資料來源 : Free On-Line Dictionary of Computing
modular arithmetic
(Or "clock arithmetic") A kind of integer
arithmetic that reduces all numbers to one of a fixed set
[0..N-1] (this would be "modulo N arithmetic") by effectively
repeatedly adding or subtracting N (the "modulus") until the
result is within this range.
The original mathematical usage considers only _equivalence_
modulo N. The numbers being compared can take any values,
what matters is whether they differ by a multiple of N.
Computing usage however, considers modulo to be an operator
that returns the remainder after integer division of its first
argument by its second.
Ordinary "clock arithmetic" is like modular arithmetic except
that the range is [1..12] whereas modulo 12 would be [0..11].
(2003-03-28)