The UCS has over 1.1 million possible code points available for use/allocation, but only the first 65,536, which is the Basic Multilingual Plane (BMP), had entered into common use before 2000.
This situation began changing when the People's Republic of China (PRC) ruled in 2006 that all software sold in its jurisdiction would have to support GB 18030.
[clarification needed] The system deliberately leaves many code points not assigned to characters, even in the BMP.
A range of code points in the S (Special) Zone of the BMP remains unassigned to characters.
The UCS-4 encoding of ISO/IEC 10646 was incorporated into the Unicode standard with the limitation to the UTF-16 range and under the name UTF-32, although it has almost no use outside programs' internal data.
In contrast, Unicode adds rules for collation, normalisation of forms, and the bidirectional algorithm for right-to-left scripts such as Arabic and Hebrew.
One such application, Xterm, can properly display all ISO/IEC 10646 characters that have a one-to-one character-to-glyph mapping[clarification needed] and a single directionality.
It can handle some combining marks by simple overstriking methods, but cannot display Hebrew (bidirectional), Devanagari (one character to many glyphs) or Arabic (both features).
The repertoire, character names, and code points of Unicode Version 2.0 exactly match those of ISO/IEC 10646-1:1993 with its first seven published amendments.