Code: The Hidden Language of Computer Hardware and Software, 2nd Edition

Chapter Fourteen

Adding with Logic Gates

Addition is the most basic of arithmetic operations, so if we want to build a computer (and that is my not-so-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 use social media to share our latest dance moves, kitchen feats, or pet antics.

The adding machine that we’ll build in this chapter will be big, clunky, slow, and noisy, at least compared to the calculators ...