The Unicode block Braille Patterns (U+2800..U+28FF) contains all 256 possible patterns of an 8-dot braille cell, thereby including the complete 6-dot cell range.[3] In Unicode, a braille cell does not have a letter or meaning defined. For example, Unicode does not define U+2817 BRAILLE PATTERN DOTS-1235 to be "R".

Braille Patterns
RangeU+2800..U+28FF
(256 code points)
PlaneBMP
ScriptsBraille
Assigned256 code points
Unused0 reserved code points
Source standardsISO 11548-1
Unicode version history
3.0 (1999)256 (+256)
Unicode documentation
Code chart ∣ Web page
Note: [1][2]

Independent script

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In themselves, braille letters do not belong to any print script, but constitute a distinct braille script. The same braille letter can be used to transcribe multiple scripts, e.g. Latin, Cyrillic, Greek and even elements of Chinese characters, as well as digits. Thus while U+2813 BRAILLE PATTERN DOTS-125 transcribes the letter h of the Latin script, as well as the digit 8, it transcribes ᄐ t- of Korean hangul and ri of Japanese kana.

The Unicode character property of braille characters is set to "So" (Symbol, other) rather than to "Lo" (Letter, other). The ISO 15924 script code for braille "Brai".[3]

Identifying, naming and ordering

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Braille dot numbering
 
Hexadecimal value of braille dots

The coding is in accordance with ISO/TR 11548-1 Communication aids for blind persons.[3] Unicode uses the standard dot-numbering 1 to 8. Historically only the 6-dot cell was used in braille. The lower two dots were added later, which explains the irregular numbering 1-2-3-7 in the left column and 4-5-6-8 in the right column. Where dots 7 and 8 are not raised, there is no distinction between 6-dot and 8-dot definitions.

The Unicode name of a specific pattern mentions the raised dots: U+2813 BRAILLE PATTERN DOTS-125 has dots 1, 2 and 5 raised. By exception, the zero dot raised pattern is named U+2800 BRAILLE PATTERN BLANK.[4]

In the 8-dot cell each dot individually can be raised or not. That creates 28=256 different patterns. By mapping each of the eight dots to a bit in a byte (in a little-endian order), and by defining "0"/"1" for not raised/raised per bit, every specific pattern generates an identifying binary number. So the pattern with dots 1-2-5 raised would yield (00010011)2, equivalent to (13)16 or (19)10.

The mapping can also be computed by adding together the hexadecimal values, seen at right, of the dots raised. So the pattern with dots 1-2-5 raised would yield 116+216+1016 = 1316. Whether computed directly in hexadecimal, or indirectly via binary, the result is added to 280016, the offset for the Braille Patterns Unicode block.

Braille symbol
Unicode character U+2813 U+28C7 U+28FF
Name BRAILLE PATTERN DOTS-125 BRAILLE PATTERN DOTS-12378 BRAILLE PATTERN DOTS-12345678
Dot numbers available 1 2 3 4 5 6 7 8 1 2 3 4 5 6 7 8 1 2 3 4 5 6 7 8
Dot raised=1 1 1 0 0 1 0 0 0 1 1 1 0 0 0 1 1 1 1 1 1 1 1 1 1
Reverse order
(lowest value right, as in decimal notation)
0 0 0 1 0 0 1 12 1 1 0 0 0 1 1 12 1 1 1 1 1 1 1 12
Hex value of dots 10+2+116 80+40+4+2+116 80+40+20+10+8+4+2+116
Total hexadecimal value 1316 C716 FF16
Into block,
offset U+280016
280016+1316=U+2813 280016+C716=U+28C7 280016+FF16=U+28FF

There is no regular mapping to the braille ASCII numbering.

Colloquial names

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The Unicode names of braille dot patterns are not the same as what many English speakers would use colloquially. In particular, Unicode names use the word dots in the plural even when only one dot is listed: thus Unicode says braille pattern dots-5 when most English-speaking users of braille would simply say "braille dot 5" or just "dot 5".

In addition, some English-speaking users of braille use the word "and" when listing only two dots. Thus braille pattern dots-45 would be spoken as "braille dots 4 and 5". The word "and" is not always used when listing many dots however.

Block

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Braille was added to the Unicode Standard in September, 1999 with the release of version 3.0.

When using punching, the filled (black) dots are to be punched.

The Unicode block for braille is U+2800 ... U+28FF:

Braille Patterns[1]
Official Unicode Consortium code chart (PDF)
  0 1 2 3 4 5 6 7 8 9 A B C D E F
U+280x
U+281x
U+282x
U+283x
(end of 6-dot cell patterns)
U+284x
U+285x
U+286x
U+287x
U+288x
U+289x
U+28Ax
U+28Bx
U+28Cx
U+28Dx
U+28Ex
U+28Fx
Notes
1.^ As of Unicode version 16.0

Font differences

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When showing braille graphically in printed instruction manuals, it can be useful to indicate the dots that are not punched, especially if a single braille cell of only one or two punched dots is shown out of context: in this case it might otherwise be difficult to judge the vertical alignment of the dots and tell the difference between, say, dots 2 and 4 versus dots 3 and 5.

The current Unicode charts, and some fonts, use empty circles to indicate dots that are not punched. This does not always render very clearly: if the circle outlines are printed heavily then it can be difficult to tell at a glance whether the dot is filled in or not. The braille package for LaTeX (and several printed publications such as the printed manual for the new international braille music code) show unpunched dots as very small dots (much smaller than the filled-in dots) rather than circles, and this tends to print better.

Some braille fonts do not indicate unpunched dots at all. Additionally, some Linux braille fonts (e.g. GNU Unifont and the DejaVu fonts) use small squares instead of small circles to indicate dots.[5]

Other uses

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The Braille Pattern characters are commonly[6][failed verification] used in terminal applications as a way to draw multiple pixels per character.

History

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The following Unicode-related documents record the purpose and process of defining specific characters in the Braille Patterns block:

References

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  1. ^ "Unicode character database". The Unicode Standard. Retrieved 2023-07-26.
  2. ^ "Enumerated Versions of The Unicode Standard". The Unicode Standard. Retrieved 2023-07-26.
  3. ^ a b c Unicode Chapter 15, section 15.10
  4. ^ Unicode chart U+2800, braille patterns
  5. ^ "Braille Pattern Dots-1358 (U+2895) Font Support". fileformat.info. Retrieved December 7, 2014.
  6. ^ "Iirelu/Braillify". GitHub. 22 July 2021.