Auxiliary memory

USB flash drives, a type of secondary storage.
The bottom surface of a compact disc, showing characteristic iridescence.
A hard disk drive with protective cover removed.

Auxiliary memory, also known as auxiliary storage, secondary storage, secondary memory or external memory, is a non-volatile memory (does not lose stored data when the device is powered down) that is not directly accessible by the CPU, because it is not accessed via the input/output channels (it is an external device). In RAM devices (as flash memory) data can be directly deleted or changed.

It is used to store a large amount of data at lesser cost per byte than primary memory; secondary storage is two orders of magnitude less expensive than primary storage.


The most common forms of auxiliary memory are flash memory, optical discs, magnetic disks and magnetic tape . The latest addition to the auxiliary memory family is flash memory. This form is much faster as compared to its predecessors, as this form of auxiliary memory does not involve any moving parts. In some laptops, this type of auxiliary memory is referred to as a solid state drive.

See also

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