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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.
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computer-science
programming
technology
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Charles Petzold |
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30ac860
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In 1948, while working for Bell Telephone Laboratories, he published a paper in the Bell System Technical Journal entitled "A Mathematical Theory of Communication" that not only introduced the word bit in print but established a field of study today known as information theory. Information theory is concerned with transmitting digital information in the presence of noise (which usually prevents all the information from getting through) and ..
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Charles Petzold |
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9622f42
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We could just as reasonably base our number system on eight (if we were cartoon characters) or four (if we were lobsters) or even two (if we were dolphins).
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Charles Petzold |
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6e94a47
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To a programmer, an operating system is defined by its API.
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Charles Petzold |
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e0bc15c
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Some people believe that Moore's Law will continue to be accurate until about 2015.
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Charles Petzold |
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9fab73e
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Programming in machine code is like eating with a toothpick.
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Charles Petzold |
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39eab69
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When the iPhone app is built, the Xamarin C# compiler generates C# Intermediate Language (IL) as usual, but it then makes use of the Apple compiler on the Mac to generate native iPhone machine code just like the Objective-C compiler. The calls from the app to the iPhone APIs are the same as though the application were written in Objective-C. For the Android app, the Xamarin C# compiler generates IL, which runs on a version of Mono on the de..
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Charles Petzold |
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af08611
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I said early on in this chapter that we would need 144 relays for our adding machine. Here's how I figured that out: Each
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Charles Petzold |
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51645fa
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Today's computers use transistors. When used in computers, transistors basically function the same way relays do, but (as we'll see) they're much faster and much smaller and much quieter and use much less power and are much cheaper. Building an 8-Bit Adder still requires 144 transistors (more if you replace the ripple carry with a look-ahead carry), but the circuit is microscopic. Chapter 13. But What About Subtraction? After you've convinc..
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Charles Petzold |
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ecfa766
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Today's computers use transistors. When used in computers, transistors basically function the same way relays do, but (as we'll see) they're much faster and much smaller and much quieter and use much less power and are much cheaper. Building an 8-Bit Adder still requires 144 transistors (more if you replace the ripple carry with a look-ahead carry), but the circuit is microscopic.
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Charles Petzold |
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b1e0bb6
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We don't carry in subtraction, however; we borrow, and that involves an intrinsically different mechanism--a messy back-and-forth kind of thing.
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Charles Petzold |
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aaac7a2
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Bits also play a part in logic, that strange blend of philosophy and mathematics for which a primary goal is to determine whether certain statements are true or false. True
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Charles Petzold |
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d17489c
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Xamarin.Forms allows you to be as platform-independent or as platform-specific as you need to be. Xamarin.Forms doesn't replace Xamarin.iOS and Xamarin.Android; rather it integrates with them.
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Charles Petzold |
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bd8f048
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In the same way that Morse code reduces written language to dots and dashes, the spoken version of the code reduces speech to just two vowel sounds. The key word here is two. Two types of blinks, two vowel sounds, two different anything, really, can with suitable combinations convey all types of information.
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Charles Petzold |
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786c1e1
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Just as Morse code provides a good introduction to the nature of codes, the telegraph provides a good introduction to the hardware of the computer.
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Charles Petzold |
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communication simply requires
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Charles Petzold |
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9131bec
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You're twelve years old. One horrible day your best friend's family moves to another town. You speak to your friend on the telephone now and then, but telephone conversations just aren't the same as those late-night sessions with the flashlights blinking out Morse code. Your second-best friend, who lives in the house next door to yours, eventually becomes your new best friend. It's time to teach your new best friend some Morse code and get ..
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Charles Petzold |
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06cf089
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a digital design engineer, you would spend long hours going through the TTL Data Book familiarizing yourself with the types of TTL chips that were available. Once you knew all your tools, you could actually build the computer I showed in Chapter 17 out of TTL chips. Wiring the chips together is a lot easier than wiring individual transistors
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Charles Petzold |
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69e68fc
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The flip side of this is that any information that can be reduced to a choice among two or more possibilities can be expressed using bits. Needless
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Charles Petzold |