Memory

The most common type of memory that most users are familiar with is ‘main memory’ or ‘RAM’ (random-access memory). It is an area in the computer system unit that temporarily holds a user’s data, operating system instructions and program instructions. The word ‘main’ is used to distinguish it from external mass storage devices such as the hard drive or disk drives. Note that the term ‘mass storage’ refers to various techniques and devices for storing large amounts of data; mass storage is distinct from memory because it retains data even when the computer is turned off. Thus mass storage is sometimes referred to as ‘auxiliary storage’. Following are definitions of common storage devices:

Storage: The area within a computer system where data can be left on a longer term basis while it is not

needed for processing.

Diskette: A small, removable, flexible plastic disk covered with a thin layer of a magnetizable substance, onto which digital data can be recorded and stored. Also known as a floppy disk.

Hard drive: The storage area within the computer itself, where megabytes of space are available to store bits of information. It is also known as a hard disk.

Optical disk: It is a storage device that uses reflecting surfaces and laser technology to read and write data on a disk. It is also called as a laser disk.

Magnetic tape: A continuous plastic strip covered with magnetic oxide; the tape is divided into parallel tracks onto which data may be recorded by selectively magnetizing parts of the surface, or spots, in each of the tracks. The data can then be stored and reused.

Other types of memory include
ROM (read only memory): Unlike RAM, ROM is non-volatile and permits the user to read data. Computers always contain a small amount of read-only memory that holds instructions for starting up the computer.
PROM (programmable read-only memory): It is a memory chip on which we can store a program. Once the PROM has been used, we cannot wipe it and use it to store something else. Like ROMs, PROMs are non-volatile.
EPROM (erasable programmable read-only memory): This is a special type of PROM that can be erased by exposing it to ultraviolet light.
EEPROM (electrically erasable programmable read-only memory): It is a special type of PROM that can be erased by exposing it to an electrical charge.