Code_ The Hidden Language of Computer Hardware and Software - Charles Petzold [1]
Here's another question that someone once asked me: "Why can't you run Macintosh programs under Windows?" My mouth opened to begin an answer when I realized that it involved many more technical issues than I'm sure my questioner was prepared to deal with in one sitting.
I want Code to be a book that makes you understand these things, not in some abstract way, but with a depth that just might even rival that of electrical engineers and programmers. I also hope that you might recognize the computer to be one of the crowning achievements of twentieth century technology and appreciate it as a beautiful thing in itself without metaphors and similes getting in the way.
Computers are constructed in a hierarchy, from transistors down at the bottom to the information displayed on our computer screens at the top. Moving up each level in the hierarchy—which is how Code is structured—is probably not as hard as most people might think. There is certainly a lot going on inside the modern computer, but it is a lot of very common and simple operations.
Although computers today are more complex than the computers of 25 years or 50 years ago, they are still fundamentally the same. That's what's so great about studying the history of technology: The further back in time you go, the simpler the technologies become. Thus it's possible to reach a point where it all makes relatively easy sense.
In Code, I went as far back as I could go. Astonishingly, I found that I could go back into the nineteenth century and use early telegraph equipment to show how computers are built. In theory at least, everything in the first 17 chapters of Code can be built entirely using simple electrical devices that have been around for over a century.
This use of antique technology gives Code a fairly nostalgic feel, I think. Code is a book that could never be titled The Faster New Faster Thing or Business @ the Speed of a Digital Nervous System. The "bit" isn't defined until page 68; "byte" isn't defined until page 180. I don't mention transistors until page 142, and that's only in passing.
So, while Code goes fairly deep into the workings of the computer (few other books show how computer processors actually work, for example), the pace is fairly relaxed. Despite the depth, I tried to make the trip as comfortable as possible.
But without little drawings of trains carrying a cargo of zeros and ones.
Charles Petzold
August 16, 2000
Chapter 1. Best Friends
code (kōd) …
3.a. A system of signals used to represent letters or numbers in transmitting messages.
b. A system of symbols, letters, or words given certain arbitrary meanings, used for transmitting messages requiring secrecy or brevity.
4. A system of symbols and rules used to represent instructions to a computer…
—The American Heritage Dictionary of the English Language
You're 10 years old. Your best friend lives across the street. In fact, the windows of your bedrooms face each other. Every night, after your parents have declared bedtime at the usual indecently early hour, you still need to exchange thoughts, observations, secrets, gossip, jokes, and dreams. No one can blame you. After all, the impulse to communicate is one of the most human of traits.
While the lights are still on in your bedrooms, you and your best friend can wave to each other from the windows and, using broad gestures and rudimentary body language, convey a thought or two. But sophisticated transactions seem difficult. And once the parents have decreed "Lights out!" the situation seems hopeless.
How to communicate? The telephone perhaps? Do you have a telephone in your room at the age of 10? Even so, wherever the phone is you'll be overheard. If your family personal computer is hooked into a phone line, it might offer soundless help, but again, it's not in your room.
What you and your best friend do own, however, are flashlights. Everyone knows that flashlights were invented to