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The first computers were huge machines that took up the space of a big apartment, and whose memory was very limited. What were they like?
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The memory of these computers was limited to about 8 kilo-octets (k). Today’s computer diskettes alone hold 1,440 k, and a CD-ROM has 600,000!
The hard disk is another vital component of modern computers. While its capacity varies, it can stock a number of programs. All of a computer’s programs are on the hard disk. Unlike random access memory which is erased every time the computer is shut down, the hard disk keeps the information we give it permanently, unless it is accidentally erased! Made up of several metal plates, the hard disk looks a lot like an ordinary computer diskette. Both rely on similar technology to stock data magnetically. Each plate is ‘magnetised’ and remains so for many years. To erase a file, you simply de-magnetise it. All this is done by the hard disk’s read/write head, a miniature magnet.
Data is read and saved on a diskette exactly the same way as on the hard disk. The only difference is that a plastic disk is used instead of metal plates.
(From l'Inter-Pôle, "Disque dur et disquettes", by François Marier, July 26, 1997.)
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