• Choose a category
• All
• Classic-Fiction

Charles Petzold

Copyright © 2009

Microsoft Press books are available through booksellers and distributors worldwide. For further information about international editions, contact your local Microsoft Corporation office or contact Microsoft Press International directly at fax (425) 936-7329. Visit our Web site at mspress.microsoft.com. Send comments to mspinput@microsoft.com.

Macintosh is a registered trademark of Apple Computer, Inc. Microsoft, MS-DOS, and Windows are either registered trademarks or trademarks of Microsoft Corporation in the United States and/or other countries. Other product and company names mentioned herein may be the trademarks of their respective owners.

Images of Charles Babbage, George Boole, Louis Braille, Herman Hollerith, Samuel Morse, and John von Neumann appear courtesy of Corbis Images and were modified for this book by Joel Panchot. The January 1975 cover of Popular Electronics is reprinted by permission of Ziff-Davis and the Ziff family. All other illustrations in the book were produced by Joel Panchot.

Unless otherwise noted, the example companies, organizations, products, people, and events depicted herein are fictitious. No association with any real company, organization, product, person, or event is intended or should be inferred.

* * *

SPECIAL OFFER: Upgrade this ebook with O’Reilly

Click here for more information on this offer!

Please note that upgrade offers are not available from sample content.

Preface to the Paperback Edition

Code rattled around in my head for about a decade before I started writing it. As I was contemplating Code and then writing it, and even after the book was published, people would ask me, "What's the book about?"

I was always reluctant to answer this question. I'd mumble something about "a unique journey through the evolution of the digital technologies that define the modern age" and hope that would be sufficient.

But finally I had to admit it: "Code is a book about how computers work."

As I feared, the reactions weren't favorable. "Oh, I have a book like that," some people would say, to which my immediate response was, "No, no, no, you don't have a book like this one." I still think that's true. Code is not like other how-computers-work books. It doesn't have big color illustrations of disk drives with arrows showing how the data sweeps into the computer. Code has no drawings of trains carrying a cargo of zeros and ones. Metaphors and similes are wonderful literary devices but they do nothing but obscure the beauty of technology.

The other comment I heard was, "People don't want to know how computers work." And this I'm sure is true. I personally happen to enjoy learning how things work. But I also like to choose which things I learn about and which I do not. I'd be hard pressed to explain how my refrigerator works, for example.

Yet I often hear people ask questions that reveal a need to know something about the inner workings of personal computers. One such common question is, "What's the difference between storage and memory?"

That's certainly a critical question. The marketing of personal computers is based on such concepts. Even novice users are expected to know how many megas of the one thing and gigas of the other thing will be necessary for their particular applications. Novice users are also expected to master the concept of the computer "file" and to visualize how files are loaded from storage into memory and saved from memory back to storage.

The storage-and-memory question is usually answered with an analogy: "Memory is like the surface of your desk and storage is like the filing cabinet." That's not a bad answer as far as it goes. But I find it quite unsatisfactory. It makes it sound as if computer architecture were patterned after an office. The truth is that the distinction between memory and storage is an artificial one and exists solely because we don't have a single storage medium that is both fast and vast as well as nonvolatile. What we know