Unified international braille

The goal of braille uniformity is to unify the braille alphabets of the world as much as possible, so that literacy in one braille alphabet readily transfers to another. Unification was first achieved by a convention of the International Congress on Work for the Blind in 1878, where it was decided to replace the mutually incompatible national conventions of the time with the French values of the basic Latin alphabet, both for languages which use Latin-based alphabets and, through their Latin equivalents, for languages which use other scripts. However, the unification did not address letters beyond these 26, leaving French and German Braille partially incompatible, and as braille spread to new languages with new needs, national conventions again became disparate. A second round of unification was undertaken under the auspices of UNESCO in 1951, setting the foundation for international braille usage today.

Braille arranged his characters in decades (groups of ten), and assigned the 25 letters of the French alphabet to them in order. The characters beyond the first 25 are the principal source of variation today.

In the first decade, only the top four dots are used; the two supplementary characters have dots only on the right. These patterns are repeated for the second decade, with the addition of a diacritic at dot 3; for the third, at dots 3 and 6; for the fourth, at 6; and for the fifth decade, by duplicating the first decade within the lower four dots.

Braille is in its origin a numeric code. Louis Braille applied the characters in numerical order to the French alphabet in alphabetical order. As braille spread to other languages, the numeric order was retained and applied to the local script. Therefore, where the alphabetical order differed from that of French, the new braille alphabet would be incompatible with French Braille. For example, French was based on a 25-letter alphabet without a w. When braille was adopted for English in the United States, the letters were applied directly to the English alphabet, so that braille letter of French x became English w, French y became English x, French z English y, and French ç English z. In the United Kingdom, however, French Braille was adopted without such reordering. Therefore, any English book published in braille needed to be typeset separately for the United States and the United Kingdom. Similarly, the letters Egyptian Arabic Braille were assigned their forms based on their nearest French equivalents, so that for example Arabic d had the same braille letters as French d. For Algerian Arabic Braille, however, the braille characters were assigned to the Arabic alphabet according to the Arabic alphabetical order, so that Algerian d was the same character as Egyptian h. Thus an Arabic book published in Algeria was utterly unintelligible to blind Egyptians and vice versa.

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