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INFS 214:
Introduction to Computing
Session 6 – Storage Technologies
Lecturer: Dr. Ebenezer Ankrah, Dept. of Information Studies
Contact Information: [email protected]
College of Education
School of Continuing and Distance Education
2014/2015 – 2016/2017
Session Overview
• A very important feature of a very computer is the ability to save, or
store information. This is done by the storage devices. This session
explains the types and categories of storage devices that are used in
the computer environment.
• At the end of the session, the student will
– Understand and differentiate between the various types of storage
devices
– Be able to give examples of storage devices
– Understand the different characteristics of storage devices
– Be able to identify the components of some of the storage devices
– Be able to differentiate between technologies underpinning the storage
devices
DR. EBENEZER ANKRAH
Slide 2
Session Outline
The key topics to be covered in the session are as follows:
• Introduction to Storage Devices
• Magnetic Disk
• Optical Disc
DR. EBENEZER ANKRAH
Slide 3
Reading List
• Hutchinson, S. E., & Sawyer, S. C. (2013). Computers: The user
perspective. Boston: Irwin McGraw-Hill. (Chapter 4)
• O’Leary, T. J., & O’Leary, L. I. (2014). Computer Today. Boston:
McGraw Hill. (Chapter 9)
• Williams, B. K., & Sawyer, S. C. (2014). Using Information
Technology: A practical introduction to computers and
communications (11th ed.). McGraw-Hill Education. (Chapter
5)
DR. EBENEZER ANKRAH
Slide 4
Topic One
INTRODUCTION TO STORAGE
DEVICES
DR. EBENEZER ANKRAH
Slide 5
Introduction to Storage Devices
• A very important feature of a very computer is the ability to
save, or store information. This is done on the storage
devices. Computer memory is also known as primary
storage. It is usually referred to as Random Access Memory
(RAM). It is closely related to the central processing unit but
separate from it.
• Memory holds the data when;
– It is input to the system and before it is processed.
– After it has been processed but before it has been released to the
output device.
– Holds the programmes (computer instructions) needed by the
central processing unit.
DR. EBENEZER ANKRAH
Slide 6
Introduction to Storage Devices
• Memory consists of electronic circuits, just as the CPU does.
Memory electronically stores letters, special characters such
as cedi signs and decimal points, and images.
• Turning on a personal computer activates its memory, turning
it off causes anything stored in memory to disappear. Primary
storage is therefore said to be volatile. It loses all of its
contents when power to the system unit is shut off or
disrupted.
• This volatility results in a need for more permanent or nonvolatile storage. This need for other storage devices for longterm storage of data that can be reused is provided by
secondary storage devices.
DR. EBENEZER ANKRAH
Slide 7
Introduction to Storage Devices
• Storage devices are devices that store
data/information (all things being equal). There are
two types of storage technologies - the magnetic and
the optical. The capacity of the storage device is
measured in bytes. It ranges from kilobyte to
megabyte, gigabyte, terabyte, etc.
DR. EBENEZER ANKRAH
Slide 8
Introduction to Storage Devices
• The memory unit of a digital computer typically has a main (or
primary) memory, cache, and secondary (or auxiliary)
memory.
• The main memory holds data and instructions for immediate
use by the computer’s ALU. It receives this information from
an input device or an auxiliary storage unit.
• In most cases, the main memory is a high-speed randomaccess memory (RAM) — i.e., a memory in which specific
contents can be accessed (read or written) directly in a very
short time regardless of the sequence (and hence location) in
which they were recorded.
DR. EBENEZER ANKRAH
Slide 9
Introduction to Storage Devices
• Two types of main memory are possible with
random-access circuits
– Static random-access memory (SRAM) and
– Dynamic random-access memory (DRAM).
DR. EBENEZER ANKRAH
Slide 10
Introduction to Storage Devices
• The cache is an extremely fast part of the main memory.
In SRAM-based memory, it is of small capacity that has
faster access time than the main memory and that
temporarily stores data and part of a program for quicker
processing by the ALU.
• Secondary storage provides permanent or non-volatile
storage. Using secondary storage devices, data and
programmes can be retained after the computer has
been shut off. This is accomplished by writing and
reading files. Writing is the process of saving information.
Reading is the process of accessing information.
DR. EBENEZER ANKRAH
Slide 11
Introduction to Storage Devices
• Characteristics of Secondary Storage
– Media or Medium: is the actual physical material that
holds the data and programs.
– Capacity: measures how much a particular storage
medium can hold.
– Read/Write: Storage devices are hardware that reads data
and programmes from storage media. Most also write to
storage media.
– Access speed or Access time: measures the amount of
time required by the storage device to retrieve data and
programs.
DR. EBENEZER ANKRAH
Slide 12
Questions
• Individual Assignment:
– List some of the magnetic disks
• Forum Question:
– Distinguish between magnetic technology and
optical technology
DR. EBENEZER ANKRAH
Slide 13
Topic Two
MAGNETIC DISK
DR. EBENEZER ANKRAH
Slide 14
Magnetic Disk
• A magnetic disk is a storage device that uses a
magnetization process to write, rewrite and access data. It
is covered with a magnetic coating and stores data in the
form of tracks, spots and sectors. Hard disks, zip disks and
floppy disks are common examples of magnetic disks.
• A memory device, such as a floppy disk, a hard disk, or a
removable cartridge, that is covered with a magnetic
coating on which digital information is stored in the form of
microscopic, magnetized regions.
DR. EBENEZER ANKRAH
Slide 15
Magnetic Disk
• Floppy Disks
• Floppy disks are removable storage media. The traditional floppy
disk holds 1.44 MB. High capacity floppy disks hold much more. As
a result of the small amount of data that they can contain, they are
almost phased out and replaced by other types.
• Floppy disks, often called diskettes or simply disks, are portable or
removable storage media. They are typically used to store and
transport word processing, spreadsheet, and other types of files.
• They use flat circular pieces of Mylar plastic that have been coated
with a magnetic material. Floppy Disk Drives (FDD) store data and
programs by altering the electromagnetic charges on the disk’s
surface to represent ones and zeros.
DR. EBENEZER ANKRAH
Slide 16
Magnetic Disk
• Floppy disks are also called flexible disks and floppies.
This is because the plastic disk inside the diskette cover is
flexible, not rigid. There are several types of floppy disks
with different capacities ranging from the traditional
floppy disk to a variety of high capacity floppy disks.
•
• The traditional floppy disk is the 1.44 MB 3½-inch disk.
Al-though introduced over 20 years ago, they are still in
use. The most common type is labelled 2HD, which
means “two-sided, high-density.” Two­-sided indicates
that data can be stored on both sides of the disk. Density
refers to how tightly the bits (electromagnetic charges)
can be packed next to one an-other.
DR. EBENEZER ANKRAH
Slide 17
Magnetic Disk
• Zip disks are produced by
Iomega and typically have
a 100 MB, 250 MB, or
750MB capacity. Internal
Zip drives are a standard
feature on many of
today’s system units.
External Zip drives are
generally connected to
the system unit using a
USB port.
DR. EBENEZER ANKRAH
Slide 18
Magnetic Disk
• HiFD disks from the Sony Corporation have a
capacity of 200 MB or 720MB. They have one major
advantage over Zip disks. Their drives are able to
read and store data on today's 1.44 MB traditional
disk as well as on their own higher capacity disks.
• Super Disks are produced by Imation and have a 120
MB or 240 MB capacity. Like HiFD drives, Super Disk
disk drives are able to use today's 1.44 MB standard
disks. Each of these will likely improve its capacity
and speed in the near future.
DR. EBENEZER ANKRAH
Slide 19
Magnetic Disk
• Hard Disks
• While internal hard disks provide fast access, they have a
fixed amount of storage and cannot be easily removed
from the system cabinet. Hard-disk cartridges, also
known as removable hard disks, are as easy to remove as
a cassette from a videocassette recorder.
• The amount of storage available to a computer system is
limited only by the number of cartridges. Hard-disk
cartridges are used primarily to complement an internal
hard disk. Because the cartridges are easily removed,
they are particularly useful to protect or secure sensitive
information.
DR. EBENEZER ANKRAH
Slide 20
Magnetic Disk
• Pc Cards Credit card-size
hard-disk cartridges
called PC Card hard disks
are available for
notebook computers with
typical capacities up to 5
giga-bytes. Two wellknown PC Card hard disks
are IBM's Micro drive and
Toshiba's MKS002.
DR. EBENEZER ANKRAH
Slide 21
Magnetic Disk
• Hard-disk packs are
removable storage devices used
to store massive amounts of
information. Their capacity far
exceeds the other types of hard
disks. Although you may never
have seen one, it is almost certain
that you have used them.
• Microcomputers that have access
to the Internet, minicomputers,
or mainframes often have access
to external hard-disk packs
through communication lines.
Banks and credit card companies
use them to record financial
information.
DR. EBENEZER ANKRAH
Slide 22
Topic Three
OPTICAL DISC
DR. EBENEZER ANKRAH
Slide 23
Optical Disc
• OPTICAL DISKS
• Optical disks use laser technology to provide high
capacity storage. CD and DVD are optical disk
formats. Data Play disks are for digital photography
and music.
• Today's optical disks can hold up to fifty gigabytes
of data. That is the equivalent of over several
million typewritten pages or a medium -sized
library all on a single disk.
DR. EBENEZER ANKRAH
Slide 24
Optical Disc
• Compact Disk
• Compact disc (CD), used to be one of the most widely
used optical formats. CD drives are standard on many
microcomputer systems. Typically, CD drives can store
from 650 MB (megabytes) to 1 GB (gigabyte) of data on
one side of a CD.
• One important characteristic of CD drives is their
rotational speed. This speed is important because it
determines how fast data can be transferred from the
CD.
DR. EBENEZER ANKRAH
Slide 25
Optical Disc
• For example, a 24X or 24-speed CD drive can transfer
3.6 MB per second, while a 48X drive can transfer 7.2
MB per second. The faster the drive, the faster data
can be read from the CD and used by the computer
system.
• There are four basic types of CDs: These are Read
only, Write once, Rewritable and Picture and Photo
CDs.
DR. EBENEZER ANKRAH
Slide 26
Optical Disc
• Read Only CD ROM
• Read Only CD ROM Stands for compact disc-read only
memory, it is similar to a commercial music CD. Read
only CD means it cannot be written on or erased by the
user.
• Thus, you as a user have access only to the data
imprinted by the publisher. CD-ROMs are used to
distribute large databases and references. They are also
used to distribute large software application packages.
DR. EBENEZER ANKRAH
Slide 27
Optical Disc
• Write Once CD
• Write Once-CD-R, which stands for CD-recordable,
can be written to once. After that they can be read
many times without deterioration but cannot be
written on or erased.
• CD-R drives, also known as CD burners, are often
used to archive data and to record music
downloaded from the Internet.
DR. EBENEZER ANKRAH
Slide 28
Optical Disc
• Rewritable CD
• Rewriteable-CD-RW stands for compact disc rewritable.
Also known as erasable optical disks, these disks are very
similar to CD-Rs except that the disk surface is not
permanently altered when data is recorded.
• Because they can be changed, CD-RWs are often used to
create and edit multimedia presentations. One limitation
of CD-R and CD-RW disks is that older CD-ROM drives
may not be able to read them. Most newer CD-ROM
drives are multi-read or able to read both CD-R and CDRW disks.
DR. EBENEZER ANKRAH
Slide 29
Optical Disc
• Picture & Photo CDs
• Picture CDs and Photo CDs use a special format developed by
Eastman Kodak to store digital images. Picture CDs are less
expensive and typically used by non-professionals.
• Today, most film developers provide traditional printed
pictures and digital images. The digital images are delivered
by the Internet or by Picture CD.
• These disks are typically single-session, meaning that all
images must be transferred at one time to the CD. Photo CDs,
however, are multi-session, meaning that new images can be
added at any time.
DR. EBENEZER ANKRAH
Slide 30
Optical Disc
• Digital Versatile Disc
• DVD stands for digital versatile disc or digital video disc.
This is a format that is rapidly replacing CDs as the
standard optical disk.
• DVD drives are very similar to CDs except that more data
can be packed into the same amount of space. DVD discs
can store 4.7 GB to 17 GB on a single DVD disk, about -17
times the capacity of CDs.
• There are three basic types of DVDs similar to CDs: read
only, write once, and rewriteable.
DR. EBENEZER ANKRAH
Slide 31
Optical Disc
• Read Only DVD-ROM
• Read only-DVD-ROM stands For Digital Versatile Disc Read
Only Memory. DVD-ROM drives are also known as DVD
players. DVD-ROMs are having a major impact on the video
market.
• While CD-ROMs are effective for distributing music, they can
only contain just over an hour of fair quality video. DVD-ROMs
can provide over two hours of very high-quality video and
sound comparable to that found in motion picture theatres.
• The motion picture industry has shifted video distribution
from video cassettes to DVD-ROMs.
DR. EBENEZER ANKRAH
Slide 32
Optical Disc
• Write Once
• Write once-DVD-R, DVD+R and DVD+R DL are competing write
once formats. All stand for DVD recordable. Each has a slightly
different way in which they format their disks.
• Fortunately, most new DVD players can use either format.
DVD-R and DVD+ R drives are typically used to create
permanent archives for large amounts of data and to record
videos.
• The DVD+R DL stores up to 8.5 GB because the DL stands for
double layer
DR. EBENEZER ANKRAH
Slide 33
Optical Disc
• Rewriteable DVD
• Rewriteable DVD - Unfortunately, there are several
competing rewriteable formats and few DVD players
can read all the standards.
• The three most widely used formats are DVD-RW,
DVD+RW, and DVD-RAM. DVD-RW and DVD+ RW
stand for DVD rewritable. DVD-RAM stands for DVD
random-access memory.
DR. EBENEZER ANKRAH
Slide 34
Other Types of Secondary Storage
• Other types of secondary storage are:
– Solid-state storage does not have moving parts.
– Internet drives use the Internet to store data and
information.
– Magnetic tape provides sequential access for backup.
– Blu-Ray Technology is a new optical technology emerging.
DR. EBENEZER ANKRAH
Slide 35
Optical Disc
• Solid-state storage does not have moving parts.
• Internet drives use the Internet to store data and
information.
• Magnetic tape provides sequential access for backup.
• Blu-Ray Technology
DR. EBENEZER ANKRAH
Slide 36
References
• Hutchinson, S. E., & Sawyer, S. C. (2013). Computers: The
user perspective. Boston: Irwin McGraw-Hill.
• O’Leary, T. J., & O’Leary, L. I. (2014). Computer Today.
Boston: McGraw Hill.
• Williams, B. K., & Sawyer, S. C. (2014). Using Information
Technology: A practical introduction to computers and
communications (11th ed.). McGraw-Hill Education.
DR. EBENEZER ANKRAH
Slide 37
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