MINISTRY OF PRIMARY AND SECONDARY EDUCATION

COMPUTER SCIENCE SYLLABUS NOTES

FORMS 1 – 4
2015 - 2022

The syllabus consists of the following topics:

Hardware and Software

Application of Computer Science
Data Representation
Communication Networks and Internet technologies
Security and Ethics
Systems Analysis and Design
Algorithm Design and Problem Solving
Programming
Databases
Web Design
Technopreneurship

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 HARDWARE
What Is Computer?

Definitions:
1. An electronic device that works under the control of stored programs to automatically
accept, store and process data into information
2. It is an electronic and digital data processing machine.
3. It is an electronic and digital data processing machine which works with stored programs.
4. It is an electronic machine capable of accepting, processing, storing and output data or
information

Definition of terms
Electronic- it uses electricity to perform its functions.
Digital- accept and process data in binary form/digits i.e. zeros and ones.
Processing- Transforming data into information.
Machine- Anything which makes work easier.
Stored Program- Set of instructions kept for execution.
Program - a set of coded instructions which a computer follows

Data: Data- Refers to raw facts/unprocessed information/ raw facts and figures of an
activity. It can just be a list of numbers, names or a combination of these. Data is meaningless
and needs to be processed. Data cannot be used for decision making purposes as it is meaningless.
Information: Refers to processed data which is meaningful to the user. It is data that has been
converted into meaningful form. In general it is processed data. Information can be understood and
therefore can be used for decision making purposes. Information is meaningful. To get relevant
information, data entered into the computer must be relevant, accurate and up-to-date. If data
entered into the computer is wrong (Garbage In) the results will also be wrong (Garbage Out),
and is generally referred to as Garbage-In Garbage-Out (GIGO). It is a rule stating that the quality
of the output is a function of the quality of the input; put garbage in and you get garbage out.
Therefore the accuracy of the results produced by the computer depends on how accurate the user
enters data, functions, formulae and codes program procedures.

CHARACTERISTICS OF A COMPUTER

 It is electronic: - can only work when there is electricity.

 It is a device: a machine.
 Is controlled by programs: Works according to instructions, written in computer language,
given by the user for it to perform a specific tasks.
 Is automatic in operation: Can work with minimum or no human intervention.
 Can accept data: data can be entered into the computer through various means and
the computer accepts it.
 Can store data and programs: Data and programs entered into the computer can be stored for
future use.

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CONFIGURATION DIAGRAM OF A COMPUTER SYSTEM

INPUT DEVICES CENRAL OUTPUT DEVICES

e.g Keyboard, PROCESSING e.g Monitor,
mouse etc UNIT(CPU) Printer etc

STORAGE MEDIA
e.g Hard disk

ADVANTAGES OF USING COMPUTERS

 They process data at very high speed thus large volumes of goods can be
produced.
 Computers are very accurate in making calculations and thus ensure that no
calculation errors occur.
 Computers are very reliable to use since they rarely makes mistakes.
 Computers store large volumes of data for a long period of time.
 Computers cut labour costs as they can perform duties that need many people.
 They replace humans and thus cut labour costs on wages, medical aid, retirement benefits,
leave payments, etc.
 Computers can work for 24 hours a day with no complains as humans.
 They do not get tired.
 Computers create employment for the community, for example, computer
teachers (tutors), programmers, computer technicians, database administrators,
etc.
 High quality goods are produced using computers.
 Ensures efficient, easier and faster communication through the internet.
DISADVANTAGES OF USING COMPUTERS
 Continuous usage can lead to health problems like Repetitive Strain Injury (RSI),
back ache, eye problems, etc.
 Lead to increase in computer crime (the use of computer to perform unlawful
activities) like computer fraud (improper electronic transfer of funds from one
account to another using computer).
 Hacking (Obtaining unauthorised accessed to protected and secure computer
systems or network, usually using intelligent methods), music and software piracy (illegal
copying, selling and buying copyrighted software without certification.).
 Data theft using computers, sending of viruses, etc.
 Copyright: A document granting exclusive right to use, publish and sell software,
musical or artistic work.
 Can lead to unemployment since computers can replace human labour as in car
assemblies.
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  Expenses related to repairs, maintenance and safety can be high.
 They only work when there is electricity.

End-user: A person or organisation who are the final beneficiaries of a program or a

device like a computer.

ELEMENTS OF A COMPUTER

The main elements (components) of a computer are classified into Hardware elements and
Software elements

HARDWARE

Hardware refers to tangible devices of a computer. These are parts of a computer that exits in
physical form, for example mouse, keyboard.

Hardware is grouped into: Input Hardware, Processing Hardware, Output Hardware, Storage
hardware/devices

INPUT HARDWARE/ INPUT DEVICES

These are devices used to enter data into the computer, for example mouse and keyboard.
Below are some of the input hardware and their uses:

KEYBOARD
Keyboards allow you to
input letters, numbers, and
other symbols into a computer that often
function as commands. It is a device used to
enter data and instructions into the computer
by typing. It is similar to the traditional
typewriter. It is used to enter alphabetic
letters (A-Z-both lower case and upper case),
numbers (0-9) and other special characters
like the %, $, coma, ?, and the space.

*NB: - A character is any single symbol,

digit or letter that can be entered into the
computer. These characters can be numeric
(numbers 0-9, positive and negative),
alphabetic (letters A-Z, both lower and upper
case), alphanumeric data (a combination of both numeric and alphabetic characters) and special
characters (space, $, >, etc.).

*NB: - Control Character: - Refers to non-printable character code or number in the character set
that do not represent a written symbol. These are mostly used in peripheral devices control and
for communication purposes, for example, carriage return, tab or backspace; and others typed by
depressing a key and the control key at the same time.

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*NB:-Extended Binary-Coded-Decimal Interchange Code (EBCDIC) an 8-bit character set and
encoding representing 256 alphanumeric and special characters

- ASCII - American Standard Code for Information Interchange: - a code for information exchange
between computers made by different companies; in which a string of 7 binary digits represents
each character; used in most microcomputers. Each character has its ASCII binary code that can be
understood by the computer.

Keyboard entry of data is manual and its excessive use without breaks will cause Repetitive Strain
Injury (RSI).
Advantages Disadvantages
Enables fast entry of new Users with arm/wrist problems can find keyboards hard to use
text into a document
Very easy to use Fairly large and take up desk space
Information appears on Entering data can be slow when compared to direct data entry (e.g.
the screen as it is typed scanning a bank card)
so it is easy to verify
(check for correctness)

MOUSE
It is a mouse shaped device used to enter data and instructions into the
computer by clicking. It can also be used for pointing and selecting items.
Clicking is the process of pressing and releasing the mouse button. It is a fast
method of entering data and for selecting items.

Advantages Disadvantages
Faster to select an option compared to People with poor hand movement or
using a keyboard. disabilities can find mice difficult
Mice enable easy navigation around Easily damaged and ball mice pick up dirt and
applications and internet become clogged/blocked
Small and take up very little space Hard to use without flat surface

TRACKBALL
It is an input device with a small ball that can be moved by passing the
palm of your hand over it. This will move an arrow on the screen. It is
used to draw designs and to select options from menu. It is mostly
found on laptop computer

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 Advantages Disadvantages
People with limited hand/wrist Trackerball tend to be more expensive than mice
movement find the easier to
use
Pointer can be positioned more
accurately on the screen than
with a mouse
Take up less desk space than a
mouse as they do not need to
be moved around

SCANNER

This is an input device used to convert images from paper into electrical
signals for input into the computer. The images can then be edited, printed
or saved. Mostly used to scan pictures, photographs, etc. A scanner can be
connected to a computer using USB, Firewire, Parallel, or a SCSI port. The
picture shows an example of a flatbed photo scanner, the Epson V300.

Advantages Disadvantages
Images can be stored for later editing The quality of the scanned images can be limited
at a later date depending on the quality of the scanner.
Scanners are much faster than having Images lose quality during the scanning process
to type in the documents again
You can scan in damaged documents Images can take up a lot of disk space
then repair using Graphic Editing
software

TOUCH SCREEN
A screen display on which you could enter data by pointing with a finger on intended option, used
on (ATMs)-Automated Teller Machines, cell phones, computers, etc.
Opti
touc

Advantages Disadvantages

Faster to select an option compared to using a People with poor hand movement or
keyboard. disabilities can find touchpad difficult
Touchpads enable easy navigation around More difficult to control the pointer when
applications and internet compared with the mouse
Included in the laptop so no need for separate More difficult to perform operations such as
mouse. This helps improve portability drag and drop
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 Can be used even when there are no flat
surfaces available
Don’t get clogged with dirt as ball mice can

MICROPHONE
It is an analogue input device that recognises human voice for data entry
into the computer.

A microphone is used in voice recognition systems (voice synthesis). These are

computerised systems that allow users to communicate with the computer by talking
(voice input). These systems are now over 90% accurate and are appropriate for the handicapped,
especially those without hands. They are very fast in entering data and in giving instructions to
the computer. They are speaker independent and can recognise natural language. However,
older systems were not speaker independent and allowed the user to speak slowly, using specific
words that were programmed for it to understand. Multimedia speakers, sound cards, a
microphone and voice recognition software are needed in voice recognition systems.

Advantages Disadvantages
Faster to read in text rather than type it in Sound files can be quite large and take up
using a keyboard memory
Sound input onto your computer can be Voice recognition software isn’t very accurate
edited using Sound Manipulation and can lead to errors (e.g. cannot tell the
Software difference between “their” and “there”).
Voice recognition can be used to make
tasks safer. (Like using voice to operate a
radio in a car

LIGHT PEN
A ballpoint shaped device used to enter data by writing on an ink pad. It is also used to make
alterations on the screen to the drawings, to write directly on the screen and to select commands.

GRAPHICS TABLET

Devices used to provide interface for drawing on the screen and links with the
light pen. Alternatively referred to as a drawing tablet and pen tablet,
a graphics tablet is a hardware input device that enables an artist to draw
or sketch digitally using a pen or stylus. They are helpful because they
provide a more natural and precise feel than a standard computer mouse.

DIGITAL CAMERA
A device use to capture photographs, films, videos or a combination of both
for entry into the computer where they can be edited.

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 Advantages Disadvantages
No film needed. No developing costs to Digital cameras can be very expensive
view the pictures
Images can be viewed immediately and Quality images can be quite large in size and
unwanted images can be deleted can take up a lot of memory
Images can be copied, edited, enlarged or Resolution (quality) of digital images are still
enhanced not as good as traditional printed images
Images can be added to websites or
documents

WEBCAM
A webcam is a hardware camera connected to a computer that allows anyone
connected to the Internet to view either still pictures or motion video of a user or
other object. Today, most webcams are either embedded into the display
with laptop computers or connected to the USB or Fire Wireport on the computer.
A digital camera designed to take digital photographs and transmit them over the
internet.

Advantages Disadvantages
Webcams can be left on Picture is often of poor quality (image break
constantly. They only activate up)
themselves when you need them
Allow people to have face to face They need to be connected to a computer and
conversations without needing to internet connection in order to work
travel

Common uses of webcams include:

 Chatting: Webcams are commonly used to allow people to see each other whilst chatting
over the internet. Formally this is called 'teleconferencing'
 Tourists: There are hundreds of webcams dotted around the world that are pointed to an
interesting scene such as the outside view of a lab in the Arctic or maybe the Niagara
Falls. The web cam is attached to a computer which sends an image to a server on the
internet on a regular basis. People then connect to the server to see the latest image.
 Security: Webcams can also be used to capture an image only if movement is detected in
the scene in front of it so they are widely used in burglar alarm and other security
equipment

BAR CODE READER

These are devices at Point of Sale Terminals (POS) that read bar
codes on products for automatic data entry into the computer. Mostly
used in library systems, luggage handling systems at airports,
warehouse stock control, etc.
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Bar codes are numbered vertical lines and spaces of varying size on products that provide data for
such a product to the computer when read by bar code readers. If the bar code reader fails to read
the bar codes, data is entered manually through the keyboard by entering the numbers below the
bar codes.

Advantages Disadvantages
Webcams can be left on constantly. They Picture is often of poor quality (image
only activate themselves when you need break up)
them
Allow people to have face to face They need to be connected to a
conversations without needing to travel computer and internet connection in
order to work

Bar codes have the following advantages:

 They are cheap and easy to use.
 They are very accurate in entering data.
 They are a very fast means of entering data since they are an automatic data
entry method.
 Customers can be served quickly as it increases speed and efficiency.
 Automatic re-ordering of goods in supermarkets is possible.
 Automatic stock taking is possible.
 Need for fewer people in the stores thereby cutting labour expenses.
 Out of date items can be automatically identified, there is no need to remember
prices (supermarkets).
 It becomes easier to do price changes.

Information found on bar codes includes:

 Product name
 Check digit.
 Product number.
 Country of origin.
 Manufacturer’s number.
 Weight
How the computer system checks that the barcode has been read correctly: either the computer
performs the following:

Calculates the check digit; remainder = 0 if barcode has been read correctly OR uses the weights
and modulus 11 and use remainder
DOCUMENT READERS

These are devices used for entering data automatically into the computer by reading through
documents.

These include:

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  Optical Mark Recognition (OMR),
 Optical Character Recognition (OCR)
 Magnetic Ink Character Recognition (MICR)

OPTICAL MARK RECOGNITION (OMR)

The Optical Mark Readers use light sensitive devices to sense pencil
marks on a piece of paper for automatic data entry into the computer.
Light is reflected from the document onto the Optical Mark Reader
which records the output. It then records low intensity/zero intensity at
certain points. OMR is mostly used in marking multiple choice exams at
ZJC and „O‟ Level and reading pupils‟ registers. OMR is fast and
accurate in entering data. An Optical Mark Reader is the device that is
used for automatic data entry in OMR systems. OMR allows for the processing of
hundreds or thousands of physical documents per hour.

Advantages Disadvantages
Very fast way of inputting information. Forms need to be accurately designed to make
(10,000 forms can be read per hour) sure that the marks/shading are in correct
position to be read by the device.
100% accurate as documents are fed in If forms have been incorrectly filled in they
automatically and no need for user input. cannot be read properly.
(This means that they have to be manually
checked which takes a lot of time and costs a
lot)
Can only read shaded areas (Cannot input or
read text).

OPTICAL CHARACTER RECOGNITION (OCR)

It is the use of light sensitive devices to recognise alphabetic characters and numbers on a
sheet of paper for automatic data entry into the computer. Mostly used by insurance
companies, in billing systems and processing of Bank Giro-forms. An Optical Character
Reader is the device that is used for automatic data entry in OCR systems.
Advantages Disadvantages
Much faster way of entering The system can have difficulty reading
information into the computer handwriting.
compared with using a keyboard.
Cheaper than paying someone to Not a very accurate technique
manually enter information.
100% accurate as there is no manual As it is not 100% accurate, information needs to be
entering of information. (Device does manually checked for errors. This is time
it automatically) consuming.

MAGNETIC INK CHARACTER RECOGNITION (MICR)

A method of automatically entering data into the computer by

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reading characters on documents past a magnetised field with iron oxide, e.g. reading
numbers on the bottom of a cheque. A Magnetic Ink Character Reader is the device
that is used for automatic data entry in MICR systems.

Advantages Disadvantages
Greater security than OCR because the Only a very limited number of different
special ink characters cannot be changed. characters can be read.
NO manual input… therefor less errors. Both Reader and Magnetic Ink are more
(User just swipes information through the expensive than other methods of automatic data
reader). entry

Information can still be read even is

someone writes over the magnetic ink
characters (Like with a signature).

SENSORS
An object whose purpose is to detect events or changes in its environment then
provide corresponding output e.g temperature sensor, pressure sensor, light
sensor, sounds sensor, humidity or moisture sensor, water level sensor,
movement sensor, switch or button sensor, proximity sensor etc

REMOTE CONTROL
Component of an electronic device such as television set, DVD player, radio etc.
to operate the device wirelessly from short distances.

ADVANTAGES:

 Portable
 Easy to use
 Convenient
 Saves energy (human)

DISADVANTAGES:

 Easily lost
 Need to be quiet close to object

NUMERIC KEYPAD

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 A numeric keypad, number pad, numpad, or ten key is the palm-sized,
17-key section of a standard computer keyboard, usually on the far right.
It provides calculator-style efficiency for entering numbers. The numpad's
keys are digits 0 to 9, addition (+), subtraction (-) , multiplication (*)
and division (/) symbols, a decimal point (.), Num Lock, and Enter.
Laptop keyboards often do not have a numpad, but may provide numpad
input by holding a modifier key (typically labeled "Fn") and operating
keys on the standard keyboard. Particularly large laptops (typically those
with a 17 inch screen or larger) may have space for a real numpad, and
many companies sell separate numpads which connect to the host laptop by a USB connection
(many of these also add an additional spacebar off to the side of the zero where the thumb is
located, as well as an additional 00 key typical of modern adding machines and cash registers).

Advantages Disadvantages
Faster than keyboard for entering numeric Can be difficult to use due to small keys
information
Usually small devise (like mobile phones) Difficult (but not possible) to enter text
are easy to carry information.

JOYSTICK
An alternative to the mouse but specifically used for playing video games. There are
many different types, the more sophisticated respond to movement in 3 axis
directions, as well as having a number of configurable buttons.
It is also a pointing device used to move the cursor position on the screen. It
consists of a small vertical liver fitted on a base. Liver is used to move the cursor
on the screen. It has a click, double click and drag and drop switch.

Advantages of joysticks Disadvantages of joysticks

They give a better gaming experience
Some people find joysticks more difficult to
for racing or flying styles of computer
control than a traditional mouse.
games
Joysticks are not particularly robust and can
break easily if too much force is used on
them.

MAGNETIC STRIPE READER

Magnetic strips are usually found on the back of most credit cards, cheque`
guarantee cards, loyalty cards, membership cards etc. The magnetic strip
can hold personal details such as account number and name. The strip can
contain
n up to 60 characters, stored magnetically.

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 ADVANTAGES DISADVANTAGES
Simple for people to use - little or no
Very limited storage capacity for data
training
Data can be easily destroyed by strong magnetic
Cards are inexpensive to produce
fields
Data on the cards can be altered if Not always secure as thieves can obtain the
necessary. readers and read the data on the card.
Security is improved by the use of PIN
numbers to confirm that the person is the
rightful card owner

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OUTPUT HARDWARE/ OUTPUT DEVICES
These are devices that display or output information/work which has been processed/being
processed/done by the computer in a readable format to users or devices used to display and
produce data and information held inside the computer, for example: speakers, Graph plotters,
Projector, Screen, Printer etc

SPEAKERS
Speaker is a hardware device connected to a computer's sound card
that outputs sound generated by the computer.
When computers were originally released, they had on-board speakers that
generated a series of different tones and beeps. As multimedia and games
became popular, higher quality computer speakers began to be released that
required additional power. Because computer sound cards are not powerful
enough to power a nice set of speakers, today's speakers are self-powered, relatively small in
size, and contain magnetic shielding.

ADVANTAGES DISADVANTAGES
They are provided with the computer. They can take up a fair amount of desk-space,
compared to headphones.
They're very simple to operate. They can distract people around you therefore
disrupting a communal work area.
They help blind people who would otherwise
have difficulty using a computer.
They can be useful for alerting computer
users, even when they're busy, such as in
pop-ups.

HEADPHONES

Sometimes referred to as earphones, headphones are a hardware device that either

plugs into your computer (line out) or your speakers to privately listen to audio
without disturbing anyone else. The picture is an example of a USB headset from
Logitech with a microphone and a popular solution for computer gaming.

Advantages
 The sound can only be heard by the user (mostly)
 Portability - lightweight and easy to carry around
 Can listen to music on the move
 Although prices vary, many headphones and earphones are inexpensive

Disadvantages
 If music is played too loudly or for long periods of time there is a risk of permanent
hearing loss
 Often not aware of surrounding noises such as cars in traffic or people talking

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  If the music is too loud or the headphones not fitted correctly then others can hear an
annoying sound from them.
 Can be uncomfortable to wear for long periods of time.
 If the device is large e.g. a computer, it is not easy to move about the room while wearing
the headphones

BRAILLE READER
A braille reader, also called a braille display, is an electronic device
that allows a blind person to read the text displayed on a computer
monitor. The computer sends the text to the output device, where it is
converted to Braille and "displayed" by raising rounded pins through a
flat surface on the machine.
Braille readers come in various forms, including large units (about the
size of a computer keyboard) and smaller units, designed to work
with laptops and tablet computers. There are also Braille reader apps for smartphones and tablets
that work in conjunction with a Bluetooth-connected Braille output device

SCREEN READER
A screen reader is any application that tries to read what is on a computer monitor using sound
or some other device. More specifically, a screen reader attempts to identify and interpret data
that is being sent as output for display. Once the data has been interpreted, it is presented to the
user in some way; for instance a simulated voice, a Braille output device, or text-to-
speech software. Screen readers are quite helpful to those who are visually impaired, blind,
learning disabled, or unable to read. Common examples include Narrator for
Windows, VoiceOver for Mac OS, and ChromeVox for Chrome OS.

Advantages, Benefits and Different Uses of a Screen Reader

 It allows a blind person to use the computer
 It allows a blind person to create a document using a word processor like MS Word
 A blind can now read any article on the internet
 Also in writing email
 In social networking
 In writing a computer program
 If they want to communicate through instant messaging software
 If they want to make a blog
 They can also play some computer games, audiogames.net has a collection of accessible
games for the blind
 With the help of a screen reader, blind musicians now use an audio editing software to
record, edit and save their songs for example

Disadvantages of a Screen Reader

 Because visually impaired people only listen to a screen reader reading the text displayed
on the screen, they don’t usually have the chance to know the correct spelling of a certain
word especially when it’s not that common like medical terms etc. Sure they can make a
screen reader to read character by character after they hear a word that they don’t know
the spelling but its time consuming.

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  Screen readers use a computer sounding voice and some people find this very boring.
Some companies are doing their best to create speech synthesizers that can mimic how
human read a sentence; like the proper intonation.

PLOTTERS
Plotters are used to produce a hard copy of schematics, high quality
drawings and other similar applications.

They are used by engineers, architects and map-makers to draw plans of

buildings, diagrams of machines or large scale maps. They can also be
used for many other similar tasks.

A plotter differs from a printer in that it draws images using a pen that can be lowered, raised and
moved across the paper to form continuous lines. The electronically controlled pen is moved
around the paper by computer controlled motors.

Advantages of plotters
 Plotters can work on very large sheets of paper while maintaining high resolution.
 They can print on a wide variety of flat materials including plywood, aluminum, sheet
steel, cardboard, and plastic.
 Plotters allow the same pattern to be drawn thousands of time without any image
degradation.
Disadvantages
 Plotters are quite large when compared to a traditional printer.
 Plotters are also much more expensive than a traditional printer.

PROJECTOR

A projector is an output device that can take images generated by a

computer and reproduce them on a large, flat (usually lightly colored)
surface. For example, projectors are used in meetings or in class to
help ensure that all participants or students can view the information
being presented.

Advantages of Projectors

 Large-Sized Picture: Digital projectors can be used to create extremely large sized
images akin to those seen in a cinema hall. Although a movie projector with very large
light output can generate images of up to 300", even commonly available digital
projectors are capable of producing sharp pictures as big as 120".
 Advantage While Creating Small Images: Even if the projector is used to produce
smaller sized images of up to 60", it can still save you a lot of money when compared to a
LCD TV of the same size. Moreover, the picture at this size is very bright and can even
be used with a few lights on.
 Saves on Space: A ceiling mount projector does not occupy any space on the floor and
remains mostly unseen when not in use. Even a retractable screen can be put out of sight

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 when not in use, which is better than a bulky television set that is difficult to move
frequently.
 Ease of Installation: Other than ceiling mount projectors that need an expert for
installation, a normal projector is easy to setup and can be done without much effort.

Disadvantages of Projectors

 Light Can Play Spoilsport: A projector works best when operated in low light
conditions as the pictures produced are clearer and brighter. This can often prove to be a
disadvantage when you are addressing a conference where your audience needs to take
down notes.
 Costly Maintenance: The maintenance cost of home theatre projectors is often on the
higher side than that of a LCD television. The lamp of a projector needs to be replaced
occasionally, depending on your usage and the projector model.
 Separate Speakers Required: A movie projectors either has no audio of its own or has
very little sound that is inadequate if you want to watch movies or television programs.
Therefore, setting up home theatre projectors requires purchasing a separate audio
system.
 Ceiling Mount Projectors: If you are looking to ceiling mount your movie projector to
save up on floor space, it should be noted that the process can be a little tricky and may
require the services of an expert. Also, a projection screen will require separate
installation.

MONITOR
Also called screen or Visual Display Unit (VDU). It is the main way of getting the
processed data out of the computer. Monitors produce soft copy. Soft copy means
it is not tangible and can easily be changed. A monitor (or screen) is the most
commonly used output device. They come in many different shapes, sizes and
forms. In an exam question, you will need to be able to choose the best type of
monitor and then explain your reasons.

The picture on a monitor is made up of thousands of tiny coloured dots called pixels. The quality
and detail of the picture depends on the number of pixels that the monitor can display. The
higher the number of pixels, the better quality the output.

Larger monitors make working at the computer much easier on the eyes, but the larger the
monitor, the more money it costs!

PRINTERS

Printers produce “hard copy” printed on permanent material. Hard copy means it is
tangible and cannot be easily change.

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ACTUATORS
Used to generate physical movement from signals sent by the computer which can be sent
through wireless transmission or cables.

An actuator is often part of a computer control system. The actuator is a mechanical device or
motor which carries out the action or decision made by the control system. For example the lens
of this digital camera moves in and out according to how much zoom is wanted.

This movement is controlled by an 'actuator'. In this case it is a tiny electric motor that is
controlled by a computer control system within the camera.So an actuator can be absolutely tiny
or it can be truly massive such as the devices that open and shut the Thames flood barrier gates.

But they all do the same thing, namely allow a computer to control movement or action.

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PROCESSING DEVICES
These are devices used to convert and to manipulate data as per user requirement. The sole
processing device of a computer is the processor, which is inside the Central Processing
Unit (CPU) casing. Processing involves sorting of data, updating records, searching certain
records, adding a sequence of numbers, and others.
Functions of the processor include:

 Controls the sequence of instructions.

 Processes all instructions given by the user.
 Give commands to all parts of the computer.
 Carry out data processing like making calculation to data given by the user.

Most of the computers have micro-computers (small execution chip found in microcomputers).
With MS-DOS (Microsoft Disk Operating System) computers, chips progressed from 286, 386 and
486 processors. Intel Corporation then developed Pentium processors, ranging from Pentium 1,
Pentium 2, Pentium 3 and Pentium 4, with each processor being faster than the preceding one.
Pentium 4 processors have a speed of about 2.6 GHz. Newer chips are faster in processing. The
speed of a processor determines the speed and function of a computer.

Until the 1980s, most computers had one processor, but recent ones have two or more processors
(called co-processors), those with two processors are called dual processors. Two or more
processors share loads and therefore perform operations faster. The speed of a computer is also
determined by the clock speed for each microprocessor. This speed is measures in Megahertz
(MHz).

The structure of the CPU or Processor is as illustrated below:

ARITHMETIC
CPU
AND LOGIC
UNIT

INPUT CONTROL OUTPUT

UNIT

MAIN
MEMORY

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The processor comprises of: Arithmetic and Logic Unit (ALU) and the Control Unit (CU)

Arithmetic and Logic Unit (ALU) Functions

 Carries out arithmetic operations like add, subtract, divide, etc - Performs logic operations,
like AND, OR, etc

(b) Control Unit (CU)

 It coordinates and controls all hardware operations; It carries out the Fetch-Execute Cycle.
ALU operations on data are first loaded into the accumulator register, which store
instructions, data being processed and results of an operation.

Arithmetic and Logic Unit

This unit performs the arithmetic and logical operations on the data and instructions supplied by
the input devices, under the command from the control unit. The basic arithmetic operations
performed are addition, subtraction, multiplication and division, which are built into the control
unit. In addition to arithmetic operations computer can perform logical operations as well e.g.
comparing two or more numbers or letters, making decision according to the defined criteria, etc.
this is a place where data is manipulated and the result are communicated to memory.
Control Unit
This is the most important unit in a computer system. It supervises the entire operation of a
computer system; it acts as a traffic policeman, which controls the traffic of data and electronic
signals between various units and components of computer. It instructs the input device when to
start and stop the input to memory, it transfer the input information from memory to arithmetic
and logic unit, it selects the proper operations to be carried out, it directs the memory unit when
to start and stop the transfer of information to output unit, etc. therefore the function of control

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unit in a computer is to maintain order and direct the flow of operations in a proper manner. It
acts like central nervous system for various units of a computer.
Central Processing Unit
Control Unit, Arithmetic Logic Unit of a computer system are together known as Central
Processing Unit (CPU). The CPU is the brain of a computer system. In human body, the brain
takes all major decisions and other part of the body function as directed by the brain. Similarly,
in a computer system, all major calculations and comparisons takes place inside the CPU and the
CPU is responsible for activating and controlling the operations of other units of the computer
system.

THE FETCH AND EXECUTE CYCLE

Step 1. Fetch instruction: In the instruction phase, the computer’s control unit fetches the
instruction to be executed from memory. Microprocessor gets software instruction telling it what
to do with data.
Step 2. Decode instruction: Then the
instruction is decoded so the central
processor can understand what is to be
done. Microprocessor determines what the
instructions mean.

Step 3. Execute the instruction: In the

execution phase, the ALU does what it is
instructed to do, making either an
arithmetic computation or a logical
comparison. Microprocessor performs the
instruction.

Step 4. Store results: Then the results are stored in the registers or in memory.
Step 3 & 4 are called the execution phase. The time it takes to complete the execution phase is
called the EXECUTION TIME (E-time).
After both phases have been completed for one instruction, they are again performed for the
second instruction, and so on.

Buses
 A bus is a pathway through which data and signals are transferred from one device to
another in the computer system.
 They are a set of parallel wires connecting two or more components of the computer.
 Buses can be internal or external.
 Buses can be generally referred to as system bus and this connect the CPU, memory and
I/O devices.
 Each bus is a shared transmission medium, so that only one device can transmit along a
bus at any one time.
 Multiple devices can be connected to the same bus
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The main types of buses are:
- Data bus:
 Used for carrying data from memory to the processor and between I/O ports.
 Comprises of either 8, 16, 32 or 64 separate parallel lines
 Provide a bi-directional path for data and instruction’s between computer components.
This means that the CPU can read data from memory and input ports and also send data
to memory and output ports.
 The width of the bus determines the overall system performance. For example, if the data
bus is 8 bits wide, and each instruction is 16 bits long, then the processor must access the
main memory twice during each instruction cycle

- Address bus:
 Used for transferring memory addresses from the processor when it is accessing main
memory
 They are used to access memory during the read or write process
 The width of the address bus determines the maximum possible memory capacity of the
computer.
 This a uni-directional bus (one way). The address is send from CPU to memory and I/O
ports only.

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- Control bus:
 The purpose of the control bus is to transmit commands, timing and specific status
information between system components. Timing signals indicate the validity of data and
address information. Command signals specify operations to be performed. Specific
status signals indicate the state of a data transfer request, or the status of request by a
components to gain control of the system bus
 This is a bi-directional bus used for carrying control signals (Signals can be transferred in
both directions).
 They carry signals to enable outputs of addressed port and memory devices
 Control signals regulate activities on the bus.
 Control buses transmit command, timing and status information between computer
components.

Fan
A fan is used to cool the processor. It blows away hot air so that the processor remains cool.

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STORAGE DEVICES
These are devices used to store data and programs for future use.

STORAGE UNIT
Data and instructions entered into a computer system through input units have to be stored inside
the computer before actual processing starts. Similarly, results produced by the computer after
processing have to be kept somewhere inside the computer system before being passed on to an
output unit. Moreover, a computer must also preserve intermediate results for ongoing
processing. Storage unit of a computer system caters to all these need. It provides space for
storing data and instructions, intermediate results, and the results for output.

Methods of storing data:

Refers to ways files and records are stored on a storage media, that is the arrangement of data.

These include:
- Serial Storage: Data is stored as they occur without following any order, as on magnetic tapes.
- Sequential Storage: Data is stored using a predefined order, either in ascending or descending
order of a key field, as occurs on magnetic tapes.
- Direct (Random) Storage: Data is stored in a random way using an index, as on diskettes,
hard disks, CD-ROMs, etc.

Methods of Accessing Data

These are methods used to retrieve data held on storage media. These include:
(1) Serial Access: Data is retrieved in the order it is stored, reading files one after another from
the first until the required data is found in an unsorted list of records. It is very slow and time
wasting in accessing records far away from the first position but is faster to access data at first
position of the disk. It is used in magnetic tapes.

(2) Sequential Access: Data is retrieved in the order stored, from the first until the required data
is found, using a key field in a sorted list of records, as in magnetic tapes.
(3) Direct (Random) Access: Data is retrieved by going directly to the needed file, as applied in
hard disks, diskettes, CD-ROM, DVD-ROM, Memory Sticks, etc. It is a very fast method of
accessing data.

MEASUREMENT OF STORAGE CAPACITY

It is important that you understand a little about the measurements used to define storage
capacities:

Bit: Computer are digital. This means they work by processing ones and zeros. The basic one or
zeros is called a bit of information.
Byte: There are eights bits in a Byte.
KB - Kilobyte: There are approximately a thousand bytes in a KB (also called a KByte)
MB - Megabyte: There are approximately a million bytes in a MB (also called a MByte)

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GB - Gigabyte: There are approximately a thousand, million bytes in a GB (also called a GByte)
TB - Terabyte: There are approximately a million, million bytes in a TB (also called a TByte).

UNIT ABREVIATION STORAGE

Bit B Binary digit 1 or 0
Nibble 4 bits
Byte B 8 bits
Kilobyte KB 1024 Bytes
Megabyte MB 1024 KB
Gigabyte GB 1024GB
Terabyte TB 1024 TB
Petabyte PB 1024 PB
Exabyte EB 1024 EB
Zetabyte ZB 1024 ZB
Yottabyte YB 1024 YB

TYPES OF MEMORY
Storage unit of all computers is comprised of the following two types of storage:
 Primary memory/storage and
 Secondary memory/ storage

PRIMARY STORAGE
Primary storage, also known as main storage or memory, is used to hold pieces of program
instruction and data, intermediate result of processing, and recently produced result of those jobs
on which computer is currently working. These pieces of information are represented
electronically in the main memory chip’s circuitry and while it remains in the main memory,
CPU can access it directly at a very fast speed. It is volatile in nature i.e. as soon as the computer
is switched off or reset, the information hold by it is erased. Primary storage normally has limited
storage capacity and is very expensive. In modern computers it is made up of semiconductors.

TYPES OF PRIMARY MEMORY

Primary memory is subdivided in two types:

1. RAM:- Random access memory and

2. ROM:- Read Only Memory

1. Random Access Memory (RAM)

Random Access Memory (RAM) is the best known form of computer

memory. The Read and write (R/W) memory of a computer is called
RAM. The RAM is a volatile memory; it means information written to it
can be accessed as long as power is on. As soon as the power is off, it
cannot be accessed. RAM holds data and processing instructions
temporarily until the CPU needs it. RAM is considered “random access”
because you can access any memory cell directly if you know the row and

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column that intersect at that cell. RAM is made in electronic chips made of so called
semiconductor material, just like processors and many other types of chips.

2. Read Only Memory (ROM)

One major type of memory that is used in PCs is called read - only memory or ROM for short.
ROM is a type of memory that normally can only be read, as opposed to RAM which can be both
read and written.

There are two main reasons that read-only memory is used for certain functions within the
PC:
 Permanence: The values stored in ROM are always there, whether the power is on or
not. A ROM can be removed from the PC, stored for an indefinite period of time, and
then replaced, and the data it contains will still be there. For this reason, it is called non-
volatile storage.
 Security: The fact that ROM cannot easily be modified provides a measure of security
against accidental (or malicious) changes to its contents.

DIFFERENCE BETWEEN RAM AND ROM

RAM ROM
1 Is Volatile Non-volatile
2 Stores user’s programs and data during Contains boot-up file and BIOS
usage
3 Needs top-up (to be upgraded/increased) Do not need top-up
4 Stores data temporarily Stores data permanently
5 Writable Memory Read Only (not Writable)
6 Has bigger storage capacity Has less storage capacity

SECONDARY STORAGE
Secondary Storage of a computer is also known as auxiliary storage, is used to take care of the
limitations of primary storage. That is, it supplements the limited storage capacity and volatile
characteristic of primary storage. This is much cheaper than the primary storage and can retain
information even when the computer switches off or resets. Secondary storage holds the program
instructions, data and information of those jobs on which the computer system is not currently
working but needs to hold them for processing later.

STORAGE MEDIA
Regardless of the repository model that is used, the data has to be stored on some data storage
medium.

Magnetic tape
Magnetic tape has long been the most commonly used medium for bulk data storage, backup,
archiving, and interchange. Tape has typically had an order of magnitude better capacity-to-price
ratio when compared to hard disk, but recently the ratios for tape and hard disk have become a
lot closer. There are many formats, many of which are proprietary or specific to certain markets
like mainframes or a particular brand of personal computer. Tape is a sequential access medium,

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so even though access times may be poor, the rate of continuously writing or reading data can
actually be very fast. Some new tape drives are even faster than modern hard disks.

Magnetic tapes have the following advantages:

 Data can be arranged in an ordered sequence.

 They are re-usable, that is can be overwritten several times.
 Suitable for high hit rate processing systems like payroll, billing systems, etc.
 They last for a very long period of time, and thus can be used to keep historical records.
 They are very cheap to buy.
 They store very large volumes of data, of up to 20 GB.
 They are small, robust, and portable and provide low cost storage per GB.

However, they have the following disadvantages:

 It takes too long to find (search for) a needed record in a long list of data records.
 It is very difficult to update record held in a magnetic tape.
 It takes too long to update records, time wasting.
 They are prone to humid (moist) conditions.
 They are very slow to write to and read from

Hard disk (internal and external)

Stores your operating system, application programs and data. When you save data, it is normally
saved to the hard disk.

The capacity-to-price ratio of hard disk has been rapidly improving for many years. This is
making it more competitive with magnetic tape as a bulk storage medium. The main advantages
of hard disk storage are low access times, availability, capacity and ease of use.[8] External disks
can be connected via local interfaces like SCSI, USB, FireWire, or eSATA, or via longer
distance technologies like Ethernet, iSCSI, or Fibre Channel. Some disk-based backup systems,
such as Virtual Tape Libraries, support data deduplication which can dramatically reduce the
amount of disk storage capacity consumed by daily and weekly backup data. The main
disadvantages of hard disk backups are that they are easily damaged, especially while being
transported (e.g., for off-site backups), and that their stability over periods of years is a relative
unknown.

Hard disks have the following advantages:

 It is easier to access data stored on hard disks.
 They have a long life span, of about 5 years or more.
 Provides direct access to data.
 It is easier and faster to update data on hard disks.
 They are more robust.
 Have large storage capacity, about 300 GB or more.
 Very reliable to use

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OPTICAL STORAGE
Optical storage devices save data as patterns of dots that can be read using light. A laser beam is
the usual light source.

The data on the storage medium is read by bouncing the laser beam off the surface of the
medium. If the beam hits a dot it is reflected back differently to how it would be if there were no
dot. This difference can be detected, so the data can be read.

CD / DVD: These have largely replaced diskettes as a way of supplying programs. They can
hold a lot more data. Recordable CDs, DVDs, and Blu-ray Discs are commonly used with
personal computers and generally have low media unit costs. However, the capacities and speeds
of these and other optical discs are typically an order of magnitude lower than hard disk or
tape.R, Many optical disk formats are WORM type, which makes them useful for archival
purposes since the data cannot be changed. The use of an auto-changer or jukebox can make
optical discs a feasible option for larger-scale backup systems. Some optical storage systems
allow for cataloged data backups without human contact with the discs, allowing for longer data
integrity
Dots can be created using the laser beam (for media that is writable such as CD-Rs). The beam is
used in a high-power mode to actually mark the surface of the medium, making a dot. This
process is known as ‘burning’ data onto a disc.

Uses of compact disks:

 Transferring data from one computer to another.
 Creating backup storage for programs and data.
 Booting the computer when loading the operating system or restoring damaged system
files (system repair).

Advantages of CDs:
 Provide fast and direct access to data.
 Has large storage capacity of about 750 MB.
 Produces high quality sound and pictures.
 It is a multi-media device.

Disadvantages of CDs: Can be affected by direct sunlight. Less durable. They can easily get
scratched. Not so easy nor fast to save data on them

This is a magnified view of the dots on the surface of a CD.

The different patterns of dots correspond to the data stored on the disc.

Read-Only Optical Discs

Read-only optical discs have data written onto them when they are
manufactured. This data cannot be changed.

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CD-ROM
Compact Disc - Read-Only Memory (CD-ROM) discs can hold around800MB of
data. The data cannot be altered (non-volatile), so cannot be accidently deleted. CD-
ROMs are random-access devices.
CD-ROMs are used to distribute all sorts of data: software (e.g. office applications
or games), music, electronic books (e.g. an encyclopaedia with sound and video.)

DVD-ROM
Digital Versatile Disc - Read-Only Memory (DVD-ROM) discs can hold
around 4.7GB of data (a dual-layer DVD can hold twice that). DVD-ROMs
are random-access devices.
DVD-ROMs are used in the same way as CD-ROMs (see above) but, since they
can hold more data, they are also used to store high-quality video.

High Capacity Optical Discs

Blu-Ray
Blu-Ray disks are a recent replacement for DVDs. A Blu-Ray disc can hold 25 -
50GB of data (a dual-layer Blu-Ray disc can hold twice that). Blu-Ray discs
are random-access devices.
Blu-Ray discs are used in the same way as DVD-ROMs (see above) but, since
they can hold more data, they are also used to store very high-quality, high-
definition (HD) video.
The 'Blu' part of Blu-Ray refers to the fact that the laser used to read the disc
uses blue light instead of red light. Blue light has a shorter wave-length than
red light (used with CDs and DVDs).

Using a blue laser allows more data to be placed closer together on a Blu-Ray disc, than on a
DVD or CD, so Blu-Ray has a much higher storage capacity than these older discs.

HD DVD
High-density DVD (HD-DVD) discs can hold around 15GB of data (a dual-layer
HD-DVD can hold twice that). HD-DVDs are random-access devices.
HD-DVD discs are used in the same way as DVD-ROMs (see above) but, since
they can hold more data, they are also used to store very high-quality, high-
definition (HD) video.
The HD-DVD format was launched at the same time as Blu-Ray. For about a year
they competed to be the 'next DVD'. For various reasons, Blu-Ray won the fight,
and the HD-DVD format has been abandoned.
Recordable Optical Discs
Recordable optical discs can have data written onto them (‘burnt’) by a computer user using a
special disc drive (a disc ‘burner’).
CD-R and DVD-R
CD-Recordable (CD-R) and DVD-recordable (DVD-R) discs can have data burnt onto them,
but not erased. You can keep adding data until the disc is full, but you cannot remove any data or
re-use a full disc.

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CD-RW and DVD-RW
CD-ReWritable (CD-RW) and DVD-ReWritable (DVD-RW) discs, unlike CD-Rs and DVD-Rs,
can have data burnt onto them and also erased so that the discs can be re-used.
When CD-Rs and DVD-Rs are burnt, the laser makes permanent marks on the silver-coloured
metal layer. This is why these discs cannot be erased.

When CD-RWs and DVD-RWs are burnt the laser makes marks on the metal layer, but in a way
that can be undone. So these discs can be erased.

DVD-RAM
DVD-Random Access Memory (DVD-RAM) discs are a type of re-writable DVD.
They often come in a floppy-disc style case (to protect the disc).

DVD-RAM discs have a similar capacity to a normal DVD, holding4.7GB of

data. DVD-RAM discs are random-access devices.

DVD-RAM discs are used in many camcorders (video recording cameras).

The discs are much higher quality than normal DVD-RWs and can reliably store
data for up to 30 years. This means that they are often used for video and data
back-up and archiving.

Uses of DVDs:
 Transferring large volumes of data from one computer to another.
 Creating backup storage for programs and data.
 Booting the computer when loading the operating system or restoring damaged system
files (system repair)

Advantages of DVDs:
 Provide fast and direct access to data.
 Has large storage capacity of about 4.7 GB or more.
 Produces high quality sound and pictures.
 It is a multi-media device.

Disadvantages of DVDs:
 Can be affected by direct sunlight.
 Less durable.
 They can easily get scratched.

Caring for DVDs, VCDs and CDs:

 Do not expose them to direct sunlight.
 Do not touch the recording surface.
 Use soft marker for labelling and not ball point.
 Keep them free form dust conditions.

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SOLID STATE STORAGE
USB Flash Drives: These are small, stick-like devices that plug into a USB port. They can stores
Gigabytes of information and are an easy way to transfer data from one
computer to another. There are security considerations attached to use of
these devices as it is easy to copy large amounts of data to these devices
and then take that information out of the office, for this reason many
companies ban the use of these devices. When using a USB flash drive
the drive is listed within the Windows Explorer program in exactly the
same way that your hard disk is. It will have a drive letter associated with
it.

Also known as flash memory, thumb drives, USB flash drives, CompactFlash, SmartMedia,
Memory Stick, Secure Digital cards, etc., these devices are relatively expensive for their low
capacity in comparison to hard disk drives, but are very convenient for backing up relatively low
data volumes. A solid-state drive does not contain any movable parts unlike its magnetic drive
counterpart, making it less susceptible to physical damage, and can have huge throughput in the
order of 500Mbit/s to 6Gbit/s. The capacity offered from SSDs continues to grow and prices are
gradually decreasing as they become more common.

Storage capacity ranges from 1 GB, 2 GB, 4 GB, 8 GB and 32 GB.

Advantages of Memory Sticks:

 have a long life span about 3 yrs.
 Have large storage capacity about 32 GB or more.
 Provide direct access to data.
 Very cheap to buy.
 Portable since they can fit in a pocket.

Disadvantages of Flash Drives:

 Older machines have no sockets to plug in memory sticks.
 They need software/drivers installed for them to work.
 They can get lost easily.
 Virus spread quickly through them.

REMOTE BACKUP SERVICE/ONLINE STORAGE

With the advent of high speed internet connections it is now possible to store your files online.
This allows you to access your files from any computer with an Internet connection. If you wish
you can also give permission for other people to access your files, for example you could allow
family members to access your digital photo collection.

As broadband Internet access becomes more widespread, remote backup services are gaining in
popularity. Backing up via the Internet to a remote location can protect against some worst-case
scenarios such as fires, floods, or earthquakes which would destroy any backups in the
immediate vicinity along with everything else.

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There are, however, a number of drawbacks to remote backup services.
 First, Internet connections are usually slower than local data storage devices. Residential
broadband is especially problematic as routine backups must use an upstream link that's
usually much slower than the downstream link used only occasionally to retrieve a file
from backup. This tends to limit the use of such services to relatively small amounts of
high value data.
 Secondly, users must trust a third party service provider to maintain the privacy and
integrity of their data, although confidentiality can be assured by encrypting the data
before transmission to the backup service with an encryption key known only to the user.
Ultimately the backup service must itself use one of the above methods so this could be
seen as a more complex way of doing traditional backups.

Diskette (floppy disk): The original IBM PC did not have a hard disk, the operating system,
programs and data had to be contained in one or two
diskettes. Later a hard disk was added, after which point
diskettes were used for supplying programs which could
be installed (i.e. copied) to the hard disk, or you could
back up small amounts of data to the diskette. Most
modern PCs are no longer supplied with a diskette drive,
due to the fact that diskettes are unreliable and are easily
damaged. They only hold very small amounts of data.

During the 1980s and early 1990s, many personal/home

computer users associated backing up mostly with
copying to floppy disks. However, the data capacity of
floppy disks failed to catch up with growing demands,
rendering them effectively obsolete.

Uses of diskettes are:

 Creating backups for small amounts of data.
 Transferring small amounts of data from one computer to another.
 Booting up the computer in case of system failure, for system recovery.
 Storage of small programs and data.

Advantages of Diskettes:
 They are portable (easy to carry around as they can fit in a shirt pocket.).
 Conceals less electricity.
 Most are high Double Density Diskettes.

Disadvantages of Diskettes:
 have very short life span (not durable).
 Can be affected by humid conditions.
 Can easily be affected by dusty conditions.
 Can easily be damaged if placed close to the screen for a long time.
 Takes long to read data into memory than from a hard disk.

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  Hold very small amount of data, 1.44 MB.

Caring for diskettes:

 Do not place them near magnetised field or near the computer screen.
 Keep them free from dust.
 Keep of dry place.
 Do not expose them to direct sunlight.

Network Drives: Seen by your computer as a normal drive, but in reality the network drive is a
folder located on another computer which is connected to the network.

ZIP DRIVE
Zip Drives: Similar to diskettes in shape but does not flop. Data is stored in a random way. Data
is accessed in a random way. Storage capacity is 100 MB.
Advantages of Zip Drives:
 They are portable (easy to carry around as they can fit in a shirt
pocket.).
 Conceals less electricity.
 Relatively cheap
 Most are high Double Density drives.
 More durable than diskettes
 Good for archiving data

Disadvantages of Zip Drives:

 Hold small amount of data of about 100 MB.
 Not as compact as USB flash drive
 Slow data transfer rates

*NB: - Virtual Memory – Refers to temporary storage (on hard disk) used by the computer to
run programs that need more memory (RAM) than the computer has. For example, programs
could have access to 4 gigabytes of virtual memory on a computer's hard drive, even if the
computer has only 32 megabytes of RAM.

HARDWARE MAINTENANCE
Computer hardware maintenance involves taking care of the computer's physical components,
such as its keyboard, hard drive and internal CD or DVD drives. Cleaning the computer, keeping
its fans free from dust, and defragmenting its hard drives regularly are all parts of a computer
hardware maintenance program.
Maintaining hardware helps to extend the computer's lifespan. It helps to prevent wear and tear,
and keeps the system functioning smoothly.

SYSTEM MAINTENANCE

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Keep your system functioning smoothly by managing hard drive space, scanning for system
errors and regularly defragmenting the hard drive. Virus protection is also important, as some
viruses can interfere with computer hardware.

PHYSICAL MAINTENANCE
Keeping computers away from dust and dirt, keeping them clean and avoiding extreme
temperature changes all help to maintain hardware. Keep liquids away from the computer.
Solvents should never be used to clean a computer; rather, you should wipe the monitor and
keyboard regularly with a soft cloth.

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