Halfwidth and Fullwidth Forms (Unicode block) explained

Blockname:Halfwidth and Fullwidth Forms
Rangestart:FF00
Rangeend:FFEF
Symbols:Variant width characters
1 0 0:216
1 1:7
3 2:2
Note:[1] [2] [3]

Halfwidth and Fullwidth Forms is the name of a Unicode block U+FF00 - FFEF, provided so that older encodings containing both halfwidth and fullwidth characters can have lossless translation to/from Unicode. It is the second-to-last block of the Basic Multilingual Plane, followed only by the short Specials block at U+FFF0 - FFFF. Its block name in Unicode 1.0 was Halfwidth and Fullwidth Variants.[4]

Range U+FF01 - FF5E reproduces the characters of ASCII 21 to 7E as fullwidth forms. 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+FF61 - FF9F encodes halfwidth forms of katakana and related punctuation in a transposition of A1 to DF in the JIS X 0201 encoding – see half-width kana.

The range U+FFA0 - FFDC encodes halfwidth forms of compatibility jamo characters for Hangul, in a transposition of their 1974 standard layout. It is used in the mapping of some IBM encodings for Korean, such as IBM code page 933, which allows the use of the Shift Out and Shift In characters to shift to a double-byte character set.[5] Since the double-byte character set could contain compatibility jamo, halfwidth variants are needed to provide round-trip compatibility.[6] [7]

Range U+FFE0 - FFEE includes fullwidth and halfwidth symbols.

Block

The block has variation sequences defined for East Asian punctuation positional variants.[8] [9] They use (VS01) and (VS02):

Variation sequences for punctuation alignment
U+ FF01 FF0C FF0E FF1A FF1B FF1F Description
base code point ！ ， ． ： ； ？
base + VS01 ！︀ ，︀ ．︀ ：︀ ；︀ ？︀ corner-justified form
base + VS02 ！︁ ，︁ ．︁ ：︁ ；︁ ？︁ centered form

An additional variant is defined for a fullwidth zero with a short diagonal stroke: U+FF10 FULLWIDTH DIGIT ZERO, U+FE00 VS1 (０︀).[10] [9]

History

The following Unicode-related documents record the purpose and process of defining specific characters in the Halfwidth and Fullwidth Forms block:

Count L2 ID WG2 ID Document
1.0.0 U+FF01..FF5E, FF61..FFBE, FFC2..FFC7, FFCA..FFCF, FFD2..FFD7, FFDA..FFDC, FFE0..FFE6 216 (to be determined)
doc)
1.1 U+FFE8..FFEE 7 (to be determined)
3.2 U+FF5F..FF60 2
N2344
N2345R
N2403

See also

References

Notes and References

  1. Web site: Unicode 1.0.1 Addendum. The Unicode Standard. 1992-11-03. 2016-07-09.
  2. Web site: Unicode character database. The Unicode Standard. 2023-07-26.
  3. Web site: Enumerated Versions of The Unicode Standard. The Unicode Standard. 2023-07-26.
  4. Web site: 3.8: Block-by-Block Charts . The Unicode Standard . version 1.0 . Unicode Consortium.
  5. Web site: ICU Demonstration - Converter Explorer. demo.icu-project.org. 7 May 2018.
  6. Web site: Halfwidth and Fullwidth blame.
  7. Web site: Conversion Data - Old location of the ICU User Guide.
  8. Web site: L2/17-436: Proposal to add standardized variation sequences for fullwidth East Asian punctuation. 2018-01-21. Ken. Lunde.
  9. Web site: Unicode Character Database: Standardized Variation Sequences . The Unicode Consortium.
  10. Web site: L2/15-268: Proposal to Represent the Slashed Zero Variant of Empty Set. 2015-10-30. Barbara. Beeton. Asmus. Freytag. Laurențiu. Iancu. Murray. Sargent.

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