modulus operator - Newbie Question

1. Google for "n1256.pdf". That's the latest free draft of the C Standard. That means _everything_ about C is in there, including the modulo operator (and you can look up modulus as well, which is something completely different If you are serious about programming, get it.

2. a % b is the division remainder. 20 divided by 3 equals 6 with a remainder of 2. Therefore 20 / 3 -> 6, and 20 % 3 -> 2.

3. To get a feeling for it, write a loop that prints i and i % 7, say for i = 1 to 100.

 

An excellent suggestion. It's not really possible to see its effect on a single example. I also suggest printing i / 7 at the same time, so one can see how integer division (also called truncating division) works.

One can think of it as the remainder after division, or as "circular arithmetic", such as with a clock.
http://en.wikipedia.org/wiki/Modular_arithmetic