Page 73 - Bebop to The Boolean Boogie An Unconventional Guide to Electronics Fundamentals, Components, and Processes

54 ChuptevSewen

Dwo-Decimal (Base-12)
Number systems with bases other than ten have sprouted up like weeds
throughout history. Some cultures made use of duo-decimal (base-12) systems;
instead of counting fingers they counted finger-joints. The thumb is used to
point to the relevant joint and, as each finger has three joints, the remaining
fingers can be used to represent values from 1 through 12 (Figure 7-4).
This system is particularly useful if one
Thumb is used wishes to count up to twelve while still main-
taining a free hand to throw a spear at someone
whom, we may assume, is not a close friend.
This form of counting may explain why the
ancient Sumerians, Assyrians, and Babylonians
divided their days into twelve periods, six for
day and six for night. The lengths of the periods
were adjusted to the seasons (since the length of
daylight compared to night time varies through-

out the year), but were approximately equal to
Figure 7-4. Using finger joints two of our hours. In fact, the Chinese use a form
to count in duo-decimal of this system to the present day (Figure 7-5).

11:00pm 0 1:00arn = HouroftheRat
1:00am 0 3:00arn = Houroftheox
3:00arn 0 5:00arn = HouroftheTiger

5:00arn 0 700arn = HouroftheHare
700am 0 9:00arn = HouroftheDragon
9:00arn 0 11:00arn Hourofthe5nake
11:OUarn 0 1:OOpm = Hourofthe Horse
1:00pm 0 3:00prn = HouroftheRarn
3:00prn 0 5:OOprn = Hour ofthe Monkey
5:00prn 0 700pm = Hourofthecock
700prn 0 9:00prn = Hourofthe Dog
9:00prn 0 11:OOprn = Hourofthe Boar

Figure 7-5. The Chinese twelve-hour day