International Components for Unicode (ICU) is an

open-source Open source is source code that is made freely available for possible modification and redistribution. Products include permission to use the source code, design documents, or content of the product. The open-source model is a decentralized sof ...

project of mature C/ C++ and Java libraries for

Unicode Unicode, formally The Unicode Standard,The formal version reference is is an information technology standard for the consistent encoding, representation, and handling of text expressed in most of the world's writing systems. The standard, ...

support, software

internationalization In economics, internationalization or internationalisation is the process of increasing involvement of enterprises in international markets, although there is no agreed definition of internationalization. Internationalization is a crucial strateg ...

, and software globalization. ICU is widely portable to many operating systems and environments. It gives applications the same results on all platforms and between C, C++, and Java software. The ICU project is a technical committee of the

Unicode Consortium The Unicode Consortium (legally Unicode, Inc.) is a 501(c)(3) non-profit organization incorporated and based in Mountain View, California. Its primary purpose is to maintain and publish the Unicode Standard which was developed with the intent ...

and sponsored, supported, and used by IBM and many other companies. ICU provides the following services:

text handling, full character properties, and

character set Character encoding is the process of assigning numbers to graphical characters, especially the written characters of human language, allowing them to be stored, transmitted, and transformed using digital computers. The numerical values tha ...

conversions; Unicode

regular expression A regular expression (shortened as regex or regexp; sometimes referred to as rational expression) is a sequence of characters that specifies a search pattern in text. Usually such patterns are used by string-searching algorithms for "find" ...

s; full Unicode sets; character, word, and line boundaries; language-sensitive

collation Collation is the assembly of written information into a standard order. Many systems of collation are based on numerical order or alphabetical order, or extensions and combinations thereof. Collation is a fundamental element of most office fil ...

and searching; normalization, upper and lowercase conversion, and script

transliteration Transliteration is a type of conversion of a text from one script to another that involves swapping letters (thus ''trans-'' + '' liter-'') in predictable ways, such as Greek → , Cyrillic → , Greek → the digraph , Armenian → or ...

s; comprehensive locale data and resource bundle architecture via the

Common Locale Data Repository The Common Locale Data Repository Project, often abbreviated as CLDR, is a project of the Unicode Consortium to provide locale data in XML format for use in computer applications. CLDR contains locale-specific information that an operating sys ...

(CLDR); multiple calendars and

time zone A time zone is an area which observes a uniform standard time for legal, commercial and social purposes. Time zones tend to follow the boundaries between countries and their subdivisions instead of strictly following longitude, because i ...

s; and rule-based formatting and parsing of dates, times, numbers, currencies, and messages. ICU provided complex text layout service for Arabic, Hebrew, Indic, and Thai historically, but that was deprecated in version 54, and was completely removed in version 58 in favor of HarfBuzz. ICU provides more extensive internationalization facilities than the standard libraries for C and C++.

Unicode 14.0 Unicode, formally The Unicode Standard,The formal version reference is is an information technology standard for the consistent encoding, representation, and handling of text expressed in most of the world's writing systems. The standard, wh ...

is supported. ICU 67 supports Unicode 13.0 and handles removal of Great Britain from the EU. ICU 64 supports Unicode 12.0, while ICU 64.2 added support for Unicode 12.1, i.e. the single new symbol for current Japanese

Reiwa is the current era of Japan's official calendar. It began on 1 May 2019, the day on which Emperor Akihito's elder son, Naruhito, ascended the throne as the 126th Emperor of Japan. The day before, Emperor Akihito abdicated the Chrysanthem ...

era (but support for it has also been backported to older ICU versions down to ICU 4.8.2). ICU 58 (with Unicode 9.0 support) is the last version to support older platforms such as

Windows XP Windows XP is a major release of Microsoft's Windows NT operating system. It was release to manufacturing, released to manufacturing on August 24, 2001, and later to retail on October 25, 2001. It is a direct upgrade to its predecessors, Wind ...

and

Windows Vista Windows Vista is a major release of the Windows NT operating system developed by Microsoft. It was the direct successor to Windows XP, which was released five years before, at the time being the longest time span between successive releases of ...

. Support for AIX, Solaris and

z/OS z/OS is a 64-bit operating system for IBM z/Architecture mainframes, introduced by IBM in October 2000. It derives from and is the successor to OS/390, which in turn was preceded by a string of MVS versions.Starting with the earliest: ...

may also be limited in later versions (i.e. building depends on compiler support). ICU has been included as a standard component with Microsoft Windows since

Windows 10 Windows 10 is a major release of Microsoft's Windows NT operating system. It is the direct successor to Windows 8.1, which was released nearly two years earlier. It was released to manufacturing on July 15, 2015, and later to retail on ...

version 1703. ICU has historically used

UTF-16 UTF-16 (16-bit Unicode Transformation Format) is a character encoding capable of encoding all 1,112,064 valid code points of Unicode (in fact this number of code points is dictated by the design of UTF-16). The encoding is variable-length, as cod ...

, and still does only for Java; while for C/C++

UTF-8 UTF-8 is a variable-length character encoding used for electronic communication. Defined by the Unicode Standard, the name is derived from ''Unicode'' (or ''Universal Coded Character Set'') ''Transformation Format 8-bit''. UTF-8 is capable of ...

is supported, including the correct handling of "illegal UTF-8". ICU 70 updated to Unicode 14 and added support for

emoji An emoji ( ; plural emoji or emojis) is a pictogram, logogram, ideogram or smiley embedded in text and used in electronic messages and web pages. The primary function of emoji is to fill in emotional cues otherwise missing from typed convers ...

properties of strings and C++20 compilers. ICU 71 adds e.g. phrase-based line breaking for Japanese (earlier methods didn't work well for short Japanese text, such as in titles and headings) and support for Hindi written in Latin letters (hi_Latn), also referred to as "

Hinglish Hinglish, a portmanteau of Hindi and English, is the macaronic hybrid use of English and languages of the Indian subcontinent, and especially Hindi. It involves code-switching or translanguaging between these languages whereby they are freel ...

" and updates to the time zone data version 2022a.

Origin and development

After Taligent became part of IBM in early 1996,

Sun Microsystems Sun Microsystems, Inc. (Sun for short) was an American technology company that sold computers, computer components, software, and information technology services and created the Java programming language, the Solaris operating system, ZFS, ...

decided that the new Java language should have better support for internationalization. Since Taligent had experience with such technologies and were close geographically, their Text and International group were asked to contribute the international classes to the

Java Development Kit The Java Development Kit (JDK) is a distribution of Java Technology by Oracle Corporation. It implements the Java Language Specification (JLS) and the Java Virtual Machine Specification (JVMS) and provides the Standard Edition (SE) of the Java ...

as part of the JDK 1.1 internationalization APIs. A large portion of this code still exists in the and packages. Further internationalization features were added with each later release of Java. The Java internationalization classes were then ported to C++ and C as part of a library known as ICU4C ("ICU for C"). The ICU project also provides ICU4J ("ICU for Java"), which adds features not present in the standard Java libraries. ICU4C and ICU4J are very similar, though not identical; for example, ICU4C includes a Regular Expression API, while ICU4J does not. Both frameworks have been enhanced over time to support new facilities and new features of Unicode and

(CLDR). ICU was released as an open-source project in 1999 under the name IBM Classes for Unicode. It was later renamed to International Components For Unicode. In May, 2016, the ICU project joined the Unicode consortium as technical committee ''ICU-TC'', and the library sources are now distributed under the Unicode license.

MessageFormat

A part of ICU is the MessageFormat class, a formatting system that allows for any number of arguments to control the plural form (, ) or more general

switch-case In computer programming languages, a switch statement is a type of selection control mechanism used to allow the value of a variable or expression to change the control flow of program execution via search and map. Switch statements function som ...

-style selection () for things like

grammatical gender In linguistics, grammatical gender system is a specific form of noun class system, where nouns are assigned with gender categories that are often not related to their real-world qualities. In languages with grammatical gender, most or all nouns ...

. These statements can be nested. ICU MessageFormat was created by adding the plural and selection system to an identically-named system in

Java SE Java Platform, Standard Edition (Java SE) is a computing platform for development and deployment of portable code for desktop and server environments. Java SE was formerly known as Java 2 Platform, Standard Edition (J2SE). The platform uses J ...

Alternatives

An alternative for using ICU with C++, or to using it directly, is to use Boost.Locale, which is a C++ wrapper for ICU (while also allowing other backends). The claim for using it rather than ICU directly is that "is absolutely unfriendly to C++ developers. It ignores popular C++ idioms (the STL, RTTI, exceptions, etc), instead mostly mimicking the Java API." Another claim, that ICU only supports UTF-16 (and thus a reason to avoid using ICU) is no longer true with ICU now also supporting UTF-8 for C and C++.

References

External links

*
International Components for Unicode transliteration services

Online ICU editor
{{Unicode navigation Unicode Component-based software engineering Digital typography Pattern matching Internationalization and localization Free computer libraries

Origin and development

MessageFormat

Alternatives

See also

References

External links