Every day, we achieve great feats using our computers. When we "upload" a photo to Facebook, millions of pieces of information are transmitted through multiple internet links that are susceptible to errors; however, ultimately, a flawless copy of the photo reaches its destination. Without even knowing it, we use public key encryption to transmit confidential information, such as credit card numbers, and we use digital signatures to verify the identity of the websites we visit. How do our computers perform these tasks with such ease? This is the first book that answers the above question in a language that everyone can understand, revealing the amazing ideas that drive personal computers, laptops, and smartphones. Using illustrative examples, John MacCormick explains the basic "tricks" used by nine types of computational algorithms. These revolutionary algorithms have changed our world: this book unlocks their secrets and reveals the amazing ideas that our computers use every day.