Topics: Braille, Character encoding, ASCII Pages: 2 (600 words) Published: March 17, 2013
The Braille alphabet
Braille can be seen as the world's first binary encoding scheme for representing the characters of a writing system. The system as originally invented by Braille consists of two parts: 1. A character encoding for mapping characters of the French language to tuples of six bits or dots. 2. A way of representing six-bit characters as raised dots in a Braille cell. 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 63 possible combinations (26 - 1 = 63), 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. In addition to simple encoding, modern Braille transcription uses contractions to increase reading speed. (See: Grade 2 Braille) Writing Braille

Braille may be produced using a slate and stylus in which each dot is created from the back of the page, writing in mirror image, by hand, or it may be produced on a Braille typewriter or Perkins Brailler, or produced by a Braille embosser attached to a computer. It may also be rendered using a refreshable Braille display. 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 combination of 8 dots are...
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