# Code: The Hidden Language of Computer Hardware and Software

## Charles Petzold

Language: English

Pages: 400

ISBN: 0735611319

Format: PDF / Kindle (mobi) / ePub

What do flashlights, the British invasion, black cats, and seesaws have to do with computers? In CODE, they show us the ingenious ways we manipulate language and invent new means of communicating with each other. And through CODE, we see how this ingenuity and our very human compulsion to communicate have driven the technological innovations of the past two centuries.
Using everyday objects and familiar language systems such as Braille and Morse code, author Charles Petzold weaves an illuminating narrative for anyone who’s ever wondered about the secret inner life of computers and other smart machines.
It’s a cleverly illustrated and eminently comprehensible story—and along the way, you’ll discover you’ve gained a real context for understanding today’s world of PCs, digital media, and the Internet. No matter what your level of technical savvy, CODE will charm you—and perhaps even awaken the technophile within.

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16 The division signs can be replaced with negative powers of two: 1 x 22 + 0 x 21 + 1 x 20 + 1 x 2-1 + 1 x 2-2 + 0 x 2-3 + 1 x 2-4 Or the negative powers of two can be calculated by starting at 1 and repeatedly dividing by 2: 1 x 4+ 0 x 2+ 1 x 1+ 1 x 0.5+ 1 x 0.25+ 0 x 0.125+ 1 x 0.0625 By this calculation, the decimal equivalent of 101.1101 is 5.8125. In decimal scientific notation, the normalized significand should be greater than or equal to 1 but less than 10. Similarly,.

Paper with rows and columns generally used for doing series of calculations. VisiCalc replaced the paper with the video display, allowing the user to move around the spreadsheet, enter numbers and formulas, and recalculate everything after a change. What was amazing about VisiCalc is that it was an application that could not be duplicated on larger computers. A program such as VisiCalc needs to update the screen very quickly. For this reason, it wrote directly to the random access memory used.

Principles, you can make a 3-Line-to-8-Line Decoder or a 4-Line-to-16-Line Decoder, and so forth. The simplified version of the cat-selection expression was (N x ((M x (W + T)) + (F x (1 – W)))) + B For every + sign in this expression, there must be an OR gate in the circuit. For every x sign, there must be an AND gate. The symbols down the left side of the circuit diagram are in the same order as they appear in the expression. These signals come from the switches wired with inverters and.

Eventually burned out. This was a fact of life that people lived with. Those who owned tube radios were accustomed to replacing tubes periodically. The telephone system was designed with a lot of redundancy, so the loss of a tube now and then was no big deal. (No one expects the telephone system to work flawlessly anyway.) When a tube burns out in a computer, however, it might not be immediately detected. Moreover, a computer uses so many vacuum tubes, that statistically they might be burning out.

Solely because we don't have a single storage medium that is both fast and vast as well as nonvolatile. What we know today as "von Neumann architecture"—the dominant computer architecture for over 50 years—is a direct result of this technical deficiency. 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.