Braille is a tactile writing system used by people who are visually impaired. It is traditionally written with embossed paper. Braille users can read computer screens and other electronic supports using refreshable braille displays. They can write braille with the original slate and stylus or type it on a braille writer, such as a portable braille notetaker or computer that prints with a braille embosser.

Braille is named after its creator, Louis Braille, a Frenchman who lost his sight as a result of a childhood accident. In 1824, at the age of fifteen, he developed a code for the French alphabet as an improvement on night writing. He published his system, which subsequently included musical notation, in 1829. The second revision, published in 1837, was the first small binary form of writing developed in the modern era.

Braille cells are not the only thing to appear in braille text. There may be embossed illustrations and graphs, with the lines either solid or made of series of dots, arrows, bullets that are larger than braille dots, etc. A full braille cell includes six raised dots arranged in two columns, each column having three dots. The dot positions are identified by numbers from one to six. There are 64 possible combinations, including no dots at all for a word space. A cell can be used to represent a letter, digit, punctuation mark, or even a word.

Historically, there have been three principles in assigning the values of a linear script (print) to Braille: Using Louis Braille's original French letter values; reassigning the braille letters according to the sort order of the print alphabet being transcribed; and reassigning the letters to improve the efficiency of writing in braille.

A third principle was to assign braille codes according to frequency, with the simplest patterns (quickest ones to write with a stylus) assigned to the most frequent letters of the alphabet. Such frequency-based alphabets were used in Germany and the United States in the 19th century (see American Braille), but with the invention of the braille typewriter their advantage disappeared, and none are attested in modern use they had the disadvantage that the resulting small number of dots in a text interfered with following the alignment of the letters, and consequently made texts more difficult to read than Braille's more arbitrary letter-assignment. Finally, there are braille scripts which don't order the codes numerically at all, such as Japanese Braille and Korean Braille, which are based on more abstract principles of syllable composition.

In 1951 David Abraham, a woodworking teacher at the Perkins School for the Blind produced a more advanced Braille typewriter, the Perkins Brailler. In 1991 Ernest Bate developed the Mountbatten Brailler, an electronic machine used to type braille on braille paper, giving it a number of additional features such as word processing, audio feedback and embossing. This version was improved in 2008 with a quiet writer that had an erase key.

Braille is usually read in printed forms such as paper books written in braille, braille public signals and also on Braille e-books. Currently more than 1% of all printed books have been translated into braille.

In 1960, 50% of legally blind, school-age children were able to read braille in the U.S. According to the 2015 Annual Report from the American Printing House for the Blind, there were 61,739 legally blind students registered in the U.S. Of these, 8.6% (5,333) were registered as braille readers, 31% (19,109) as visual readers, 9.4% (5,795) as auditory readers, 17% (10,470) as pre-readers, and 34% (21,032) as non-readers.

A key turning point for braille literacy was the passage of the Rehabilitation Act of 1973, an act of Congress that moved thousands of children from specialized schools for the blind into mainstream public schools. Because only a small percentage of public schools could afford to train and hire braille-qualified teachers, braille literacy has declined since the law took effect. Braille literacy rates have improved slightly since the bill was passed, in part because of pressure from consumers and advocacy groups that has led 27 states to pass legislation mandating that children who are legally blind be given the opportunity to learn braille.

Though braille is thought to be the main way blind people read and write, in Britain (for example) out of the reported two million blind and low vision population, it is estimated that only around 15,00020,000 people use braille. Younger people are turning to electronic text on computers with screen reader software instead, a more portable communication method that they can 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.

The contraction rules take into account the linguistic structure of the word; thus, contractions are generally 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. 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.

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