finding and fixing a wrong bit among seven: the numbers of the failed checks add up to its position
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 boxes are the check positions (1, 2 and 4); a check’s row repeats the bits it counts. The word on this sheet is an example.
In the late 1940s Richard Hamming ran his jobs on a Bell Labs relay computer. On weekdays it stopped when it detected an error and flashed lights for the operators; after hours and at weekends it simply moved on to the next job. Hamming worked weekends and kept having to start again from scratch. “If the machine can detect an error, why can’t it locate the position of the error and correct it?” he recalled. Hamming published his answer in 1950 in the Bell System Technical Journal.
Why the numbers can be trusted. Every countable number here is computed from data rather than typed in, and the sheet must pass 4 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