Computer storage devices hold data permanently even when the computer is turned off. There are two main categories of storage devices: magnetic storage and optical storage. Magnetic storage uses magnetic media like hard drives, floppy disks, and tape to store data through magnetic encoding. Optical storage uses optical discs like CDs, DVDs, and Blu-ray discs to store data through making physical marks readable with laser light. Storage devices have evolved significantly over time to increase capacity and portability.

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CHAPTER 4
(Computer Storage)

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COMPUTER STORAGE
• A computer can function
with only processing,
memory, input, and
output devices. To be
really useful, however, a
computer also needs a
place to keep program
files and related data
when they are not in use.
• The purpose of STORAGE is
to hold data permanently

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COMPUTER STORAGE CATEGORIES
• The purpose of storage devices is to hold data
– even when the computer is turned off – so
data can be used whenever it is needed.
• Storage involves 2 Processes:
1. WRITING DATA – or recording data on the
surface of a disk or tape -- where it is stored
for later use.
2. READING DATA – or retrieving the data
from the surface of a disk or tape -- and then
transferring it into the computer’s memory.

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• STORAGE MEDIA – The Physical materials
on which the data is stored
• STORAGE DEVICES – The Hardware
components that write data to, and read it
from storage media.
• DISK DRIVE – The device that holds the disk
COMPUTER STORAGE TERMS

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1. MAGNETIC
STORAGE
2. OPTICAL
STORAGE
2 MAIN CATEGORIES OF STORAGE
DEVICES

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• Magnetic storage and magnetic recording are terms
from engineering referring to the storage of data on a
magnetized medium.
• Magnetic storage uses different patterns of
magnetization in a magnetizable material to store data
and is a form of non-volatile memory. The information
is accessed using one or more read/write heads. As of
2009, magnetic storage media, primarily hard disks,
are widely used to store computer data as well as
audio and video signals.
• In the field of computing, the term magnetic storage is
preferred and in the field of audio and video
production, the term magnetic recording is more
commonly used.
MAGNETIC STORAGE

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EXAMPLES OF
MAGNETIC STORAGE
MEDIA

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HARD DRIVE
• A hard disk drive (hard
disk, hard drive,HDD) is
a non-volatile storage
device for digital data.
• It features one or more
rotating rigid platters on
a motor-driven spindle
within a metal case.
• Data is encoded
magnetically by
read/write heads that
float on a cushion of air
above the platters.

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FLOPPY DRIVE
• A floppy disk is a data
storage medium that is
composed of a disk of thin,
flexible ("floppy")
magnetic storage medium
encased in a square or
rectangular plastic shell.
• Originally announced as
the "Type 1 Diskette" by
IBM in 1973, the industry
then adopted the terms
"floppy disk" or "floppy."

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DATA TAPE BACK-UP
• A tape drive is a
data storage device that reads
and writes data on a
magnetic tape. It is typically
used for off-line, archival
data storage.
• Tape media generally has a
favorable unit cost and long
archival stability.
• A tape drive provides
sequential access storage,
unlike a disk drive, which
provides random access

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MINI DV TAPE
• DV is a format for
recording and
playing back
digital video.
• It was launched in
1995 with joint
efforts of leading
producers of video
camera recorders.

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MAGNETIC STRIPE CARD
• A magnetic stripe card is a
type of card capable of
storing data by modifying
the magnetism of tiny iron-
based magnetic particles
on a band of magnetic
material on the card.
• The magnetic stripe,
sometimes called a
magstripe, is read by
physical contact and
swiping past a reading
head.

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OPTICAL STORAGE
• Optical storage is a term from engineering referring to
the storage of data on an optically readable medium.
• Data is recorded by making marks in a pattern that can
be read back with the aid of light.
• A common modern technique used by computers
involves a tiny beam of laser light precisely focused on
a spinning disc.
• Optical storage differs from other data storage
techniques that make use of other technologies such as
magnetism or semiconductors.
• The term optical drive usually refers to a device in a
computer that can read CD-ROMs or other optical discs.

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EXAMPLES OF
OPTICAL STORAGE
MEDIA

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FLASH MEMORY CARD
• is an electronic
flash memory
data storage device used
for storing digital contents.
They are commonly used in
many electronic devices,
including digital cameras,
mobile phones,
laptop computers,
MP3 players, and
video game consoles. They
are small, re-recordable,
and they can retain data

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USB FLASH DRIVE
• A USB flash drive consists
of a flash memory
data storage device
integrated with a USB
(Universal Serial Bus) 1.1
or 2.0 interface.
• USB flash drives are
typically removable and
rewritable, and
physically much smaller
than a floppy disk

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DVD–ROM
• DVD, also known as Digital
Video Disc or Digital Versatile
Disc, is an optical disc
storage media format, and
was invented and developed
by Philips, Sony, Toshiba,
and Time Warner in 1995.
• Its main uses are video and
data storage. DVDs are of the
same dimensions as compact
discs (CDs), but are capable
of storing more than six
times as much data.

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CD–ROM
• CD-ROM "compact disc
read-only memory") is a
pre-pressed compact disc
that contains data
accessible to, but not
writable by, a computer
for data storage and
music playback, the 1985
“Yellow Book” standard
developed by Sony and
Philips adapted the
format to hold any form
of binary data.

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COMPUTER STORAGE EVOLUTION