Braille Dot Number Converter

In short Braille cells are described by which of their dots are raised, numbered 1, 2 and 3 down the left column and 4, 5 and 6 down the right, with 7 and 8 added underneath in computer braille. So the letter h is written "125" and the number sign is "3456". This converts those dot numbers into real Unicode braille characters and reads any braille character back into its dot numbers. The conversion is arithmetic rather than a lookup, and knowing that is genuinely useful: the Unicode block starts at U+2800 and each dot sets one bit, dot 1 the lowest and dot 8 the highest. So the character for any set of dots is U+2800 plus the sum of those bits, which is why there are exactly 256 braille characters and why they sit in a block in that order. Six-dot braille uses the first 64. The two places this matters in practice are embossing and file formats, where cells are specified by dot number rather than by letter, and debugging, where seeing that a cell is "1345" rather than "145" tells you immediately that a stray dot 3 turned a d into an n. Enter 0 for a blank cell, which is U+2800 itself and is a real character rather than an ordinary space.