International Components for Unicode

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International Components for Unicode
Developer(s)IBM and many other companies.
Initial release1999
Stable release
64.2 / 17 April 2019; 4 months ago (2019-04-17)[1]
Repository Edit this at Wikidata
Written inC/C++ and Java
Operating systemCross-platform
Typelibraries for Unicode and internationalization
LicenseUnicode License

International Components for Unicode (ICU) is an open-source project of mature C/C++ and Java libraries for Unicode support, software internationalization, 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 sponsored, supported, and used by IBM and many other companies.[2]

ICU provides the following services: Unicode text handling, full character properties, and character set conversions; Unicode regular expressions; full Unicode sets; character, word, and line boundaries; language-sensitive collation and searching; normalization, upper and lowercase conversion, and script transliterations; comprehensive locale data and resource bundle architecture via the Common Locale Data Repository (CLDR); multi-calendar and time zones; 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.[3]

ICU provides more extensive internationalization facilities than the standard libraries for C and C++. ICU 62 supports Unicode 11.0, and older versions supports Unicode 10.0, but not for older platforms such as Windows XP, Windows Vista, AIX, Solaris, or z/OS.

ICU has historically used UTF-16, and still does only for Java; while for C/C++ UTF-8 is supported,[4] including the correct handling of "illegal UTF-8".[5]

Origin and development[edit]

After Taligent became part of IBM in early 1996, Sun Microsystems 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 as part of the JDK 1.1 internationalization APIs.[6] A large portion of this code still exists in the java.text and java.util packages. Further internationalization features were added with each later release of Java.

The Java internationalization classes were then ported to C++ and C[7] 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 Common Locale Data Repository (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.[8] 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.[9]

See also[edit]


  1. ^ "International Components for Unicode / [icu-announce] ICU 64.2 Released".
  2. ^ "ICU - International Components for Unicode".
  3. ^ "Layout Engine - ICU User Guide".
  4. ^ "UTF-8 - ICU User Guide". Retrieved 2018-04-03.
  5. ^ "#13311 (change illegal-UTF-8 handling to Unicode "best practice")". Retrieved 2018-04-03.
  6. ^ Laura Werner (1999). "Getting Java ready for the world: A brief history of IBM and Sun's internationalization efforts".
  7. ^ "ICU User Guide".
  8. ^ "ICU Project Management Committee".
  9. ^ "ICU joins the Unicode Consortium". Unicode, Inc. 2016-05-16. Retrieved 2016-08-01.

External links[edit]