The Hidden Language of Computer Hardware and Software

Code

Charles Petzold

Code Sözleri ve Alıntıları

Code sözleri ve alıntılarını, Code kitap alıntılarını, Code en etkileyici cümleleri ve paragragları 1000Kitap'ta bulabilirsiniz.
If the resolution of the video display is 640 pixels horizontally by 480 pixels vertically, the total amount of memory required is 921,600 bytes, or nearly a megabyte. The number of bits per pixel is sometimes referred to as the color depth or color resolution.
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Digital computer memory stores only bits, so anything that we want to work with on the computer must be stored in the form of bits.
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Reklam
For example, TXT indicates a text file (that is, a file containing only ASCII codes), and COM (which is short for command ) indicates a file containing 8080 machine-code instructions—a program.
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The computer that we've built is constructed from relays, wires, switches, and lightbulbs. All of these things are "hardware". In contrast, the instructions and other numbers that we enter into memory are called "software". It's "soft" because it can be changed much more easily than the hardware can. Generally, in computer programs, we can distinguish between code (which refers to the instructions themselves) and data, which are the numbers that the code manipulates.
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A file system is a method of disk storage in which data is organized into "files". A file is simply a collection of related data that occupies one or more sectors in the disk. Most important, each file is identified by a 'name' that helps you remember what the file contains. You can think of the disk as resembling a file cabinet in which each file has a little tab that indicates the name of the file.
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While the two-dimensional image of a video display or a television might seem complex, the image is actually composed of a single continuous beam of light that sweeps across the screen very rapidly. The beam begins in the upper left corner and moves across the screen to the right, whereupon it zips back to the left to begin the second line. Each horizontal line is known as a "scan line". The movement back to the beginning of each of these lines is known as the "horizontal retrace". When the beam finishes the bottom line, it zips from the lower right corner of the screen to the upper left corner (the vertical retrace) and the process begins again. For American television signals this happens 60 times a second, which is known as the "field rate". It's fast enough so that the image doesn't appear to be flickering.
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So for each second of sound, a compact disk contains 44,100 samples of 2 bytes each. But you probably want stereo as well. So double that for a total of 176,400 bytes per second. That's 10,584,000 bytes per minute of sound. (Now you know why digital recording of sound wasn't common before the 1980s.) The full 74 minutes of stereo sound on the CD requires 783,216,000 bytes.
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Sometimes people squabble over whether programming is an art or a science. On the one hand, you have college curricula in Computer Science, and on the other hand, you have books such as Donald Knuth's famous The Art of Computer Programming series. "Rather," wrote physicist Richard Feynman, "computer science is like engineering—it is all about getting something to do something."... Occasionally, a programming problem incites flashes of creativity and insight, and that's the "art" part. But programming is mostly a designing and building process not unlike erecting a bridge.
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Controlled repetition or 'looping' is what separates computers from calculators.
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One thousand twenty-four bytes is known as a 'kilobyte', and herein lies much confusion. The prefix kilo (from the Greek 'khilioi', meaning a thousand) is most often used in the metric system. For example, a kilogram is 1000 grams and a kilometer is 1000 meters. But here I'm saying that a kilobyte is 1024 bytes - not 1000 bytes.
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With the same logic that lets us call 1024 bytes a kilobyte, we can also refer to 1024 kilobytes as a 'megabyte'. (The Greek word megas means great.) Megabyte is abbreviated MB. The Greek word gigas means giant, so 1024 megabytes are called a gigabyte, which is abbreviated GB. Similarly, a terabyte (teras means monster) equals 1,099,511,627,776 bytes. Terabyte is abbreviated TB.
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During the Second World War, the British Broadcasting Corporation prefaced some radio broadcasts with the beginning of Beethoven's Fifth Symphony - BAH, BAH, BAH, BAHMMMMM- which Ludwig didn't know at the time he composed the music is the Morse code V, for victory.
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Digital data is 'discrete' data -data that has certain specific distinct values. Analog information is 'continuous' and varies throughout an entire range.
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