Elementary students around the globe are taught to count using a base-10 number system. We form numbers using the 10 digits of our base-10 system, which is zero through nine. Readers discover other number systems people have used throughout history. With a binary system, computers only use two digits: 0 and 1. So how does a computer count to 10? Readers will learn the answer inside this book. Also included is a review of hexadecimal numbers, which serve as the old basis of assembly languages and can still be found today setting colors on the web. This volume meets math standards addressing number systems other than base 10.