Braille
Assignment

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.

Under international consensus, most braille alphabets follow the French sorting order for the 26 letters of the basic Latin alphabet, and there have been attempts at unifying the letters beyond these 26 (see international braille), though differences remain, for example, in German Braille. This unification avoids the chaos of each nation reordering the braille code to match the sorting order of its print alphabet, as happened in Algerian Braille, where braille codes were numerically reassigned to match the order of the Arabic alphabet and bear little relation to the values used in other countries (compare modern Arabic Braille, which uses the French sorting order), and as happened in an early American version of English Braille, where the letters w, x, y, z were reassigned to match English alphabetical order. A convention sometimes seen for letters beyond the basic 26 is to exploit the physical symmetry of braille patterns iconically, for example, by assigning a reversed n to ñ or an inverted s to sh. (See Hungarian Braille and Bharati Braille, which do this to some extent.)

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 that do not order the codes numerically at all, such as Japanese Braille and Korean Braille, which are based on more abstract principles of syllable composition.

Texts are sometimes written in a script of eight dots per cell rather than six, enabling them to encode a greater number of symbols. (See Gardner–Salinas braille codes.) Luxembourgish Braille has adopted eight-dot cells for general use; for example, accented letters take the unaccented versions plus dot 8.
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