XML Companion, The, Third Edition

Character entity references

Entity references can be used to represent any character. Though rarely needed for widely used characters such as 'a' and '3', this mechanism is widely used for less familiar characters, and as an alternative means to represent characters that could be confused with markup delimiters. All character entity references are built-in entities, so no explicit declarations are necessary. The entity names in this case consist of a leading '#' symbol:

&#...;

The rest of the name is a number that represents the position of the character in its character set. A decimal value in the range '0' to '127' represents an ASCII character. The reference '&' refers to the ampersand character, '&'. A value in the range '0' to '255' ...