Fullwidth ASCII variants
Halfwidth CJK punctuation
Halfwidth Katakana variants
Halfwidth Hangul variants
Fullwidth symbol variants
Halfwidth symbol variants
In CJK 4E00–9FFF (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.