The Abacus A Pocket Computer Author:Jesse Dilson The abacus is as useful and efficient a machine today as it was when it was first created centuries ago. Whether you're an expert in the latest computer technology 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, and divid... more »ing on this ingenious and fun-to-use mathematical tool.