1/8/2024 0 Comments Markdown plus minus symbolIn the table below, the "Standard" column indicates the first version of the HTML DTD that defines the character entity reference. The HTML 5 specification requires the use of the standard DTDs and does not allow users to define additional entities. The HTML 5 DTDs define many named entities, references to which act as mnemonic aliases for certain Unicode characters. List of character entity references in HTML The final "Name" column cites the character via its canonical UCS/Unicode name. The "Standard" column indicates the first version of XML that includes the entity. The decimal equivalent of the code point is then shown in parentheses. The "Unicode code point" column cites the character via standard UCS/Unicode "U+" notation, which shows the character's code point in hexadecimal. To render the character, the format &name is used for example, & renders as &. The "Character" column shows the character. The initial "Name" column mentions the entity's name. The table below lists the five XML predefined entities. XML also allows other named entities of any size to be defined on a per-document basis. The entities can be explicitly declared in a DTD, as well, but if this is done, the replacement text must be the same as the built-in definitions. The XML specification defines five "predefined entities" representing special characters, and requires that all XML processors honor them. The XML specification does not use the term "character entity" or "character entity reference". However, the advent of Unicode has largely superseded them. Numerous other entity sets have been developed for special requirements, and for major and minority scripts. The HTML 5 specification additionally provides mappings from the names to Unicode character sequences using JSON. HTML 5 HTML5 adopts the XML entities as named character references, however it restates them without reference to their sources and does not group them into sets. This set can support the requirements of XHTML, MathML and as an input to future versions of HTML. XML Entity Sets The W3C MathML Working Group took over maintenance of the ISO public entity sets, combined with the MathML and documents them in XML Entity Definitions for Characters. MathML Entity Sets The W3C developed a set of entity declarations for MathML characters. HTML Entity Sets Early versions of HTML built in small subsets of these, relating to characters found in three Western 8-bit fonts. The American Mathematical Society also contributed entities for mathematical characters. Standard public entity sets for characters ISO Entity Sets SGML supplied a comprehensive set of entity declarations for characters widely used in Western technical and reference publishing, for Latin, Greek and Cyrillic scripts. The semicolon is required, unless marked otherwise in the table below (see ). Where name is the case-sensitive name of the entity. The format is the same as for any entity reference: The entity must either be predefined (built into the markup language) or explicitly declared in a Document Type Definition (DTD). 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 hhhh may mix uppercase and lowercase, though uppercase is the usual style. The nnnn or hhhh may be any number of digits and may include leading zeros. The x must be lowercase in XML documents. Where nnnn is the code point in decimal form, and hhhh is the code point in hexadecimal form. An entity declaration is created by using the syntax in a Document Type Definition (DTD).Ī numeric character reference refers to a character by its Universal Character Set/ Unicode code point, and uses the format: This article lists the character entity references that are valid in HTML and XML documents.Ī character entity reference refers to the content of a named entity. In SGML, HTML and XML documents, the logical constructs known as character data and attribute values consist of sequences of characters, in which each character can manifest directly (representing itself), or can be represented by a series of characters called a character reference, of which there are two types: a numeric character reference and a character entity reference.
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