4.1. The Modulus Operator¶
The modulus operator works on integers (and integer expressions) and
yields the remainder when the first operand is divided by the second.
In C++, the modulus operator is a percent sign,
%. The syntax is exactly
the same as for other operators:
This program shows the difference between the division operator and the modulus operator.
The first operator, integer division, yields 2. The second operator yields 1. Thus, 7 divided by 3 is 2 with 1 left over.
The modulus operator turns out to be surprisingly useful. For example,
you can check whether one number is divisible by another: if
x % y is
zero, then x is divisible by y.
Also, you can use the modulus operator to extract the rightmost digit or
digits from a number. For example,
x % 10 yields the rightmost digit of
x (in base 10). Similarly
x % 100 yields the last two digits.