Storage : Introduction

All information systems need to store data. This may be done temporarily whilst inputs are processed to produce outputs or for much longer periods of time.

For example :

• A school uses a database package to keep a record of the achievements of its students. These records are kept for the seven year period that each student attends the school.
• A student is using a graphics package to draw a logo on the screen. The graphics package must store the colour of each pixel in the logo so that it can be printed.

A computerised information system must be able to store both programs (e.g. a word processing package) and data (e.g. a word processed letter).

A storage device stores programs and data either temporarily or permanently. All information systems contain two different types of storage :

Immediate Access Store (IAS)	Immediate access store holds programs and data that the user is currently working with.
Backing Store	Backing store keeps data and programs when the computer is turned off.

Immediate access store is also known as main store or primary store. Backing store is also known as secondary store.

The capacity (amount of data) that a storage device can hold varies significantly between different devices. Units such as bytes, kilobytes and megabytes are used to describe a storage device's capacity. Other factors such as speed of data access, cost and portability will also determine which storage device is the most appropriate one to use for a particular application.

Select a storage device from the table below to find out about it or read through the rest of this topic to learn more about all of the different storage devices.

Immediate Access Store
RAM
ROM
Backing Store
Magnetic Disks		Floppy Disk
		Hard Disk
		Zip Disk
		Jaz Disk
Optical Disks		CD-ROM
		CD-R
		CD-RW
		DVD-ROM
		DVD-RAM
Magnetic Tape
Flash Memory Devices

GCSE ICT Companion 04 - (C) P Meakin 2004