Types of Storage Device
An Ever-Growing Need
The earliest personal computers provided very little space for stor-
ing data. Some PCs did not feature disk drives at all. Instead, they
stored programs and data on standard audio cassette tapes.
When the earliest PC hard disks came on the scene, they stored
only 10 MB of data. Still, compared to a floppy disk (which then
of space amount
with capacities of 40 GB, 80 GB, or more. You can easily find
and many are external-meaning they can connect to any com-
puter via a USB or FireWire port.
In addition to floppy disks and hard drives, today’s computer
ring” devices that store hundreds of megabytes to digital video
discs, which make it easy to transfer several gigabytes of data.
of storage four
This lesson examines the primary types
today’s personal computers. You’ll learn how each type of
device stores and manages data.
Categorizing Storage Devices
in The purpose of a storage device is to
hold data-even when the computer is
turned off-so the data can be used
whenever it is needed. Storage involves
two processes:
>> Writing, or recording, the data
so it can be found later for use.
>> Reading the stored data, then
transferring it into the computer’s
memory.
The physical materials on which
data is stored are called storage media.
The hardware components that write
data to, and read data from, storage
media are called storage devices.
a storage medium (medium is the singular form of the word media); a disk
drive is a storage device.
are magnetic storage
One commonly
age and optical storage. Although most storage devices and media employ c
storage-is increasingly being used in computer systems, but is more
technology or the other, some use both. A third category of storage-solid-state
Because they all use the same medium (the material on which the data is stored),
use similar techniques for writing and reading data. The surfaces of diskettes,
Diskettes contain a single thin disk, usually made of plastic. This disk is flexi
ble, which is why diskettes are often called floppy disks. A diskette stores data on
both sides of its disk (numbered as side 0 and side 1), and each side has its
own read/write head. High-capacity floppy disks contain a single
more data than a normal floppy disk, as you will see
later. Hard disks usually contain multiple disks,
which are called platters because they are made of
a rigid mHard Disk
How Data Is Stored on a Disk
magnet can be used to make another. For example,
you can make a magnet by taking an iron bar and
stroking it in one direction with a magnet. The iron bar
becomes a magnet itself, because its iron molecules align
themselves in one direction. Thus, the iron bar becomes
polarized; that is, its ends have opposite magnetic polarity.
You also can create a magnet by using electrical current to polarize a piece of
iron, as shown in Figure 5A.3. The process results in an electromagnet; you can
and strength of the current.
Magnetic storage devices use a similar principle to store data. Just as a transis
tor can represent binary data as “on” or “off,” the orientation of a magnetic field
can be used to represent data.
transistor: that is, it can represent “on” and “off” without a continual source of
electricity.
The surfaces of magnetic disks and tapes are coated with millions of tiny iron
Another way to make a magnet is
to wrap a wire coil around an iron
bar and send an electric current
through the coil. This produces an
electromagnet.
If you reverse the direction of
the current, the polarity of the
magnet also reverses.aterial such as aluminum.
MAGNETIC SURFACE
generate magnetic fields in the iron on the storage medium as the head passes
over the disk or tape.
strings of 1s and Os by alternating the direction of the current in the electromag-
nets.
To read data from a magnetic surface, the process is reversed. The read/write
magnetic fields, which represent bits of data. The storage medium charges the
data is sent from the read/write head into memory.
How Data is Organized on a Magnetic Disk
specific point
and many are external-meaning they can connect to any com-
puter via a USB or FireWire port.
In addition to floppy disks and hard drives, today’s computer
ring” devices that store hundreds of megabytes to digital video
discs, which make it easy to transfer several gigabytes of data.
of storage four
This lesson examines the primary types
today’s personal computers. You’ll learn how each type of
device stores and manages data.
Categorizing Storage Devices
in The purpose of a storage device is to
hold data-even when the computer is
turned off-so the data can be used
whenever it is needed. Storage involves
two processes:
>> Writing, or recording, the data
so it can be found later for use.
>> Reading the stored data, then
transferring it into the computer’s
memory.
The physical materials on which
data is stored are called storage media.
The hardware components that write
data to, and read data from, storage
media are called storage devices.
a storage medium (medium is the singular form of the word media); a disk
drive is a storage device.
are magnetic storage
One commonly
age and optical storage. Although most storage devices and media employ c
storage-is increasingly being used in computer systems, but is more
technology or the other, some use both. A third category of storage-solid-state
Because they all use the same medium (the material on which the data is stored),
use similar techniques for writing and reading data. The surfaces of diskettes,
Diskettes contain a single thin disk, usually made of plastic. This disk is flexi
ble, which is why diskettes are often called floppy disks. A diskette stores data on
both sides of its disk (numbered as side 0 and side 1), and each side has its
own read/write head. High-capacity floppy disks contain a single
more data than a normal floppy disk, as you will see
later. Hard disks usually contain multiple disks,
which are called platters because they are made of
a rigid mHard Disk
How Data Is Stored on a Disk
magnet can be used to make another. For example,
you can make a magnet by taking an iron bar and
stroking it in one direction with a magnet. The iron bar
becomes a magnet itself, because its iron molecules align
themselves in one direction. Thus, the iron bar becomes
polarized; that is, its ends have opposite magnetic polarity.
You also can create a magnet by using electrical current to polarize a piece of
iron, as shown in Figure 5A.3. The process results in an electromagnet; you can
and strength of the current.
Magnetic storage devices use a similar principle to store data. Just as a transis
tor can represent binary data as “on” or “off,” the orientation of a magnetic field
can be used to represent data.
transistor: that is, it can represent “on” and “off” without a continual source of
electricity.
The surfaces of magnetic disks and tapes are coated with millions of tiny iron
Another way to make a magnet is
to wrap a wire coil around an iron
bar and send an electric current
through the coil. This produces an
electromagnet.
If you reverse the direction of
the current, the polarity of the
magnet also reverses.aterial such as aluminum.
MAGNETIC SURFACE
generate magnetic fields in the iron on the storage medium as the head passes
over the disk or tape.
strings of 1s and Os by alternating the direction of the current in the electromag-
nets.
To read data from a magnetic surface, the process is reversed. The read/write
magnetic fields, which represent bits of data. The storage medium charges the
data is sent from the read/write head into memory.
How Data is Organized on a Magnetic Disk
specific point