Today, it's hard to imagine life without computers. They help us with every part of our lives — whether it's writing a paper for school or buying a candy bar at the corner store. But it took thousands of years for humankind to develop the sophisticated machines we take for granted these days.

Start your tour at The Abacus, and learn a little bit about the world's first computer. This simple device was invented in China around 500 B.C., and was also used by the ancient Japanese and the Aztecs. The abacus is still used today by schoolchildren around the world — in fact, you've probably used one yourself! At this site, you can try adding, subtracting, multiplying, and dividing online using several different models of abaci.

Next stop, Calculating Machines! Here you can check out a chronology of the earliest calculators, and, if you have a Java-enabled browser, try one out for yourself.