Just an added thought to Moles post, put can come in REAL handy in a lot of situations. For example, I'm working on a stupid Black Jack game in J# for school. Well, since computers think mainly in numbers, you almost HAVE to use the % operator.
What I'm saying is you have 52 cards, 1-52, right? Well, you randomly pick a card, and if it's 25, you need to know what suit it's in and what it's value is. So after setting the rules, it's easy with that operator.