Unicode
source from: http://www.cl.cam.ac.uk/~mgk25/unicode.html
The international standard ISO 10646 defines the Universal Character Set (UCS). UCS is a superset of all other character set standards. It guarantees round-trip compatibility to other character sets.
ISO 10646 defines formally a 31-bit character set. The most commonly used characters, including all those found in older encoding standards, have been placed in one of the first 65534 positions (0x0000 to 0xFFFD). This 16-bit subset of UCS is called the Basic Multilingual Plane (BMP) or Plane 0.
UCS assigns to each character not only a code number but also an official name. A hexadecimal number that represents a UCS or Unicode value is commonly preceded by "U+" as in U+0041 for the character "Latin capital letter A". The UCS characters U+0000 to U+007F are identical to those in US-ASCII (ISO 646 IRV) and the range U+0000 to U+00FF is identical to ISO 8859-1 (Latin-1). The range U+E000 to U+F8FF and also larger ranges outside the BMP are reserved for private use. UCS also defines several methods for encoding a string of characters as a sequence of bytes, such as UTF-8 and UTF-16.