Binary "%" computes the modulus of two numbers.Given integer operands
$a and $b: If $b is positive, then "$a % $b" is $a minus the largest
multiple of $b that is not greater than $a.  If $b is negative then
"$a % $b" is $a minus the smallest multiple of $b that is not less than
$a (i.e. the result will be less than or equal to zero).  Note that
when "use integer" is in scope "%" gives you direct access to the mod-
ulus operator as implemented by your C compiler.  This operator is not
as well defined for negative operands, but it will execute faster.