The Unicode Standard is the universal character encoding standard used for representation of text for computer processing. Versions of the Unicode Standard are fully compatible and synchronized with the corresponding versions of International Standard ISO/IEC 10646. For example, Unicode 6.1 contains all the same characters and code points as ISO/IEC 10646:2012. The Unicode Standard provides additional information about the characters and their use. Any implementation that is conformant to Unicode is also conformant to ISO/IEC 10646.
Unicode provides a consistent way of encoding multilingual plain text and brings order to a chaotic state of affairs that has made it difficult to exchange text files internationally. Computer users who deal with multilingual text—business people, linguists, researchers, scientists, and others—will find that the Unicode Standard greatly simplifies their work. Mathematicians and technicians, who regularly use mathematical symbols and other technical characters, will also find the Unicode Standard valuable.
The design of Unicode is based on the simplicity and consistency of ASCII, but goes far beyond ASCII's limited ability to encode only the Latin alphabet. The Unicode Standard provides the capacity to encode all of the characters used for the written languages of the world. To keep character coding simple and efficient, the Unicode Standard assigns each character a unique numeric value and name.
The Unicode Standard and ISO/IEC 10646 support three encoding forms (UTF-8, UTF-16, UTF-32) that use a common repertoire of characters. These encoding forms allow for encoding as many as a million characters. This is sufficient for all known character encoding requirements, including full coverage of all historic scripts of the world, as well as common notational systems.
What Characters Does the Unicode Standard Include?
The Unicode Standard defines codes for characters used in all the major languages written today. Scripts include the European alphabetic scripts, Middle Eastern right-to-left scripts, and many scripts of Asia.
The Unicode Standard further includes punctuation marks, diacritics, mathematical symbols, technical symbols, arrows, dingbats, emoji, etc. It provides codes for diacritics, which are modifying character marks such as the tilde (~), that are used in conjunction with base characters to represent accented letters (ñ, for example). In all, the Unicode Standard, Version 6.1 provides codes for 110,181 characters from the world's alphabets, ideograph sets, and symbol collections.
The majority of common-use characters fit into the first 64K code points, an area of the codespace that is called the basic multilingual plane, or BMP for short. There are sixteen other supplementary planes available for encoding other characters, with currently over 860,000 unused code points. More characters are under consideration for addition to future versions of the standard.
The Unicode Standard also reserves code points for private use. Vendors or end users can assign these internally for their own characters and symbols, or use them with specialized fonts. There are 6,400 private use code points on the BMP and another 131,068 supplementary private use code points, should 6,400 be insufficient for particular applications.
Encoding Forms
Character encoding standards define not only the identity of each character and its numeric value, or code point, but also how this value is represented in bits.
The Unicode Standard defines three encoding forms that allow the same data to be transmitted in a byte, word or double word oriented format (i.e. in 8, 16 or 32-bits per code unit). All three encoding forms encode the same common character repertoire and can be efficiently transformed into one another without loss of data. The Unicode Consortium fully endorses the use of any of these encoding forms as a conformant way of implementing the Unicode Standard.
UTF-8 is popular for HTML and similar protocols. UTF-8 is a way of transforming all Unicode characters into a variable length encoding of bytes. It has the advantages that the Unicode character