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UNICODE

PI Vermaes   verpister@gmail.com     To: | Home | TOC Gray | Bottom |

Unicode provides a unique number for every character,
no matter what the platform,
no matter what the program,
no matter what the language.

Incorporating Unicode into client-server or multi-tiered applications and websites offers significant cost savings over the use of legacy character sets. Unicode enables a single software product or a single website to be targeted across multiple platforms, languages and countries without re-engineering. It allows data to be transported through many different systems without corruption.

The Unicode Standard specifies the representation of text in modern software products and standards.

Unicode provides a consistent way of encoding multilingual plain text and brings order to a chaotic state of affairs that has made it difficult to exchange text files internationally. Computer users who deal with multilingual text -- business people, linguists, researchers, scientists, and others -- will find that the Unicode Standard greatly simplifies their work. Mathematicians and technicians, who regularly use mathematical symbols and other technical characters, will also find the Unicode Standard valuable.

The design of Unicode is based on the simplicity and consistency of ASCII, but goes far beyond ASCII's limited ability to encode only the Latin alphabet. The Unicode Standard provides the capacity to encode all of the characters used for the written languages of the world. To keep character coding simple and efficient, the Unicode Standard assigns each character a unique numeric value and name.

The Unicode Standard and ISO/IEC 10646 support three encoding forms that use a common repertoire of characters. These encoding forms allow for encoding as many as a million characters. This is sufficient for all known character encoding requirements, including full coverage of all historic scripts of the world, as well as common notational systems.

The Unicode Standard does not define glyph images. The standard defines how characters are interpreted, not how glyphs are rendered. The software or hardware-rendering engine of a computer is responsible for the appearance of the characters on the screen. The Unicode Standard does not specify the size, shape, nor style of on-screen characters.

UTF-8 support has improved dramatically over the last few years and many people now use UTF-8 on a daily basis in:

and in any other places where byte sequences used to be interpreted in ASCII.

In UTF-8 mode, terminal emulators such as xterm or the Linux console driver transform every keystroke into the corresponding UTF-8 sequence and send it to the stdin of the foreground process. Similarly, any output of a process on stdout is sent to the terminal emulator, where it is processed with a UTF-8 decoder and then displayed using a 16-bit font.

Full Unicode functionality with all bells and whistles (e.g. high-quality typesetting of the Arabic and Indic scripts) can only be expected from sophisticated multi-lingual word-processing packages. What Linux supports today on a broad base is far simpler and mainly aimed at replacing the old 8- and 16-bit character sets. Linux terminal emulators and command line tools usually only support a Level 1 implementation of ISO 10646-1 (no combining characters), and only scripts such as Latin, Greek, Cyrillic, Armenian, Georgian, CJK, and many scientific symbols are supported that need no further processing support. At this level, UCS support is very comparable to ISO 8859 support and the only significant difference is that we have now thousands of different characters available, that characters can be represented by multibyte sequences, and that ideographic Chinese/Japanese/Korean characters require two terminal character positions (double-width).

Level 2 support in the form of combining characters for selected scripts (in particular Thai) and Hangul Jamo is in parts also available (i.e., some fonts, terminal emulators and editors support it via simple overstringing), but precomposed characters should be preferred over combining character sequences where available. More formally, the preferred way of encoding text in Unicode under Linux should be Normalization Form C as defined in Unicode Technical Report #15.