دانلود رایگان مقاله انگلیسی نوارگردان مغناطیسی به همراه ترجمه فارسی
| عنوان فارسی مقاله: | نوارگردان مغناطيسی |
| عنوان انگلیسی مقاله: | Magnetic tape |
| رشته های مرتبط: | مهندسی کامپیوتر، سخت افزار |
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| کد محصول | F305 |
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بخشی از ترجمه فارسی مقاله: نوارگردان هاي مغناطیسی براي كامپيوترها شبيه به نوار گردان ها در يك سيستم استريو است.روي كامپيوترهاانها مي توانندبا نوعی چرخ باز شوند. روث كامپيوترهای بزرگ يا نوعي كاست به طور نمونه استفاده مي شود وروي ريز كامپيوترهاوكامپيوترههاي متوسط. Decimal value Left chars. Right chars. يك خط تيره از يك تا چهار حوزه تيره نزديك ساخته شده است هر رقم وسيمال داراي دو خط تيره و دو فاصله روشن است. كاراكترها روي نيمه راست با يك خط تيره و در اخر با يك فاصله روشن شروع مي شود.هر كاراكتر غلط داراي يك عدد فرد از يكهاست.هر كد كاراكتر درست داراي يك عدد زوج از يكها است دستگاهاي خروجي اطلاعات را از حافظه كامپيوتر به دنياي بيرون انتقال ميدهد . شكل 1.15 مسيري كه دادهها از حافظه اصلي به يك دستگاه خروجي برده ميشوند نشان ميدهد در خروجي جريان داده ها روي خط يكساني استفاده شده با دستگاه هاي ورودي است. |
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بخشی از مقاله انگلیسی: magnetic tape drives for computers are similar to the tape drives in a stereo system. On computers they can be the open reel type typically used on mainframes or the cassette type typically used on microcomputers and workstations. In the stereo the tape stores music but in a computer the tape stores information as bits the major advantage of tapes compared to disks is cost. Tapes are much less expensive per byte than disks. The disadvantage of tapes is that they are accessed sequentially and therefore they are slower than disks. If you need some information near the beginning of a tape and the read/write head happens to be near the end. You must rewind the tape sequentially passing over all the information in between the access method for magnetic tape versus disks is analogous to stereo cassettes versus audio compact discs. You can change selection on a compact disc much faster than on a cassette because of the access method. Because of their slow access . tapes are usually used for backup or archival storage . typical tape backup capacities are 10 to 100 G byte. The mouse which is moved on a desk is a popular hand-held input device. As the mouse is moved on the desk it gives a small arrow on the computer screen showing the identical motion. You can move the mouse to point the arrow at command selections or objects on the screen .then make the selection by pressing a button on a mouse . a mouse is specially valuable for graphic input because the arrow can be used to draw figures on the screen. Most of the figures in this book were produced using a mouse. The bar code reader is another efficient input device . perhaps the most common bar code is the universal product code(UPC) on grocery store items (figure 1.13) each digit in the UPC symbol has seven vertical data elements. Each data element can be light or dark photocells inside the bar code reader detect the light and dark region and convert them to bits. Light elements are read as zeros and dark elements as ones. Figure 1.14 shows the correspondence between light and dark regions and bits for two digits from the night half of the UPC symbol in figure 1.13. Figure 1.13 The UPC symbol from a package of cereal. The left digits identify the manufacturer. The right five digits its identify the product .The Quaker company code is 30000 , and the 1007 Natural cereal code is 06700 Figure 1.14 Part of the UPC symbol from the Quaker cereal box. Visually, groups of adjacent dark regions look like thick bars Table 1.3 shows the UPC correspondence between decimal and binary values. The code is different for the characters on the left half and those on the right half. A dark bar is composed of from one to four adjacent dark region. E ach decimal digit has two dark bars and two light spaces . the characters on the left half begin with a light space and end with a dark bar. And the characters on the right half begin with a light space. Each left characters has an odd number of ones .and each right characters has an even number of ones. Decimal value Left chars. Right chars. 0 0001101 1110010 1 0011001 1100110 2 0010011 1101100 3 0111101 1000010 4 0100011 1011100 5 0110001 1001110 6 0101111 1010000 7 0111011 1000100 8 0110111 1001000 9 0001011 1110100 Table 1.3 Bit patterns for the decimal digits in the UPC symbol. Output Devices Output devices transmit information from the memory of the computer to the outside world. Figure 1.15 shows the path that the data takes from main memory to an output device. On output data flows on the same bus used by the input devices. • Disk drives • Magnetic tape drives • Screens • Printers Figure1.15 The data path for output. Information flows from main memory on the bus to the output device. Notice that disk and tape drives can serve as both input and output devices. That is similar to a stereo cassette. Which can both record and play back music. When disks and tapes are used for input the process is called reading .when they are used for output the process is called writing. |
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