verifying the two check digits of an account number with a pencil, nine digits at a time
Built as a memo rather than a table: the thing worth hanging it up for reads across the room, with the full reference in smaller type below it.
Three sizes in one archive — from a sheet on the fridge to a poster on the wall.
Shaded: the country code and check digits, wherever they stand. The number on this sheet is a made-up example.
Before dividing, B becomes 11, so both B1 and 1B turn into 111, and no remainder can tell them apart. The same goes for M2 and 2M — 222, X3 and 3X — 333. In a British number such a typo is caught by the format, not by the division: there the check digits are followed by four letters, then fourteen digits, and a digit where a letter belongs stands out at once.
Why the numbers can be trusted. Every countable number here is computed from data rather than typed in, and the sheet must pass 2 independent checks before it is allowed to build — how many items there are, the order they come in, and the claim in the highlighted box itself. If one fails, there is no file.
ten tasks, the year of each, the system, the figure — and the human it was measured against
all 128 positions: the column is the three high bits, the row is the four low ones
who published each standard, when, what it does to the sound, and how many bits per second it allows
forty bits to a quantum: five bytes, eight characters and five padding cases