Wednesday, January 31, 2007


I once went to a lecture by Richard Hamming in which he talked about what it takes to be a great scientist. One of his points was that to distinguish yourself from the rest of the pack you have to be very precise about you're saying, because even the average professional scientist has an incomplete understanding of the meaning of the terms and symbols of his or her field.

I was reminded of that today when a group of otherwise intelligent people at my place of work were trying to remember which of the symbols on a power switch meant off and which meant on. Here is the correct answer, for the sake of reference.

This arrangement makes some sense in retrospect, but there were numerous hypotheses about which symbol meant what. One, which is probably correct, is that the line represents 1 (or on) and the circle is 0 (or off). For the boolean-aware, that makes sense. However, i also heard that the circle represents a completed circuit (hence on); and i heard the converse, that a line represents a closed switch while the circle indicates an open switch.

What's interesting though is that these symbols don't have an obvious meaning for everyone, so you basically just have to know which symbol corresponds to which state. For me, this begs the question: Are these symbols really an improvement over the words "On" and "Off"? (or the equivalent words in some other language). At least those symbols are unambiguous for some portion of the population.

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