CHAPTER 3: STORAGE DEVICES AND MEDIA
*Data backup and access
Copying of data and transferring it to a different medium in case a problem happens to the
main storage device or the main files. (Ex. Storing server data on magnetic tape)
*Reasons of backing up data:


Safeguard data to save it from failure of data
Safeguard data from hackers (corruption/deletion)
In case files need to be used somewhere else
Note: Data can still be effected by viruses even if backed-up
*Serial access: - Accessing each record until the wanted record is found



When updating files; the original file is called the master file
The additional data added to the master file is called the transaction file
The updated tape is the new master file
Here’s how the process goes:



Transaction File is stored in the same order as the Master File
The file is added to the master file to make a new master file
The two records are compared and if there are new files on the transaction file, then
they are compared and the new files are transferred
Process is repeated until a new updated master file is made
*Direct access: - Computer calculates where it should store the data and moves to the data
through its calculations, making the process much faster
*Magnetic Storage Media
1. Hard Disk Drive: - fixed hard drives are in all computers, and are the main storage
device for storage.
Uses
Advantages
Disadvantages
Store OS/systems
software and
working files
Storing applications
which need fast
retrieval
In real-time systems
Very fast data
transfer rate
Easily damaged if
correct shutdown
isn’t carried out
Many moving parts
File servers for
network computers
Very large memory
capacities
Read/Write
operations can be
pretty noisy
2. Portable HDDs
Uses
Advantages
Disadvantages
As backup systems
Very fast data
access time/data
transfer rate
Easily damaged if
dropped or
subjected to strong
magnetic fields
Transfer data
between computers
Large memory
capacity
Method of
transferring data
between computers
3. Magnetic Tapes: - Very thin strip of plastic coated with magnetic layer which is a set
of 1s and 0s. It uses serial access causing it to be nearly useless in real-time
Uses
Advantages
Disadvantages
Batch processing
processes (clearing
of cheques, utility
billing)
Back-up media
Generally less
expensive in
comparison to HDDs
Slow data access
time
Robust technology
In long term
archiving of data
since they are
known to be stable
Fast data transfer
rate
Huge data storage
capacity
Another tape is
needed when
updating data
Affected by
magnetic fields
*Optical storage media
CDs and DVDs are optical storage devices which are read and written to by laser light. The
thin layer of metal alloy is light sensitive, and uses organic dye to store data.
Three types of CDs/DVDs: - R( Write once only)/ROM(Read from only)/RW(Read from
and written to many times
DVDs have dual layering, and a red laser is uses to read the second layer through fractions
of millimeters
1. CD-ROM/DVD-ROM:- Read only, cannot be written to
Uses
Advantages
Disadvantages
CD-ROM used to store
Hold more data than Have slow data
music/files/software/gam floppy disks
transfer rate/data
access rate
es
DVD-ROM stores films/more Less expensive
sophisticated
than HDDs
files/software
Both used in applications
where there is a need to
prevent deletion of data
2. CD-R/DVD-R:- Recordable only once then become ROM
Uses
Advantages
Disadvantages
Home recordings of
music
Store data for later
use or transfer to
another computer
Cheaper than RW
Only recorded once
Once burned,
they are similar
to ROM
Not all CD players
are able to
play them
3. CD-RW/DVD-RW:- Rewritable media and do not become ROM
Uses
Advantages
Record television
programs
Can be written over Relativel
many times
y
expensiv
e
Can use different file Possible to
accidentally rewrite
formats
data
Data can be
added to at a
later stage
CCTV systems
Disadvantages
4. DVD-RAM: Use number of concentric tasks
 Allows simultaneous read and write operations
 Allow numerous read and write operations
 Can be written to and read from many times
Uses
Advantages
Recording devices Long life
Camcorders
to store
Very reliable- have built in
verification
Disadvantages
Not compatible as R/RW
formats
Expensive
movies
Fast access and large storage
Can read and write data at same
time
Superseded by new technology
5. Blu-Ray disks:- Fundamentally different to DVDs in the following ways: A blue laser is used to read data instead of a red one
 Blu-Ray stores data by 5 more times than DVDs
 Disks do not suffer from birefringence (rays refracting and reflecting causing
errors to happen)
 Come with secure encryption systems
Uses
Advantages
Disadvantages
Home
video
consoles
Storing and playing
back movies
Data storage or
backup
Camcorders can
use it
Store highdefinition movies
Expensive
Fast data transfer
rate
Fastest data access
speed
Come with secure
encryption systems
Encryption
problems
Fewer movie
titles on blu-ray
Note: Optical storage media are proving to be obsolete, since data can be stored on harddisks or streamed (like movies).
*Solid State Storage
Are rapidly taking over HDDs due to the following reasons









1.
No moving parts so they are thinner
All data is retrieved no matter it’s storage location
Do not depend on magnetic properties, but on the movement of electrons inside it
More reliable
Lighter
Don’t have to get up to speed
Lower power consumption
Much cooler than HDDs
Faster data access
Memory sticks:- Store several gigabytes and are connected through USB ports
Uses
Advantages
Disadvantages
Transferring files between
computers
Security device to prevent piracy
Compact/Portable Can’t write-protect data
Robust
Easy to lose
No need for
additional software
Not affected by
magnetic fields
User can corrupt data they
remove it incorrectly
2. Flash memory cards:- Use EEPROM
Uses
Advantages
Disadvantages
Storing photos on
cameras
Mobile phone
memory cards
Compact
Expensive per
gigabyte of memory
Have a finite life
In MP3 players to
store music
Back-up source in
computer held
devices
Can be
easily
removed
Very robust
Lower storage
capacity than HDDs
CHAPTER 4: NETWORKS AND EFFECTS OF USING THEM

Networks:
A Network is two or more computers or other electronic devices connected together so
that they can exchange data.
Network allows computers to share files, resources.
A computer that is not connected to a network is known as Stand-alone computer.
Network connections are created using cables (wires), radio signals or by satellite links.
Using a computer connected to a network, allows us to:





Easily share files and data.
Share resources such as printer, scanner and internet connections.
Communicate with other network users (email, video conferencing, chatting, etc).
Store data centrally (by using server) for ease of access and backup.
Keep all of our settings centrally we can use any work
station (PC). If we use a computer connected to the internet,
we can:




Make use of online services such as e-commerce (shopping), e-banking, etc.
Get access to a huge range of information.
Access forms of entertainment (games, music, videos, etc.)
Join online communities (e.g., Facebook,
MySpace, etc.). What are the disadvantages of a
Network?
Using a computer connected to a Network means that:






The computer is vulnerable to hackers.
If the network breaks, many tasks become very difficult to perform.
Your computer can more easily be attacked by a virus.
We have to be careful about revealing personal information.
We have to be careful to avoid suspect websites that might contain malware.
We have to be aware that information found on the internet is not always accurate or reliable.

Explain the following terms.
Client: Client computers are the normal computers that user can use it to get
their work done. Server: Servers are special, powerful computers that provide
services to the client computers. The services are:




Providing a central, common file storage area.
Sharing hardware, such as printers.
Controlling who can or cannot have access to the network.
Sharing internet connections.
Servers are more expensive than normal computers. In a small network, one server might
provide all of these services. In a larger network, there might be many servers sharing the
work.
There are three types of Networks:



LAN – Local Area Network
WLAN – Wireless Local Area Network
WAN – Wide Area Network

Local Area Network or LAN :
Is usually within one building or not over a large geographical area. A LAN consists of a
number of computers and devices, e.g., printers, which will be connected to hubs or
switches.
Advantages




The sharing of resources (such as expensive peripherals and application software).
Communication between users.
A network Administrator to control and monitor all aspects of networking.
E.g., changing password, monitoring
internet, etc. Disadvantages





Easier spread of viruses through the whole network.
The development of queues for printer, which can be frustrating.
Slower access to networks, such as internet.
Increased security risk as compared to stand alone computers.
If the main server breaks down, in most cases, the network will no longer function.

Wireless Local Area Networks or WLANs
Similar to LANs, but there are no wires or cables.
They provide wireless network communication over very short distances (a few
meters) usually radio or infra-red signals instead of cables.
Devices known as access points are connected into the wired network, at fixed locations.
Because of the limited range, most commercial WLANs need several access points, to
permit uninterrupted wireless communication.
The access point receives and transmits data between the WLAN and the wired network
structure. Advantages

All computers can access the same services and resources. E.g., printers, scanners,
internet access, etc.
 There is no cabling to individual computers and devices so safety is improved.
 The system is more flexible since, users can move their laptops from their desks.
 Adding new computers and devices is a very easy task and costs are
reduced, since no extra cabling is needed.
Disadvantages

Security is a big issue, since anyone with a WLAN enabled laptop or computer, can
access a network if it can pick up a signal.


There may be problems of interference, which can affect the signal.
Data transfer is slower than LAN.

Wide Area Network (WAN):
A Wide Area Network is formed by a number of LANs being connected together through
either a router or modem. Some companies setup private WANs. This is expensive but
comes with an advantage of much enhanced security and speed. It is common to use an
Internet Service Provider (ISP) for connections to the internet and communicate through
this network system.
Advantages


A WAN is a network that extends over a large area.
WAN can be connected using optical fibre cable, satellite link,
radio signals, etc. Disadvantages



Very expensive.
Limited access.
Data access slows down if spread over
huge area. Write the difference between LAN
and WAN.
LAN
LAN is confined to a very small area.
Usually located in a single building.
Uses cables, wireless, infra-red which
are usually queued by the
organization.
We can restrict or block any websites.

WAN
WAN covers wide geographical areas.
E.g. Between cities, countries and even
continents.
Usually located between many buildings
and
countries.
It uses wireless, satellite links, which are
globally organized.
WAN has very fast speed.
Bluetooth (Personal Area Network):
Bluetooth is a wireless network technology designed for very short range connections (just a few
metres).
The idea of Bluetooth is to get rid of all those cables, that connects our computer to
peripheral devices such as printers, mouse, keyboard, etc.
Bluetooth devices contain small, low power, radio transmitters and receivers.
When devices are in range of Bluetooth devices, they detect each other and can
be connected. With this system, it is possible to create small home networks.
The range is however quite small (about 10
metres). Typical uses of Bluetooth





Connecting a wireless keyboard to a computer.
Connecting a wireless mouse to a computer.
Using a wireless headset with a mobile phone.
Printing wirelessly from a computer or PDA.
Transferring data or music from a computer to a MP3 player.

Wi-Fi:

Wi-Fi refers to any system, where it is possible to connect to a network or to single
computer through wireless communication.
E.g., Laptop computers which are Wi-Fi enabled can connect to devices like printer, keyboard,
etc.
Wi-Fi system rely on some form of ‘AP’ (Access Point), which uses radio
frequency technology to enable the device to receive and send signals.
It is not a short form of wireless Fidelity.
It is a trademark name for any product which is based on IEEE 802.11 standard.
Wi-Fi hotspots are places where you can access Wi-Fi (free or paid).
They exist in public places such as airports, hotels, internet cafes’, etc.
It is possible to log on to free Wi-Fi unless they are protected by password.
Software exists which can be loaded in a laptop which then searches for nonprotected Wi-Fi system.
The practice of driving around in a car looking for these unsecured Wi-Fi hotspot
is known as war driving and possess a security risk.










Networking Hardware (Devices):

Modem
Modem means modulator and demodulator and is a device which converts a computers
digital signal into analogue signal and digital to analogue signal and transmission over
existing telephone lines.
Modems are used to allow computers to connect to network over long distances using
existing telephone networks.
Dial-up modem operate at the speed of about 60 kilobits per second, which is
very slow. Modern broadband operate at 11,000 kilobits per second.

Hub
Hubs are hardware devices that can have a number of devices or computers connected to them.
Its main task is to take data which receives through one of the ports and then send out this
data from all of the ports.
Each computer or device will receive the data, whether it is
relevant or not. Hub is used at the centre of star topology.
Hub is a dumb device, if it receives a message, it sends it to every computer
on the network. This means that hub-based networks are not very secure.

Switch
Switch is like a hub.
It is a device which connects number of computers together to
make a LAN. The use of a switch is at the center of star
topology.
The switch has cables plugged into computers to connect to a network.
A switch is a more intelligent device than a hub. If it receives a message, it checks who it is
addressed and only sends it to that specific computer.
Because of this, networks that use switches are more secure than those that use hubs,
but also a little more expensive.
Switch only sends packets of data to the computer, it reduces the amount of data on the
network, thus speeding up the network.

Bridges
Bridges are used to connect LANs together.
When one of the LAN sends a message, all the devices on the LAN receive
the message. This increases the amount of data flowing on the LAN.
Often a large LAN is divided into a series of smaller LANs.
If a message is sent from one computer in a LAN to another computer in a different LAN,
then the message needs to pass between the LANs usng the bridge.
A bridge therefore, usually has only two ports in order to connect one LAN to another LAN.

Router
Routers are hardware devices that read the address information to determine the final
destination of the packets.
Each computer linked to the internet is given a number which is called Internet Protocol
address (IP address). This address is like 123.456.7.89 and is unique for each device.
When data is transferred from one network to another, the data is put
into packets. The packets contain details of the destination address of
the network it is intended for.
Computers on the same network have the same first part of the IP address and this is used
to locate a particular network.

Firewall
Is a device or a piece of software that is placed between your computer and the rest of the
network (where the hacker is).
If you wish to protect your whole LAN from the hacker on the internet. You would place a
firewall between the LAN and internet connection.
A firewall blocks un-authorised connections being made to your computer or a LAN.
Normal data is allowed through the firewall, e.g., Emails, Web pages, but all other data is blocked.

Internet:
The internet is the world wide collection of networks which allows a user to send and
receive emails, chat or browse the World Wide Web (WWW).
WWW or web is the part of the internet which the user can access by using web browsers.
A web browser is a software that allows a user to access and interact with web pages and files on the
web.

Web Page
Web pages are documents on a computer screen which may consist of text, pictures, sound, video, etc.

Web Site
Web site consists of many of the web pages linked together. A web is made up of millions
of websites and web pages.
e.g. www.google.com
The web site shows the hyperlink to allow user to navigate between web pages. These
hyperlinks are often shown as Blue underlined text or sometimes a small hand appears
under a picture or under some text indicating that link to web pages or web sites.
Web browsers use URL (Uniform Resource Locator) to
retreive files. URL’s are a standard way of locating
resources on the internet.
They are usually a set of four numbers.
The URL indicates:
Protocol://site address/Path/Filename where


Protocol is usually HTTP
Site address consists of host computer name, domain name, domain type and the country name.
o Computer name is usually www
o Domain name is name of website
o Domain type is commonly one of the following
o .com, .org, .net, .mil, .gov
o country name .in, .uk
o file path is a URL of the web page
Thus, full url could be:
http://www.cie.org.uk/exams/ict.pdf

Accessing the Internet:
An ISP is a company that provides access to the internet to the user and usually a paid service.
When a user registers with an ISP, an account is set up and they are given login details
which include username and password.
There are three common ways of accessing the internet offered by service providers.



Dial up internet access
Cable internet access
DSL (Digital Subscriber line)

Dial up internet access:
It is the slowest internet connection (60 kbps).
The user connects to the internet via telephone lines by dialing one of the number supplied from the ISP.
ISP contracts are usually for hours per month of internet access time and additional charges
are incurred if this is exceeded.
A big disadvantage is that if the telephone line is tied up while a dial up modem is in operation.

Cable internet access
Local cable television operators give a user access to the internet through their own cable
network using a cable network model.

DSL – Digital Subscriber Line
The fastest download speed can be obtained by using DSL broad band connection
(about 11,000 kbps) This is often offered through wireless interface which requires an
access point and a router.
Broadband has the advantage of always being on because it does not tie up the telephone line.

Intranet:
An intranet is the name given to a private network that provides similar services to the
internet like email, messaging, web page, etc.
Intranet is a computer network based on internet technology that is designed to meet the
internal need for sharing information within a single organization or company.
However, these services are only for the users of intranet, they are private not
public. Businesses and other organizations often have intranet, for use by
their employees
Advantages:
 It is safer since there is less chance of external hacking or viruses.
 It is possible to prevent employees accessing unwanted websites.
 Companies can ensure that information available is specific to their needs.
 It is easier to send sensitive messages that will remain within
the company. Typical uses of intranet




Internal emails and instant messaging between the workers.
Company’s workers or employees can view internal web pages only.
E.g., Company’s calender, Company’s strategies, etc
Sharing of internal documents
Difference between internet and intranet:
Internet
The term internet comes from the phrase
‘International Network’.
Intranet
The term intranet comes from the phrase
‘Internal restricted access network’.
Used to give local information relevant to the
Covers topics of global interest
company.
Possible to block certain internet web sites
It is difficult to block certain web sites from
using
intranet.
internet.
Can be accessed from anywhere provided An intranet requires password entry and
user has
can only
an ISP account.
be accessed from agreed points.
Will not give full protection against
An intranet is behind the firewall which gives
hackers and viruses.
protection against hackers and viruses.
Information used in intranet is stored on local
Information cannot be stored on local server. servers which makes it more secure from
outside agencies.

Network Issues and Communication

Policing of the internet/Reliability and desirability of websites/Security issues
These were all discussed in chapter 10, please refer to that summary in order to revise these concepts.

Authentication
Authentication is usually used to verify that data comes from a trusted and secure source.
Some of the forms of authentication are: Digital certificates
 Biometrics
 Magnetic stripe
In many applications, RFID chips and tags can be used to authenticate data, here’s an
example of how it occurs in passport control:Passport page containing data
such as photo and name is
placed on the reader
Photograph and data read are
compared to those stored on
the central database
Microchip on the page is read
by the RFID and so is the facial
image
Owner of passport looks at
camera, which takes a
photograph of them

Ways of preventing and minimizing risk of viruses
1- Antivirus software:Running antivirus in the background on a computer keeps checking for virus attacks, and has
the following features and tasks:





Checks software/files before they are run on a computer
Compares possible viruses with those in the database
Checks software for types of behavior which could indicate
Any detected viruses are placed in quarantine and deleted or stay there until the
user chooses to do so
Need to be kept up-to-date, since new viruses are always discovered
Full system checks need to be done weekly, to make sure no viruses are dormant
2- Avoiding viruses on the internet
Always look out for HTTPS in the URL or a green lock before accessing a website. In
addition, when someone gives you a URL, copy and paste the address rather than clicking
on a hyperlink, as to avoid spam. Lastly, don’t open suspicious attachments in E-Mails.
3- Viruses from Hardware devices
Always scan the device you are plugging into the computer before using it. In addition,
don’t plug any device you get into the computer, because it can be infected with a virus.

Data protection acts
These acts are usually set by governments to protect citizens from their data being
incorrectly or inaccurately stored. In many countries, failure to abide by these acts can
lead to a fine, and sometimes an imprisonment
There are a number of ways to prevent data from being unlawfully taken:




Don’t leave personal info lying around on desks
Lock filing cabinets at the ending of the day
Do not leave data on an unattended computer monitor
Use passwords and IDs
Make sure that info sent online is not
sensitive There are main principals for DPA,
some of them are:







Data must be lawfully obtained and processed
Data can be processed for stated purposes only
Data must be relevant and adequate
Data must be accurate
Data should not be kept longer than needed
Data must be processed with the subject’s rights
Data must be kept in a secure place
Data should not be transferred out of the country

Faxing and Emails
There are two basic ways of
faxing: - 1- Physical
Faxing Machines: In this way, a document is sent through a fax machine to another, by inputting the
receiver’s fax number and telephone line number. This can be a slow process if the line is
busy, or many documents are being sent.
2- E-Faxing (or E-Mail):Usually, E-Mailing would mean that an account’s address is used and a message with
content and/or attachments is sent to the address. Afterwards, the recipient will log into
the account and read the message
Traditional faxing
More likely to be intercepted, since the document
needs to be printed out
Signatures on fax printed documents are legally
accepted
Poor Quality of documents
Telephone line being busy can delay the
document
Can be slow if more than 1 document needs to be
sent
Emails
More secure
No need to print the document
Much better quality of document and can be
modified
Can send and receive documents anywhere
with ISP
Much easier to send to multiple recipients
Access to an Email is more likely than a fax
machine

Video Conferencing
Is a form of communication that uses both video and audio, and is done in real-time.
Usually used in face to face conversations, especially in companies
Here a few things to consider before starting any video conference:





Agree a time and place for the conference
Delegates should log in to the conference beforehand
Conference needs to be set-up beforehand
Webcams should be placed in correct positions
Microphones should be placed between all delegates, so everyone is heard
Important for one person to be the main contact, so that it could go smoothly
Here are the peripherals needed to run a video conference
Hardware
Webcams
Large
monitors/Display
Microphones
Speakers
Software
Webcam/Microphone drivers: So that audio and video can be
correctly
transferred to other delegates
Coder-Decoder/Compression-Decompression: the first one is used
to code and decode the data sent over, while the second is used to
compress and decompress the data so it can travel
Echo-Cancellation software: Allows communication to occur in realtime, and synchronizes all the communication together
There are some issues with video conferencing: 






Lag
Jerking of images
Can be very expensive to set up and maintain
Time zones can cause an issue
Training people to use the program is expensive and time consuming
Can be demotivating for employees who want to travel
Relies on good internet connection
However, there are some advantages for video conferencing:
 Much easier to access documents of work, since delegates are at their workplace
 Possible to hold them at short notice
 Reduces costs of Travelling/Accommodation/Need to travel away from work for 2-3 days
 Can be safer, since delegates might need to travel to insecure places

Audio Conferencing
Usually, audio conferencing can be done through a telephone line or VoIP. As for VoIP, it
can be done using the drag and drop feature, and needs a solid and strong internet
connection. Users who do not have internet can also join using their telephone numbers.
Here is the process of audio conferencing: -
-Contact an audio conferencing provider for organizer’s PIN and participant’s PIN
-Give the PIN to each participant
-at the start of the conference organizer types in his PIN
-Each participant dials the number and enters the PIN

Web Conferencing
Web conferencing uses the internet and the WWW to permit a
conference to take place in real-time. Usually, it is used in the
following applications:  Business meetings to discuss new ideas
 Presentations
 Online education and training
There is one requirement, which is high speed and stable internet.
The organizer controls who can speak and at which times, while
the delegates have the
Some of the features of web conferencing are: Slide presentations can be posted during the conference
 Possible to draw on a whiteboard using the mouse/keyboard
 Possible to transmit images while the conference is going on
 Documents can be shared by uploading them on the website, before the
start of the conference
 Can communicate through audio/video/instant messaging