How Computers Really Work

How Computers Really Work: A Hands-On Guide to the Inner Workings of the Machine is an approachable, hands-on guide to understanding how computers work, from low-level circuits to modern software. Published by No Starch Press.

The Book

How Computers Really Work cover art

How Computers Really Work takes an informal approach to technical topics. Each chapter covers one foundational aspect of computing. Exercises and hands-on projects throughout are designed to help you learn. Exercises mostly involve mental problem solving, while projects allow you to try various aspects of computing: building a circuit, writing software, and so forth.

You will learn about electrical circuits, learn how to read a circuit diagram, and build a working circuit. You’ll learn how computer hardware like processors, memory, and input/output work and fit together; how low-level machine code runs on a processor, and how to examine the machine code of software running on a computer. You’ll gain an understanding of the differences between programming languages like C and Python; examine operating systems; use tools to explore your local network and the internet, and build a simple web page.

Computing is everywhere, and as our society depends more and more on technology, we need individuals who understand computing broadly. This book will help you construct a mental picture of how computing works, enabling you to then dig deeper into the topics that interest you.

How Computers Really Work is published by No Starch Press.

The Author

Photo of Matthew Justice

Matthew Justice is a software engineer. He spent 17 years at Microsoft where he took on various roles, including debugging the Windows kernel, developing automated fixes, and leading a team of engineers responsible for building diagnostic tools and services. He has worked on low-level software (the operating system) and on software far removed from the underlying hardware (such as web applications). Matthew has a degree in electrical engineering. When he's not writing code or building circuits, Matthew enjoys spending time with his family, hiking, reading, arranging music, and playing old video games.

Resources for Readers

Online content referenced in the book:


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“Much more understandable than most books of this type, even when the author delves deeply into machine code, programming languages, operating systems and the internet. He details 41 hands-on projects, including games, running a web server, and so on. It's just right for the would-be software engineer.”
— Joy Schwabach, The Arkansas Democrat Gazette's On Computers column

“I have to say that the really stand-out stuff in this book are the activities. This book covers a vast scope of material and being able to put ALL of it into hands-on practical experience is a brilliant move... I would have given my right arm for this breadth of coverage when I was at the right age for it. But really, this would be incredible for anyone with a curiosity about computers.”
— David, Goodreads review

“[Author] Justice nails it. He gives a concise--but extremely lucid--explanation of electronics, binary numbers, and gates--and then goes on to explain how a computer really works! It is the best explanation of the CPU, memory arrays, buses, etc that I've ever encountered--and all without any prerequisite knowledge of a computer language. I cannot recommend this book too highly.”
— Dr. L., Amazon review

How Computers Really Work is by far the best foundational book I've ever read! Thank you @matthewjustice for putting it all together. Respect!”
— Ernest Addae, @Earnaddae on Twitter

In the Media

The Wall Street Journal interviewed the author and mentioned How Computers Really Work in a story about computers generating heat.

The David Bramante Show interviewed the author to discuss How Computers Really Work.

TechTarget conducted a networking-focused interview of the author and provided a book excerpt.