the main memory. CPU Cache Main Memory Fast Slow Figure . Cache Memory Arrangement . Secondary Storage Devices A computer generally has limited amount of main memory which is expensive and volatile.
To store data and programs permanently, secondary storage devices are used. Secondary storage devices serve as a supportive storage to main memory and they are non-volatile in nature, secondary storage is also called as Backup storage . . Hard Disks Hard disk is a magnetic disk on which you can store data.
The hard disk has the stacked arrangement of disks accessed by a pair of heads for each of the disks. The hard disks come with a single or double sided disk. . .
Compact Disc (CD) A CD or CD-ROM is made from . millimeters thick, polycarbonate plastic material. A thin layer of aluminium or gold is applied to the surface. CD data is represented as tiny indentations known as serves as a PROM, but the content can be erased using ultraviolet rays.
EPROM retains its contents until it is exposed to ultraviolet light. The ultraviolet light clears its contents, making it possible to reprogram the memory. An EPROM differs from a PROM, PROM can be written only once and cannot be erased. EPROMs are used widely in personal computers because they enable the manufacturer to change the contents of the PROM to replace with updated versions or erase the contents before the computer is delivered.
Figure . Erasable Programmable Read Only Memory Most of the EPROM chips have a transparent area at the top surface which is covered by stickers. If it gets removed, the ultraviolet light in the sunlight may erase the contents. .
. . Electrically Erasable Programmable Read Only Memory (EEPROM) Electrically Erasable Programmable Read Only Memory is a special type of PROM that can be erased by exposing it to an electrical charge. Like other types of PROM, EEPROM retains its contents even when the power is turned off.
Comparing with all other types of ROM, EEPROM is slower in performance. . . Cache Memory The cache memory is a very high speed and expensive memory,