Code: The Hidden Language of Computer Hardware and Software, First Edition

Chapter 12. A Binary Adding Machine

Addition is the most basic of arithmetic operations, so if we want to build a computer (and that is my hidden agenda in this book), we must first know how to build something that adds two numbers together. When you come right down to it, addition is just about the only thing that computers do. If we can build something that adds, we’re well on our way to building something that uses addition to also subtract, multiply, divide, calculate mortgage payments, guide rockets to Mars, play chess, and foul up our phone bills.

The adding machine that we’ll build in this chapter will be big, clunky, slow, and noisy, at least compared to the calculators and computers of modern life. What’s most interesting is that we’re ...