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Computer systems use memory to store data. Memory should not be confused with hard disk space. In general, memory is used for programs and data that are currently being used. Hard disks store data permanently.

Data that is lost when power is removed is volatile.

Data that is not lost when power is removed is non-volatile.

Many different types of memory, with varying characteristics, are used for different jobs in a computer system. These are described on the following pages

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