The Braille system is a method that is widely used by blind people to read and write. Braille was devised in 1821 by Louis Braille, a Frenchman. Each Braille character or cell is made up of six dot positions, arranged in a rectangle containing two columns of three dots each. A dot may be raised at any of the six positions to form sixty-four (26) permutations, including the arrangement in which no dots are raised. For reference purposes, a particular permutation may be described by naming the positions where dots are raised, the positions being universally numbered 1 to 3, from top to bottom, on the left, and 4 to 6, from top to bottom, on the right. For example, dots 1-3-4 would describe a cell with three dots raised, at the top and bottom in the left column and on top of the right column, i.e., the letter m. The lines of horizontal Braille text are separated by a space, much like visible printed text, so that the dots of one line can be differentiated from the Braille text above and below. Punctuation is represented by its own unique set of characters.
The Braille system was based on a method of communication originally developed by Charles Barbier in response to Napoleon's demand for a code that soldiers could use to communicate silently and without light at night called night writing. Barbier's system was too complex for soldiers to learn, and was rejected by the military. In 1821 he visited the National Institute for the Blind in Paris, France, where he met Louis Braille. Braille identified the major failing of the code, which was that the human finger could not encompass the whole symbol without moving, and so could not move rapidly from one symbol to another. His modification was to use a 6 dot cell — the Braille system — which revolutionized written communication for the blind.
Today different Braille codes (or code pages) are used to map character sets of different languages to the six bit cells. Different Braille codes are also used for different uses like mathematics and music. However, because the six-dot Braille cell only offers 64 possible combinations, of which some are omitted because they feel the same (having the same dots pattern in a different position), many Braille characters have different meanings based on their context. Therefore, character mapping is not one-to-one.
Braille generally consists of cells of six raised dots arranged in a grid of two dots horizontally by three dots vertically. The dots are conventionally numbered 1, 2, and 3 from the top of the left column and 4, 5, and 6 from the top of the right column. The presence or absence of dots gives the coding for the symbol. Dot height is approximately 0.02 inches (0.5 mm); the horizontal and vertical spacing between dot centers within a Braille cell is approximately 0.1 inches (2.5 mm); the blank space between dots on adjacent cells is approximately 0.15 inches (3.75 mm) horizontally and 0.2 inches (5.0 mm) vertically. A standard Braille page is 11 inches by 11.5 inches and typically has a maximum of 40 to 43 Braille cells per line and 25 lines.
English Braille codes the letters and punctuation, and some double letter signs and word signs directly, but capitalization and numbers are dealt with by using a prefix symbol. In practice, Braille produced in the United Kingdom does not have capital letters.
Braille has been extended to an 8-dot code, particularly for use with Braille embossers and refreshable Braille displays. In 8-dot Braille the additional dots are added at the bottom of the cell, giving a matrix 4 dots high by 2 dots wide. The additional dots are given the numbers 7 (for the lower-left dot) and 8 (for the lower-right dot). Eight-dot Braille has the advantages that the case of an individual letter is directly coded in the cell containing the letter and that all the printable ASCII characters can be represented in a single cell. All 256 (28) possible combinations of 8 dots are encoded by the Unicode standard. Braille with six dots is frequently stored as Braille ASCII.
The first ten letters of the alphabet and the numbers 1 through 0 are formed using only the top four dots (1, 2, 4, and 5). Adding dot 3 forms the next ten letters, and adding dot 6 forms the last five letters (except w) and the words and, for, of, the, and with. Omitting dot 3 from the letters U-Z and the five word symbols forms nine digraphs (ch, gh, sh, th, wh, ed, er, ou, and ow) and the letter w.
The question mark is represented by dots 2-3-6—the same as the opening quotation mark. Therefore the placement of the dots—before a word or after a word—will determine which symbol it is.
Opening and closing parentheses are shown with the same symbol. Therefore, the placement context will determine whether the parentheses is opening or closing.
Braille also includes a number of whole word contractions, for example the word Braille becomes a three cell word brl.
|⠓||H 8||⠠||Capital sign|
|⠊||I 9||⠼||Number sign|
Although it is possible to transcribe Braille by simply substituting the equivalent Braille character for its printed equivalent, such a character-by-character transcription (known as Grade 1 Braille) is used only by beginners.
Braille characters are much larger than their printed equivalents, and the standard 11" by 11.5" (28 cm × 30 cm) page has room for only 25 lines of 43 characters. To reduce space and increase reading speed, virtually all Braille books are transcribed in what is known as Grade 2 Braille, which uses a system of contractions to reduce space and speed the process of reading. As with most human linguistic activities, Grade 2 Braille embodies a complex system of customs, styles, and practices. The Library of Congress's Instruction Manual for Braille Transcribing runs to nearly 200 pages. Braille transcription is skilled work, and Braille transcribers need to pass certification tests.
In English, the system of Grade 2 Braille contractions begins with a set of 23 words which are contracted to single characters. Thus the word but is contracted to the single letter b, can to c, do to d, and so on. Even this simple rule creates issues requiring special cases; for example, d is, specifically, an abbreviation of the verb do; the noun do representing the note of the musical scale is a different word, and must be spelled out.
Portions of words may be contracted, and many rules govern this process. For example, the character with dots 2-3-5 (the letter "f" lowered in the Braille cell) stands for "ff" when used in the middle of a word. At the beginning of a word, this same character stands for the word "to" although the character is written in Braille with no space following it. At the end of a word, the same character represents an exclamation point.
The contraction rules take into account the linguistic structure of the word; thus, contractions are not to be used when their use would alter the usual Braille form of a base word to which a prefix or suffix has been added. And some portions of the transcription rules are not fully codified and rely on the judgment of the transcriber. Thus, when the contraction rules permit the same word in more than one way, preference is given to "the contraction that more nearly approximates correct pronunciation."
Grade 3 Braille is a system that includes many additional contractions, almost a shorthand; it is not used for publication, but is used mostly for individuals for their personal convenience.
The current series of Canadian banknotes have raised dots on the banknotes that indicate the denomination and can be easily identified by visually impaired people; this 'tactile feature' does not use standard Braille but, instead, a system developed in consultation with blind and visually impaired Canadians after research indicated that not all potential users read Braille.
Mexican bank notes also have special raised symbols to make them identifiable by the visually impaired.
Though Braille is thought to be the main way blind people read and write, in Britain (for example) out of the reported two-million visually impaired population, it is estimated that only around 15-20 thousand people use Braille. Younger people are turning to electronic text on computers instead; a more portable communication method that they can also use with their friends. A debate has started on how to make Braille more attractive and for more teachers to be available to teach it.
There are many extensions of Braille for additional letters with diacritics, such as ç, ô, é.
When Braille is adapted to languages which do not use the Latin alphabet, the blocks are generally assigned to the new alphabet according to how it is transliterated into the Latin alphabet, and the alphabetic order of the national script (and therefore the natural order of Latin Braille) is disregarded. Such is the case with Russian, Greek, Hebrew, Arabic, and Chinese. In Greek, for example, gamma is written as Latin g, despite the fact that it has the alphabetic position of c; Hebrew bet, the second letter of the alphabet and cognate with the Latin letter b, is sometimes pronounced /b/ and sometimes /v/, and is written b or v accordingly; Russian ts is written as c, which is the usual letter for /ts/ in those Slavic languages that use the Latin alphabet; and Arabic f is written as f, despite being historically p, and occurring in that part of the Arabic alphabet (between historic o and q). Esperanto letters with circumflexes, ĉ, ĝ, ĥ, ĵ and ŝ, are written as those letters without circumflexes with a filled sixth dot. Therefore the letter ĵ has the same representation as the English w and to write a w in Esperanto, the dot 3 is filled (dots 2-3-4-5-6 are used for w instead of dots 2-4-5-6) The ŭ, used in Esperanto also, is as the u but the first dot is moved to the fourth place.
Greater differences occur in Chinese Braille. In the case of Mandarin Braille, which is based on Zhuyin rather than the Latin Pinyin alphabet, the traditional Latin Braille values are used for initial consonants and the simple vowels. However, on Latin Braille for many of the initial consonants and simple vowels (based on romanizations of a century ago), but the blocks pull double duty, with different values depending on whether they're placed in syllable-initial or syllable-final position. For instance, the block for Latin k represents old-style Cantonese k (g in Yale and other modern romanizations) when initial, but aak when final, while Latin j represents Cantonese initial j but final oei.
However, at least three adaptations of Braille have completely reassigned the Latin sound values of the blocks. These are, Japanese Braille, Korean Braille, and Tibetan Braille.
In Japanese Braille, alphabetic signs for a consonant and vowel are combined into a single syllabic block; in Korean Braille, the consonants have different syllable-initial and syllable-final forms. These modifications made Braille much more compatible with Japanese kana and Korean hangul, but meant that the Latin sound values could not be maintained.