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[Martin Musatov]

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Bi-directional text

The writing systems of some languages, such as Hebrew and Arabic are
written from right to left. When Latin-based text is mixed with these
languages in the same sentence, each type of text should be written in
its own direction. This is known as bi-directional text. This can get
quite complex when multiple levels of quotation are used.
Many computer programs fail to display bi-directional text correctly.
For example, the Hebrew Tetragrammaton (יהוה) should be spelled
yodh(י) heh(ה) waw(ו) heh(ה) from right to left. Some web browsers may
display the Hebrew text in this article in the opposite direction.

Very few languages may be written in either direction. Such was the
case with Egyptian hieroglyphics, where the signs had a distinct
"head" that faced the beginning of a line and "tail" that faced the
end.

Some ancient Greek inscriptions, Tuareg and Hungarian runes were
written in opposite directions on alternate lines, a style called
boustrophedon.

Bidirectional script support is the capability of a computer system to
correctly display bi-directional text. The term is often shortened to
the jargon term BiDi.

Early computer installations were designed only to support a single
writing system, typically for left-to-right scripts based on the Latin
alphabet only. Adding new character sets and character encodings
enabled a number of other left-to-right scripts to be supported, but
did not easily support right-to-left scripts such as Arabic or Hebrew,
and mixing the two was not practical. It is possible to simply flip
the left-to-right display order to a right-to-left display order, but
doing this sacrifices the ability to correctly display left-to-right
scripts. With bidirectional script support, it is possible to mix
scripts from different languages on the same page, regardless of
writing direction.

In particular, Unicode provides complete BiDi support, with detailed
rules as to how mixtures of left-to-right and right-to-left languages
are to be encoded and displayed. In Unicode encoding, all characters
are stored in writing order, and software works out which direction on
the page or screen the script should be displayed.


External links
http://www.langbox.com/bidimozilla/
http://crl.nmsu.edu/~mleisher/ucdata.html
http://mac.plonter.co.il/plonwiki/BidiWiki
http://nontroppo.org/wiki/OperaAndBiDiLanguages
http://www.the-right-to-flash.com/about.php

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