explicitly that you actually need. 
 Note: The ICU test suites cannot be compiled with this setting.</li>
 <li>utf_old.h:
 All of utf_old.h is deprecated or obsolete. 
 Beginning with ICU 60,
 you should define <code>U_HIDE_OBSOLETE_UTF_OLD_H</code> to 1
 (via -D or uconfig.h, as above).
 Use of any of these macros should be replaced as noted
 in the comments for the obsolete macro. 
 Note: The ICU test suites can be compiled with this setting.</li>
 <li>.dat file: By default, the ICU data is built into
 a shared library (DLL). This is convenient because it requires no
 install-time or runtime configuration,
 but the library is platform-specific and cannot be modified.
 A .dat package file makes the opposite trade-off:
 Platform-portable (except for endianness and charset family, which
 can be changed with the icupkg tool)
 and modifiable (also with the icupkg tool).
 If a path is set, then single data files (e.g., .res files)
 can be copied to that location to provide new locale data
 or conversion tables etc. 
 The only drawback with a .dat package file is that the application
 needs to provide ICU with the file system path to the package file
 (e.g., by calling <code>u_setDataDirectory()</code>)
 or with a pointer to the data (<code>udata_setCommonData()</code>)
 before other ICU API calls.
 This is usually easy if ICU is used from an application where
 <code>main()</code> takes care of such initialization.
 It may be hard if ICU is shipped with
 another shared library (such as the Xerces-C++ XML parser)
 which does not control <code>main()</code>. 
 See the <a href="http://userguide.icu-project.org/icudata">User Guide ICU Data</a>
 chapter for more details. 
 If possible, we recommend building the .dat package.
 Specify <code>--with-data-packaging=archive</code>
 on the configure command line, as in 
 <code>runConfigureICU Linux --with-data-packaging=archive</code> 
 (Read the configure script's output for further instructions.
 On Windows, the Visual Studio build generates both the .dat package
 and the data DLL.) 
 Be sure to install and use the tiny stubdata library
 rather than the large data DLL.</li>
 <li>Static libraries: It may make sense to build the ICU code
 into static libraries (.a) rather than shared libraries (.so/.dll).
 Static linking reduces the overall size of the binary by removing
 code that is never called. 
 Example configure command line: 
 <code>runConfigureICU Linux --enable-static --disable-shared</code></li>
 <li>Out-of-source build: It is usually desirable to keep the ICU
 source file tree clean and have build output files written to
 a different location. This is called an "out-of-source build".
 Simply invoke the configure script from the target location:
<pre>~/icu$ git clone export https://github.com/unicode-org/icu.git
~/icu$ mkdir icu4c-build
~/icu$ cd icu4c-build
~/icu/icu4c-build$ ../icu/icu4c/source/runConfigureICU Linux
~/icu/icu4c-build$ make check</pre> 
 (Note: this example shows a relative path to
 <code>runConfigureICU</code>. If you experience difficulty,
 try using an absolute path to <code>runConfigureICU</code>
 instead.)
 </li>
 </ul>
 <h4>ICU as a System-Level Library</h4>
 If ICU is installed as a system-level library, there are further
 opportunities and restrictions to consider.
 For details, see the Using ICU as an Operating System Level Library
 section of the <a href="http://userguide.icu-project.org/design">User Guide ICU Architectural Design</a> chapter.
 <ul>
 <li>Data path: For a system-level library, it is best to load
 ICU data from the .dat package file because the file system path
 to the .dat package file can be hardcoded. ICU will automatically set
 the path to the final install location using U_ICU_DATA_DEFAULT_DIR.
 Alternatively, you can set <code>-DICU_DATA_DIR=/path/to/icu/data</code>
 when building the ICU code. (Used by source/common/putil.c.) 
 Consider also setting <code>-DICU_NO_USER_DATA_OVERRIDE</code>
 if you do not want the "ICU_DATA" environment variable to be used.
 (An application can still override the data path via
 <code>u_setDataDirectory()</code> or
 <code>udata_setCommonData()</code>.</li>
 <li>Hide draft API: API marked with <code>@draft</code>
 is new and not yet stable. Applications must not rely on unstable
 APIs from a system-level library.
 Define <code>U_HIDE_DRAFT_API</code>, <code>U_HIDE_INTERNAL_API</code>
 and <code>U_HIDE_SYSTEM_API</code>
 by modifying unicode/utypes.h before installing it.</li>
 <li>Only C APIs: Applications must not rely on C++ APIs from a
 system-level library because binary C++ compatibility
 across library and compiler versions is very hard to achieve.
 Most ICU C++ APIs are in header files that contain a comment with
 <code>\brief C++ API</code>.
 Consider not installing these header files.</li>
 <li>Disable renaming: By default, ICU library entry point names
 have an ICU version suffix. Turn this off for a system-level installation,
 to enable upgrading ICU without breaking applications. For example: 
 <code>runConfigureICU Linux --disable-renaming</code> 
 The public header files from this configuration must be installed
 for applications to include and get the correct entry point names.</li>
 </ul>

<h3><a name="UserConfig" href="#UserConfig" id="UserConfig">User-Configurable Settings</a></h3>
 ICU4C can be customized via a number of user-configurable settings.
 Many of them are controlled by preprocessor macros which are
 defined in the <code>source/common/unicode/uconfig.h</code> header file.
 Some turn off parts of ICU, for example conversion or collation,
 trading off a smaller library for reduced functionality.
 Other settings are recommended (see previous section)
 but their default values are set for better source code compatibility.

In order to change such user-configurable settings, you can
 either modify the <code>uconfig.h</code> header file by adding
 a specific <code>#define ...</code> for one or more of the macros
 before they are first tested,
 or set the compiler's preprocessor flags (<code>CPPFLAGS</code>) to include
 an equivalent <code>-D</code> macro definition.

<h3><a name="HowToBuildWindows" href="#HowToBuildWindows" id=
 "HowToBuildWindows">How To Build And Install On Windows</a></h3>

Building International Components for Unicode requires:

<ul>
 <li>Microsoft Windows</li>

<li>Microsoft Visual C++ (part of <a href="https://www.visualstudio.com/">Visual Studio</a>) (from either Visual Studio 2015 or Visual Studio 2017)</li>
 
 <li>Optional: A version of the <a href="https://developer.microsoft.com/windows/downloads">Windows 10 SDK</a> (if you want to build the UWP projects)</li>
 </ul>
 <a href="#HowToBuildCygwin">Cygwin</a> is required if using a version of MSVC other than the one
 compatible with the supplied project files or if other compilers are used to build ICU. (e.g. GCC)

The steps are:

<ol>
 <li>Unzip the <tt>icu-XXXX.zip</tt> file into any convenient location. 
 <ul class="no-left-margin">
 <li>You can use the built-in zip functionality of Windows Explorer to do this.
 Right-click on the .zip file and choose the "Extract All" option from the context menu.
 This will open a new window where you can choose the output location to put the files.</li>
 <li>Alternatively, you can use a 3rd party GUI tool like 7-Zip or WinZip to do this as well.</li>
 </ul>
 </li>

<li>Be sure that the ICU binary directory, (ex: &lt;ICU&gt;<tt>\bin\</tt>), is
 included in the PATH environment variable. The tests will
 not work without the location of the ICU DLL files in the path.
 Note that the binary directory name can depend on what architecture you select when you compile ICU.
 For x86 or 32-bit builds, the binary directory is "<tt>bin</tt>". Whereas for x64 or 64-bit builds
 the binary directory is "<tt>bin64</tt>".
 </li>

<li>Open the "&lt;ICU&gt;<tt>\source\allinone\allinone.sln</tt>" solution
 file in 'Visual Studio 2017'. (This solution includes all the
 International Components for Unicode libraries, necessary ICU building
 tools, and the test suite projects). Please see the 
 <a href="#HowToBuildWindowsCommandLine">command line note below</a> if you want to
 build from the command line instead.</li>

<li>If you are building using 'Visual Studio 2015' instead, or if you are building the UWP projects and you have a different
 version of the Windows 10 SDK installed you will first need to modify the two "<tt>Build.Windows.*.props</tt>" files
 in the "<tt>allinone</tt>" directory before you can open the "allinone" solution file.
 Please see the notes below about <a href="#HowToUseOtherVSVersions">building with other versions of Visual Studio</a> and the 
 notes on <a href="#HowToRetargetTheWin10SDK">re-targeting the Windows 10 SDK for the UWP projects</a> for details. Alternatively,
 you can <a href="#HowToSkipBuildingUWP">skip building the UWP projects</a> entirely as well.
 </li>
 
 <li>Set the active platform to "Win32" or "x64" (See <a href="#HowToBuildWindowsPlatform">Windows platform note</a> below)
 and configuration to "Debug" or "Release" (See <a href="#HowToBuildWindowsConfig">Windows configuration note</a> below).</li>

<li>Choose the "Build" menu and select "Rebuild Solution". If you want to
 build the Debug and Release at the same time, see the <a href=
 "#HowToBuildWindowsBatch">batch configuration note</a> below.</li>

<li>Run the tests. They can be run from the command line or from within Visual Studio.

<h4>Running the Tests from the Windows Command Line (cmd)</h4>
 <ul>
 <li>The general syntax is: 
 <div class="indent">
 <tt>&lt;ICU&gt;\source\allinone\icucheck.bat Platform Configuration</tt>
 </div>
 </li>
 <li>So, for example for x86 (32-bit) and Debug, use the following: 
 <samp>&lt;ICU&gt;\source\allinone\icucheck.bat x86 Debug</samp>
 For x86 (32-bit) and Release:
 <samp>&lt;ICU&gt;\source\allinone\icucheck.bat x86 Release</samp>
 For x64 (64-bit) and Debug:
 <samp>&lt;ICU&gt;\source\allinone\icucheck.bat x64 Debug</samp>
 For x64 (64-bit) and Release:
 <samp>&lt;ICU&gt;\source\allinone\icucheck.bat x64 Release</samp>
 </li>
 </ul>

<h4>Running the Tests from within Visual Studio</h4>

<ol>
 <li>Run the C++ test suite, "<tt>intltest</tt>". To do this: set the active startup
 project to "intltest", and press Ctrl+F5 to run it. Make sure that it
 passes without any errors.</li>

<li>Run the C test suite, "<tt>cintltst</tt>". To do this: set the active startup
 project to "cintltst", and press Ctrl+F5 to run it. Make sure that it
 passes without any errors.</li>

<li>Run the I/O test suite, "<tt>iotest</tt>". To do this: set the active startup
 project to "iotest", and press Ctrl+F5 to run it. Make sure that it passes
 without any errors.</li>
 </ol>
	 </li>

<li>You are now able to develop applications with ICU by using the
 libraries and tools in <tt>&lt;ICU&gt;\bin\</tt>. The headers are in
 <tt>&lt;ICU&gt;\include\</tt> and the link libraries are in
 <tt>&lt;ICU&gt;\lib\</tt>. To install the ICU runtime on a machine, or ship
 it with your application, copy the needed components from
 <tt>&lt;ICU&gt;\bin\</tt> to a location on the system PATH or to your
 application directory.</li>
 </ol>

<a name="HowToUseOtherVSVersions" id="HowToUseOtherVSVersions">
 Building with other versions of Visual Studio Note:</a>
 The particular version of the MSVC compiler tool-set (and thus the corresponding version of Visual Studio) that
 is used to compile ICU is determined by the "<tt>PlatformToolset</tt>" property. This property is stored in two
 different shared files that are used to set common configuration settings amongst the various ICU "<tt>*.vcxproj</tt>" project files.
 
 For the non-UWP projects, this setting is in the shared file called "<tt>Build.Windows.ProjectConfiguration.props</tt>" located
 in the "allinone" directory.
 
 For the UWP projects, this setting is in the shared file called "<tt>Build.Windows.UWP.ProjectConfiguration.props</tt>", also 
 located in the "allinone" directory.
 
 The value of <tt>v140</tt> corresponds to the Visual Studio 2015 compiler tool set, whereas the value of
 <tt>v141</tt> corresponds to the Visual Studio 2017 compiler tool set.
 
 In order to build the non-UWP projects with Visual Studio 2015 you will need to modify the file
 called "<tt>Build.Windows.ProjectConfiguration.props</tt>" to change the value of the <tt>PlatformToolset</tt> property.
 
 Note however that Visual Studio 2017 is required for building the UWP projects.
 
 
 Please consider: Using older versions of the MSVC compiler is generally not recommended due to the improved support for the C++11 standard
 in newer versions of the compiler.
 
 <a name="HowToRetargetTheWin10SDK" id="HowToRetargetTheWin10SDK">
 Re-targeting the Windows 10 SDK for the UWP projects Note:</a>
 
 If the version of the Windows 10 SDK that you have installed does not match the version used by the UWP projects, then you 
 will need to "retarget" them to use the version of the SDK that you have installed instead.
 
 There are two ways to do this:
 <ul>
 <li>In Visual Studio you can right-click on the UWP projects in the 'Solution Explorer' and select the
 option 'Retarget Projects' from the context menu. This will open up a window where you can select the
 SDK version to target from a drop-down list of the various SDKs that are installed on the machine.</li>

<li>Alternatively, you can manually edit the shared file called "<tt>Build.Windows.UWP.ProjectConfiguration.props</tt>"
 which is located in the "allinone" directory. You will need to change the of the
 "<tt>WindowsTargetPlatformVersion</tt>" property to the version of the SDK that you would like to use instead.</li>
 </ul>
 
 
 <a name="HowToBuildWindowsCommandLine" id=
 "HowToBuildWindowsCommandLine">Using MSBUILD At The Command Line Note:</a>
 You can build ICU from the command line instead of using the Visual Studio GUI.
 
 Assuming that you have properly installed Visual Studio to support command line building, you 
 should have a shortcut for the "Developer Command Prompt" listed in the Start Menu.
 (For Visual Studio 2017 you will need to install the "Desktop development with C++" option).
 
 <ul>
 <li>Open the "Developer Command Prompt" shortcut from the Start Menu. (This will open up a new command line window).</li>
 <li>From within the "Developer Command Prompt" change directory (<tt>cd</tt>) to the ICU source directory.</li>
 <li>You can then use either '<tt>msbuild</tt>' directly, or you can use the '<tt>devenv.com</tt>' command to build ICU.</li>
 <li>Using <tt>MSBUILD</tt>:</li>
 <ul class="no-left-margin">
 <li>To build the 32-bit Debug version, use the following command line: 
 <code>'msbuild source\allinone\allinone.sln /p:Configuration=Debug /p:Platform=Win32'</code>.</li>
 <li>To build the 64-bit Release version, use the following command line: 
 <code>'msbuild source\allinone\allinone.sln /p:Configuration=Release /p:Platform=x64'</code>.</li>
 </ul>
 <li>Using <tt>devenv.com</tt>:</li>
 <ul class="no-left-margin">
 <li>To build the 32-bit Debug version, use the following command line: 
 <code>'devenv.com source\allinone\allinone.sln /build "Debug|Win32"'</code>.</li>
 <li>To build the 64-bit Release version, use the following command line: 
 <code>'devenv.com source\allinone\allinone.sln /build "Release|x64"'</code>.</li>
 </ul>
 </ul>
 
 <a name="HowToSkipBuildingUWP" id=
 "HowToSkipBuildingUWP">Skipping the UWP Projects on the Command Line Note:</a>
 You can skip (or omit) building the UWP projects on the command line by passing the argument
 '<code>SkipUWP=true</code>' to either MSBUILD or devenv.
 
 <ul>
 <li>For example, using <tt>MSBUILD</tt>:</li>
 <ul class="no-left-margin">
 <li>To skip building the UWP projects with a 32-bit Debug build, use the following command line: 
 <code>'msbuild source\allinone\allinone.sln /p:Configuration=Debug /p:Platform=Win32 /p:SkipUWP=true'</code>.</li>
 <li>To skip building the UWP projects with a 64-bit Release version, use the following command line: 
 <code>'msbuild source\allinone\allinone.sln /p:Configuration=Release /p:Platform=x64 /p:SkipUWP=true'</code>.</li>
 </ul>
 </ul>
 
 You can also use Cygwin with the MSVC compiler to build ICU, and you can refer to the <a href=
 "#HowToBuildCygwin">How To Build And Install On Windows with Cygwin</a>
 section for more details.

<a name="HowToBuildWindowsPlatform" id=
 "HowToBuildWindowsPlatform">Setting Active Platform
 Note:</a> Even though you are able to select "x64" as the active platform, if your operating system is
 not a 64 bit version of Windows, the build will fail. To set the active platform, two different possibilities are:

<ul>
 <li>Choose "Build" menu, select "Configuration Manager...", and select
 "Win32" or "x64" for the Active Platform Solution.</li>

<li>Another way is to select the desired build configuration from "Solution
 Platforms" dropdown menu from the standard toolbar. It will say
 "Win32" or "x64" in the dropdown list.</li>
 </ul>

<a name="HowToBuildWindowsConfig" id=
 "HowToBuildWindowsConfig">Setting Active Configuration
 Note:</a> To set the active configuration, two different
 possibilities are:

<ul>
 <li>Choose "Build" menu, select "Configuration Manager...", and select
 "Release" or "Debug" for the Active Configuration Solution.</li>

<li>Another way is to select the desired build configuration from "Solution
 Configurations" dropdown menu from the standard toolbar. It will say
 "Release" or "Debug" in the dropdown list.</li>
 </ul>

<a name="HowToBuildWindowsBatch" id="HowToBuildWindowsBatch">Batch
 Configuration Note:</a> If you want to build the Win32 and x64 platforms and
 Debug and Release configurations at the same time, choose "Build" menu, and select "Batch
 Build...". Click the "Select All" button, and then click the "Rebuild"
 button.

<h3><a name="HowToBuildCygwin" href="#HowToBuildCygwin" id=
 "HowToBuildCygwin">How To Build And Install On Windows with Cygwin</a></h3>

Building International Components for Unicode with this configuration
 requires:

<ul>
 <li>Microsoft Windows</li>

<li>Microsoft Visual C++ (from Visual Studio 2015 or newer, when gcc isn't used).</li>

<li>
 Cygwin with the following installed:

<li>ranlib</li>

<li>man (if you plan to look at the man pages)</li>
 </ul>
 </li>
 </ul>

There are two ways you can build ICU with Cygwin. You can build with gcc
 or Microsoft Visual C++. If you use gcc, the resulting libraries and tools
 will depend on the Cygwin environment. If you use Microsoft Visual C++, the
 resulting libraries and tools do not depend on Cygwin and can be more easily
 distributed to other Windows computers (the generated man pages and shell
 scripts still need Cygwin). To build with gcc, please follow the "<a href=
 "#HowToBuildUNIX">How To Build And Install On UNIX</a>" instructions, while
 you are inside a Cygwin bash shell. To build with Microsoft Visual C++,
 please use the following instructions:

<ol>
 <li>Start the Windows "Command Prompt" window. This is different from the
 gcc build, which requires the Cygwin Bash command prompt. The Microsoft
 Visual C++ compiler will not work with a bash command prompt.</li>

<li>If the computer isn't set up to use Visual C++ from the command line,
 you need to run vcvars32.bat. For example: 
 "<tt>C:\Program Files (x86)\Microsoft Visual Studio 14.0\VC\bin\vcvars32.bat</tt>"
 can be used for 32-bit builds or 
 "<tt>C:\Program Files (x86)\Microsoft Visual Studio 14\VC\bin\x86_amd64\vcvarsx86_amd64.bat</tt>"
 can be used for 64-bit builds on Windows x64.</li>

<li>Unzip the icu-XXXX.zip file into any convenient location. Using command
 line zip, type "unzip -a icu-XXXX.zip -d drive:\directory", or just use
 WinZip.</li>

<li>Change directory to "icu/source", which is where you unzipped ICU.</li>

<li>Run "<tt>bash <a href="source/runConfigureICU">./runConfigureICU</a>
 Cygwin/MSVC</tt>" (See <a href="#HowToWindowsConfigureICU">Windows
 configuration note</a> and non-functional configure options below).</li>

<li>Type <tt>"make"</tt> to compile the libraries and all the data files.
 This make command should be GNU make.</li>

<li>Optionally, type <tt>"make check"</tt> to run the test suite, which
 checks for ICU's functionality integrity (See <a href=
 "#HowToTestWithoutGmake">testing note</a> below).</li>

<li>Type <tt>"make install"</tt> to install ICU. If you used the --prefix=
 option on configure or runConfigureICU, ICU will be installed to the
 directory you specified. (See <a href="#HowToInstallICU">installation
 note</a> below).</li>
 </ol>

<a name="HowToWindowsConfigureICU" id=
 "HowToWindowsConfigureICU">Configuring ICU on Windows
 NOTE:</a> 
 
 Ensure that the order of the PATH is MSVC, Cygwin, and then other PATHs. The configure
 script needs certain tools in Cygwin (e.g. grep).
 
 
 Also, you may need to run <tt>"dos2unix.exe"</tt> on all of the scripts (e.g. configure)
 in the top source directory of ICU. To avoid this issue, you can download
 the ICU source for Unix platforms (icu-xxx.tgz).
 
 In addition to the Unix <a href=
 "#HowToConfigureICU">configuration note</a> the following configure options
 currently do not work on Windows with Microsoft's compiler. Some options can
 work by manually editing <tt>icu/source/common/unicode/pwin32.h</tt>, but
 manually editing the files is not recommended.

<ul>
 <li><tt>--disable-renaming</tt></li>

<li><tt>--enable-tracing</tt></li>

<li><tt>--enable-rpath</tt></li>

<li><tt>--enable-static</tt> (Requires that U_STATIC_IMPLEMENTATION be
 defined in user code that links against ICU's static libraries.)</li>

<li><tt>--with-data-packaging=files</tt> (The pkgdata tool currently does
 not work in this mode. Manual packaging is required to use this mode.)</li>
 </ul>

<h3><a name="HowToBuildUNIX" href="#HowToBuildUNIX" id="HowToBuildUNIX">How
 To Build And Install On UNIX</a></h3>

Building International Components for Unicode on UNIX requires:

<ul>
 <li>A C++ compiler installed on the target machine (for example: gcc, CC,
 xlC_r, aCC, cxx, etc...).</li>

<li>An ANSI C compiler installed on the target machine (for example:
 cc).</li>

<li>A recent version of GNU make (3.80+).</li>

<li>For a list of z/OS tools please view the <a href="#HowToBuildZOS">z/OS
 build section</a> of this document for further details.</li>
 </ul>

Here are the steps to build ICU:

<ol>
 <li>Decompress the icu-X.Y.tgz (or
 icu-X.Y.tar.gz) file. For example, <samp>gunzip -d &lt; icu-X.Y.tgz | tar xvf -</samp></li>

<li>Change directory to <code>icu/source</code>.
 <samp>cd icu/source</samp>
 </li>

<li>Some files may have the wrong permissions.<samp>chmod +x runConfigureICU configure install-sh</samp></li>

<li>Run the <a href="source/runConfigureICU">runConfigureICU</a>
 script for your platform. (See <a href="#HowToConfigureICU">configuration
 note</a> below).</li>

<li>Now build: <samp>gmake</samp> (or just <code>make</code> if GNU make is the default make on
 your platform) to compile the libraries and all the data files. The proper
 name of the GNU make command is printed at the end of the configuration
 run, as in <tt>"You must use gmake to compile ICU"</tt>.
 
 Note that the compilation command output may be simplified on your platform. If this is the case, you will see just:
 <tt>gcc ... stubdata.c</tt>
 rather than
 <tt>gcc -DU_NO_DEFAULT_INCLUDE_UTF_HEADERS=1 -D_REENTRANT -I../common -DU_ATTRIBUTE_DEPRECATED= -O2 -Wall -std=c99 -pedantic -Wshadow -Wpointer-arith -Wmissing-prototypes -Wwrite-strings -c -DPIC -fPIC -o stubdata.o stubdata.c</tt>
 
 If you need to see the whole compilation line, use "gmake VERBOSE=1". The full compilation line will print if an error occurs.
 </li>

<li>Optionally,<samp>gmake check</samp> will run the test suite, which
 checks for ICU's functionality integrity (See <a href=
 "#HowToTestWithoutGmake">testing note</a> below).</li>

<li>To install, <samp>gmake install</samp> to install ICU. If you used the --prefix=
 option on configure or runConfigureICU, ICU will be installed to the
 directory you specified. (See <a href="#HowToInstallICU">installation
 note</a> below).</li>
 </ol>

<a name="HowToConfigureICU" id="HowToConfigureICU">Configuring ICU
 NOTE:</a> Type <tt>"./runConfigureICU --help"</tt> for help on how
 to run it and a list of supported platforms. You may also want to type
 <tt>"./configure --help"</tt> to print the available configure options that
 you may want to give runConfigureICU. If you are not using the
 runConfigureICU script, or your platform is not supported by the script, you
 may need to set your CC, CXX, CFLAGS and CXXFLAGS environment variables, and
 type <tt>"./configure"</tt>.
 HP-UX users, please see this <a href="#ImportantNotesHPUX">note regarding
 HP-UX multithreaded build issues</a> with newer compilers. Solaris users,
 please see this <a href="#ImportantNotesSolaris">note regarding Solaris
 multithreaded build issues</a>.

ICU is built with strict compiler warnings enabled by default. If this
 causes excessive numbers of warnings on your platform, use the --disable-strict
 option to configure to reduce the warning level.

<a name="HowToTestWithoutGmake" id="HowToTestWithoutGmake">Running
 The Tests From The Command Line NOTE:</a> You may have to set
 certain variables if you with to run test programs individually, that is
 apart from "gmake check". The environment variable ICU_DATA
 can be set to the full pathname of the data directory to indicate where the
 locale data files and conversion mapping tables are when you are not using
 the shared library (e.g. by using the .dat archive or the individual data
 files). The trailing "/" is required after the directory name (e.g.
 "$Root/source/data/out/" will work, but the value "$Root/source/data/out" is
 not acceptable). You do not need to set ICU_DATA if the
 complete shared data library is in your library path.

<a name="HowToInstallICU" id="HowToInstallICU">Installing ICU
 NOTE:</a> Some platforms use package management tools to control the
 installation and uninstallation of files on the system, as well as the
 integrity of the system configuration. You may want to check if ICU can be
 packaged for your package management tools by looking into the "packaging"
 directory. (Please note that if you are using a snapshot of ICU from Git, it
 is probable that the packaging scripts or related files are not up to date
 with the contents of ICU at this time, so use them with caution).

<h3><a name="HowToBuildZOS" href="#HowToBuildZOS" id="HowToBuildZOS">How To
 Build And Install On z/OS (OS/390)</a></h3>

You can install ICU on z/OS or OS/390 (the previous name of z/OS), but IBM
 tests only the z/OS installation. You install ICU in a z/OS UNIX system
 services file system such as HFS or zFS. On this platform, it is important
 that you understand a few details:

<ul>
 <li>The makedep and GNU make tools are required for building ICU. If it
 is not already installed on your system, it is available at the <a href=
 "http://www-03.ibm.com/servers/eserver/zseries/zos/unix/bpxa1toy.html">z/OS UNIX -
 Tools and Toys</a> site. The PATH environment variable should be updated to
 contain the location of this executable prior to build. Failure to add these
 tools to your PATH will cause ICU build failures or cause pkgdata to fail
 to run.</li>

<li>Since USS does not support using the mmap() function over NFS, it is
 recommended that you build ICU on a local filesystem. Once ICU has been
 built, you should not have this problem while using ICU when the data
 library has been built as a shared library, which is this is the default
 setting.</li>

<li>Encoding considerations: The source code assumes that it is compiled
 with codepage ibm-1047 (to be exact, the UNIX System Services variant of
 it). The pax command converts all of the source code files from ASCII to
 codepage ibm-1047 (USS) EBCDIC. However, some files are binary files and
 must not be converted, or must be converted back to their original state.
 You can use the <a href="as_is/os390/unpax-icu.sh">unpax-icu.sh</a> script
 to do this for you automatically. It will unpackage the tar file and
 convert all the necessary files for you automatically.</li>

<li>z/OS supports both native S/390 hexadecimal floating point and (with
 OS/390 2.6 and later) IEEE 754 binary floating point. This is a compile
 time option. Applications built with IEEE should use ICU DLLs that are
 built with IEEE (and vice versa). The environment variable IEEE390=0 will
 cause the z/OS version of ICU to be built without IEEE floating point
 support and use the native hexadecimal floating point. By default ICU is
 built with IEEE 754 support. Native floating point support is sufficient
 for codepage conversion, resource bundle and UnicodeString operations, but
 the Format APIs require IEEE binary floating point.</li>

<li>z/OS introduced the concept of Extra Performance Linkage (XPLINK) to
 bring performance improvement opportunities to call-intensive C and C++
 applications such as ICU. XPLINK is enabled on a DLL-by-DLL basis, so if
 you are considering using XPLINK in your application that uses ICU, you
 should consider building the XPLINK-enabled version of ICU. You need to
 set ICU's environment variable <code>OS390_XPLINK=1</code> prior to
 invoking the make process to produce binaries that are enabled for
 XPLINK. The XPLINK option, which is available for z/OS 1.2 and later,
 requires the PTF PQ69418 to build XPLINK enabled binaries.</li>

<li>ICU requires XPLINK for the icuio library. If you want to use the
 rest of ICU without XPLINK, then you must use the --disable-icuio
 configure option.</li>

<li>The latest versions of z/OS use <a
 href="https://www.ibm.com/support/knowledgecenter/SSLTBW_2.2.0/com.ibm.zos.v2r2.cbcux01/oebind6.htm">XPLINK
 version (C128) of the C++ standard library</a> by default. You may see <a
 href="https://www.ibm.com/support/knowledgecenter/SSLTBW_2.2.0/com.ibm.zos.v2r2.cbcux01/oebind5.htm">an
 error</a> when running with XPLINK disabled. To avoid this error,
 set the following environment variable or similar:

<pre><samp>export _CXX_PSYSIX="CEE.SCEELIB(C128N)":"CBC.SCLBSID(IOSTREAM,COMPLEX)"</samp></pre>
 </li>

<li>When building ICU data, the heap size may need to be increased with the following
 environment variable:

<pre><samp>export _CEE_RUNOPTS="HEAPPOOLS(ON),HEAP(4M,1M,ANY,FREE,0K,4080)"</samp></pre>
 </li>

<li>The rest of the instructions for building and testing ICU on z/OS with
 UNIX System Services are the same as the <a href="#HowToBuildUNIX">How To
 Build And Install On UNIX</a> section.</li>
 </ul>

<h4>z/OS (Batch/PDS) support outside the UNIX system services
 environment</h4>

By default, ICU builds its libraries into the UNIX file system (HFS). In
 addition, there is a z/OS specific environment variable (OS390BATCH) to build
 some libraries into the z/OS native file system. This is useful, for example,
 when your application is externalized via Job Control Language (JCL).

The OS390BATCH environment variable enables non-UNIX support including the
 batch environment. When OS390BATCH is set, the libicui18nXX.dll,
 libicuucXX.dll, and libicudtXXe.dll binaries are built into
 data sets (the native file system). Turning on OS390BATCH does not turn off
 the normal z/OS UNIX build. This means that the z/OS UNIX (HFS) DLLs will
 always be created.

Two additional environment variables indicate the names of the z/OS data
 sets to use. The LOADMOD environment variable identifies the name of the data
 set that contains the dynamic link libraries (DLLs) and the LOADEXP
 environment variable identifies the name of the data set that contains the
 side decks, which are normally the files with the .x suffix in the UNIX file
 system.

A data set is roughly equivalent to a UNIX or Windows file. For most kinds
 of data sets the operating system maintains record boundaries. UNIX and
 Windows files are byte streams. Two kinds of data sets are PDS and PDSE. Each
 data set of these two types contains a directory. It is like a UNIX
 directory. Each "file" is called a "member". Each member name is limited to
 eight bytes, normally EBCDIC.

Here is an example of some environment variables that you can set prior to
 building ICU:
<pre>
<samp>OS390BATCH=1
LOADMOD=USER.ICU.LOAD
LOADEXP=USER.ICU.EXP</samp>
</pre>

The PDS member names for the DLL file names are as follows:
<pre>
<samp>IXMIXXIN --&gt; libicui18nXX.dll
IXMIXXUC --&gt; libicuucXX.dll
IXMIXXDA --&gt; libicudtXXe.dll</samp>
</pre>

You should point the LOADMOD environment variable at a partitioned data
 set extended (PDSE) and point the LOADEXP environment variable at a
 partitioned data set (PDS). The PDSE can be allocated with the following
 attributes:
<pre>
<samp>Data Set Name . . . : USER.ICU.LOAD
Management class. . : **None**
Storage class . . . : BASE
Volume serial . . . : TSO007
Device type . . . . : 3390
Data class. . . . . : LOAD
Organization . . . : PO
Record format . . . : U
Record length . . . : 0
Block size . . . . : 32760
1st extent cylinders: 1
Secondary cylinders : 5
Data set name type : LIBRARY</samp>
</pre>

The PDS can be allocated with the following attributes:
<pre>
<samp>Data Set Name . . . : USER.ICU.EXP
Management class. . : **None**
Storage class . . . : BASE
Volume serial . . . : TSO007
Device type . . . . : 3390
Data class. . . . . : **None**
Organization . . . : PO
Record format . . . : FB
Record length . . . : 80
Block size . . . . : 3200
1st extent cylinders: 3
Secondary cylinders : 3
Data set name type : PDS</samp>
</pre>

<h3><a name="HowToBuildOS400" href="#HowToBuildOS400" id=
 "HowToBuildOS400">How To Build And Install On The IBM i Family (IBM i, i5/OS OS/400)</a></h3>

Before you start building ICU, ICU requires the following:

<ul>
 <li>QSHELL interpreter installed (install base option 30, operating system)
 </li>

<li>ILE C/C++ Compiler installed on the system</li>

<li>The latest IBM tools for Developers for IBM i &mdash;
 <a href='https://www-356.ibm.com/partnerworld/wps/servlet/ContentHandler/pw_com_porting_tools_index'>https://www-356.ibm.com/partnerworld/wps/servlet/ContentHandler/pw_com_porting_tools_index</a>
 
 
 </li>
 </ul>

The following describes how to setup and build ICU. For background
 information, you should look at the <a href="#HowToBuildUNIX">UNIX build
 instructions</a>.

<ol>
 <li>
 Copy the ICU source .tgz to the IBM i environment, as binary.
 Also, copy the <a href='as_is/os400/unpax-icu.sh'>unpax-icu.sh</a> script into the same directory, as a text file.
 </li>

<li>
 Create target library. This library will be the target for the
 resulting modules, programs and service programs. You will specify this
 library on the OUTPUTDIR environment variable.
<pre>
<samp>CRTLIB LIB(libraryname)
ADDENVVAR ENVVAR(OUTPUTDIR) VALUE('libraryname') REPLACE(*YES) </samp></pre>
 </li>

<li>
 Set up the following environment variables and job characteristics in your build process
<pre>
<samp>ADDENVVAR ENVVAR(MAKE) VALUE('gmake') REPLACE(*YES)
CHGJOB CCSID(37)</samp></pre></li>

<li>Fire up the QSH (all subsequent commands are run inside the qsh session.)
 <pre><samp>qsh</samp></pre>
 </li>

<li>Set up the PATH: <pre><samp>export PATH=/QIBM/ProdData/DeveloperTools/qsh/bin:$PATH:/QOpenSys/usr/bin</samp></pre>
 </li>

<li>Unpack the ICU source code archive:
 <pre><samp>gzip -d icu-X.Y.tgz</samp></pre>
 </li>

<li>Run unpax-icu.sh on the tar file generated from the previous step.
 <pre><samp>unpax-icu.sh icu.tar</samp></pre></li>

<li>Build the program ICULD which ICU will use for linkage.
 <pre><samp>cd icu/as_is/os400
qsh bldiculd.sh
cd ../../..</samp></pre>
 </li>

<li>Change into the 'source' directory, and configure ICU. (See <a href="#HowToConfigureICU">configuration
 note</a> for details). Note that --with-data-packaging=archive and setting the --prefix are recommended, building in default (dll) mode is currently not supported.
 <pre><samp>cd icu/source
./runConfigureICU IBMi --prefix=/path/to/somewhere --with-data-packaging=archive</samp></pre>
</li>

<li>Build ICU. (Note: Do not use the -j option) <pre><samp>gmake</samp></pre></li>

<li>Test ICU. <pre><samp>gmake check</samp></pre>
 (The <tt> QIBM_MULTI_THREADED=Y</tt> flag will be automatically applied to intltest -
 you can look at the <a href=
 "https://www.ibm.com/support/knowledgecenter/ssw_ibm_i_73/rzahw/rzahwceeco.htm">
 iSeries Information Center</a> for more details regarding the running of multiple threads
 on IBM i.)</li>
 </ol>

<h3><a name="HowToCrossCompileICU" href="#HowToCrossCompileICU" id="HowToCrossCompileICU">How To Cross Compile ICU</a></h3>
		This section will explain how to build ICU on one platform, but to produce binaries intended to run on another. This is commonly known as a cross compile.
		Normally, in the course of a build, ICU needs to run the tools that it builds in order to generate and package data and test-data.In a cross compilation setting, ICU is built on a different system from that which it eventually runs on. An example might be, if you are building for a small/headless system (such as an embedded device), or a system where you can't easily run the ICU command line tools (any non-UNIX-like system).
		To reduce confusion, we will here refer to the "A" and the "B" system.System "A" is the actual system we will be running on- the only requirements on it is are it is able to build ICU from the command line targetting itself (with configure or runConfigureICU), and secondly, that it also contain the correct toolchain for compiling and linking for the resultant platform, referred to as the "B" system.
		The autoconf docs use the term "build" for A, and "host" for B. More details at: <a href="http://www.gnu.org/software/autoconf/manual/html_node/Specifying-Names.html#Specifying-Names">http://www.gnu.org/software/autoconf/manual/html_node/Specifying-Names.html</a>
		Three initially-empty directories will be used in this example:
		<table summary="Three directories used in this example" class="docTable">
			<tr>
				<th align="left">/icu</th><td>a copy of the ICU source</td>
			</tr>
			<tr>
				<th align="left">/buildA</th><td>an empty directory, it will contain ICU built for A (MacOSX in this case)</td>
			</tr>
			<tr>
				<th align="left">/buildB</th><td>an empty directory, it will contain ICU built for B (HaikuOS in this case)</td>
			</tr>
		</table>

<ol>
		<li>Check out or unpack the ICU source code into the /icu directory.You will have the directories /icu/source, etc.</li>
		<li>Build ICU in /buildA normally (using runConfigureICU or configure):
<pre class="samp">cd /buildA
sh /icu/source/runConfigureICU MacOSX
gnumake
</pre>
		</li>
		<li>Set PATH or other variables as needed, such as CPPFLAGS.</li>
		<li>Build ICU in /buildB 
			"<code>--with-cross-build</code>" takes an absolute path.
<pre class="samp">cd /buildB
sh /icu/source/configure --host=i586-pc-haiku --with-cross-build=/buildA
gnumake</pre>
		</li>
		<li>Tests and testdata can be built with "gnumake tests".</li>
	</ol>

<h2><a name="HowToPackage" href="#HowToPackage" id="HowToPackage">How To
 Package ICU</a></h2>

There are many ways that a person can package ICU with their software
 products. Usually only the libraries need to be considered for packaging.

On UNIX, you should use "<tt>gmake install</tt>" to make it easier to
 develop and package ICU. The bin, lib and include directories are needed to
 develop applications that use ICU. These directories will be created relative
 to the "<tt>--prefix=</tt>dir" configure option (See the <a href=
 "#HowToBuildUNIX">UNIX build instructions</a>). When ICU is built on Windows,
 a similar directory structure is built.

When changes have been made to the standard ICU distribution, it is
 recommended that at least one of the following guidelines be followed for
 special packaging.

<ol>
 <li>Add a suffix name to the library names. This can be done with the
 --with-library-suffix configure option.</li>

<li>The installation script should install the ICU libraries into the
 application's directory.</li>
 </ol>

Following these guidelines prevents other applications that use a standard
 ICU distribution from conflicting with any libraries that you need. On
 operating systems that do not have a standard C++ ABI (name mangling) for
 compilers, it is recommended to do this special packaging anyway. More
 details on customizing ICU are available in the <a href=
 "http://userguide.icu-project.org/">User's Guide</a>. The <a href=
 "#SourceCode">ICU Source Code Organization</a> section of this readme.html
 gives a more complete description of the libraries.

<table class="docTable" summary=
 "ICU has several libraries for you to use.">
 <caption>
 Here is an example of libraries that are frequently packaged.
 </caption>

<tr>
 <th scope="col">Library Name</th>

<th scope="col">Windows Filename</th>

<th scope="col">Linux Filename</th>

<th scope="col">Comment</th>
 </tr>

<tr>
 <td>Data Library</td>

<td>icudtXYl.dll</td>

<td>libicudata.so.XY.Z</td>

<td>Data required by the Common and I18n libraries. There are many ways
 to package and <a href=
 "http://userguide.icu-project.org/icudata">customize this
 data</a>, but by default this is all you need.</td>
 </tr>

<tr>
 <td>Common Library</td>

<td>icuucXY.dll</td>

<td>libicuuc.so.XY.Z</td>

<td>Base library required by all other ICU libraries.</td>
 </tr>

<tr>
 <td>Internationalization (i18n) Library</td>

<td>icuinXY.dll</td>

<td>libicui18n.so.XY.Z</td>

<td>A library that contains many locale based internationalization (i18n)
 functions.</td>
 </tr>

<tr>
 <td>Layout Extensions Engine</td>

<td>iculxXY.dll</td>

<td>libiculx.so.XY.Z</td>

<td>An optional engine for doing paragraph layout that uses
 parts of ICU.
 HarfBuzz is required.</td>
 </tr>

<tr>
 <td>ICU I/O (Unicode stdio) Library</td>

<td>icuioXY.dll</td>

<td>libicuio.so.XY.Z</td>

<td>An optional library that provides a stdio like API with Unicode
 support.</td>
 </tr>

<tr>
 <td>Tool Utility Library</td>

<td>icutuXY.dll</td>

<td>libicutu.so.XY.Z</td>

<td>An internal library that contains internal APIs that are only used by
 ICU's tools. If you do not use ICU's tools, you do not need this
 library.</td>
 </tr>
 </table>

Normally only the above ICU libraries need to be considered for packaging.
 The versionless symbolic links to these libraries are only needed for easier
 development. The X, Y and Z parts of the name are the
 version numbers of ICU. For example, ICU 2.0.2 would have the name
 libicuuc.so.20.2 for the common library. The exact format of the library
 names can vary between platforms due to how each platform can handles library
 versioning.

<h2><a name="ImportantNotes" href="#ImportantNotes" id=
 "ImportantNotes">Important Notes About Using ICU</a></h2>

<h3><a name="ImportantNotesMultithreaded" href="#ImportantNotesMultithreaded"
 id="ImportantNotesMultithreaded">Using ICU in a Multithreaded
 Environment</a></h3>

Some versions of ICU require calling the <code>u_init()</code> function
 from <code>uclean.h</code> to ensure that ICU is initialized properly. In
 those ICU versions, <code>u_init()</code> must be called before ICU is used
 from multiple threads. There is no harm in calling <code>u_init()</code> in a
 single-threaded application, on a single-CPU machine, or in other cases where
 <code>u_init()</code> is not required.

In addition to ensuring thread safety, <code>u_init()</code> also attempts
 to load at least one ICU data file. Assuming that all data files are packaged
 together (or are in the same folder in files mode), a failure code from
 <code>u_init()</code> usually means that the data cannot be found. In this
 case, the data may not be installed properly, or the application may have
 failed to call <code>udata_setCommonData()</code> or
 <code>u_setDataDirectory()</code> which specify to ICU where it can find its
 data.

Since <code>u_init()</code> will load only one or two data files, it
 cannot guarantee that all of the data that an application needs is available.
 It cannot check for all data files because the set of files is customizable,
 and some ICU services work without loading any data at all. An application
 should always check for error codes when opening ICU service objects (using
 <code>ucnv_open()</code>, <code>ucol_open()</code>, C++ constructors,
 etc.).

<h4>ICU 3.4 and later</h4>

ICU 3.4 self-initializes properly for multi-threaded use. It achieves this
 without performance penalty by hardcoding the core Unicode properties data,
 at the cost of some flexibility. (For details see Jitterbug 4497.)

<code>u_init()</code> can be used to check for data loading. It tries to
 load the converter alias table (<code>cnvalias.icu</code>).

These ICU versions require a call to <code>u_init()</code> before
 multi-threaded use. The services that are directly affected are those that
 don't have a service object and need to be fast: normalization and character
 properties.

<code>u_init()</code> loads and initializes the data files for
 normalization and character properties (<code>unorm.icu</code> and
 <code>uprops.icu</code>) and can therefore also be used to check for data
 loading.

<h4>ICU 2.4 and earlier</h4>

ICU 2.4 and earlier versions were not prepared for multithreaded use on
 multi-CPU platforms where the CPUs implement weak memory coherency. These
 CPUs include: Power4, Power5, Alpha, Itanium. <code>u_init()</code> was not
 defined yet.

<h4><a name="ImportantNotesHPUX" href="#ImportantNotesHPUX" id=
 "ImportantNotesHPUX">Using ICU in a Multithreaded Environment on
 HP-UX</a></h4>

When ICU is built with aCC on HP-UX, the <a
 href="http://h21007.www2.hp.com/portal/site/dspp/menuitem.863c3e4cbcdc3f3515b49c108973a801?ciid=eb08b3f1eee02110b3f1eee02110275d6e10RCRD">-AA</a>
 compiler flag is used. It is required in order to use the latest
 &lt;iostream&gt; API in a thread safe manner. This compiler flag affects the
 version of the C++ library being used. Your applications will also need to
 be compiled with -AA in order to use ICU.

<h4><a name="ImportantNotesSolaris" href="#ImportantNotesSolaris" id=
 "ImportantNotesSolaris">Using ICU in a Multithreaded Environment on
 Solaris</a></h4>

<h5>Linking on Solaris</h5>

In order to avoid synchronization and threading issues, developers are
 suggested to strictly follow the compiling and linking
 guidelines for multithreaded applications, specified in the following
 SUn Solaris document available from Oracle. Most notably, pay strict attention to the
 following statements from Sun:

<blockquote>
 To use libthread, specify -lthread before -lc on the ld command line, or
 last on the cc command line.

To use libpthread, specify -lpthread before -lc on the ld command line,
 or last on the cc command line.
 </blockquote>

Failure to do this may cause spurious lock conflicts, recursive mutex
 failure, and deadlock.

Source: "Multithreaded Programming Guide, Compiling and
 Debugging", Sun Microsystems, 2002 
 <a href=
 "https://docs.oracle.com/cd/E19683-01/806-6867/compile-74765/index.html">https://docs.oracle.com/cd/E19683-01/806-6867/compile-74765/index.html</a>

Note, a version of that chapter from a 2008 document update covering both Solaris 9
 and Solaris 10 is available here: 
 <a href=
 "http://docs.oracle.com/cd/E19253-01/816-5137/compile-94179/index.html">http://docs.oracle.com/cd/E19253-01/816-5137/compile-94179/index.html</a>

<h3><a name="ImportantNotesWindows" href="#ImportantNotesWindows" id=
 "ImportantNotesWindows">Windows Platform</a></h3>

If you are building on the Windows platform, it is important that you
 understand a few of the following build details.

<h4>DLL directories and the PATH setting</h4>

As delivered, the International Components for Unicode build as several
 DLLs, which are placed in the "&lt;ICU&gt;\bin64" directory. You must
 add this directory to the PATH environment variable in your system, or any
 executables you build will not be able to access International Components for
 Unicode libraries. Alternatively, you can copy the DLL files into a directory
 already in your PATH, but we do not recommend this. You can wind up with
 multiple copies of the DLL and wind up using the wrong one.

<h4><a name="ImportantNotesWindowsPath" id=
 "ImportantNotesWindowsPath">Changing your PATH</a></h4>

Windows 2000/XP and above: Use the System Icon in the Control
 Panel. Pick the "Advanced" tab. Select the "Environment Variables..."
 button. Select the variable PATH in the lower box, and select the lower
 "Edit..." button. In the "Variable Value" box, append the string
 ";&lt;ICU&gt;\bin64" to the end of the path string. If there is
 nothing there, just type in "&lt;ICU&gt;\bin64". Click the Set button,
 then the OK button.

Note: When packaging a Windows application for distribution and
 installation on user systems, copies of the ICU DLLs should be included with
 the application, and installed for exclusive use by the application. This is
 the only way to insure that your application is running with the same version
 of ICU, built with exactly the same options, that you developed and tested
 with. Refer to Microsoft's guidelines on the usage of DLLs, or search for the
 phrase "DLL hell" on <a href=
 "http://msdn.microsoft.com/">msdn.microsoft.com</a>.

<h3><a name="ImportantNotesUNIX" href="#ImportantNotesUNIX" id=
 "ImportantNotesUNIX">UNIX Type Platform</a></h3>

If you are building on a UNIX platform, and if you are installing ICU in a
 non-standard location, you may need to add the location of your ICU libraries
 to your LD_LIBRARY_PATH or LIBPATH
 environment variable (or the equivalent runtime library path environment
 variable for your system). The ICU libraries may not link or load properly
 without doing this.

Note that if you do not want to have to set this variable, you may instead
 use the --enable-rpath option at configuration time. This option will
 instruct the linker to always look for the libraries where they are
 installed. You will need to use the appropriate linker options when linking
 your own applications and libraries against ICU, too. Please refer to your
 system's linker manual for information about runtime paths. The use of rpath
 also means that when building a new version of ICU you should not have an
 older version installed in the same place as the new version's installation
 directory, as the older libraries will used during the build, instead of the
 new ones, likely leading to an incorrectly build ICU. This is the proper
 behavior of rpath.

<h2><a name="PlatformDependencies" href="#PlatformDependencies" id=
 "PlatformDependencies">Platform Dependencies</a></h2>

<h3><a name="PlatformDependenciesNew" href="#PlatformDependenciesNew" id=
 "PlatformDependenciesNew">Porting To A New Platform</a></h3>

If you are using ICU's Makefiles to build ICU on a new platform, there are
 a few places where you will need to add or modify some files. If you need
 more help, you can always ask the <a href=
 "http://site.icu-project.org/contacts">icu-support mailing list</a>. Once
 you have finished porting ICU to a new platform, it is recommended that you
 contribute your changes back to ICU via the icu-support mailing list. This
 will make it easier for everyone to benefit from your work.

<h4>Data For a New Platform</h4>

For some people, it may not be necessary for completely build ICU. Most of
 the makefiles and build targets are for tools that are used for building
 ICU's data, and an application's data (when an application uses ICU resource
 bundles for its data).

Data files can be built on a different platform when both platforms share
 the same endianness and the same charset family. This assertion does not
 include platform dependent DLLs/shared/static libraries. For details see the
 User Guide <a href="http://userguide.icu-project.org/icudata">ICU
 Data</a> chapter.

ICU 3.6 removes the requirement that ICU be completely built in the native
 operating environment. It adds the icupkg tool which can be run on any
 platform to turn binary ICU data files from any one of the three formats into
 any one of the other data formats. This allows a application to use ICU data
 built anywhere to be used for any other target platform.

WARNING! Building ICU without running the tests is not
 recommended. The tests verify that ICU is safe to use. It is recommended that
 you try to completely port and test ICU before using the libraries for your
 own application.

<h4>Adapting Makefiles For a New Platform</h4>

Try to follow the build steps from the <a href="#HowToBuildUNIX">UNIX</a>
 build instructions. If the configure script fails, then you will need to
 modify some files. Here are the usual steps for porting to a new
 platform:

<ol>
 <li>Create an mh file in icu/source/config/. You can use mh-linux or a
 similar mh file as your base configuration.</li>

<li>Modify icu/source/aclocal.m4 to recognize your platform's mh file.</li>

<li>Modify icu/source/configure.in to properly set your platform C
 Macro define.</li>

<li>Run <a href="http://www.gnu.org/software/autoconf/">autoconf</a> in
 icu/source/ without any options. The autoconf tool is standard on most
 Linux systems.</li>

<li>If you have any optimization options that you want to normally use, you
 can modify icu/source/runConfigureICU to specify those options for your
 platform.</li>

<li>Build and test ICU on your platform. It is very important that you run
 the tests. If you don't run the tests, there is no guarentee that you have
 properly ported ICU.</li>
 </ol>

<h3><a name="PlatformDependenciesImpl" href="#PlatformDependenciesImpl" id=
 "PlatformDependenciesImpl">Platform Dependent Implementations</a></h3>

The platform dependencies have been mostly isolated into the following
 files in the common library. This information can be useful if you are
 porting ICU to a new platform.

<ul>
 <li>
 unicode/platform.h.in (autoconf'ed platforms) 
 unicode/pXXXX.h (others: pwin32.h, ppalmos.h,
 ..): Platform-dependent typedefs and defines:

<ul>
 <li>Generic types like UBool, int8_t, int16_t, int32_t, int64_t,
 uint64_t etc.</li>

<li>U_EXPORT and U_IMPORT for specifying dynamic library import and
 export</li>

<li>String handling support for the char16_t and wchar_t types.</li>
 </ul>
 
 </li>

<li>
 unicode/putil.h, putil.c: platform-dependent
 implementations of various functions that are platform dependent:

<ul>
 <li>uprv_isNaN, uprv_isInfinite, uprv_getNaN and uprv_getInfinity for
 handling special floating point values.</li>

<li>uprv_tzset, uprv_timezone, uprv_tzname and time for getting
 platform specific time and time zone information.</li>

<li>u_getDataDirectory for getting the default data directory.</li>

<li>uprv_getDefaultLocaleID for getting the default locale
 setting.</li>

<li>uprv_getDefaultCodepage for getting the default codepage
 encoding.</li>
 </ul>
 
 </li>

<li>
 umutex.h, umutex.c: Code for doing synchronization in
 multithreaded applications. If you wish to use International Components
 for Unicode in a multithreaded application, you must provide a
 synchronization primitive that the classes can use to protect their
 global data against simultaneous modifications. We already supply working
 implementations for many platforms that ICU builds on. 
 
 </li>

<li>umapfile.h, umapfile.c: functions for mapping or
 otherwise reading or loading files into memory. All access by ICU to data
 from files makes use of these functions. 
 
 </li>

<li>Using platform specific #ifdef macros are highly discouraged outside of
 the scope of these files. When the source code gets updated in the future,
 these #ifdef's can cause testing problems for your platform.</li>
 </ul>
 <hr />
 Copyright &copy; 2016 and later: Unicode, Inc. and others. License &amp; terms of use:
 <a href="http://www.unicode.org/copyright.html">http://www.unicode.org/copyright.html</a> 
 Copyright &copy; 1997-2016 International Business Machines Corporation and others.
 All Rights Reserved.
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