magnetic disk

Definition: Circular, plastics disk carrying magnetic material on which data can be stored. * The disk is coated with a thin film of ferric oxide or other magnetic material. * The polarity i.e. positive or negative charge of small areas of the coating can be changed or read off by a head carrying a current which rides just above but not touching the disk: the sequence of positive/negatives constitutes the machine code for the data. * This principle is the foundation of most computer storage systems, from hard-disk drives to removeable media such as digital tape, floppy disk, Zip, etc.

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