I’ve been dealing with the phenomenon of similar looking characters. I can’t tell you how many times I have entered a “code” only to find I misinterpreted one or more characters because they look similar.

The problem is some characters look alike. The font used is also a factor. But in thinking about this, I realize VIN numbers for automobiles don’t have this problem.

Some common examples are

  • the letter “B” and the numeral “8”
  • the letter “I” and the numeral “1”
  • the letter “O” and the numeral “0”
  • those are the most obvious, but there are others that are kind of similar, but

  • the letter “A” and the numeral “4”
  • the letter “Q” and the letter “O” which already looks like the numeral “0”
  • the letter “Z” and the numeral “7”
  • Giving weight to the numerals and tossing out any letters that have possible visual similarities, I’ve settled on the following characters that should be allowed for use in codes

    0 1 2 3 4 5 6 7 8 9
    C D E F G H J K L M N P R S T U V W X Y

    I’ve thrown out the letters, A, B, I, O, Q, Z

    So, we’re left with a Base 30 vocabulary

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