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In contrast, a character entity reference refers to a character by the name of an entity which has the desired character as its replacement text. The entity must either be predefined (built into the markup language) or explicitly declared in a Document Type Definition (DTD). The format is the same as for any entity reference: &name;
A Unicode character is assigned a unique Name (na). [1] The name 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 tables below list the number of bytes per code point for different Unicode ranges. Any additional comments needed are included in the table. The figures assume that overheads at the start and end of the block of text are negligible. N.B. The tables below list numbers of bytes per code point, not per user visible "character" (or "grapheme ...
A "character" may use any number of Unicode code points. [21] For instance an emoji flag character takes 8 bytes, since it is "constructed from a pair of Unicode scalar values" [22] (and those values are outside the BMP and require 4 bytes each). UTF-16 in no way assists in "counting characters" or in "measuring the width of a string".
Unicode was designed to provide code-point-by-code-point round-trip format conversion to and from any preexisting character encodings, so that text files in older character sets can be converted to Unicode and then back and get back the same file, without employing context-dependent interpretation.
This led to the idea that text in Chinese and other languages would take more space in UTF-8. However, text is only larger if there are more of these code points than 1-byte ASCII code points, and this rarely happens in the real-world documents due to spaces, newlines, digits, punctuation, English words, and (depending on document format) markup.
An abstract character repertoire (ACR) is the full set of abstract characters that a system supports. Unicode has an open repertoire, meaning that new characters will be added to the repertoire over time. A coded character set (CCS) is a function that maps characters to code points (each code point represents one character). For example, in a ...
The Unicode Consortium and the ISO/IEC JTC 1/SC 2/WG 2 jointly collaborate on the list of the characters in the Universal Coded Character Set.The Universal Coded Character Set, most commonly called the Universal Character Set (abbr. UCS, official designation: ISO/IEC 10646), is an international standard to map characters, discrete symbols used in natural language, mathematics, music, and other ...