An easy-to-use guide to the world's first computer, from its historical origins and how it works to how to use it to perform an array of mathematical feats.The abacus is as efficient and useful a tool today as it was when it was first devised many centuries ago. Whether you're a computer expert or you're mastering arithmetic and word problems for the first time, it won't take long to learn the basics (and even the not-so-basics) of adding, subtracting, multiplying,...