Editing Katakana (section)

=== Hiragana and katakana ===
{{Unreferenced section|date=September 2009}}
{{main|Half-width kana}}
In addition to the usual {{nihongo|full-width|全角|''zenkaku''}} display forms of characters, katakana has a second form, {{nihongo|[[Half-width kana|half-width]]|半角|''hankaku''}}. The half-width forms were originally associated with the [[JIS X 0201]] encoding. Although their display form is not specified in the standard, in practice they were designed to fit into the same rectangle of pixels as Roman letters to enable easy implementation on the computer equipment of the day. This space is narrower than the square space traditionally occupied by Japanese characters, hence the name "half-width". In this scheme, diacritics (dakuten and handakuten) are separate characters. When originally devised, the half-width katakana were represented by a single byte each, as in JIS X 0201, again in line with the capabilities of contemporary computer technology.

In the late 1970s, two-byte character sets such as [[JIS X 0208]] were introduced to support the full range of Japanese characters, including katakana, hiragana and kanji. Their display forms were designed to fit into an approximately square array of pixels, hence the name "full-width". For backward compatibility, separate support for half-width katakana has continued to be available in modern multi-byte encoding schemes such as Unicode, by having two separate blocks of characters – one displayed as usual (full-width) katakana, the other displayed as half-width katakana.

Although often said to be obsolete, the half-width katakana are still used in many systems and encodings. For example, the titles of [[mini disc]]s can only be entered in ASCII or half-width katakana, and half-width katakana are commonly used in computerized cash register displays, on shop receipts, and Japanese digital television and DVD subtitles. Several popular Japanese encodings such as [[Extended Unix Code|EUC-JP]], [[Unicode]] and [[Shift JIS]] have half-width katakana code as well as full-width. By contrast, [[ISO/IEC 2022|ISO-2022-JP]] has no half-width katakana, and is mainly used over [[SMTP]] and [[NNTP]].