Magnetic media

Chapter Magnetic media

Teach Yourself Electricity and Electronics Third Edition Book
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Summary of Contents

Teach Yourself Electricity and Electronics Third Edition Book

  • RAM that doesn’t need a backup battery. Another asset is that data can be moved fromplace to place in large chunks. This process is called block memory transfer.IC memory storage capacityIt’s difficult to write about the amount of data that can be stored in an IC memory, sim-ply because the numbers keep increasing so fast. The best way to keep track of thetechnology is to look at the advertisements for personal computers (PCs). These useRAM ICs in practical, affordable appliances.This book was written with word-processing software on a PC with 640 kilobytes(640 KB) RAM. A kilobyte is about 1,000 bytes; this is about 200 words of text. A dou-ble-spaced manuscript page in pica type size (10 characters per inch) has about 200words. Thus, the RAM in this computer can theoretically hold 640 typewritten pages.That’s an average novel.By the time you read this, PCs will probably have several megabytes (MB), per-haps even 1,000 MB, of RAM. A megabyte is about 1,000 KB or a million bytes.How much RAM is really needed by the average PC user? Technology eventuallycomes up against a point of diminishing returns. In consumer word processing, this isalready happening. But in other computer endeavors, such as graphics, simulations, in-teractive games, and high-level mathematics, more RAM simply means more accurate,more realistic, faster, and more powerful results. As technological capabilities increase,demand has a way of following along. (Have you ever noticed this in regards to yourspending habits versus your income?) The largest RAMs are found in computers usedby commerce and the government.Trendier than fashionNew technologies for IC memory are constantly in the research-and-development (R &D) phase. Thus, you’ll hear and read abbreviations and acronyms not mentioned here.So rapidly does the art advance, that manufacturers have trouble keeping their owndatabooks up to date. It’s even worse than the fashion industry. In electronic technol-ogy, once something is obsolete, it never comes back. You can’t store today’s PROMsand hope that they’ll be of any use to your grandchildren.Magnetic mediaFor permanent storage of information, magnetic media are commonly used. These in-clude magnetic tape and magnetic disks. They’re compact (especially modern disks anddiskettes) and easy to reprogram. But they are damaged by heat, and their contents canbe destroyed by magnetic fields.Audio tapeThe earliest computers used audio tape to store data. Printed matter was recorded onthe tape using audio-frequency-shift keying (AFSK). This can still be done, but disksare more often used in modern computers, especially personal computers. Nowadays,tape is used mainly for storing voice, music, and/or image data.Audio tapes are available in reel-to-reel or cassette form. You’ve used them forrecording voices and/or music, or at least for enjoying your favorite musical talent. 532 Integrated circuits and data storage media