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

The classic guide to how computers work, updated with new chapters and interactive graphics

"For me, Code was a revelation. It was the first book about programming that spoke to me. It started with a story, and it built up, layer by layer, analogy by analogy, until I understood not just the Code, but the System. Code is a book that is as much about Systems Thinking and abstractions as it is about code and programming. Code teaches us how many unseen layers there are between the computer systems that we as users look at every day and the magical silicon rocks that we infused with lightning and taught to think."

- Scott Hanselman, Partner Program Director, Microsoft, and host of Hanselminutes

Computers are everywhere, most obviously in our laptops and smartphones, but also our cars, televisions, microwave ovens, alarm clocks, robot vacuum cleaners, and other smart appliances. Have you ever wondered what goes on inside these devices to make our lives easier but occasionally more infuriating?

For more than 20 years, readers have delighted in Charles Petzold's illuminating story of the secret inner life of computers, and now he has revised it for this new age of computing. Cleverly illustrated and easy to understand, this is the book that cracks the mystery. You'll discover what flashlights, black cats, seesaws, and the ride of Paul Revere can teach you about computing, and how human ingenuity and our compulsion to communicate have shaped every electronic device we use.

This new expanded edition explores more deeply the bit-by-bit and gate-by-gate construction of the heart of every smart device, the central processing unit that combines the simplest of basic operations to perform the most complex of feats. Petzold's companion website, CodeHiddenLanguage.com, uses animated graphics of key circuits in the book to make computers even easier to comprehend.

In addition to substantially revised and updated content, new chapters include:

• Chapter 18:  Let's Build a Clock!
• Chapter 21:  The Arithmetic Logic Unit
• Chapter 22:  Registers and Busses
• Chapter 23:  CPU Control Signals
• Chapter 24:  Jumps, Loops, and Calls
• Chapter 28: The World Brain

From the simple ticking of clocks to the worldwide hum of the internet, Code reveals the essence of the digital revolution.

Online Sample Chapters

Bit by Bit by Bit

Logic with Switches

Sample Pages

Download the sample pages (includes Chapters 6 and 11)

Table of Contents

Preface to the Second Edition

Chapter One: Best Friends

Chapter Two: Codes and Combinations

Chapter Three: Braille and Binary Codes

Chapter Four: Anatomy of a Flashlight

Chapter Five: Communicating Around Corners

Chapter Six: Logic with Switches

Chapter Seven: Telegraphs and Relays

Chapter Eight: Relays and Gates

Chapter Nine: Our Ten Digits

Chapter Ten: Alternative 10s

Chapter Eleven: Bit by Bit by Bit

Chapter Twelve: Bytes and Hexadecimal

Chapter Thirteen: From ASCII to Unicode

Chapter Fourteen: Adding with Logic Gates

Chapter Fifteen: Is This for Real?

Chapter Sixteen: But What About Subtraction?

Chapter Seventeen: Feedback and Flip-Flops

Chapter Eighteen: Let's Build a Clock!

Chapter Nineteen: An Assemblage of Memory

Chapter Twenty: Automating Arithmetic

Chapter Twenty-One: The Arithmetic Logic Unit

Chapter Twenty-Two: Registers and Busses

Chapter Twenty-Three: CPU Control Signals

Chapter Twenty-Four: Loops, Jumps, and Calls

Chapter Twenty-Five: Peripherals

Chapter Twenty-Six: The Operating System

Chapter Twenty-Seven: Coding

Chapter Twenty-Eight: The World Brain

Errata

We've made every effort to ensure the accuracy of this book and its companion content. Any errors that have been confirmed since this book was published can be downloaded below.

Download the errata (114 KB .doc)

Download replacement figures:
Chapter 8, Figure 52 (2 KB .svg)
Chapter 11, Figure 5 (125 KB .svg)
Chapter 11, Figure 6 (152 KB .svg)
Chapter 11, Figure 7 (156 KB .svg)
Chapter 11, Figure 19 (116 KB .svg)
Chapter 20, Figure 14 (1 KB .svg)
Chapter 23, Figure 01 (1 KB .svg)
Chapter 23, Figure 15 (83 KB .svg)

If you find an error, you can report it to us through our Submit errata page.