Unicode character property

The Unicode Standard assigns character properties to each code point.[1] These properties can be used to handle "characters" (code points) in processes, like in line-breaking, script direction right-to-left or applying controls. Slightly inconsequently, some "character properties" are also defined for code points that have no character assigned, and code points that are labeled like "<not a character>". The character properties are described in Standard Annex #44.[2]

Properties have levels of forcefulness: normative, informative, contributory, or provisional. For simplicity of specification, a character property can be assigned by specifying a continuous range of code points that have the same property.

A Unicode character is assigned a unique Name (na).[1] The name, in English, is composed of uppercase letters A–Z, digits 0–9, - (hyphen-minus) and <space>. Some sequences are excluded: names beginning with a space or hyphen, names ending with a space or hyphen, repeated spaces or hyphens, and space after hyphen are not allowed. The name is guaranteed to be unique within Unicode, and can be used to identify a code point and its character. Ideographic characters, of which there are tens of thousands, are named in the pattern "cjk unified ideograph-hhhh". For example, U+4E00 CJK UNIFIED IDEOGRAPH-4E00. Formatting characters are named too: U+00A0   NO-BREAK SPACE.

Starting from Unicode version 2.0, the published name for a code point will never change. In the event of a misspelling in a publication, a correct name will later be assigned to the code point as a Character Name Alias. Within the whole range of names, an alias is unique too.

Apart from these normative names, informal names can be assigned. These are usually other commonly used names for a character, used for illustration, but these informal names are not guaranteed to be unique.

These code points do not have a Name (na=""): Controls (General Cc), Private use (Co), Surrogate (Cs), Non-characters (Cn) and Reserved (Cn). They may be referenced, informally, by a generic or specific meta-name, called "Code Point Labels": <control>, <control-0088>, <reserved>, <noncharacter-hhhh>, <private-use-hhhh>, <surrogate>. Since these labels contain <>-brackets, they can never appear as a Name, which prevents confusion.

In version 2.0 of Unicode, many names were changed. From then on the rule "a name will never change" came into effect, including the strict (normative) use of alias names. Disused version 1.0-names were moved to the property Alias, to provide some backward compatibility.

Each code point is assigned a value for General Category. This is one of the character properties that are also defined for unassigned code points, and code points that are defined "not a character".

This page was last edited on 18 June 2018, at 21:36 (UTC).
Reference: https://en.wikipedia.org/wiki/General_Category under CC BY-SA license.

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