Half-width Kana - History

History

ASCII is defined as a 7-bit character set and has room for 128 characters. However, since this standard was designed for the United States, it does not contain characters and symbols, such as the yen (¥) symbol needed to represent Japanese currency, nor did it include space for characters from other alphabets, such as kana or kanji – thus Japanese characters could not be encoded. Further, Japanese characters, both kana and kanji, are drawn on a square grid, while Latin characters are generally written more narrowly – thus Japanese characters could not be displayed either.

JIS X 0201 was developed in 1969, a time when computers were generally incapable, both by software design and hardware resources, of representing the thousands of Chinese-based kanji characters used in Japanese. As a compromise, this standard encoded katakana (only – not hiragana or kanji) as a small set of characters, assigned in the upper byte value range of 0x80–0xFF. This allowed 8-bit processors to encode and process Japanese text phonetically (as katakana), though without being able to process hiragana or kanji. These katakana characters were in turn displayed as "half-width kana" – a new, unorthodox, narrower form factor to fit the same width as the monospaced Latin alphabets machines were capable of printing and displaying. Encoding-wise, JIS X 0201 is a variant extension of ASCII – it includes additional characters, and does not exactly agree with ASCII on the overlapping part (the Latin character section).

Half-width kana were developed as "...the first Japanese characters encoded on computers because they are used for Japanese telegrams."

To make katakana fit into the narrower cell area allowed, some compromises were made. For example, the diacritical marks dakuten and handakuten are treated as separate characters instead of being part of the preceding character. This compromise led many to consider "half-width kana" visually unattractive, and causes problems for many computer programs today.