* The binary digits of 0 and 1 are nice because they can be conveniently represented by anything that has two states: an electrical switch that’s on or off, a beam of coherent light that’s there or not, or even (as we shall soon see) a bunch of crabs that are present or absent. But keep in mind that binary isn’t mandatory! Computers have been built on other number systems, including the 0s, 1s, and 2s of three-digit trinary, and as long as you can come up with a way to represent these digits, feel free to explore whatever number system interests you the most.