From now on, we can forget about wires and switches and work with the abstraction of logic blocks operating on 1’s and 0’s, a simple step that allows us to pass from the realm of engineering into the realm of mathematics. This is the most abstract chapter in the book; it will show you how the methods used to construct a tic-tac-toe machine can be used to construct almost any function. In it, we’ll define a powerful set of building blocks: logical functions and finite-state machines. With these elements, it’s easy to build a computer.