Universal Coded Character Set

The Universal Coded Character Set (UCS), 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. The UCS contains just over 128,000 abstract characters, as of Unicode 9.0, each identified by an unambiguous name and an integer number called its code point.

Characters (letters, numbers, symbols, ideograms, logograms, etc.) from the many languages, scripts, and traditions of the world are represented in the UCS with unique code points. The inclusiveness of the UCS is continually improving as characters from previously unrepresented writing systems are added.

Since 1991, the Unicode Consortium and the ISO have developed The Unicode Standard ("Unicode") and ISO/IEC 10646 in tandem. 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. After Unicode 3.0 was published in February 2000, corresponding new and updated characters entered the UCS via ISO/IEC 10646-1:2000. In 2003, parts 1 and 2 of ISO/IEC 10646 were combined into a single part, which has since had a number of amendments adding characters to the standard in approximate synchrony with the Unicode standard.

The UCS has over 1.1 million possible code points available for use/allocation, but only the first 65,536 (the Basic Multilingual Plane, or 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. This required software intended for sale in the PRC to move beyond the BMP.

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