Computer Notes Unit 1 (Detailed Notes).pdf

DETAILED
COMPUTER
NOTES:
LEARNING UNIT 1 : BASIC CONCEPTS
OF ICT
DEPARTMENT OF APPLIED INFORMATICS AND
MATHEMATICAL SCIENCES
WALTER SISULU UNIVERSITY

TABLE OF CONTENTS
UNIT 1: BASIC CONCEPTS OF ICT ............................................................................................3
1.1. Understanding the Basic Concepts of IT....................................................................3
Information Society................................................................................................................3
1.1.1 What is a Computer?...................................................................................................3
A computer System.................................................................................................................4
Components of a computer System..................................................................................4
1.2 TYPES OF COMPUTERS.....................................................................................................4
Mainframe...................................................................................................................................4
Minicomputers..........................................................................................................................5
Personal Computer..................................................................................................................5
Network Computer (NC).........................................................................................................5
Portable Computers (laptops, notebooks, palmtops and tablets)...........................5
1.3 ELEMENTS OF A COMPUTER ..........................................................................................6
1.3.1 Categories of Computer Hardware .........................................................................6
Category A: Input Devices....................................................................................................6
Category B: Central Processing Unit (processing device)..........................................7
Components of a CPU.............................................................................................................7
Category C: Memory (Primary Storage) ...........................................................................8
Category D: Storage Devices (secondary storage)........................................................8
Examples of storage devices:...............................................................................................9
Frequent Savings and Backups...........................................................................................9
Category E: Output Devices.................................................................................................9
Category F: Communication Hardware..........................................................................10
Categories of Computer Software ....................................................................................11
Functions of operating software system.......................................................................11
GRAPHICAL USER INTERFACE (GUI)..............................................................................11
Software Development.........................................................................................................12
1.4. NETWORKS .........................................................................................................................14
1.4.1 Telecommunications.................................................................................................15
1.4.2 Internet..........................................................................................................................16
Connecting to the Internet................................................................................................17

Search Engines .......................................................................................................................17
E-commerce.............................................................................................................................17
Email ..........................................................................................................................................17
1.5. Computer in Everyday Life ...........................................................................................17
Computers at Home..............................................................................................................17
Computers in Business ........................................................................................................18
Computers in Education .....................................................................................................18
Computers in Industry.........................................................................................................18
Computers in Government.................................................................................................19
Computers in Healthcare....................................................................................................19
1.6. Information Security.......................................................................................................19
1.7. Computer Viruses .............................................................................................................20
Types of Viruses .....................................................................................................................20
Spread of Computer Viruses ..............................................................................................21
Protection against Viruses .................................................................................................21
Measures You Can Take To Protect Yourself from Viruses:...................................21
1.8. Copyright and Law ...........................................................................................................22
Health and Safety ..................................................................................................................22

LEARNING UNIT 1: BASIC CONCEPTS OF ICT
1.1. Understanding the Basic Concepts of IT
An Information Technology (IT) system concerns the processing, storage and/or
transfer of information. Information can take many different forms such as
words, numbers, pictures, sounds or videos.
An IT System consists of computers, the telecommunications network and other
programmable electronic devices. IT is often seen as a very daunting subject
because it involves many different specialist areas. However, the basic principle
of IT is to simply help us to improve the way we deal with information in all areas
of our lives.
IT is used in business, industry, government, education, health care and
everyday home/social life. Computers enable us to process information and
perform specific tasks much more quickly than we often do ourselves.
IT Systems are usually very flexible and can be made to perform a wide range
of different tasks. IT networks allow us to distribute and share information very
quickly.
Information Society
We live in an “Information Society” where the effective use of information is
regarded as the defining element of the 20th – 21st centuries.
1.1.1 What is a Computer?
A computer is an electronic device that uses set of instructions to perform tasks
based on the given input to produce output.
Figure 1.1 Hardware parts of a computer system and their
interactions/cooperation
MEMORY: ROM+RAM+CACHE
INPUT
DEVICE
EXTENAL (SECONDARY) MEMORY
STORAGE DEVICES: USB Flash drive, CD/DVD drives, Memory card
OUTPUT
DEVICE
CENTRAL PROCESSING UNIT (CPU)
CONTROL UNIT ARITHMETIC LOGIC UNIT

A computer System
A system is a group of related components and operations that interact to
perform tasks to achieve a common goal.
Parts of a computer System
• Input: Raw data entered electronically then is converted into a form that can
be processed by a computer.
• Processing: Data is manipulated to transform it into information.
• Output: Information, which has been processed from data and is usable by
people.
• Storage: Data, information and programs are stored in a computer in a form
that a computer can process.
Components of a computer System
• Hardware: Physical components of a computer that we can touch.
• Software: Programs that control the computer and make it function
• Data/Information: The purpose of a computer system is to convert data into
information
o Data: Raw materials that need to be processed
o Information: Manipulated or processed data
• Procedures: Description of how things are done in step by step to accomplish
result/results.
• People: People constitute the most important component of a computer
system; they operate computer hardware and create computer software.
• Communications: when one computer system is setup to share data and
information electronically with another computer system.
1.2 TYPES OF COMPUTERS
There are many types of computers that are used for a variety of different needs.
Mainframe
A mainframe is a large and powerful computer that is capable of serving a vast
number of users at the same time. Users do not sit down in front of the
mainframe itself, they connect to it using another smaller computer (or dumb
terminal). The terminal consists simply of keyboard and screen to enter and
display information. The terminal does not store or process data itself,
Mainframes need to process and store data and information, for many different
users. Therefore they require much more processing powers and storage capacity
than other computers (they are generally faster and have more memory) and

hence can be very expensive.
Large corporate and government data processing departments often use a
mainframe computer. Mainframes allow information to be centrally stored and
controlled.
Minicomputers
A minicomputer is a smaller, less powerful version of a mainframe. A
minicomputer is often cheaper due to its lower processing power and storage
capacity (as compared to a mainframe). However, a minicomputer is not able to
serve as many users at once. In a similar manner to use a mainframe, users do
not sit down in front of the minicomputer itself. They connect to it using a smaller
computer or a dumb terminal. Minicomputers are often used by small and
medium sized companies or by departments in very large organizations (to
provide a centralized storage of information and computer programs)
Personal Computer
A computer (most mostly used in homes/offices) is usually known as a PC (short
for Personal Computer). Because they are usually found on user’s desks, they
are also sometimes called Desktop Computers. A typical PC consists of a system
unit housing CPU (central processing unit), disk drives, a Video Display Unit
(VDU), a keyboard and a mouse mounted in a motherboard. PCs can be used
for thousands of different tasks from creating a simple document to controlling
a large industrial machine.
Network Computer (NC)
A network computer is a low-cost version of the PC. NC’s are designed to connect
to and be managed by a central computer (i.e. a mainframe or minicomputer).
Every time the Network Computer is switched on (booted), it retrieves the latest
version of the software it needs from the central computer. Network Computers
tend to have slightly less processing power and storage capacity than PCs and
are substantially less expensive. However, a Network Computer cannot be used
if it is not connected to the central computer. NCs tend to be used in call centers,
help desk, and data processing departments where users do not require the
flexibilities of a PC – but instead need to access central software and information.
One main advantage is that when software requires an upgrade, only the central
computer is updated instead of having to update each individual machine.
Portable Computers (laptops, notebooks, palmtops and tablets)
Portable Computers can be carried around easily and use a Liquid Crystal
Display (LED) and a special re-chargeable battery.

A laptop computer (also often called notebook) is similar to a personal
computer, except that it comprises an integrated unit. Instead of separate
monitor, the lid contains a screen and keyboard is built into the base. It is
portable computer designed to fit inside a briefcase. Laptops have most of the
features and components provided by the PCs and offer the same level of
flexibility in performing a wide range of tasks. However, the size of a laptop makes
it costlier to manufacture than a PC.
A palmtop computer is a hand-held device; palmtops also known as a Personal
Digital Assistants (PDA) do not have quite the same features and components
as PCs. They are used mostly as personal organizers to store contact information
to access internet and emails. PDAs which can act as mobile phones and text
messenger plus use the Internet are known as smartphones. PDAs which can
use many different media such as the Internet, music files and act as radios or
Global Positioning Systems are known as multimedia PDAs.
Tablets are mobile computers which, instead of using a keyboard or mouse, use
a touchscreen (which can be activated by a fingertip) or a screen which allows
the use of a stylus or digital pen. They are often used by delivery people or
warehouse stock-takers who would find even a laptop too heavy for their work.
Tablet can also be used to store files, access emails and to surf internet.
1.3 ELEMENTS OF A COMPUTER
A computer consists of two main elements: hardware and software
1.3.1 Categories of Computer Hardware
A computer is based on three operations: entering the data (inputting),
processing it, and presenting the processed data in some way (called outputting).
Category A: Input Devices
They are used to feed commands and data into the computer. Some examples of
input devices are:
Keyboard: This is used to enter data into a computer. With keyboard, you can
enter commands, select menu options and enter data/values into applications.
Mouse: The mouse is used to point and click on items/icons/menus on screen.
Light pen: A special pen that let you draw directly onto the screen, or click on
buttons and menus.
Touch screen: (also categorized as an input/output device) similar to the
ordinary TV screen. Has a thin, transparent layer of plastic covering, hat is

touch-sensitive. When you touch a part of the screen, it has the same effect as
if you clicked on that area with a mouse.
Joystick: A handheld stick that can be moved around in any direction. Used
mainly for playing games.
Touchpad: Often used on laptops. With a touchpad, you can move the cursor
on the screen by touching the pad and moving your finger around. The two
buttons, on the touchpad, simulate the use of the buttons of the mouse.
Trackball: Instead of using a mouse, you can also use a trackball. The trackball
generally provides the same functionality as a mouse; however, you do not have
to move the unit, to move the mouse pointer. Instead you can use your thumb
on a roller-ball to move the cursor on the screen.
Graphics Pad: This is a square piece of material that is used to draw pictures.
Scanner: Used to scan images and documents into a computer. Can be flatbed
or hand-held. Also used for Optical Character Recognition (OCR) and to scan
microfilm, transparencies and negatives.
Voice Input Device: It convert a human speech into digital code by comparing
the electrical patterns stored in a computer
Category B: Central Processing Unit (processing device)
Known as a CPU, CPU is the brain of the computer. CPU is housed inside the
system unit. It interprets and caries out instructions to manipulate the data into
information. It has internal clock that is oscillating at a defined speed, providing
a heartbeat for the processor’s work. The speed of a clock is measured MHz
(million cycles per second), GHz (billion instructions per second) or more
depending on a design of that CPU.
Components of a CPU
• Control Unit: tells the rest of the computer system how to carry out a
program’s instructions, that is, it supervises the entire operations of the
processor. It retrieves instructions from the main memory, breaks each
instructions into series of steps that can be carried out. It controls the
transfer of data between main memory and input/output devices.
• Arithmetic Logic Unit: it performs the calculations and logical operations
within the computer.
• Registers: Are storage locations inside the processor; they keep track of
the overall status of the program that is running, the location of the next

instruction, the location of the current instruction, operands of the
instructions and results.
Because CPU runs more quickly than other components of the computer,
immediate access memory (cache) is usually incorporated as a buffer to maintain
a constant flow of the data to and from the CPU. CPU requires a fan to keep it
cool while the computer is on as CPU often generates quite a lot of heat.
Category C: Memory (Primary Storage)
This is where information is stored for retrieval and processing.
ROM(Read Only Memory): Is a special type of memory that is permanent, it
contains all the information the computer needs to switch itself on, check that
all its systems are working well and to tell the PC what things are plugged on it.
It cannot be changed or written by you. It stays the same even if the computer
is shut down. ROM is non-volatile, it keeps the data even if the computer is
switched off.
RAM (Random Access Memory): RAM is used in a PC to temporarily store the
data when an application is running (when it is being used). RAM is also used to
store program instructions and feed information to the CPU to process it. RAM
is not permanent, when you switch off the PC; the contents of RAM are lost or
emptied.
There are two main uses of RAM in a computer system: main memory and
cache.
Main Memory (or system memory): Main memory is the largest amount of RAM
installed on the motherboard of the PC. It is used to run software applications
and temporarily store data that is entered by the user. Every piece of software
needs a certain amount of main memory to operate efficiently.
Cache: Cache is a very fast type of RAM directly attached to particular
components such as the CPU, hard disk or graphics card. Cache enables an
amount of data to be copied from the main memory so the component can access
it more quickly.
Category D: Storage Devices (secondary storage)
Storage devices are designed to retain data and instructions in a relatively
permanent form. After data is entered in a computer, it must be saved as a file
to preserve its contents after the computer is switched of.

Examples of storage devices:
Hard disk: Usually fixed inside the computer and stores large volumes of data,
which can be accessed and retrieved quickly.
Floppy disk drive: A floppy disk drive is a hard disk, but with removable disk
called floppies, floppy disks or diskettes. Floppies can be used to transfer small
files from one PC to another (up to 1.4 MB).
ZIP/ JAZ drives are another type of floppy drives that use special disks instead
of floppy disks. Zip disk can hold about 100 times as much as floppy disk. JAZ
disks can hold much more data.
CD-ROM/DVD-ROM DRIVE: CD-ROM (compact disk-read only memory) drives
read data from CD’s that can hold up to 800MB’s of data (standards sizes are
650MB’s and 700MB’s).DVD- ROM (Digital versatile disk) drives can store up to
17 gigabytes of data and are designed for video and multimedia applications.CD-
R, CD-RW, DVD-R and DVD-RW drives allow you to write your own CD’s and
DVD’s. Both CD’S and DVD’s disk are read-only after burning and can be read
in almost any CD and DVD drive. CD-RW and DVD-RW disks allow you to delete
and overwrite (re-write) data and re-use the disks.
Frequent Savings and Backups
It is good practice to save your work at regular intervals. This prevents data loss
resulting from a power cut or a system error. If you are working on a document,
and your PC crashes or has a power cut, and you have not saved your
document, you will lose it!
To protect against loss or damage of files on your computer’s disk, make regular
backup automatically overnight. For critically important data, make regular
backups and keep them away from the office-i.e., it won’t help you much if the
building burns down with your backups inside.
Use the Internet so search for other examples of storage devices and backup
services.
Category E: Output Devices
Output devices are devices that the computer uses to send the results of
processed data out. They present information in a form that users can
understand.
Output can be divided into two forms:

1. Softcopy: The information that is shown on a display screen. The
screen/monitor/visual display unit (VDU) is the part of the computer that
displays the current process or application. There are several types of VDU
such as the CRT (Cathode Ray Tube) and Flat Screen/LCD style. CRTs are
cheaper but take up more desktop space whereas Flat Screen/LCD style
take up less room, often display a much sharper screen but generally
much more expensive.
2. Hardcopy: The information that has been printed out on paper and is
tangible.
Examples of hardcopy output devices:
Printers are used to transfer information from the computer onto paper.
There are many different types of printers presented below:
o Laser: These are large, expensive printers that work like a photocopier.
They usually have very high quality printouts and can print very fast.
o Inkjet and Double-jet: They are smaller, cheaper printers that use a little
cartridge to spray a jet of ink onto the paper. They are fairly quiet and of
good quality, but are not as fast or produce such high quality output as a
laser printer. These printers are sometimes known as line printers because
they print each page one line at a time.
o Dot matrix/impact: An older type of printer that uses a ribbon and a
print head, like a typewriter. They are very loud and extremely slow.
However, they are very much cheaper.
o Plotter: This is a special type of printer that draws pictures based on
commands from a computer. They are used by engineers and designers
who need to draw complicated diagrams.
Category F: Communication Hardware
Communication hardware facilitates connections between a groups of connected
computers.
i. Modem: is made out of two words “modulation” and “demodulation”. It is a
device that enables a computer to transmit data via telephone lines.
Modulation: Conversion of analogue signals to digital form so that the
receiving computer can process them
Demodulation: is a conversion of digital signal into analogue form so
that data can be sent via telephone lines.

ii. Cables: allow computers to communicate directly with one another, data
does not go via telephone lines.
iii. Repeaters: regenerate weak signals to original form.
iv. Routers and bridges: direct or route network traffic to specified
destinations.
v. Gateways: connect different types of network.
Categories of Computer Software
Systems software (operating system) is the software that runs the computer-
this is usually called the operating system. Systems software is the term used
to describe programs that enable the computer to function, improve its
performance and access the functionality of the hardware. Microsoft Windows
is the operating system a lot of people use. However, there are other form of
system software such as UNIX, Linux, 0S2, BcOS, OS-X (MacOS) and so on.
Functions of operating software system
The operating system makes the computer function following some of the
FUNCTIONS of the operating system
1. Boot-up the computer
2. Control the hard drives: This includes formatting and defragmenting disks as
well as saving files to and retrieving files from disk.
3. Control input devices such as keyboard, mouse, etc.
4. Control output devices such printer.
5. Control external ports. Ports are external connections that enable peripheral
devices to be connected to the computer. Common types of ports are serial,
parallel, USB,VGA,HDMI.
6. Provide functionality for computers to be linked in a network.
7. Provide the foundation for application software to be launched.
8. Enable application software to access and use the hardware.
GRAPHICAL USER INTERFACE (GUI)
GUI is designed to simplify the work of the user. The interface consists of
programs and commands represented as presented as little pictures or graphic
symbols called icons.

Applications software includes programs that really do work for the users.
Following are examples of applications software.
Word Processing used for, creating, formatting and checking texts documents.
Examples include Microsoft word, lotus, OpenOffice.org writer, WordPro and
Corel WordPerfect.
Spreadsheets: consists of a table containing rows, columns and cells. When
numbers entered into cells, formulae can be applied- enabling complex
calculations to be carried out. Examples include Microsoft Excel, OpenOffice.org
CalcLotus 1-2-3, and Corel QuattroPro.
Database: Enables you to store, organize, and retrieve information. Databases
can search through thousands of records very quickly and display data into a
table format. They can be used to store many different types of information.
Examples include Microsoft Access, Sybase, Lotus Approach and Corel Paradox.
Presentation: Enables you to create sophisticated business presentations that
can be displayed as an on-screen slide show or printed on to transparencies.
Examples include Microsoft PowerPoint, OpenOffice.org Impress, lotus Freelance
Graphics and Corel Presentations.
Communication: Allows you to send and receive faxes and emails and to also
browse the Internet. Examples of email programs include Microsoft Outlook,
Microsoft Outlook Express, Evolution and Lotus Notes. Examples of Internet
browsers include Microsoft Internet Explorer, Mozilla Firefox and Netscape
Navigator.
Graphics/Design: Graphics programs can perform a wide range of functions
such as editing bitmaps, drawing, painting, 3D graphics, animations, video,
multimedia and web design. Examples include Adobe Photoshop, JASC Paint
Shop Pro, Corel DRAW, AutoCAD and Adobe Premiere.
Multimedia/Games: These applications incorporate text, graphics, sound, video
and animations. Educational Software often uses a lot of multimedia techniques.
Software Development
The design of IT systems can be a complex process that requires careful planning
and management. Computer professionals develop computer systems. Systems
analysts and programmers are the main people work on systems development.
System analyst is an information specialist who performs system analysis,
design and implementation. Programmers code the actual application using

programming languages (special software for creating applications) according to
the design specifications developed by system analysts. The process of systems
development is a cycle of preliminary investigation, analysis, design,
programming (development), testing, implementation and maintenance. Figure
1.2 shows each stage within the software development (system
development) life cycle.
• Beta versions
Sometimes software is released to public before it has been fully tested.
These pre-release versions of the software are known as Beta Versions.
• Software Bugs
Software programs are often so large and complex, most of the time the
people testing them can’t find all the errors and problems. After a program
has been out for a while, users notice that there are little things wrong
with the software here and there, these things are called bugs. When the
number of bugs found in software increase, a patch, or service pack is
Preliminary
Investigation
Requirements
Analysis
System
and
Software
design
Implementatioin
and Testing
System testing
Operation
and
Mentenance
• This is usually the longest
stage of the lifecycle. The
newly developed system is
installed and put into use
(operated). Data from the
old system may be
converted to be used in the
new system. Feedback is
obtained from users to
locate problems and
identify further
improvements. Additional
system maintenance is
undertaken as an on-going
process.
•Conduct preliminary
investigation, propose
alternative solutions
and describe the cost
and benefits of each
solution. Submit a
preliminary plan with
recommendations.
•The analysis produce a feasibility
report that defines the requirements
of the new system and recommends
whether or not they can be met.
Alternatives may also be suggested
such as a reduced system to match the
costs and needs of the project.
•
• This stage involves designers working out
how the software should look and behave.
The design addresses the functions
required and the operation of the
software to fit a particular problem it’s
designed to solve. There are two parts of
the design stage. The first part addresses
the hardware system requirements
(Computer, network, input and output
devices etc.). This stage is known as the
system design. The second part of the
design stage concerns the identification of
the software components. This stage is
known as the software design process.
• Once the software has been designed, the
programmers write various functions and
routines that make the software and
commands function. Each module of the
system is built according to the outline
design until the entire system is complete.
At the final stage, it has to
be tested and have any
mistakes fixed. Only then
the software is released.

often released. This is a little add-on program that fixes most of the bugs
that people have found.
1.4. NETWORKS
A computer network consists of two or more computers that are connected
together and are able to share information and resources with each other,
enabling group working. They could be in the same room, in the same building
or on the opposite sides of the world.
There are several benefits to using a network:
• If you have two or more PCs but only one printer, the PCs can all connect
up to the printer and share it.
• As well as sharing recourses such as printer, PCs on a network can also
share files and data.
• To help people work together better, users can send messages to each
other through their connected computers – this is called electronic mail
or email
A workgroup is a group of computers on a network that can share data (folders
and files) and resources (printers, modems etc.).
A network card is used to link a PC in a network.
There are two main type of network:
• LAN (Local Area Network): This is a small network, connecting computers
spread out over a fairly small, local area- either in the same building or few
buildings. LANs are connected by a system of cables that allows the
computers to talk to each other. The computers must also have network
cards installed in order to get them connected to the network. An individual
computer on a network is known as a workstation. The workstation is
connected to a server. The server generally run a network operating system
and provide services such as shared data stores, access to software,
communication services and internet access. Differed network drives may
appear on a network when a user log-into a network (via username and
password).
There are two common types of Local Area Networks as follows:
▪ Client-Server network: a network of connected computers and
peripherals with a centralized server that facilitates the sharing of
network data, software and hardware resources. Machines that
provide service to other computers are called Servers and the

computers that make use of those service are called clients or
workstations.
▪ Peer-to-Peer networks: A network on which all computers have
equal status, computers communicate directly with each other
without relying on the server.
• WAN (Wide Area Network): This is a larger network, connecting computers
spread out over a wide area – usually the whole country, or around the
world. WANs use the telephone cables (the PSTN- Public Switched Data
Network) in addition to satellite, radio and other communication methods.
WANs also use more powerful computers named servers. WANs are often
groups of individual LANs spread over a number of sites and connected
using various communication links.
• Intranet: is a smaller, closed version of the Internet, and can only be
accessed by authorized members of an organization. Intranets are local
networks that use the same programs as the Internet to pass information
between computers within a company or organization.
• Extranet: is an Intranet which is partially accessible to authorized
outsiders. Extranet is more than one Intranet that is linked using Internet
technology.
• Internet: a world-wide computer network consisting millions and millions
of computing devices. Internet to be discussed in the next sections.
1.4.1 Telecommunications
Telecommunication networks are often used to transmit data between computers
and networks. The following are common telecommunication technologies in a
network:
• Modem: a device that allows a computer to connect to a telephone line (or
broadband network) to access the internet as well as send/receive emails.
A standard telephone modem converts information into analogue form and
back again. This is referred to as modulation and demodulation.
• PSTN: The Public Switched Telephone Network is the standard telephone
network, originally designed to transmit audio signals and is relatively
slow when transmitting computer data. The PSTN is however, a much
cheaper and more readily available service in most homes and offices.
• ISDN: Integrated Services Digital Network is a similar way of transferring
data between computers, but in a digital manner. It doesn’t need to convert
data into analogue and back again, so it is kindly faster.
• DSL: Digital Subscriber Line- A method for moving data over a regular
phone lines. A DSL circuit is much faster than a regular phone connection,

and the wires coming into the subscriber’s premises are the same (copper)
wires used for regular phone service. DSL is now a popular alternative to
leased lines and ISDN, being faster than ISDN and less costly than
traditional leased lines.
• ADSL: Asymmetric Digital Subscriber Line allows for transfer speed of 9
megabits per second into the computer and up to 800 kilobits per second
back up the telephone lines.
• Fax: A fax works in a similar way to a modem – in fact, it is like a scanner
or photocopier combined with a modem. You put a piece of paper in it, the
fax scans words or pictures on the paper, and sends it down the telephone
line. A fax at the other end receives the information, and prints out an
exact copy of the original.
1.4.2 Internet
Internet is a global computer network allowing communications with millions
of computer users and access to resources from around the world. The
Internet consists of a huge number of computers and networks all connected
together by telephone lines, cables and other telecommunication services.
You can use internet to share information with others around the world.
Different types of computing devices and networks can transfer data with the
use of the same TCP/IP protocol (Transmission Control Protocol/Internet
Protocol).
The Internet consists of three main parts:
• The World Wide Web (www) is the part of the internet consisting of all
the sites (website) that can be accessed using a web browser. In order
for a browser to access a website, the website must contain files that
have a particular format constructed using Hyper Text Markup
Language (HTML).
• Email-refers to the way in which messages can be sent over internet.
• File Transfer Protocol (FTP)-method by which files are transferred from
one computer to another over the internet.
Sometimes the phrases The Internet and World Wide Web are used
interchangeably. However, to strictly correct, the Internet refers to all computers
and cables that make up the network and the World Wide Web refers to the pages
of information that are stored on those computers. The Internet also sometimes
referred to as The Information Superhighway.

Connecting to the Internet
To access the Internet (from home), you need a modem (using particular
telecommunication service) and you need to subscribe to a certain Internet
Service Provider (ISP). This is a company that specializes with setting up Internet
connections and provides a username and password. Once you have connected
to the Internet, you can send and receive emails and browse the World Wide Web
using your web browser.
Search Engines
There are millions of web pages on the Internet. To browse for information, you
can use a search engine to quickly find what you’re look for. Some examples of
search engines are www.google.com, www.yahoo.com, www.ananzi.co.za,
www.bing.com and so on.
E-commerce
E-commerce (Electronic Commerce) or online business refers to the transaction
of business activities on the Internet. E-commerce is safe to use, as your credit
details are encrypted when transmitted over the Internet. When encrypted, these
details are coded so that hackers cannot decode or read them.
Email
Email can be sent over the Internet to anyone in the world as long as they have
access to the Internet and email software. Email is much quicker than traditional
postal system. An email address identifies the mailbox used by a user. Email is
also useful for sending attachments. An attachment can be any file, e.g. a Word
document, an Excel spreadsheet, a digital photograph etc.
1.5. Computer in Everyday Life
Computers are in common use today as they can be used to process large
amounts of data in short amount of time. Many areas of modern society take
advantage of the power of computing.
Computers at Home
Many people have a PC at home, either for work or entertainment. Some of the
common uses for a home PC are:
• Playing computerized video games.
• Working from home (known as teleworking)
• Managing your finances (spreadsheets), Internet banking etc.
• Time management through the use of personal organizer packages to store
and arrange meetings, birthdays and the like.

• Word processing (writing letters), doing homework etc.
• Internet browsing for information or shopping on the internet
Computers in Business
Many companies use IT for administration, communication, to sell products
online, to develop software and support services. Computer uses in business
field can be categorized as follows:
• Offices: Companies can use computers to store their records, keep track
of their customers, or even help to run the business
• Shops: Shops and supermarkets use IT on their checkout counters to scan
in the barcode on the item you purchase. This type of that is commonly
used is EPOS (Electronic Point of Sale).
• Libraries: Libraries usually put barcodes on books to scan when a book is
borrowed or returned. This allows libraries to keep an up-to-date database
of all their stock and monitor which books are out on loan or overdue
Computers in Education
It is very important to have some computer skills in today’s working world. As
well as storing student details, names, addresses, academic records and so on,
most schools now have some form of computer education. Students are to
communicate with others on other learning institutions. Students write reports
using the computers and also use CBT (Computer Based Training) material to
study, and also to search and find useful information.
Computers in Industry
In addition to business systems, further examples of industrial systems include
photographic processing systems, washing machines, speed trap cameras,
control manufacturing processes, etc.
Other common uses of computers relating Industry are as follows:
• CAD (Computer Aided Design): use of computers to produce a technical
drawing and schematics. Drawings can be manipulated in 2D and 3D and
can be linked to CAM (Computer Aided Manufacturing) to enable data to
be loaded into a machine in the manufacturing of parts.
• Robotics: Industries use robotics to carry out tasks that would be difficult
or dangerous for a human to undertake. Most robots have programmed
arms to manipulate items (such as when manufacturing a car etc.). These
devices are controlled by computer systems and instructions.

• Environmental: Monitoring and control systems are used to control
central heating, weather stations, detectors for pollution levels etc.
• Traffic Control: Computer systems are used to control traffic lights that
receive messages from sensors pointing to the road. When sensors do not
detect traffic, they signal the control computer to indicate that the way is
clear and that it can change to red to allow traffic from other directions to
pass. Often such systems are also controlled by timing and use the sensors
to adjust the timing of the lights according to the amount of traffic in order
to keep the flow of traffic smooth.
Computers in Government
Government departments make use of the power of computing to keep track
of the records such as population, tax records, and voting register for
examples.
Computers in Healthcare
Computers are used to capture patient records, control diagnostics
instruments and equipment, perform ambulance scheduling and tracking,
conduct medical research and provide online services.
1.6. Information Security
When thinking about the term ‘Information Technology’, often people think of
them physical devices associated with IT. However, information or data is most
the most valuable part of a computer system, because it is the least easily
replaced aspect of IT if lost.
Information security means that computers along with the data stored in them,
need to be protected from natural disaster, acts of sabotage, theft, viruses and
unlawful access.
Computers like a clean, dust-free environment, good ventilation and a stable,
vibration-free surface. The computer system should be protected against fire,
flood, power failure, etc. Data has to be backed up frequently. Backups should
be stored in a secure area at a different site. Never keep backups on the same
site as the system as they could be stolen or destroyed along with the rest of the
system.
The following are common means of protecting data in a computer system:
• Username and password: To protect information and access on a computer
or multi-user network, username and passwords are used to log into the
system. Most software also let you password-protect a document so that

only you or someone who knows the password, can read them. When
choosing a password, select one that is easy to remember. Do not write the
password down anywhere. Never make the password so obvious such as
your birthday, name, surname, etc. Most people’s passwords can be easily
guessed if they are too obvious. Choose a password that has a combination
of letters (uppercase and lowercase letters), numbers and special symbols.
• Access rights: Organizations often apply access rights to different
individuals or categories of computer users. When a user logs-into the
network, the system checks their rights and displays commands, data or
drives accordingly.
• Data Encryption: Data should be encrypted; encryption scrambles the
data and makes it unintelligible without the use of a key. The key is used
to decipher the data.
• Firewalls: A firewall is a first line of defense against hackers. It is a
computer program that is installed on a computer that connects a network
to the internet. The firewall analyses the data that pass in and out of the
network. It is programmed to follow certain rules which enable it to decide
whether or not to allow that data.
1.7. Computer Viruses
A computer Virus is a program that is deliberately created to cause annoyance,
alter or delete the data. Some viruses can cause computer systems to slow down
to the point they are not usable. One of the features of viruses is that they are
designed to replicate and spread.
Types of Viruses
• Trojan: is a virus that hides itself inside another legitimate program.
When the program is used, the virus is released and can begin its work of
replication and annoyance or damage.
• Worm: Is a program that replicates itself over and over in the computer’s
memory until the computer can barely function. One of the signs of
invasion by a worm is the slowness of the computers.
• Time bomb: is a virus which lies dormant until a certain date or time or
for a period of time. At this date or time, the virus suddenly becomes active
and carries out whatever task it is programmed to do.
• Logic bomb: it is similar to a time bomb, except that instead of becoming
active at a certain time, it becomes active when a particular activity
happens, e.g. Instead of formatting a diskette, the virus causes the hard
drive to be formatted.

• File Virus: manifest itself in the memory and resides there until a certain
program has been activated.
• Boot Sector Virus: insinuates itself on to the boot sector of a diskette or
hard drive. Every time the computer is switched on, the virus gains control
of the system and copies itself onto the hard drive.
Spread of Computer Viruses
Viruses can spread in the number of ways; five of the common ways are as
follows:
1. Downloads from the internet.
2. Pirated Software.
3. Exchange of diskettes.
4. In attachments to emails and emails themselves
5. In documents. Micro-viruses can be hidden in ordinary documents,
spreadsheets and presentations.
Protection against Viruses
One of the measures to protect against computer viruses is anti-virus software.
Anti-virus software scans files for pieces of code, called signatures, which it
recognizes as part of a virus. Updating anti-virus software mostly involves
updating the signature file, which it could be done on frequent basis. This has
to be done especially when you receive files from outside sources. No anti-virus
software is perfect; it is only as good as techniques it uses for detecting viruses
and the currency of the signature file. There is always a chance that a virus will
go undetected.
When a virus is detected, the software will attempt to remove the virus. This is
called cleaning or disinfecting. It sometimes happens that the system can detect
the virus but not get rid of it. In this case, you will be usually be given the option
of deleting or quarantining the infected file. When the file is quarantined, it is
made unusable and so unable to spread the virus.
Measures You Can Take To Protect Yourself from Viruses:
1. Install good antivirus software and update it on regular basis.
2. Scan all diskettes before reading (opening) them
3. Enable the auto-protection feature on the anti-virus software to scan
emails.
4. Be wary of emails from unknown sources, particularly if they contain
attachments.
5. Use Internet Service Provider that scans emails before delivery

6. Do not download files/software from unknown Internet sites
7. Be careful of using diskettes from unknown sources
8. Do not install pirated software.
1.8. Copyright and Law
Copyright is the legally protected right to publish and distribute any literacy,
musical, artistic or software material, etc. Copyright laws grant the creator the
exclusive right to reproduce, distribute, perform and display the work publicly.
Someone else who wishes to use must obtain written permission.
End-user license Agreement or single-user license agreement grants a user the
right to install and use software, usually on one computer or for one user and to
make a backup copy of the software. The software may not be installed on a
network or given, rented or given or sold to another user without being removed
from the initial user’s computer.
One has to understand the following terms:
• Software piracy means illegally copying or distributing copyrighted
software, it is illegal and unethical.
• Freeware is software that is offered free to anyone, it usually has some
restrictions such as it may not be resold or its source should be
acknowledged.
• Shareware is software that is available for users to copy and try out, but
it does require that if one would like to continue using it, they pay the
developer a fee.
• Open Source Software transfers some of the rights to the user. It makes
the source code available to the developers who want to modify and
improve on the code. It may be modified and redistributed but the modified
product also has to include the source code.
• Public Domain Software is software on which there is no copyright or the
copyright has expired. The only restriction on this type of software is that
you may not apply for copyright on it. It can be copied, redistributed and
even sold without restriction.
Health and Safety
Using a computer is generally safe; however there a number of hazards to avoid.
Most them arise if you use the computer for long periods without a break, take
regular breaks to rest eyes, muscles and joints. Others arise from bad posture
or inappropriate positioning of equipment. Cabling and electricity overload also
present a potential source of accidents. It is important to ensure that there is

adequate lighting, but does not cause a glare on the screen, it is also important
to make sure that there is enough air circulation in the room as computers
generate a lot of heat.
• RSI: stands for Repetitive strain injury. If you are typing and/or using the
mouse a lot, you can strain the muscles in your hand, arm, and back.
Take a short break in every hour whilst using a computer so that your
muscles have time to relax a little. Do not go longer than an hour without
a break.
• Eyes: your eyes can get strained if you have been working on a computer
for a long time without taking a break. Look away from the screen
whenever you can and focus on objects further away. You should also have
adjustable controls on your screen so you can adjust the brightness
contrast etc. Position your computer screen so that any windows that allow
in natural daylight are to the side of you not behind or in front. If you see
a window’s reflection when you look at your screen, use a window blind or
shade to reduce its brightness.
• Temperature: Computers can also generate a small amount of heat and
often make surrounding air feel dry. Ensure that you have an adequate
provision of fresh air via air conditioning or access to window. Fresh air
will also help alleviate tiredness when using a computer for many hours a
day.
• Ergonomics and posture: Ergonomics is the science of designing and
arranging objects, systems and environments so that they are comfortable,
safe and efficient for people to use. Your PC screen should be at a level
where you can see it without leaning forward or backward. You should be
able to adjust your screen tilt, swivel it in any direction. You should have
an adjustable chair that supports your back properly. Check that your
chair provides adequate lower back support. You may consider the use of
a footrest to improve your posture at a desk. The height of your desk
should be suitable for you to sit comfortable at whilst you work using a
computer. Your keyboard should be at level where your arms are parallel
to the floor. Make sure you have enough space on your desk to have your
mouse and keyboard in comfortable position.
• Cables and power adapters: Ensure that the power supply to the
computer and associated devices (such as printer, speakers etc.) is not
overloaded. An overloaded power-supply can cause overheating of power
adapters and may constitute a fire risk. Avoid cable connections that may
cause a health and safety hazard. Ensure that your computer, cables and

power supply units are positioned safety and away from an area where
people may walk.
• Food and drink: with regards to the safe use of IT equipment do not eat
and drink directly at your computer. When liquid is spilt onto a component
of a computer, such as a keyboard, the keys can short cut and the
computer may produce errors signals. Not only does this produce
unwanted input to your system but it can further damage the equipment
if left unattended. Try to avoid eating at your computer as food can become
trapped in the keyboard, causing errors during use (some keys may seem
to ‘stick` when typing ).
• General issues: Don’t leave the PC in a place where it will get very hot or
very cold. If you work in a shared environment, remember to log out of
your computer when you are not using it or if you are away from your
computer for a long period of time. When you have finished using your
computer shut it down completely. Try to keep dust away from your
computer as can build-up inside. Keep the area around your computer
tidy.

Computer Notes Unit 1 (Detailed Notes).pdf

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Computer Notes Unit 1 (Detailed Notes).pdf