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are katakana characters displayed at half their normal width (a 1:2 aspect ratio), instead of the usual square (1:1) aspect ratio. For example, the usual (full-width) form of the katakana ''ka'' is カ while the half-width form is ｶ. There are no half-width hiragana or kanji. Half-width kana were used in the early days of Japanese computing, to allow Japanese characters to be displayed on the same grid as monospaced fonts of Latin characters. Half-width hiragana or kanji were not used. Half-width kana characters are not generally used today, but find some use in specific settings, such as cash register displays, on shop receipts, Japanese digital television and DVD subtitles, and mailing address labels. Their usage is sometimes also a stylistic choice, particularly frequent in certain Internet slang. The term "half-width kana", which strictly refers only to how kana are ''displayed'', not how they are ''stored'' – is also used loosely to refer to the A0–DF (hexadecimal) block where katakana are stored in some character encodings, such as JIS X 0201 (1969) – see encodings, below. This is formally incorrect, however – this JIS standard simply specifies that katakana be stored in these locations, without specifying how they should be displayed; the confusion is because in early computing, the characters stored here were in fact displayed as half-width kana – see confusion, below. ==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. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Half-width kana」の詳細全文を読む スポンサード リンク
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