Character entity reference

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In the markup languages SGML, HTML, XHTML and XML, a character entity reference is a reference to a particular kind of named entity that has been predefined or explicitly declared in a Document Type Definition (DTD). The replacement text of the entity consists of a single character from the Universal Character Set/Unicode. The purpose of a character entity reference is to provide a way to refer to a character that is not universally encodable.

Actually, in XML at least, the term "character entity reference" is incorrect. XML has two relevant concepts:

• a "predefined entity reference" is a reference to one of the special characters denoted by <, >, &, ", or ';
• while a "character reference" (or "numeric character reference") is a construct such as   or   that refers to a character by means of its numeric Unicode codepoint.

Although in popular usage character references are often called "entity references" or even "entities", this usage is wrong. A character reference is a reference to a character, not to an entity. Entity reference refers to the content of a named entity. An entity declaration is created by using the <!ENTITY name "value"> syntax in a document type definition (DTD) or XML schema. Then, the name defined in the entity declaration is subsequently used in the XML. When used in the XML, it is called an entity reference.

[edit] See also

• SGML entity
• Character encodings in HTML
• Numeric character reference
• List of XML and HTML character entity references

[edit] External links

• Entities Table
• A Simple Character Entity Chart
• A character entity chart with images for entities
• A Clear and Quick Reference to HTML Symbol Entities Codes

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