Unicode vs ISO 10646?

By: Markus Kuhn

The Unicode Standard published by the Unicode Consortium corresponds to ISO 10646 at implementation level 3. All characters are at the same positions and have the same names in both standards.

The Unicode Standard defines in addition much more semantics associated with some of the characters and is in general a better reference for implementors of high-quality typographic publishing systems. Unicode specifies algorithms for rendering presentation forms of some scripts (say Arabic), handling of bi-directional texts that mix for instance Latin and Hebrew, algorithms for sorting and string comparison, and much more.

The ISO 10646 standard on the other hand is not much more than a simple character set table, comparable to the old ISO 8859 standards. It specifies some terminology related to the standard, defines some encoding alternatives, and it contains specifications of how to use UCS in connection with other established ISO standards such as ISO 6429 and ISO 2022. There are other closely related ISO standards, for instance ISO 14651 on sorting UCS strings. A nice feature of the ISO 10646-1 standard is that it provides CJK example glyphs in five different style variants, while the Unicode standard shows the CJK ideographs only in a Chinese variant.