Character encoding

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{language, word, form}
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A character encoding system consists of a code that pairs each character from a given repertoire with something else, such as a sequence of natural numbers, octets or electrical pulses, in order to facilitate the transmission of data (generally numbers and/or text) through telecommunication networks or storage of text in computers.

Other terms like character encoding, character set (charset), and sometimes character map or code page are used almost interchangeably, but these terms now have related but distinct meanings. See terminology section.

Contents

History

Common examples of character encoding systems include Morse code, the Baudot code, the American Standard Code for Information Interchange (ASCII) and Unicode.

Morse code was introduced in the 1840s and is used to encode each letter of the Latin alphabet and each Hindu-Arabic numeral as a series of long and short presses of a telegraph key. Representations of characters encoded using Morse code varied in length.

The Baudot code was created by Émile Baudot in 1870, patented in 1874, modified by Donald Murray in 1901, and standardized by CCITT as International Telegraph Alphabet No. 2 (ITA2) in 1930.

ASCII was introduced in 1963 and is a 7-bit encoding scheme used to encode letters, numerals, symbols, and device control codes as fixed-length codes using integers.

IBM's Extended Binary Coded Decimal Interchange Code (usually abbreviated EBCDIC) is an 8-bit encoding scheme developed in 1963.

The limitations of such sets soon became apparent, and a number of ad-hoc methods were developed to extend them. The need to support more writing systems for different languages, including the CJK family of East Asian scripts, required support for a far larger number of characters and demanded a systematic approach to character encoding rather than the previous ad hoc approaches.

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