secondary storage

storage Any non-volatile storage medium that is not

directly accessible to the processor. Memory directly

accessible to the processor includes main memory, cache

and the CPU registers. Secondary storage includes harddrives, magnetic tape, CD-ROM, DVD drives, floppydisks, punch cards and paper tape.

Secondary storage devices are usually accessed via some kind

of controller. This contains registers that can be directly

accessed by the CPU like main memory ("memory mapped").

Reading and writing these registers can cause the device to

perform actions like reading a block of data off a disk or

rewinding a tape. See also DMA.

Programs and data stored in secondary storage must first be

loaded into main memory before the processor can use them.

(1997-11-05)