When I heard this question, I queried the use of the word 'digit' in this context. In normal usage, 1, 2, 3 etc. are digits, but A, B, C etc. are letters. Are there 16 digits in the hexadecimal system, or are there ten digits and six letters?
Wikipedia seems to agree with me, because it refers to them as 'symbols' rather than 'digits'. According to dictionary.com, however, 'digit' is correct, because a digit can be "any of the symbols of other number systems, as 0 or 1 in the binary."
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