|Common Storage Devices Lesson 3–3
• Differentiate between internal
and external storage
• List commonly used magnetic
• 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
• 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.
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
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
CD-ROM----650 MB – 700 MB
(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
daily backup of files
load new program
Figure 3.3.3 CDs and DVDs
are popular components in both
computers and home entertainment