Martin Erwig - Once Upon an Algorithm: How Stories Explain Computing

When people ask about my work, the conversation quickly turns to the question of what computer science is. To say computer science is the science of computers is misleading (though strictly speaking not incorrect) because most people will take computerto mean PC or laptop and conclude that computer scientists spend their time constructing hardware. On the other hand, defining computer science as the study of computation is simply kicking the can down the road, since it immediately raises the question of what computation is.

Over the years, I have come to realize that teaching by just introducing concept after concept doesnt work very well; it is simply too abstract. Nowadays, I typically start by describing computer science as the study of systematic problem solving. Everybody knows what a problem is, and everybody has seen solutions as well. After explaining this view through an example, I often get the chance to introduce the concept of an algorithm, which allows me to point out important differences between computer science and mathematics. Most of the time, I dont need to talk about programming languages, computers, and related technical matters, but even if it comes to that, the concrete problem makes it easy to illustrate these concepts. Once Upon an Algorithmis an elaboration of this approach.

Computer science is a relatively new member of the science club, and sometimes it seems it has not yet earned the respect granted to serious scientific disciplines like physics, chemistry, and biology. Think of a movie scene involving a physicist. You will probably see someone discussing complicated formulas written on a blackboard or supervising an experiment wearing a lab coat. The physicist is shown as a reputable scientist whose knowledge is treasured. Now imagine a similar scene involving a computer scientist. Here you will likely see some nerdy guy sitting in a dark, messy room and staring at a computer screen. He is frantically typing on a keyboard, probably trying to break some code or password. In both scenes, an important problem is being solved, but while the physicist might provide some plausible explanation of how it can be solved, the solution of the computer problem remains mysterious, often magical, and much too complex to be explained to a nonspecialist. If computer science is unexplainable to laypeople, why would anyone ever try to know more about it or understand it?

The subject of computer science is computation,a phenomenon that affects everybody. I am not talking only about cell phones, laptops, or the internet. Consider folding a paper airplane, driving to work, cooking a meal, or even DNA transcription, a process that occurs in your cells millions of times while you are reading this sentence. These are all examples of computationa systematic way of problem solvingeven though most people would not perceive them as such.

Science provides us with a basic understanding of how the natural world works, and it gives us the scientific method for reliably establishing that knowledge. What applies to science in general holds for computer science, too, especially since we encounter computation in so many different forms and so many different situations. A basic understanding of computation thus provides benefits similar to a basic knowledge of physics, chemistry, and biology in making sense of the world and tackling many real-world problems more effectively. This aspect of computation is often referred to as computational thinking.

A major goal of this book is to emphasize the general nature of computation and thus the wide applicability of computer science. My hope is that this will spark a broader interest in computer science and a desire to learn more about it.

I first identify computation in everyday activities and then explain corresponding computer science concepts through popular stories. The everyday situations are taken from a typical workday: getting up in the morning, having breakfast, commuting to work, episodes at the workplace, a doctors appointment, a hobby activity in the afternoon, having dinner, and reflecting on the days events in the evening.