JIS X 0201

JIS X 0201, a Japanese Industrial Standard developed in 1969 (then called JIS C 6220 until the JIS category reform), was the first Japanese electronic character set to become widely used. It is either a 7-bit encoding or an 8-bit encoding, although the 8-bit form is dominant for modern use (or was until Unicode, e.g. UTF-8 took over). The full name of this standard is ''7-bit and 8-bit coded character sets for information interchange'' ().

The first 96 codes comprise an ISO 646 variant, mostly following ASCII with some differences, while the second 96 character codes represent the phonetic Japanese katakana signs. Since the encoding does not provide any way to express hiragana or kanji, it is only capable of expressing simplified written Japanese. Nevertheless, it is possible to express, at least phonetically, the full range of sounds in the language. In the 1970s, this was acceptable for media such as text mode computer terminals, telegrams, receipts or other electronically handled data.

JIS X 0201 was supplanted by subsequent encodings such as Shift JIS (which combines this standard and JIS X 0208) and later Unicode.

History

The Comite Consultatif International Telephonique et Telegraphique (CCITT) introduced the International Telegraph Alphabet No.2 (ITA2) code as an international standard, which was the 5-bit Latin encoding. Most countries have their own national standards based on this. In Japan, the Agency of Industrial Science and Technology (AIST) standardized it as the 6-bit character codes of JIS C 0803-1961 (''Keyboard layout and codes for teleprinters''), which combined with katakana characters. However, it didn't match the industry requirements because the character map was small, and the code layout was impractical. The AIST considered a practical character encoding to replace various codes used in Japan.

In 1963, ISO introduced a draft of ISO R 646 (''6 and 7-bit coded character sets for information processing interchange''). AIST committed the conjunction of ISO R 646 and katakana mapping to the Information Processing Society of Japan (IPSJ). IPSJ formed the code standardization committee. The committee didn't adopt the 6-bit form of ISO's draft because the katakana set couldn't fit into its character map. The early JIS draft mapped small katakana characters next to each of their normal katakana characters. It was considered to be convenient for sorting by Gojūon order. Some committee members criticized it would complicate the mechanic of keyboards which only handled normal katakana characters. The later draft mapped small katakana characters to positions 0xA7-0xAF. In 1966, the fourth draft of ISO specified the national currency symbol at 0x24, and the JIS committee planned to map the yen sign. The first edition of ISO 646 was published in 1967. It specified the ASCII's dollar sign 0x24 as an invariant character, so the JIS committee decided to replace the ASCII's backslash 0x5c (one of variant characters) with the yen sign.

JIS C 6220 (''Codes for information interchange'', 情報交換用符号) was published in 1969. Its number was changed to JIS X 0201 due to the JIS category reform in 1987, and the name was changed to ''7-bit and 8-bit coded character sets for information interchange'' (7ビット及び8ビットの情報交換用符号化文字集合) in the 1990 edition.

The character set of JIS X 0201 had been widely used in Japan. The Nationwide Banking Data Communication System (全国銀行データ通信システム), the largest funds transfer system in Japan, was established in 1973. Transaction messages between banks used a subset of JIS X 0201. The system was used until 2018, and it was replaced by the ZEDI (The Nationwide Banking Electronic Data Interchange System, 全銀EDIシステム) which could handle hiragana and kanji characters. In 1978, the JIS C 6226 (JIS X 0208) 2-byte character set was developed to express hiragana and kanji characters. It includes katakana characters, but their codes and layout are different from JIS X 0201. Computer manufacturers developed their own extensions of JIS X 0208 to retain compatibility with JIS X 0201. In 1982, the Microsoft Kanji encoding scheme ( Codepage 932 of MS-DOS) and Digital Research's SJC26 (for Japanese CP/M-86) were developed to combine JIS X 0201 single-byte encoding and JIS X 0208 double byte encoding without shift out and shift in characters. They were called Shift JIS, which became the industrial standard for personal computers.

Implementation details

The first half (Roman set) of JIS X 0201 constitutes a Japanese variant of ISO 646, amounting to ASCII with backslash (\) and tilde (~) replaced by yen (¥) and overline (‾), while the second half (Kana set) consists mainly of katakana. Control characters are specified in JIS X 0211.

In the 7-bit format, the shift out control character (0x0E) switches to the Kana set and shift in