Auxiliary memory

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.

Forms

The most common forms of auxiliar 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 predecessors, as this form of auxiliary memory does not involve any moving parts. In some laptops, such as Apple's MacBook Air line and MacBook Pro with Retina Display line, solid state drive.