International Language Environments Guide

Unicode Overview

Unicode is the universal character encoding standard used for representation of text for computer processing. Unicode is fully compatible with the international standards ISO/IEC 10646-1:2000 and ISO/IEC 10646–2:2001, and contains all the same characters and encoding points as ISO/IEC 10646. The Unicode Standard provides additional information about the characters and their use. Any implementation that conforms to Unicode also conforms to ISO/IEC 10646.

Unicode provides a consistent way of encoding multilingual plain text and facilitates exchanging international text files. Computer users who deal with multilingual text, business people, linguists, researchers, scientists, and others find that the Unicode Standard greatly simplifies their work. Mathematicians and technicians who regularly use mathematical symbols and other technical characters also find the Unicode Standard valuable.

The maximum possible number of code points Unicode can support is 1,114,112 through seventeen 16-bit planes. Each plane can support 65,536 different code points.

Among the more than one million code points that Unicode can support, version 4.0 curently defines 96,382 characters at plane 0, 1, 2, and 14. Planes 15 and 16 are for private use characters, also known as user-defined characters. Planes 15 and 16 together can support total 131,068 user-defined characters.

Unicode can be encoded using any of the following character encoding schemes:

UTF-8 is a variable-length encoding form of Unicode that preserves ASCII character code values transparently. This form is used as file code in Oracle Solaris Unicode locales.

UTF-16 is a 16-bit encoding form of Unicode. In UTF-16, characters up to 65,535 are encoded as single 16-bit values. Characters mapped above 65,535 to 1,114,111 are encoded as pairs of 16-bit values (surrogates).

UTF-32 is a fixed-length, 21-bit encoding form of Unicode usually represented in a 32-bit container or data type. This form is used as the process code (wide-character code) in Oracle Solaris Unicode locales.

For more details on the Unicode Standard and ISO/IEC 10646 and their various representative forms, refer to the following sources:

Unicode Locale: en_US.UTF-8 Support

The Unicode/UTF-8 locales support Unicode 4.0. The en_US.UTF-8 locale provides multiscript processing support by using UTF-8 as its codeset. This locale handles processing of input and output text in multiple scripts, and was the first locale with this capability in the Oracle Solaris operating system. The capabilities of other UTF-8 locales are similar to those of en_us.UTF-8. The discussion of en_US.UTF-8 that follows applies equally to these locales.

Note –

UTF-8 is a file-system safe Universal Character Set Transformation Format of Unicode/ISO/IEC 10646-1 formulated by X/Open-Uniforum Joint Internationalization Working Group (XoJIG) in 1992 and approved by ISO and IEC, as Amendment 2 to ISO/IEC 10646-1:1993 in 1996. This standard has been adopted by the Unicode Consortium, the International Standards Organization, and the International Electrotechnical Commission as a part of Unicode 4.0 and ISO/IEC 10646-1.

Unicode locales in the Oracle Solaris environment support the processing of every code point value that is defined in Unicode 4.0 and ISO/IEC 10646-1 and 10646-2. Supported scripts include pan-European and Asian scripts and also complex text layout scripts for the Arabic, Hebrew, Indic, and Thai languages.

Note –

Some Unicode locales, notably the Asian locales, include more Kanji or Hanzi glyphs.

Due to limited font resources, the current Oracle Solaris Unicode locales include character glyphs from the following character sets.

If you try to view characters for which the en_US.UTF-8 locale does not have corresponding glyphs, the locale displays a no-glyph glyph instead, as shown in the following illustration:

The preceding context describes the graphic.

The locale is selectable at installation time and may be designated as the system default locale.

The same level of en_US.UTF-8 locale support is provided for both 64-bit and 32-bit Oracle Solaris systems.

Note –

Motif and CDE desktop applications and libraries support the en_US.UTF-8 locale. However, XView™ and OLIT libraries do not support the en_US.UTF-8 locale.