Braille is a tactile code for encoding written language in the form of raised dots in a matrix pattern, used to make written words accessible to the blind. It is named after its creator, Louis Braille, who devised the first version of the system when he was 15 years old after having become blind in a childhood accident.
There are a number of variants of Braille. Only the ones designated as "Grade 1" are true character encodings, with one set of raised dots corresponding to each written character; the "Grade 2" and "Grade 3" systems are more complex, with symbols standing for abbreviated words and other shorthand, making Braille a language in its own right. Its ISO 15924 code (for types of writing scripts) is brai, with the numeric code 570.
There are also a number of variants of Braille for different languages. The original version was designed for French, resulting in some oddities such as the letter "w" not being in its normal position (it is not used in French, so it was originally omitted, then later added on to the end of the alphabet). When versions of Braille were adapted to other languages, including English, there were originally a number of incompatible versions encoding the respective languages' alphabets in the normal order for that language, resulting in different values for the same letter; later, however, more standardization was achieved and the basic 26 letters of the Latin alphabet are in the same position in the major variants, though other characters such as accented letters may vary. There are also versions for non-Latin writing systems, including Chinese and Japanese.
The Nemeth Code is an extension to Braille for advanced mathematical renderings.
The digits are encoded with the same Braille symbols as the first ten letters of the alphabet, leaving it to context to distinguish a letter from a digit. A "number sign" can be prefixed to make this distinction explicit, and this is done in the mathematical-notation variants of Braille.
In Unicode, Braille symbols are found at positions U+2800 through U+28FF.