Code_ The Hidden Language of Computer Hardware and Software - Charles Petzold [7]
The origins of an alternative type of code came from an unexpected source. Charles Barbier, a captain of the French army, had by 1819 devised a system of writing he called écriture nocturne, or "night writing." This system used a pattern of raised dots and dashes on heavy paper and was intended for use by soldiers in passing notes to each other in the dark when quiet was necessary. The soldiers were able to poke these dots and dashes into the back of the paper using an awl-like stylus. The raised dots could then be read with the fingers.
The problem with Barbier's system is that it was quite complex. Rather than using patterns of dots and dashes that corresponded to letters of the alphabet, Barbier devised patterns that corresponded to sounds, often requiring many codes for a single word. The system worked fine for short messages in the field but was distinctly inadequate for longer texts, let alone entire books.
Louis Braille became familiar with Barbier's system at the age of 12. He liked the use of raised dots, not only because it proved easy to read with the fingers but also because it was easy to write. A student in the classroom equipped with paper and a stylus could actually take notes and read them back. Louis Braille diligently tried to improve the system and within three years (at the age of 15) had come up with his own, the basics of which are still used today. For many years, the system was known only within the school, but it gradually made its way to the rest of the world. In 1835, Louis Braille contracted tuberculosis, which would eventually kill him shortly after his 43rd birthday in 1852.
Today, enhanced versions of the Braille system compete with tape-recorded books for providing the blind with access to the written word, but Braille still remains an invaluable system and the only way to read for people who are both blind and deaf. In recent years, Braille has become more familiar in the public arena as elevators and automatic teller machines are made more accessible to the blind.
What we're going to do in this chapter is dissect Braille code and see how it works. We don't have to actually learn Braille or memorize anything. We just want some insight into the nature of codes.
In Braille, every symbol used in normal written language—specifically, letters, numbers, and punctuation marks—is encoded as one or more raised dots within a two-by-three cell. The dots of the cell are commonly numbered 1 through 6:
In modern-day use, special typewriters or embossers punch the Braille dots into the paper.
Because embossing just a couple pages of this book in Braille would be prohibitively expensive, I've used a notation common for showing Braille on the printed page. In this notation, all six dots in the cell are shown. Large dots indicate the parts of the cell where the paper is raised. Small dots indicate the parts of the cell that are flat. For example, in the Braille character dots 1, 3, and 5 are raised and dots 2, 4, and 6 are not.
What should be interesting to us at this point is that the dots are binary. A particular dot is either flat or raised. That means we can apply what we've learned about Morse code and combinatorial analysis to Braille. We know that there are 6 dots and that each dot can be either flat or raised, so the total number of combinations of 6 flat and raised dots is 2 x 2 x 2 x 2 x 2 x 2, or 26, or 64.
Thus, the system of Braille is capable of representing 64 unique codes. Here they are—all 64 possible Braille codes:
If we find fewer than 64 codes used in Braille, we should question why some of the 64 possible codes aren't being used. If we find more than 64 codes used in Braille, we should question either our sanity or fundamental truths of mathematics, such as 2 plus 2 equaling 4.
To begin dissecting the code of Braille,