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.Unicode Chapter 15, section 15.10 In Unicode, a braille cell does not have a letter or meaning defined. For example, Unicode does not define to be "R".
Independent script
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 transcribes the letter h of the Latin script, as well as the digit 8, it transcribes ᄐ t- of Korean hangul and り 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".
Identifying, naming and ordering
The coding is in accordance with ISO/TR 11548-1 Communication aids for blind persons. 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: has dots 1, 2 and 5 raised. By exception, the zero dot raised pattern is named .Unicode chart U+2800, braille patterns
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.
There is no regular mapping to the braille ASCII numbering.
Colloquial names
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 in the plural even when only one dot is listed: thus Unicode says 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 would be spoken as "braille dots 4 and 5". The word "and" is not always used when listing many dots however.
Block
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:
Font differences 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.
Other uses The Braille Pattern characters are commonly used in terminal applications as a way to draw multiple pixels per character.
The messaging app Telegram sometimes uses 8-dot-Braile to denote a hidden part of a message, especially when such a hidden message is cited in another message.
History The following Unicode-related documents record the purpose and process of defining specific characters in the Braille Patterns block:
Version Count UTC ID L2 ID WG2 ID Document 3.0 U+2800..28FF 256 N1093 N1203 N1279 doc) N1342 N1339 N1345 N1353 N1409R N1453 N1541 N1588 N1612 N1603 N1770 N1703
References