Common Storage Devices Lesson 3–3 Objectives

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Common Storage Devices Lesson 3–3


• Differentiate between internal

and external storage


• List commonly used magnetic

storage devices.

• Summarize optical storage


As You Read

Classify Information Use a

T-chart to help you classify

information about magnetic and

optical storage devices as you


Key Terms

• hard drive

• floppy disk drive

• CD-ROM drive

Internal and External Storage Devices

Storage devices can be installed in your computer or connected

to it. A storage device installed inside your computer is called

an internal storage device. One that is positioned outside your

computer is referred to as an external storage device. External

hard drives are becoming more popular, as they provide an easy

way to add more storage capacity to a PC.

Common Magnetic Storage Devices

The most common magnetic storage device installed in computers

is a hard drive. You cannot see the hard drive because it

is installed inside your computer. Often, a small flashing light

on the front of a computer shows when the hard drive is in use.

External hard drives are becoming more popular, as they provide

an easy way to add more storage capacity to a PC.

Floppy Disk Drives A floppy disk drive is a storage

device with a slot that accepts floppy disks. These are

often internal storage devices, but they may also be

external. In either case, the device can read and write

data on a floppy disk, or disk-ette, which uses magnetics

to store information. Because the amount of

information floppy disks can hold is very limited

in terms of today’s needs, some computers no

longer have built-in floppy disk drives.

Other External Magnetic Devices Other

forms of magnetic storage devices include a variety

of USB-connected hard drives, which can hold up to as

much as a terabyte of data. Other external storage drives

include Zip®, Jaz®, and Rev® drives from Iomega Corporation. In

addition, devices such as Apple’s iPod, Creative Labs’ Zen™,

Figure 3.3.1 If you removed

your PC’s internal hard drive, it

would look something like this.

Storage Basics 41

© Pearson Education, Inc.

USB connector

Flash memory


Mass storage


Crystal oscillator

and Microsoft’s Zune™ function as both MP3 players (meaning

they can play the popular MP3 format) and as high-capacity

transportable storage devices.

Magneto-Optical (MO) Drives One type of drive combines

both magnetic and optical drive technologies. A magnetooptical

drive uses a removable disk that is inserted via a slot in

the front of the drive. These drives can be internal or external.

Their disks can store several gigabytes of information.

Online Storage You also can store information on a remote

computer—one that is not your own. Usually, these computers

are located on the Internet. To use online storage, you must contact

a storage service provider, or SSP. This is usually done using

the Internet but can also be done over the telephone or in person.

The SSP sets up a contract with the user to clarify who has

access and the amount and kind of information to be stored.

Many businesses use online storage as a way to keep backup

copies of their important data and to archive data they no

longer need.

Devices'>Common Flash Memory Storage Devices

Flash memory is a special kind of storage used in ROM chips

within your computer itself to store basic information about the

computer’s configuration. It is also used in memory cards and

memory sticks for digital cameras that require removable, reusable

storage. It is also used in USB flash drives (also called jump,

pen, and key drives). Most removable flash memory devices

Testing Engineer Just as computer

applications need to be tested

before they are released, so does

the information on compact discs.

People that test these devices are

known as testing engineers. Testing

engineers create a test plan for the

features and functions that will be

tested. Then they check to make

sure that the tasks work correctly

and that links on a page actually

link to the desired information. They

also examine the ease with which

you can access the information you

want from the compact disc.


Capacities of Common Storage Devices


Internal hard drive----60GB – 750 GB and more
Floppy disk----1.44 MB
MP3 player (iPod, Zen, Zune)----5 GB – 30 GB and more
Zip and Jaz drives----100 MB – 2 GB
Flash memory cards and drives----32 MB – 4 GB and more
External hard drive----40GB – 1 TB and more

(USB connection)
CD-ROM----650 MB – 700 MB
DVD----8.5 GB

(Digital Video Disks)
Figure 3.3.2 A USB flash

drive has a USB connector, a

flash memory chip, a mass

storage controller and a crystal

oscillator that allow the device to

communicate with the computer.

42 Chapter 3

© Pearson Education, Inc.

include a chip that stores data and a microcontroller that permits

the operating system to communicate with the chip. As the

technology of flash memory improves, the capacity of flash

devices increases significantly. Early flash devices held 32 MB to

256 MB, but capacities of several GB are now available. The

small size, increasing capacity, and ease of connection of these

removable devices makes them widely used as replacements for

floppy disks, Zip, and Jaz drives.

Common Optical Storage Devices

Optical storage devices let you store a lot of information and

transport it easily. The most common optical storage device is

known as a CD-ROM drive. These drives are read-only drives.

You can acess data from them but cannot use them to write data

onto a CD.

A button on the front of the drive opens a tray on which you

insert a CD. You push the button to close the tray, so you can

use the disc’s contents. Laserdisc drives, still used in some settings,

operate in much the same way. The tray must be opened

and the disc inserted before a laser can read the microscopic

patterns of data encoded on the surface of the disc.

CD Capacity A standard compact disc can hold 650 MB of

data, or 74 minutes of audio. A newer type of compact disc can

store 700 MB, or 80 minutes of audio. It also can be easily

moved from one computer to the next.

Standard CD-ROM drives are read-only devices, but newer

types of compact disc drives can write data as well as read it.

One such device is the CD-Recordable (CD-R) drive, which can

read standard CDs and write data onto special CD-R discs. You

can write data onto a CD-R disc only once, however; once data

is on the disc, it cannot be deleted or changed. Depending on

the drive and recording software you use, you may be able to

write data onto different parts of a CD-R disc at different times.

A CD-Rewritable (CD-RW) drive can write data onto special

CD-RW discs. These discs allow you to change, overwrite, and

erase data, in much the same way that you can use a floppy

disk. CD-RW discs, however, don’t work in all compact disc

drives and can’t be used for audio.

Digital Video Discs When you have very large storage

requirements, consider the digital video disc, or

DVD. A standard DVD can hold at least seven times

more information than a standard compact disc. Like

compact discs, the letters following the initials DVD

indicate whether the disc is read-only or whether you

can add information to it. With DVD-CD-RW and

DVD-RAM, you can read and write to the discs. With

DVD-ROM, you can only read information from the


Technology @ Work The availability of CD-RW technology

has allowed businesses to

store large amounts of information

at a relatively low cost. Each

option is suited for a different


Think About It!

Optical storage devices serve different

purposes. Write ROM next to

tasks for which a CD-ROM would

be most effective, R next to CD-R

tasks, and RW for tasks that

require read-write capability to do

the job.

daily backup of files

load new program

archive file

run tutorial

copy shareware

Figure 3.3.3 CDs and DVDs

are popular components in both

computers and home entertainment



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