Numeric character reference

Numeric character reference (NCR) is a common markup construct used in HTML and XML to reference characters in the Unicode standard by their corresponding number. This allows authors to include characters in their documents that cannot easily be typed on a keyboard or may not be directly supported by their document's character encoding.

Overview

A numeric character reference is composed of a series of characters that represent a specific character in a document. It starts with an ampersand (&), followed by a hash symbol (#), then the numeric value of the character, and ends with a semicolon (;). There are two types of numeric character references: decimal and hexadecimal. Decimal references are specified by the numeric value of the character, while hexadecimal references are prefixed with an "x" and use hexadecimal notation.

Decimal NCR

The decimal form of a numeric character reference is written as &# followed by the decimal number of the character and a semicolon. For example, the decimal NCR for the letter "A" is A.

Hexadecimal NCR

The hexadecimal form is written as &#x followed by the hexadecimal number of the character and a semicolon. For example, the hexadecimal NCR for the letter "A" is A.

Usage

Numeric character references are used for several reasons:

• To display characters that are not available on the keyboard.
• To include special characters that have specific meanings in HTML or XML, such as < and &, without being interpreted as markup.
• To ensure characters are displayed correctly regardless of the document's character encoding.

Examples

• The NCR for the copyright symbol © is © or ©.
• To display a less-than sign (<) in HTML, you can use the NCR < or <.

Support

All modern web browsers and XML parsers support numeric character references, making them a reliable way to include special characters in web pages and XML documents.

See Also

• Character encoding
• HTML
• XML
• Unicode