Hard drives are data storage devices used for storing and retrieving digital information using rapidly rotating disks coated with magnetic material. They were first introduced in 1956. The size of the hard drive is the most important feature. Storing data requires a form of non-volatile memory which saves the data even if the power is turned off. This is opposite to RAM memory because if the power is turned off everything gets wiped. Solid state drives have no moving parts and use NAND chips to store data in a random fashion.
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Computer Systems 