Editing Katakana (section)

==Computer encoding==
In addition to fonts intended for Japanese text and Unicode catch-all fonts (like [[Arial Unicode MS]]), many fonts intended for Chinese (such as MS Song) and Korean (such as Batang) also include katakana.

=== 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]].

===Unicode===
{{Main|Katakana (Unicode block)|Halfwidth and Fullwidth Forms (Unicode block)|Enclosed CJK Letters and Months|l3=Enclosed CJK Letters and Months (Unicode block)|Katakana Phonetic Extensions|l4=Katakana Phonetic Extensions (Unicode block)|Kana Supplement|l5=Kana Supplement (Unicode block)|Small Kana Extension|l6=Small Kana Extension (Unicode block)|Kana Extended-A|l7=Kana Extended-A (Unicode block)|Kana Extended-B|l8=Kana Extended-B (Unicode block)|CJK Compatibility}}

Katakana was added to the Unicode Standard in October, 1991 with the release of version 1.0.

The Unicode block for (full-width) katakana is U+30A0–U+30FF.

Encoded in this block along with the katakana are the ''nakaguro'' word-separation [[middle dot]], the ''chōon'' vowel extender, the katakana [[iteration mark]]s, and a [[Typographic ligature|ligature]] of [[Koto (kana)|コト]] sometimes used in vertical writing.

{{unicode chart Katakana}}

Half-width equivalents to the usual full-width katakana also exist in Unicode. These are encoded within the [[Halfwidth and Fullwidth Forms]] block (U+FF00–U+FFEF) (which also includes full-width forms of Latin characters, for instance), starting at U+FF65 and ending at U+FF9F (characters U+FF61–U+FF64 are half-width punctuation marks). This block also includes the half-width dakuten and handakuten. The full-width versions of these characters are found in the Hiragana block.

{{Unicode chart Halfwidth and Fullwidth Forms|subset=katakana}}

Circled katakana are code points U+32D0–U+32FE in the Enclosed CJK Letters and Months block (U+3200–U+32FF). A circled ン (n) is not included.

{{Unicode chart Enclosed CJK Letters and Months|subset=katakana}}

Extensions to Katakana for phonetic transcription of Ainu and other languages were added to the Unicode standard in March 2002 with the release of version 3.2.

The Unicode block for Katakana Phonetic Extensions is U+31F0–U+31FF:

{{Unicode chart Katakana Phonetic Extensions}}

Historic and variant forms of Japanese kana characters were added to the Unicode standard in October 2010 with the release of version 6.0.

The Unicode block for Kana Supplement is U+1B000–U+1B0FF:

{{Unicode chart Kana Supplement}}

The Unicode block for Small Kana Extension is U+1B130–U+1B16F:

{{Unicode chart Small Kana Extension}}

The Kana Extended-A Unicode block is U+1B100–1B12F. It contains [[hentaigana]] (non-standard hiragana) and historic kana characters.
{{Unicode chart Kana Extended-A}}

The Kana Extended-B Unicode block is U+1AFF0–1AFFF. It contains kana originally created by Japanese linguists to write [[Taiwanese Hokkien]] known as [[Taiwanese kana]].
{{Unicode chart Kana Extended-B}}

The CJK Compatibility block contains in the range U+3330-3357 square versions of katakana words, usually measure units or abbreviations of loanwords:
{{Unicode chart CJK Compatibility|subset=katakana}}

Katakana in other Unicode blocks:
* [[Dakuten]] and [[dakuten|handakuten]] diacritics are located in the [[Hiragana (Unicode block)|Hiragana block]]:
** U+3099 COMBINING KATAKANA-HIRAGANA VOICED SOUND MARK (non-spacing dakuten): ゙
** U+309A COMBINING KATAKANA-HIRAGANA SEMI-VOICED SOUND MARK (non-spacing handakuten): ゚
** U+309B KATAKANA-HIRAGANA VOICED SOUND MARK (spacing dakuten): ゛
** U+309C KATAKANA-HIRAGANA SEMI-VOICED SOUND MARK (spacing handakuten): ゜
* Two katakana-based [[emoji]] are in the [[Enclosed Ideographic Supplement|Enclosed Ideographic Supplement block]]:
** U+1F201 SQUARED KATAKANA KOKO ('here' sign): 🈁
** U+1F202 SQUARED KATAKANA SA ('service' sign): 🈂
* A katakana-based Japanese TV symbol from the [[ARIB STD-B24]] standard is in the [[Enclosed Ideographic Supplement|Enclosed Ideographic Supplement block]]:
** U+1F213 SQUARED KATAKANA DE ('data broadcasting service linked with a main program' symbol): 🈓

Furthermore, as of Unicode {{Unicode version|version=16.0}}, the following combinatory sequences have been explicitly named, despite having no precomposed symbols in the katakana block. Font designers may want to optimize the display of these composed glyphs. Some of them are mostly used for writing the [[Ainu language]], the others are called {{ill|Dakuten#Phonetic shifts|lt=''bidakuon''|ja|鼻濁音}} in Japanese. Other, arbitrary combinations with U+309A handakuten are also possible.

{| class="wikitable nounderlines" style="border-collapse:collapse;background:#FFFFFF;font-size:large;text-align:center"
| colspan="17" style="background:#F8F8F8;font-size:small" | '''Katakana named sequences'''<br />[https://unicode.org/Public/UNIDATA/NamedSequences.txt Unicode Named Character Sequences Database]
|- style="background:#F8F8F8;font-size:small"
|| Sequence name || colspan="2" style="width:20pt"  | Codepoints || style="width:20pt"  | Glyph
|-
| style="text-align:left;font-size:small;"| KATAKANA LETTER BIDAKUON NGA || style="font-size:small;" | U+30AB || style="font-size:small;" | U+309A || カ゚
|-
| style="text-align:left;font-size:small;"| KATAKANA LETTER BIDAKUON NGI || style="font-size:small;" | U+30AD || style="font-size:small;" | U+309A || キ゚
|-
| style="text-align:left;font-size:small;"| KATAKANA LETTER BIDAKUON NGU || style="font-size:small;" | U+30AF || style="font-size:small;" | U+309A || ク゚
|-
| style="text-align:left;font-size:small;"| KATAKANA LETTER BIDAKUON NGE || style="font-size:small;" | U+30B1 || style="font-size:small;" | U+309A || ケ゚
|-
| style="text-align:left;font-size:small;"| KATAKANA LETTER BIDAKUON NGO || style="font-size:small;" | U+30B3 || style="font-size:small;" | U+309A || コ゚
|-
| style="text-align:left;font-size:small;"| KATAKANA LETTER AINU CE || style="font-size:small;" | U+30BB || style="font-size:small;" | U+309A || セ゚
|-
| style="text-align:left;font-size:small;"| KATAKANA LETTER AINU TU || style="font-size:small;" | U+30C4 || style="font-size:small;" | U+309A || ツ゚
|-
| style="text-align:left;font-size:small;"| KATAKANA LETTER AINU TO || style="font-size:small;" | U+30C8 || style="font-size:small;" | U+309A || ト゚
|-
| style="text-align:left;font-size:small;"| KATAKANA LETTER AINU P || style="font-size:small;" | U+31F7 || style="font-size:small;" | U+309A || ㇷ゚
|}