Halfwidth and fullwidth forms

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A Korean command prompt (cmd.exe) showing halfwidth and fullwidth characters.

In CJK (Chinese, Japanese and Korean) computing, graphic characters are traditionally classed into fullwidth (in Taiwan and Hong Kong: 全形; in CJK and Japanese: 全角) and halfwidth (in Taiwan and Hong Kong: 半形; in CJK and Japanese: 半角) characters. With fixed-width fonts, a halfwidth character occupies half the width of a fullwidth character, hence the name.

In the days of computer terminals and text mode computing, characters were normally laid out in a grid, often 80 columns by 24 or 25 lines. Each character was displayed as a small dot matrix, often about 8 pixels wide, and an SBCS (single byte character set) was generally used to encode characters of western languages.

For a number of practical and aesthetic reasons, Han characters would need to be twice as wide as these fixed-width SBCS characters. These "fullwidth characters" were typically encoded in a DBCS (double byte character set), although less common systems used other variable-width character sets that used more bytes per character.

Halfwidth and Fullwidth Forms is also the name of a Unicode block U+FF00–FFEF.

In Unicode[edit]

Halfwidth and Fullwidth Forms
Range U+FF00..U+FFEF
(240 code points)
Plane BMP
Scripts Hangul (52 char.)
Katakana (55 char.)
Latin (52 char.)
Common (66 char.)
Symbol sets Variant width characters
Assigned 225 code points
Unused 15 reserved code points
Unicode version history
1.0.0 216 (+216)
1.1 223 (+7)
3.2 225 (+2)
Note: [1][2]

In Unicode, if a certain grapheme can be represented as either a fullwidth character or a halfwidth character, it is said to have both a fullwidth form and a halfwidth form.

Halfwidth and Fullwidth Forms is the name of Unicode block U+FF00–FFEF, the last of the Basic Multilingual Plane excepting the short Specials block at U+FFF0–FFFF.

Range U+FF01–FF5E reproduces the characters of ASCII 21 to 7E as fullwidth forms, that is, a fixed width form used in CJK computing. This is useful for typesetting Latin characters in a CJK environment. U+FF00 does not correspond to a fullwidth ASCII 20 (space character), since that role is already fulfilled by U+3000 "ideographic space."

Range U+FF65–FFDC encodes halfwidth forms of Katakana and Hangul characters – see half-width kana. Range U+FFE0–FFEE includes fullwidth and halfwidth symbols.

Halfwidth and Fullwidth Forms[1][2]
Official Unicode Consortium code chart (PDF)
  0 1 2 3 4 5 6 7 8 9 A B C D E F
U+FF0x
U+FF1x
U+FF2x
U+FF3x _
U+FF4x
U+FF5x
U+FF6x
U+FF7x ソ
U+FF8x
U+FF9x
U+FFAx  HW 
HF
U+FFBx
U+FFCx
U+FFDx
U+FFEx
Notes
1.^ As of Unicode version 7.0
2.^ Grey areas indicate non-assigned code points

See also[edit]

References[edit]

  1. ^ "Unicode character database". The Unicode Standard. Retrieved 22 March 2013. 
  2. ^ The Unicode Standard Version 1.0, Volume 1. Addison-Wesley Publishing Company, Inc. 1991 [1990]. ISBN 0-201-56788-1. 

External links[edit]