The syntax is as follows:Ĭharacter U+0026 (ampersand), followed by character U+0023 (number sign), followed by one of the following choices:
#Numeric character code#
In HTML 4 and in all versions of XHTML and XML, the code point can be expressed either as a decimal (base 10) number or as a hexadecimal (base 16) number.
These special sequences are character references.Ĭharacter references that are based on the referenced character's UCS or Unicode "code point" are called numeric character references. The SGML-based markup languages allow document authors to use special sequences of characters from the ASCII range (the first 128 code points of Unicode) to represent, or reference, any Unicode character, regardless of whether the character being represented is directly available in the document's encoding. This is generally done through some kind of "escaping" mechanism.
#Numeric character iso#
For example, the widely used encodings based on ISO 8859 can only represent, at most, 256 unique characters as one 8-bit byte each.ĭocuments are rarely, in practice, ever allowed to use more than one encoding internally, so the onus is usually on the markup language to provide a means for document authors to express unencodable characters in terms of encodable ones. Sometimes, though, for reasons of convenience or due to technical limitations, documents are encoded with an encoding that cannot represent some characters directly. Ideally, when the characters of a document utilizing a markup language are encoded for storage or transmission over a network as a sequence of bits, the encoding that is used will be one that supports representing each and every character in the document, if not in the whole of Unicode, directly as a particular bit sequence. That is, a document consists, at its most fundamental level of abstraction, of a sequence of characters, which are abstract units that exist independently of any encoding. Markup languages are typically defined in terms of UCS or Unicode characters. Numerical character reference of Unicode character Σ Σ = U+03A3: GREEK CAPITAL LETTER SIGMA (3A3 16 = Template:Decimal2Base) In SGML, HTML, and XML, the following are all valid numeric character references for the Greek capital letter Sigma ("Σ"),
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