In this lively series of essays, Tom Dean explores interesting fundamental topics in computer science with the aim of showing how computers and computer programs work and how the various subfields of computer science are connected. Along the way, he conveys his fascination with computers and enthusiasm for working in a field that has changed almost every aspect of our daily lives. The essays touch on a wide range of topics, from digital logic and machine language to artificial intelligence and searching the World Wide Web, considering such questions as: • How can a computer learn to recognize junk email? • What happens when you click on a link in a browser? • How can you program a robot to do two things at once? • Are there limits on what computers can do? The author invites readers to experiment with short programs written in several languages. Through these interactions he grounds the models and metaphors of computer science and makes the underlying computational ideas more concrete. The accompanying web site http://www.cs.brown.edu/~tld/talk/ provides easy access to code fragments from the book, tips on finding and installing software, links to online resources, exercises and sample lectures.