A range of code points in the S (Special) Zone of the BMP remains unassigned to characters. The original edition of the UCS defined UTF-16, an extension of UCS-2, to represent code points outside the BMP. It does this to allow for future expansion or to minimise conflicts with other encoding forms.
The system deliberately leaves many code points not assigned to characters, even in the BMP. This required software intended for sale in the PRC to move beyond the BMP. 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. 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.
The Universal Coded Character Set ( UCS, Unicode) is a standard set of characters defined by the international standard ISO/ IEC 10646, Information technology - Universal Coded Character Set (UCS) (plus amendments to that standard), which is the basis of many character encodings, improving as characters from previously unrepresented typing systems are added.
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