COMPUTER STUDIES COURSE GUIDE BOOK © Ali Marcel Samora Jesse
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Computer Studies Guide Book
This book is RECOMMENDED for any person acquiring relevant introductory knowledge and skills in Information Communication &Technology (ICT), from the upper-primary level, high school and college beginners in computer studies, packages and network & networking technicians. Giving relevant introductory knowledge skills in Information Communication &Technology (ICT) Š Ali Marcel Samora Jesse
All rights reserved. No part(s) of this publication maybe produced, stored in a retrieval system, or transmitted in any form or by any means(electronic, mechanical, photocopying, recording or otherwise ) without the prior permission of the publisher in writing. Some illustrations in this book have been acquired from web sites and are used for demonstration and educational purposes only. Online availability of the text and images does not imply that they may be reused without permission of the copyright holder. Any person who does any unauthorized act in relation to this publication may be liable to criminal prosecution and civil claims for damages imposed by the Authors Ali Marcel Samora Jesse Or as expressly permitted by law Typeset by Ali Marcel Samora Jesse of Marioville Ltd. Diani Printed by The Theo & Nate Concept.
This book is sold subject to the condition that it shall not by way of trade or otherwise, be left re-sold, hired out or otherwise circulated without the publisher’s prior consent in any form of binding or cover other than that in which it is published and without a similar condition including this condition being imposed on the subsequent purchase. Giving relevant introductory knowledge skills in Information Communication &Technology (ICT)
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PREFACE This Book covers comprehensively the Basic computer literacy and actual function of the system in our education system from the“A”to“O”Levels in computer studies curriculum. This Book is recommended for pupil’s of as lower level in class 4 to class 8 in the “A”. Level and in the “O” level from Form 1-4 for the computer students as well as the college beginners who takes ICT and other related course. The syllabus topics have been covered to a sufficient depth. This Book adopt a very meaningful and practical approach to the introduction to the computer studies and ICT. The networking topic is comprehensively dealt with focusing on making more networking engineers, and many other useful topics that will mould computer students into expertise. There are also exercises comprising of short and descriptive questions at the end of each sub-topics and revision questions at the end of each chapter to provide adequate assessment of pupil’s understanding of the subject at each stage.
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FORWARD With the introduction of computer studies at the primary level by the government as a subject has a created a great demand for standardised textbooks to teach the subject. I wrote this Book to ease my teaching and practices with my learners, I therfore find this Book most appropriate to meet the demands of every learner. It will be invaluable text for pupil’s, students taking computer studies and other related courses at all the stages of education from primary 4 to collage beginners. The materials presented in this Book has been well researched and is most up-to-date. The subject matter is intensively covered to adequate depth. The practical sessions and exercises that have been included in this Book are extremely useful and considered to be very helpful to the learners.
In preparing this Book, Mr. Ali Marcel Samora Jesse has drawn heavily on his experience from industry and the academia as well as extensive work with computers. The professional and logical flow of ideas in this Book is testimonials of Mr. Ali’s immense expertise and experience as a teacher and a practitioner in the ICT field. This Book is a must for all who want to became computer literate.
Mr. Ali Marcel Samora Jesse H..O. D ICT Word of Life Christian Academy
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ACKNOWLEDGEMENTS My sincere gratitude goes to the following, for the invaluable advice and research. Mrs. Nancy Mwikali, Master Samora Page Marcel, Mr. Joseph Ali Okech, Mrs. Monica Akinyi Ali, Mr. Jefferson Omari Ali, Mr. Ali David Dedan Oduor, Rev. Peter W. Odanga (Field Director Word Of Life Kenya), Mr. William Shabangu (Camp Director Word of Life Christian Academy), Mr. Charles Kiare (Principal Word of Life Christian Academy), Mr. Sylvester Ndolloh (Deputy Principal Word of life Christian Academy) and the entire staff of the Word of Life Christian Academy
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TABLE OF CONTENTS INTRODUCTION TO COMPUTER Basic terms……………………………………………........………………………………………….……….9 Parts of the computer system……………………………………………………......………………....…….11 Classification of the computers …………………………………………………………….......…...……….24 Storage unit………………………………………………………………………….......…………...………28 INTRODUCTION TO SOFTAWARES AND USAGES Introduction to software and hardware……………………………………….....…...………...……………35 Functions of the operating system……………………………………......…………………..……….……..39 Application software………………………………………………………………………......……………..46 Human ware / Orgware………………………………………………………………….......……….………46 COMPUTER VIRUS AND ANTI-VIRUS Computer virus/anti-virus …………………………………………………………......…….………………48 Symptoms of viruses in a computer system……………………………………….......…..…………..……..49 Effects of viruses in a computer…………………………………………………..…........……………..……49 Ways to curb the computer viruses………………………………………………….......……...……………49 Anti- virus…………………………………………………………………………........……………..………49 INTRODUCTION TO WINDOW 2010 Introduction………………………………………………………….…………......……….………………..50 Safety precautions of computers……………………………………..…………….......…………...………..51 Computer laboratory rules and requirements…………………………..…………....………..……….……52 Features of computer window…………………………………………………........……………..…….…...52 Creation of desktop features …………………………………………………........………………..………..52 Disk management and fragmentation ………………………………………......………………......………53 Control panel …………………………………………………………….…….............………...…...………..54 Starting and shutting down a computer system ………………………………….......………..……...……54 WORD PROCESSING AND DESKTOP PUBLISHING SOFTWARE Features of Microsoft word 2010………………………………………….……......…..........……..……….....55 The Word Processor’s Interface……………………………………………...……….........……….……..…..55 Computer Studies Guide Book
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Entering and Editing Text……………………………………………………...……..........…………………56 Formatting Text…………………………………………………………………..……..........………...….…..56 Drop cap…………………………………………………………………………………….......……………58 Special Features of Word Processing Software………………………………...………….........……..….…..58 Desktop Publishing Software……………………………………………………………….......……………61 Saving and retrieving documents……………………………………………...……….......……..………….61 MICROSOFT EXCEL 2010 Introduction ………………………………………………………………………........……..…………..…..62 Parts of Microsoft excel………………………………………………………….........…….…..……….……62 Spreadsheet Programs and Their Uses………………………………………….......………..…………..…..63 The Spreadsheet’s Interface…………………………………………………………….......……..……...…..63 Entering Data in a Worksheet- Types of Data…………………………………...……….........….…………..64 To apply borders, pattern or colors to the worksheet…………………………..………......……………….65 Entering formula in a worksheet………………………………………………...…….......…………...…….66 MICROSOFT ACCESS 2010 Introduction…………………………………………………………………………...…….......……………70 Keys………………………………………………………………………………………...........…………….72 Components of the database……………………………………………………………….....……………..72 Working with a Database - Querying a Database……………………………………….......…...…………..73 Creating new blank database………………………………………………….....…........……..…………….75 Components of access data………………………………………………..…...……….......………………..75 Printing a report……………………………………………………………………......…………………….75 MICROSOFT POWERPOINT 2010 Introduction……………………………………………………………..………………......………..………77 Features of application………………………………………………………………………..…….......….....78 Selecting text………………………………………………………………...………..……........……………78 Copying text within and between open an document……………………...………..….…………………78 Moving text within and between open an document……………….………..…………....………….……78 Deleting…………………………………………………………………………..…..….........………………79 8
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Insert tab……………………………………………………………………...…...…............….……….…….79 Design tab………………………………………………………………………………….……….......…….79 Transition tab…………………………………………………………………………………….......……….80 Animation tab…………………………………………………………………………..……….......………..80 Slide show tab…………………………………………………………………………………………......…80 Review tab…………………………………………………………………………….……………........…....81 View tab………………………………………………………………………….…………..………........…..81 MICROSOFT PUBLISHER 2010 Introduction……………………………………………………………………………….......……..……….82 Purposes of Desk Top Publisher (DTP)……………………………………………..…………..........………..82 General editing and formatting …………………………………………….…......……………….......…….82 Navigation and layout ………………………………………………………...…….........………...…..……..82 Formatting……………………………………………………………………….……........….………….…..82 Text boxes ………………………………………………………………………..........……..………….……83 INTERNET/NETWORKING, COMMUNICATION AND E-MAIL Introduction to internet and networking…………………..………………………….....………………..…98 Terms frequently used in networking …………………………………...……………......…………………98 Protocol ……………………………...................…………………………………………………............…….98 Registering an E-mail address …………….………………………………………………….......………….99 Reading mails …………………………………….………………………….………........………………….99 Sending a mail…………………………………………………………………….......………….…………..99 Attaching files ………………………………………………………….……………….......………………..99 Deleting mails ……………………………………………………………………......…...……...…………100 Forwarding messages ………………………………………………………………...…....………………100 Using draft mails………………………………………..……………………………….……........….……..100 Sign out ………………………………………………………………………………….…........……….…100 Searching contents on the internets…………………………….…………………………...……………..101 Using Google………………………………………………..……………………………..……….......……101 Examples of search engines………………………………...……….…………..……….......….……….…..101 Computer Studies Guide Book
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Types of web internet domains………………………………………………………….....……….………101 Examples of browsers ……………………………………………..………………………..…….........……102 The Uses of a Network ………………………………………………………………….………..…........….102 Networks are structured…………………………………………………………………..…….....………..103 Network Media and Hardware………………………………………………………….…………......……104 Network Software……………………………………………………………………….…………….....…104 Data Communications over Standard Telephone Lines………………………….………………..…....…104 Networks in the Home……………………………………………………………………...……….......…..107 Types of Communication Networks……………………………………………….….……………….........108 Local Area Network (LAN)…………………………………………………….....……………...........………108 Metropolitan Area Network (MAN)…………………………………………………………………........…109 Wide Area Network (WAN)……………………………………………………………...………..........…….111 Wireless Network…………………………………………………………………………….….......………112 Reference Models in Communication Networks………………………….……………………….....……114 Introduction to TCP/IP Reference Model………………………………………………………….......……114 The OSI Model - Features, Principles and Layers…………………………………………….........………...115 Functions of Different Layers……………………………………………………………………........….….117 Difference between OSI and TCP/IP Reference Model………………….……………...……..........………..131 KEY TERMS in Computer Networks………………………………………………………...............………...132 Computer Networks………………………………………………………………………………….......…134 Types of Network Topology………………………………………………..…………….……….........……139 Transmission Modes in Computer Networks…………………………………………….……........………146 Transmission Mediums in Computer Networks………………………………………….…….......………148 Network Devices………………………………………………………………………….………........……161 lesson10. Review………………………………………………………………………….........…………....169 Sample Test Paper One……………………………………………………………………….........………..172 Sample Test PaperTwo……………………………………………………………………...........………….173 Sample Test PaperThree……………………………………………………………...........………………...175 Sample Test PaperFour……………………………………………………………………………............…177 10
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Sample Test PaperFive………………………………………………………………………............………179 Sample Test PaperSix……………………………………………………………………………..............….181 Sample Test PaperSeven………………………………………………………………………............…….182 ICT Certificate level Examination……………………………………………………...............................……184
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INTRODUCTION TO COMPUTERS 1.1 - INTRODUCTION TO COMPUTERS By the end of this topic, students are supposed to be able to define the following in relation to the course:Definitions of the basic terms used in computers and related courses. A Computer is an electronic device or a machine that can be programmed to carry out a set of arithmetic or logical logarithms and process them to give a meaningfuldata which is referred to as information. Or a device or set of devices which works under the control of astored programmes which can be changed and automatically accepting and processing data to produce information. Information displayed on a screen is known as soft copy whereas the information produced on a piece of paper is known as a hard copy. A computer is: Automatic – it carries out instructions with minimum human intervention 12
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Re-programmable – it stores instruction (the programmes) these can be changed and another task performed. A data processor – it carries out operations on data (numbers or words) made up of combinations of digits to produce information. Data is a name given to a raw fact which must be in special form often in codes whilst being used by the computer. Information is meaningful data which is relevant, accurate and up to date and can be used to take actions or make decisions. Although a computer processes data, it doesn’t think for itself or understand it. If the data entered into the computer is wrong (garbage in) the result it produce will be wrong (garbage out) Command these are short instructions written in computer language that instructs a computer what to do and how to do it. Programmes are sequence of instructions written to execute or to perform specified tasks or functions Cursor is a text tool that blinks to highlight where to type the next character File a combination of related written information Click pressing the mouse button once Double clicking pressing the left mouse button twice Dragging and dropping moving an item from one place to another Boot the process of turning on the computer Back up to copy files usually from hard disk drive to a floppy disk drive PCan abbreviation for personal computer Print out a synonym for hard copy Run to start programmes Save to store data on a disk Spreadsheet a chat made up of rows and columns that help in keeping of track of records Update to replace old with new Upload to copy files from your computer to another computer or any other system Computer Studies Guide Book
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User friendly computeris supposed to be easy to learn and use Virus an unwanted malware programmes that will alter the operations of the computer system or damage your computer system NET abbreviation for the internet the term is used to denote the entire community of people with computer access
QUALITIES OF A COMPUTER Good computer qualities Automatic – performs task with minimum human intervention Storage device – stores junk information for future use if well managed Data processor – processing data to come up with desired information. Electronic device – performance by means of power /electricity
1.2 - PARTS OF THE COMPUTER SYSTEM A Computer is segmented into two major parts i.e Computer Hardware system parts Computer Software system parts Computer Hardware parts are the physical/tangible /touchable parts of the computer parts which are divided into three:Input /peripherals (mouse, keyboard, scanners microphones) Output (monitor, speakers, printers, smartcards) Storage devices (C.P.U central processing unit) The four major computer hard ware parts that forms computer set are the Mouse Keyboard Monitor Central processing unit 14
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The Mouse
An image of a class four pupil of Word of Life Christian Academy What is a Mouse? The mouse is a pointing device. You use it to move a graphical pointer on the screen. The mouse can be used to issue commands, draw, and perform other types of input tasks. It is an output device used to open or pull down in menus. It has three parts, namely: Left button -is used to open directly in windows or issue command Right button - is used to create shortcuts Scroll ball - is used to move the page up and down
Mouse Techniques Using the mouse involves five techniques Pointing; Move the mouse to move the on-screen pointer. Clicking; Press and release the left mouse buttononce. Double; clicking;Press and release the left mousebutton twice. Computer Studies Guide Book
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Dragging; hold down the left mouse button as youmove the pointer. Right-clicking; Press and release the right mouse button.
Variants of the Mouse Trackballs Track pads Integrated Pointed Devices Trackballs A trackball is like a mouse turned upside-down.Use your thumb to move the exposed ball and your fingers to press the buttons.
Track pads A track pad is a touch-sensitive pad that provides the same functionality as a mouse. To use a track pad, you glide your finger across its surface. Track pads provide a set of buttons that function like mouse buttons.
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Integrated Pointing Devices. An integrated pointing device is a small joystick built into the keyboard. To use an integrated pointing device, you move the joystick. These devices provide a set of buttons that function like mouse buttons
The Keyboard Is an input device used to feed the computer with information? It is classified as:The Standard Keyboard Layout Ergonomic Keyboards How a Keyboard Works
Standard Keyboard Layout A standard computer keyboard has about 100 keys. In Most keyboards use the QWERTY layout, named for the first six keys in the top row of letters. Standard Keyboard Layout A standard keyboard has 104 keys, it has the following keys Computer Studies Guide Book
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Typing keys– entering the characters in a computer (a,b,c or 1,2,3) Spacebar key– spacebar key is the longest key on the keyboard and it is used to create space in between the word or characters Backspace key- for deleting a character when the cursor is on the right side of the character. Shift key– for inserting keys that has two or more characters on it. Caps lock key– for changing characters in capital letters (upper case) and small letters (lower case). Tab key- for making a paragraph Page down & page up–for moving the page up and down. Enter keys- forOK option or starting a new line Shortcut keys- for commanding (CTRL +S) Service keys– for maintenance &repair (F1, F2, F8, F9, and F12) Scroll keys– for moving within the document (arrow keys) Most keyboards have keys arranged in five groups: Alphanumeric keys Numeric keypad Function keys Modifier keys Cursor-movement keys
The shortcut keys and their functions CTRL + N – New file CTRL + O – Open existing file CTRL + S - Save CTRL + Z – Undo 18
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CTRL + C – Copy CTRL + X – Cut CTRL + V – Pest CTRL + A – Select CTRL + H – Replace CTRL + F – Find CTRL +Y – Redo CTRL +B – Bold CTRL+ U – Underline CTRL + I – Italic ALT +F4 – Close ALT +F4 + U – Turn off/shutdown SHIFT +ARROWS - Select a sentence or a word F12 – save F5 - Refresh CTRL + G – Go to CTRL + P – Print Computer Studies Guide Book
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F1 – Help CTRL + L – align left CTRL + E – Align center CTRL + R – Align Right CTRL + J – Justify CTRL +> - Grow font CTRL + < - shrink font CTRL + SHIFT + F – Font face/appearance CTRL +SHIFT +P – font size Ergonomic Keyboards Long periods of keyboard use can cause injuries.
An ergonomically correct keyboard can help you avoid injuries. You also can avoid injuries by adopting correct keyboarding practices.
How a Keyboard Works When you press a keythe keyboard controller detects the keystroke. The controller places a scan code in the keyboard buffer, indicating which key was pressed. The keyboard sends the computer an interrupt request, telling the CPU to accept the keystroke. 20
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MONITOR /SCREEN/VISUAL DISPLAY UNIT (VDU) It is an output device used to display the information or programmes carried out on a computer It has three main parts namely:Desktop – it is the screen on the monitor Task bar - is the lower part of the monitor that shows the programmes carried out or minimized documents. It contains the start button or the start menu. Icons – are graphical symbols of a presentation. There are four main types of icons. My computer – shows the disk drives and hardware connected to the computer e.g CD Drive 3 ½ floppy disk drive [A], local disk /Hard disk drive [HDD] , SCANNERS & Flash disk My documents – contains letters, reports, files and other documents Recycle bin – contains deleted files and folders. Internet explorer – finds and displays information and website on the internet N/B: The information is transferred from the C.P.U to the monitor through a cable known as Visual Graphic arrays /adaptor [V.G.A] Computer Studies Guide Book
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Categories of Monitors CRT Monitors Flat-Panel Monitors Comparing Monitors Video Controllers Categories of Monitors Monitors are categorized by the technology they use: Cathode ray tube (CRT) monitors Flat-panel displays And by the way they display colors: Monochrome – One color on a black background Gray scale – Shades of gray on a white or off-white background Color – From 16 to 16 million unique colors
CRT Monitors In CRT monitors, electrons are fired at phosphor dots on the screen. The dots are grouped into pixels, which glow when struck by electrons. In color CRTs, each pixel contains a red, green, and blue dot. These glow at varying intensities to produce color images.
Flat-Panel Monitors Most flat-panel monitors use liquid crystal display (LCD) technology. 22
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Passive matrix LCD uses a transistor for each row and column of pixels. Active matrix LCD uses a transistor for each pixel on the screen. Thin-film transistor displays use multiple transistors for each pixel Flat-panel monitors take up less desk space
Comparing Monitors When comparing monitors, consider four features Size Resolution Refresh rate Dot pitch size A monitor’s size is the diagonal measurement of its face, in inches. For years, 15” monitors (13”viewing area) were standard. Today, 17” monitors (15” viewing area) are common. Larger monitors are available, but can be expensive
The diagonal size (often 15”) Resolution Resolution is the number of pixels on the screen, expressed as a matrix (such as 600x800). A 17” monitor offers resolutions from 640x480 up to 1280x1024. Computer Studies Guide Book
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The Video Graphics Array (VGA) standard is 640x480. Super VGA (SVGA) monitors provide resolutions of 800x600, 1024x768 or higher. Resolution (image sharpness) is important. (Especially for graphics, page layout, and CAD)
(Especially for graphics, page layout, and CAD) Refresh Rate Refresh rate is the number of times each second that the electron guns scan the screen's pixels. Refresh Rate Refresh rate is measured in Hertz (Hz), or cycles per second.
Refresh rate is the number of times each second that the electron guns scan the Look for a refresh rate of 72 Hz or higher. A slower rate may cause eyestrain. screen’s pixels. Refresh rate is measured in Hertz (Hz), or cycles per second. Look for a refresh rate of 72 Hz or higher. A slower rate may cause eyestrain. Fast scanning = Quick refresh (less flicker) Dot Pitch scanning = Quick refresh (less flicker) Dot pitchFast is the distance between the phosphor dots that make up a single pixel. Dot Pitch
In color monitors, three dots (red, green, and blue) comprise each pixel. Dot pitch is the distance between the phosphor dots that make up a single pixel.
Look for aIndot pitch three no dots greater than .28comprise millimeter color monitors, (red, green, and blue) each pixel. Look for a dot pitch no greater than .28 millimeter
Fine dot pitch = Crisp displays R+B R+B+G B+G 20 | P a g e Fine dot pitch = Crisp displays
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Video Controllers The video controller is an interface between the monitor and the CPU. The video controller determines many aspects of a monitor’s performance, such as resolution or the number of colors displayed. The video controller contains its own on-board processor and memory, called video RAM (VRAM). Video Control Board with Monitor Cable.
Graphic intensive applications such as games require plenty of VRAM CENTRAL PROCESSING UNIT [C.P.U] It is the nerve center of the computer system basically used for storage and processing of data to information. It contains three units namely: Arithmetic Logic Unit [A.L.U] – Is the unit that performs mathematical operations. It converts the information into simple units called [bytes] e.g Kilo bytes [KB] Megabytes [MB] Giga bytes [GB] Tera Bytes [TB] Conversion units are: 1000 bytes = 1KB 1000KB = 1MB 1000MB = 1GB 1000GB = 1TB Computer Studies Guide Book
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Control Unit (C.U) - it coordinates the other programs and helps in the arrangement in flow of information Memory Unit (M.U) - It’s the part of the computer system that holds data during the time of processing ability of a machine to recall. TYPES OF MEMORY RAM (Random Access Memory)- is a semi-permanent kind of memory that stores information on temporary basis. ROM (Read Only Memory) – is a permanent kind of memory that stores information permanently QUALITIES OF BOTH RAM & ROM NO. RAM
NO. ROM
1
1.
Semi-permanent
Permanent
2. Volatile 2. Non- volatile 3.
Can be changed hence 3.
the bigger the R.A.M
the faster the machine
Cannot be changed
4. Kept for boot process
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LESSON REVIEW 1.
Define the following terms
a. Computer b. File c. Command d. Program e. Virus 2.
Name any two types of backup storage and their characteristics
3.
Write down FOUR key computer laboratory rules & requirements
4.
List and give the function of each computer hardware parts
parts functions
5.
Explain the following terms as used on a mouse functions (3marks)
i) Click ii)
Right click
iii)
Double click
6.
Explain 5 factors considered when choosing a suitable computer
7.
Name 2 types of computer memories and give their respective qualities
8.
List some shortcut keys and their functions
9.
What are the good environmental conditions for the computers?
10.
Outline computer hardware parts and their functions
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1.3- CLASSIFICATION OF THE COMPUTERS Computers are classified into various categories in reference to the following elements: Size Data processing capacity Storage capacity Efficiency Cost The following are the categories of computers:Supercomputers Mainframe Computers Minicomputers Workstations Microcomputers or Personal Computers Supercomputers Supercomputers are the most powerful computers. They are used for problems requiring complex calculations. Because of their size and expense, supercomputers are relatively rare. Supercomputers are used by universities, government agencies, and large businesses.
CrayT90 Supercomputer
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Mainframe Computers Mainframe computers can support hundreds or thousands of users, handling massive amounts of input, output, and storage. Mainframe computers are used in large organizations where many users need access to shared data and programs. Mainframes are also used as e-commerce servers, handling transactions over the Internet.
Minicomputers Minicomputers are smaller than mainframes but larger than microcomputers. Minicomputers usually have multiple terminals. Minicomputers may be used as network servers and Internet servers.
Workstations Workstations are powerful single-user computers. Workstations are used for tasks that require a great deal of number-crunching power, such as product design and computer animation. Workstations are often used as network and Internet servers. Workstation Microcomputers or Personal Computers Microcomputers are more commonly known as personal computers. The term “PC� is applied to IBMPCs or compatible computers. Full-size desktop computers are the most common Computer Studies Guide Book
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type of PC. Notebook (laptop) computers are used by people who need the power of a desktop system, but also portability. (Potable – can easily be carried around) Handheld PCs (such as PDAs) lack the power of a desktop or notebook PC, but offer features for users who need limited functions and small size. Handheld PC
Importance of computer system •
Used for communication – E-mail social media platforms i.eFacebook twitter, snap chatsSkype’s, instagram, viber.
•
Used for learning it is used as a learning tool
•
Used for researching via search engines like Google, yahoo, DuckDuckGo.
•
Used for entertainment – through YouTube playing games watching online movies and music
•
Used by the military for spying purposes
•
Used in business to record financial detailson profit and loss accounts
Advantages/merits of using computers •
Speedy- performs task very fast and saves time compared to manual work.
•
Efficient – produces very neat and admirable work.
•
Confidential – keeps the information for further reference in the future
•
Accuracy – produces exact information needed by the user
•
Versatility – repeats the same work over and over without exhaustion.
•
Security and privacy – though the setting of passwords one is able to protect the machine and the integrity of the work.
•
Creates employment – to the experts.
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Disadvantages/demerits of computers •
Causes eye problem and fatigue
•
Loss of information due to failure of machines or virus. (Virus – is a malware/ unwanted programmes that interferes with the computers system functionabilities).
•
Loss of job opportunities to the non-experts
•
Needs experts to operate
•
Maintenance cost is high
Factors considered when choosing a suitable computer •
Cost – consider the amount t of money you have
•
Work to be done – consider the speed of the computer depending on type of work to be done
•
Durability – it should last long without getting damaged
•
Compatibility – it should be able to support peripherals needed in the office
•
Operating system – consider the suitable operating system that will support
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LESSON REVIEW 1.
List the five most common types of computer systems.
2.
Identify two unique features of supercomputers.
3.
Enumerate FIVE importance of computers in our society today
4.
Describe a typical use for mainframe computers
5.
Differentiate workstations from personal computers.
6.
Identify four types of personal computers
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1.4 - STORAGE UNIT Types of Storage Devices •
Categorizing Storage Devices
•
Magnetic Storage Devices
•
Optical Storage Devices
Categorizing Storage Devices Storage devices hold data, even when the computer is turned off. The physical material that actually holds data is calledstorage medium. The surface of a floppy disk is storage medium. The hardware that writes data to or reads data from a storage medium is called a storage device. A floppy disk drive is a storage device. The two primary storage technologies are magnetic and optical. The primary types of magnetic storage are •
Diskettes (floppy disks)
•
Hard disks
•
High-capacity floppy disks
•
Disk cartridges
•
Magnetic tap
The primary types of optical storage are: •
Compact Disk Read-Only Memory (CD-ROM)
•
Digital Video Disk Read-Only Memory (DVD-ROM)
•
CD-Recordable (CD-R)
•
CD-Rewritable (CD-RW)
•
Photo CD
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Magnetic Storage Devices •
Formatting
•
Disk Areas
•
Diskettes
•
Hard Disks
•
Disk Capacities
•
Other Magnetic Storage Devices
How Magnetic Storage Works A magnetic disk’s medium contains iron particles, which can be polarized—given a magnetic charge—in one of two directions. Each particle’s direction represents a 1 (on) or 0 (off ), representing each bit of data that the CPU can recognize. A disk drive uses read/write heads containing electromagnets to create magnetic charges on the medium. Formatting Before a magnetic disk can be used, it must be formatted—a process that maps the disk’s surface and determines how data will be stored. During formatting, the drive creates circular tracks around the disk’s surface, then divides each track into sectors. The Operating System organizes sectors into groups, called clusters, then tracks each file’s location according to the clusters it occupies. Formatted Disk
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Disk Areas
When a disk is formatted, the Operating System creates fourareas on its surface: Boot sector – stores the master boot record, a small program that runs when you first start (boot) the computer File allocation table (FAT) – a log that records each file’s location and each sector’s status Root folder – enables the user to store data on the disk in a logical way Data area – the portion of the disk that actually holds data Diskettes Diskette drives, also known as floppy disk drives, read and write to diskettes (called floppy disks or floppies). Diskettes are used to transfer files between computers, as a means for distributing software, and as a backup medium. Diskettes come in two sizes: 5.25-inch and 3.5-inch.
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Magnetic Storage Devices - Hard Disks Hard disks use multiple platters, stacked on a spindle. Each platter has two read/ write heads, one for each side. Hard disks use higher-quality media and a faster rotational speed than diskettes. Removable hard disks combine high capacity with the convenience of diskettes.
Disk Capacities Diskettes are available in different capacities, but the most common store 1.44 MB. Hard disks store large amounts of data. New PCs feature hard disks with capacities of 10 GB and higher. Other Magnetic Storage Devices High-capacity floppy disks offer capacities up to 250MB and the portability of standard floppy disks. Disk cartridges are like small removable hard disks, and can store up to 2 GB. Magnetic tape systems offer very slow data access, but provide large capacities and low cost. Due to long access times, tapedrives are used mainly for backups
Optical Storage Devices Are some of the commonly used ways or means we use today to keep our data and information e.g CD-ROM CD-ROM Speeds and Uses DVD-ROM 36
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Other Optical Storage Devices How Optical Storage Works An optical disk is high-capacity storage medium. An optical drive uses reflected light to read data. To store data, the disk’s metal surface is covered with tiny dents (pits) and flat spots (lands), which cause light to be reflected differently. When an optical drive shines light into a pit, the light cannot be reflected back. This represents a bit value of 0 (off ). A land reflects light back to its source, representing a bit value of 1 (on).
CD-ROM In PCs, the most commonly used optical storage technology is calledCompact Disk Read-Only Memory (CD-ROM). A standard CD-ROM disk can store up to 650 MB of data, or about 70 minutes of audio. Once data is written to a standard CD-ROM disk, the data cannot be altered or overwritten
CD-ROM Speeds and Uses Early CD-ROM drives were called single speed, and read data at a rate of 150 KBps. (Hard disks transfer data at rates of 5 – 15 MBps). CD-ROM drives now can transfer data at speeds of up to 7800 KBps. Data transfer speeds are getting faster. CD-ROM is typically used to store software programs. CDs can store audio and video data, as well as text and program instructions. Computer Studies Guide Book
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DVD-ROM A variation of CD-ROM is called Digital Video Disk Read-Only Memory (DVD-ROM), and is being used in place of CD-ROM in many newer PCs. Standard DVD disks store up to 9.4 GB of data—enough to store an entire movie. Dual-layer DVD disks can store up to 17 GB.
DVD disks can store so much data because both sides of the disk are used, along with sophisticated data compression technologies. Other Optical Storage Devices A CD-Recordable (CD-R) drive lets you record your own CDs, but data cannot be overwritten once it is recorded to the disk. A CD-Rewritable (CD-RW) drive lets you record a CD, and then write new data over the already recorded data. PhotoCD technology is used to store digital photographs.
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LESSON REVIEW 1.
List four types of magnetic and four types of optical storage devices.
2.
Identify three common uses for floppy disks.
3.
Name the four areas created on a magnetic disk during formatting.
4.
Explain how data is stored on the surface of magnetic and optical disks.
5.
List three variations on optical disk technology
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INTRODUCTION TO SOFTWARES AND USAGE Software is a name given to programmes, routines and procedures used to enable the computer hardware function (or set of instructions that guides the computer system to execute specific function). [A computer without Operating software is like an aero-plane without a pilot] Two main types/categories of soft wares are: Operating system software Application software System software It is the main programmes that runs a computer/set of instructions or programmes developed and installed in a computer system for the purpose of developing other programmes to ensuresfunctionability of the system It is further classified into:Operating system Communication programmes 40
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Language translators Utility programmes Operating system (O.S) They are the programmes developed to coordinate with the system to ensure smooth running of the other application. It is the graphical user interface [G.U.I] consisting of windows, and MS-Dos (Disk operating system. Examples of the operating system (O.S) UNIX DOS The Macintosh Operating System Windows 3.x OS/2 Warp Windows NT Windows 95 and 98 Linux Windows 2000 UNIX • UNIX is the oldest operating system used on PCs. • UNIX was the first multi-user, multiprocessor, multitasking operating system available for use on PCs. • Most versions of UNIX use a command-line interface, but some versions offer a GUI
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DOS DOS dominated the operating system market during the 1980s. DOS is a single-user OS that supports only 640 KB of memory. DOS features a command-line interface, and does not support multitasking or multiprocessing.(multitasking or multiprocessing is a process whereby a computer does many jobs at the same ) Because DOS provides no interface restrictions, DOS applications can look and function differently. The Macintosh Operating System The Macintosh OS supports the graphical nature of the Macintosh computer. The Mac OS brought the first truly graphical user interface to consumers. The Mac OS also brought interface conformity (identical) to the desktop. All applications running under the Mac OS, therefore, provided the same “look and feel� to the user
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Windows 3.x Windows 3.0, 3.1, and 3.11 are called the Windows 3.x family. Windows 3.x brought a GUI and multitasking capabilities to PCs running DOS. Windows 3.x is an operating environment because it ran on top of DOS, which was the actual OS.
OS/2 Warp OS/2 Warp was the first true GUI-based operating system for Intel-based PCs. OS/2 is a multitasking OS that provides support for networking and multiple users. It was the first PC OS to feature built-in speech recognition capabilities.
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Windows NT Microsoft’s Windows NT was meant as a replacement for DOS, but was too resource intensive to work on most PCs at the time of its release. Microsoft issued two versions of Windows NT—Windows NT Workstation and Windows NT Server. NT is a very powerful and robust OS, resistant to system crashes. Windows 95 and 98 Windows 95 was Microsoft’s first true GUI-based, 32-bit operating system for Intel PCs. Windows 95 supports multitasking and can run older DOS and Windows 3.x programs. Windows 98’s features include advanced Internet capabilities, an improved user interface, and enhanced file system performance, among others. 44
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Linux Linux is a recently developed version of UNIX, which is available for free or at a very low cost from various sources. Linux is a very powerful 32-bit OS that supports multitasking, multiple users, networking, and virtually any application. Linux can run on nearly any type of computer. Because of its power and openness, Linux is attracting many users, including students, teachers, Internet service providers, and others. Windows 2000 Windows 2000 features the same interface and features of Windows 98, with the file system, networking, power, and stability of Windows NT. Several versions of Windows 2000 are available, each targeting a specific user or computing environment, from home PCs to large enterprise networks Computer Studies Guide Book
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1.2
FUNCTIONS OF THE OPERATING SYETEM
The following are the functions of the operating system •
The User Interface
•
Running Programs
•
Managing Files
•
Managing Hardware
•
Utility Software
The User Interface User interface is a platform on the computer system where a user is allowed or enabled to carry his/ her tasks Graphical User Interfaces (GUIs) 46
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GUI Tools Applications and the Interface Menus Dialog Boxes Command-Line Interfaces The User Interface - Graphical User Interfaces (GUIs) Most modern operating systems, like Windows and the Macintosh OS, provide a graphical user interface (GUI). A GUI lets you control the system by using a mouse to click graphical objects on screen. A GUI is based on the desktop metaphor. Graphical objects appear on a background (the desktop), representing resources you can use.
The User Interface - GUI Tools Icons are pictures that represent computer resources, such as printers, documents, and programs. You double-click an icon to choose (activate) it, for instance, to launch a program. Computer Studies Guide Book
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The Windows operating system offers two unique tools, called the taskbar and Start button. These help you run and manage programs.
The User Interface – Applications and the Interface Applications designed to run under one operating system use similar interface elements. Under an OS such as Windows, you see a familiar interface no matter what programs you use. In a GUI, each program opens and runs in a separate window—a frame that presents the program and its documents. In a GUI, you can run multiple programs at once, each in a separate window. The application in use is said to be the active window. The User Interface - Menus GUI-based programs let you issue commands by choosing them from menus. A menu groups related commands. For example, the File menu’s commands let you open, save, and print document files. Menus let you avoid memorizing and typing command names. In programs designed for the same GUI, menus and commands are similar from one program to another
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The User Interface - Dialog Boxes A dialog box is a special window that appears when a program or the OS needs more information before completing a task. Dialog boxes are so named because they conduct a “dialog� with the user, asking the user to provide more information or make choices
The User Interface - Command-Line Interfaces Some older operating systems, such as DOS and UNIX, use command-line interfaces. Computer Studies Guide Book
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In a command-line interface, you type commands at a prompt. Under command-line interfaces, individual applications do not need to look or function the same way, so different programs can look very different
Running Programs Basic Services Sharing Information Multitasking Running Programs - Basic Services The operating system manages all the other programs that run on the PC. The operating system provides services to programs and the user, including file management, memory management, and printing To provide services to programs, the OS makes system calls—requesting other hardware and software resources to perform tasks. Running Programs - Sharing Information Some operating systems, such as Windows, enable programs to share information. You can create data in one program and use it again in other programs without re-creating it. Windows provides the Clipboard, a special area that stores data cut or copied from one document, so you can re-use it elsewhere. Running Programs - Multitasking Multitasking is the capability of running multiple processes simultaneously. A multitasking OS lets you run multiple programs at the same time. Through multitasking, you can do several chores at one time, such as printing a document while downloading a file from the Internet. 50
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There are two types of multitasking: cooperative and preemptive.
Managing Files The operating system keeps track of all the files on each disk. Users can make file management easier by creating a hierarchical file system that includes folders and subfolders arranged in a logical order
Managing Hardware The OS uses interrupt requests (IRQs) to maintain organized communication with the CPU and other pieces of hardware. Each hardware device is controlled by a piece of software, called a driver, which allows the OS to activate and use the device. Computer Studies Guide Book
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The operating system provides the software necessary to link computers and form a network.
2.3 Utility Software A utility is a program that performs a task that is not typically handled by the operating system. Some utilities enhance the operating system’s functionality. Some of the major categories of utilities include: File defragmentation Data compression Backup Antivirus Screen savers Communication programmes They provide proper communication set up on the computer system. They make up the communication parts and audios and smart cards e.g Com 1 – for drive connection 52
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Com 2 - for internet connection Language translators They translate the languages used by the computers e.g speech, dictionary Examples of the computer languages [java, Pascal visual basics, python, C++] Service utility programmes They are the programmes connected together with the hardware to execute the following functions: Back – Up: - transferring files from one disk to another for safer recovery when it gets damaged Disk clean-up: - removal of old files local disk for free space for another files Disk defragmentation: - compressing the local disk to create space for other file Scan disk: - checking of errors in the disk Tools used in storage of O.S Local disk drive (hard disk drive) [HDD] CD-ROM (Compact disk drive) or read only memory (RAM) DVD ROM (dynamic visual disk) Floppy disk Flash disk] SD card 2.4
APPLICATION SOFTWARE
Are programmes that are designed to allow a user to perform specific tasks, application software is very helpful in writing letters, sorting files, managing finances, drawing pictures analyzing numbers and even playing games examples of the application softwareare? Application packages User application programmes Application packages Computer Studies Guide Book
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These are set of instructions designed or developed to solve a particular problem in one or more organizations with little or no alteration. e.g:Word processing Microsoft word (we can use Ms- Word, word perfect, word star) Spreadsheet Microsoft excel (we can use Ms- Excel, lutus1, 2, 3&super calculator) DatabaseMicrosoft access (we can it for sorting, analyzing, filing report on data e.g Ms- Access or Database Oracle) Desktop Publication program DPP Microsoft publisher(used for creating business cards, weeding cards calendars letterheads and brochures e.gMs- Publisher, Coral Draw, Page maker Presentation Microsoft power point (used for advertising or presenting on slides show e.g Ms- Powerpoint) Internet E- Mail and internet 2.5 - Human ware / Orgware These are the programmes designed by users to suite their intended purposes within the framework scope. They are developed by experts’ programmers as per the specifications of the system analysis. e.g:Operator: a person who uses a computer for daily operations e.g printing internet services and typing etc Programmer: a person who creates and design programmes used by the operators in a computer Technician: is a person who corrects and repairs or maintains the computer errors of failures or malfunctions. Web designers: a person who creates and designs websites used by browsers on the internet Network technician: a person who corrects errors and default settings in the internet with the correct and desirable configuration. User application programmes Editing programmes - Photoshop, adobe illustrator, PhotoScape Viruses - Trojan horse, ghost 54
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Antiviruses -karspakay, Norton, bit defender, Browsers - maxilla Firefox, torch, explorer, Multimedia- vlc, player window player, shampoo burning studio.
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LESSON REVIEW 1.
List all the major PC operating systems.
2.
Identify some of the limitations of DOS.
3.
List two features that made the Macintosh OS popular.
4.
Differentiate between the terms operating environment and
operating system.
5.
List the various versions of Window
6.
Name four components found in most graphical user interfaces.
7.
Describe the operating system’s role in running software programs.
8.
Explain how the OS enables users to manage files.
9.
List three hardware management tasks performed by an OS.
10.
Name five types of utility software
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COMPUTER VIRUS AND ANTI-VIRUS
Computer Virus – is malware/malicious programmes which are designed intentionally by software developers or engineers to alter or to destroy the function ability of your computer system or files and folders. Types of computer virus Virus that affect the boot sector of a computer Virus that affects the executable files Virus that affect both the boot sector and files Virus that chew the command icon Examples of viruses Boot sector viruses Self-encrypting viruses Cluster viruses Self-changing viruses File-infecting viruses Stealth viruses
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Worms Macro viruses Bombs Joke programs Trojan Horses Bimodal viruses Polymorphic virus bipartite viruses Self-garbling virus multipartite viruses E-mail viruses Macro viruses Sources of viruses Diskettes Technicians Internet sites Free games Flash disk 3.2 - Symptoms of viruses in a computer system Programmes take too long to load Abnormal boot process Often restart of the computer system Appearance of mysterious messages on screen Hanging of the computer system Glinching of the screen Deletion of files and loss folders 3.3 - Effects of viruses in a computer System crush Hanging of machine Stop machine from running
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Failure to boot 3.4 -Ways to curb the computer viruses Use licensed and mastered programmes Install anti-virus Scan the computer frequently Check the disk before opening in the computer Use clean removable disks Regulate the public domain from using virus prone internet sites 3.5 - Anti- virus Are programmes installed to detect, cure and delete viruses from your computer system and protect them from any malware programmes Example of anti-viruses Norton Avast Mac fee Spy ware Karspasky Eset Smadal Importance of having anti – virus in a computer system Safeguard the computer system Secures the computer hardware parts from malwares Secures other computer application programmes from failures of functions Provides security to the system software from crushing
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LESSON REVIEW 1.
Define the following terms
- Virus -
Anti- virus
2.
Give ways one can tell a computer is affected by virus
3.
What are some of the ways to prevent computer virus
4.
Outline causes of computer virus
5.
Highlight few examples of both viruses and anti- virus
6.
Give types of computer viruses
7.
Assume you are ICT personnel, a client reports the mysterious loss of files and folders in his/her computer. Identify the problem and give FIVE ways of solving the identified problem
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INTRODUCTION TO WINDOWS 2016 Introduction to operating system The desktop (display properties) My computer features Starting application window Moving and sizing window File and folders Renaming files and folders Moving files from one folder to another Deleting files and folders Restoring files from the recycle bin
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Standard application package Using notepad, word pad and calculators Finding files and folders The control panel Printing a file Making short cut for programs and folders
4.2 - Introduction Programmes are set of instructions that command a computer on how to executetask and give the outcome (information) software makes the hardware operational.
4.3 - Safety precautions of computers The right type of cables should be put into use and should be properly and correctly fixed to avoid short-circuit Ensure that you have a stable supply of power for constant power distribution to machine to avoid power fluctuation Ensure that the computer is well ventilated to avoid heating Ensure there is enough lighting system to avoid any eye strain that could advance with time and bring undue side effects Make sure you are comfortable to avoid any fatigue or back strain by using standard furniture Always cover computers with dust proof to hold any little dust or moisture towards the computer system
4.4 - Computer laboratory rules and requirement Do not press unknown buttons. Do not access internet without the teacher’s permission 62
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Do not unplug cables. Do not carry liquids and snacks to the laboratory. Do not play and watch movies and music videos. Do not play games without the teacher’s permission
4.5- Creation of desktop features Desktop – is the surface interface on the computer screen.It contains features referred to as icons, FOLDERS The unit of file storage, they can be created, renamed, deleted, copied and moved How to create a folder in my computer Open in the create in location (where you want to create the folder) Right click >>new>> folder Type the name of the folder and accept by pressing the enter key Creating a sub-folder Open the already created folder Right click in the folder >>new >>folder Name the new folder and enter Renaming of the folders Go to the folder Right click on it >>go to rename>>click on rename Give the name to the folder >>accept by pressing on the enter key To move a folder and file Right click on the item you want to move Choose cut Computer Studies Guide Book
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Open the destination Right click on an empty space >> chose the option paste Deleting folders/files You can remove unwanted files using the delete command Right click on the item >>chose delete option Note that the item go to the recycle bin Restoring deleted items Open the recycle bin Right click on the item you want to retrieve Click restores
4.6 - DISK MANAGEMENT Formatting Formatting erases any prior data or information that is stored in the disk How to format a disk Insert the disk in the USB port Open on my computer icon Right click on the removable disk Chose format >>start Naming a disk Insert the disk into the USB port Open my computer Right click on the removable disk Choose rename
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Type the desired name Press enter key to accept the changes
4.7 - CONTROL PANEL It enables one to make changes on the computer settings The mouse settings to change the buttons Display properties System properties Date and time Options of other connected peripherals i.eprinters, scanners
4.8- SHUTTING DOWN It is important to shut down the computer system after you are done the work with it Go to the start menu>>click Go to the shutdown option Click to shutdown
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Word Processing and Desktop Publishing Software 5.1- Word Processing and Desktop Publishing Software Word Processing Programs and Their Uses The Word Processor’s Interface Entering and Editing Text Formatting Text Special Features of Word Processing Software Desktop Publishing Software Converting Documents into World Wide Web Pages Word Processing Programs and Their Uses Word processors provide tools for creating, editing, and formatting text-based documents. You can use a word processor to create virtually any type of document, from a 66
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simple letter to a complete book. A word processor’s formatting tools let you create professional-quality documents easily. 5.2 - The Word Processor’s Interface Most Windows-based word processors offer a similar set of tools, which you use to navigate, edit, and format documents: Document area- this is the working area on the desktop in the word processing program Menu bar – provides you with the Ms-Word menu option Toolbars – provides quick access to Ms- Word most frequently used command i.e BI U Rulers – gives the measurement on the size of the document on a work apace/area Scroll Bars – located along the right and bottom side of the screen Status Bar – gives the status of the document being worked on Title bar – located on top of the word processing document Maximize – minimize and restore button
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5.3 - Entering and Editing Text –Adding Text to a Document You create a document by entering text in the document window. A blinking insertion point shows you where characters will be placed as you type. When you type to the end of a line, the program automatically moves the insertion point to the next line. This feature is called word wrap. Entering and Editing Text – Editing a Document Making changes to an existing document is called editing. Tools are provided for erasing and retyping text quickly The Backspace and Delete keys let you erase one or more characters. Overtype mode lets you type over previously entered text. AutoCorrect can automatically correct spelling and typing errors. Undo and Redo let you reverse the effect of a previous action
Entering and Editing Text - Selecting Text Word processors let you work with entire blocks of text. You can format, move, copy, or delete a block. To work with a block of text, you must first select it, using one of many selection options. Selected text is highlighted on the screen. When you are finished working with selected text, you can deselect it.
5.4 - Formatting Text Formatting a document means controlling its appearance. Formats fall into three broad categories: Character formats 68
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Formatting Text - Character Formats Paragraph formats
You can use multiple fonts in a document, such as Arial or Times.
Document formats
Word processors let you apply different sizes – measured in points – to the text in a document.
Formatting Text - Character Formats
You You can can useapply multiple fonts in atext, document, Arial or Times. type styles to your such as bold,such italic,asand underline, among others Word processors let you apply different sizes – measured in points – to the text in a
document. You can apply type styles to your text, such as bold, italic, and underline, among others
Formatting Text - Paragraph Formats In a word processor, you create a new paragraph whenever you press Enter. You can format each paragraph in a different way.
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You can set the amount of blank space between lines in a paragraph and between paragraphs in a document. To align a paragraph, you set the space between its edges and the page’s margins. You can also indent a paragraph’s first line. Borders and shading create special effects for paragraphs. Formatting Text - Document Formats Margins are the amount of blank space between the edges of the text and the Computer Studies Guide Book
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edges of the page. Word processors let you print documents on different size paper, in portrait or landscape orientation. Headers and footers are commonly used in long documents, to provide continuing information along the top or bottom of the pages.
5.5- DROP CAP A drop cap can be used to set focus at the beginning of a paragraph in a document i.e newspaper. To apply a drop cap Select the paragraph you want to apply the drop cap On the menu bar chose insert>>>to the text panel>>>chose drop cap Write your full names and your admission number in the spaces provided above. Answer all the questions in the spaces provided Diagrams to be drawn in pencils where necessary. Among the following definition of a computer which one is the right choice? (4marks)It is a machine which saves work It is an electronic machine which takes in data, processes to give an information Computer is an electronic set of devices which works under control of a stored programs which automatically accepts and processes data to produce information and stores it for reference It is a device of an office work. Give the name of the following computer hardware parts 5.6 - Special Features of Word Processing Software Today’s word processors provide a variety of specialized tools, including Language tools Tables Mail Merge Support for graphics and sounds Templates Special Features of Word Processing Software - Language Tools Language tools can help you improve the quality of your documents by catching language errors. Language tools include: 70
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Spell checkers, which can help you find and correct misspelled words.
Grammar checkers, which help your document, conform to accepted grammatical rules. Thesauri, which can help you, make the best word choices. Special Features of Word ProcessingSoftware - Tables Tables let you set up rows and columns of information. You can format a table in dozens of ways, add headings, and more.
Special Features of Word ProcessingSoftware - Mail Merge Mail merge is the process of combining a form letter with contents of an address database. Using mail merge, you can create a standard letter and automatically make a copy for each person in your database.
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Special Features of Word ProcessingSoftware - Support for Graphics and Sounds Word processors allow you to add images to your documents. Once you add a graphic to a document, you can select it, move it, resize it, and more. You also can add sound files to a document. A sound file appears as an icon; click the icon on screen and the file plays. Special Features of Word ProcessingSoftware - Templates A template is a predesigned document. A template simplifies document design. You simply open the document and type your text.
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5.7 Desktop Publishing Software Desktop publishing (DTP) software is specialized for designing and laying out long documents, such as magazines or books. DTP software provides special tools for fine-tuning the appearance of text and graphics in a document. DTP software can produce documents that are ready to be sent to a professional printer. Converting Documents into World Wide Web Pages Word processors can create documents in HTML format, ready to be published on the World Wide Web. To create an HTML document, create a normal document then save it in HTML format. The word processor inserts all the required HTML tags. Many word processors include HTML templates, which let you easily create finished Web pages
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LESSON REVIEW •
Identify three basic word processing tools that simplify document editing.
•
Explain what is meant by “selecting” parts of a document.
•
Identify five special features commonly found in modern word processors.
•
How can one set a margin on a document?
•
Give ways how to apply a drop cap
•
Distinguish desktop publishing software from word processing software.
•
Describe how word processors can convert normal documents into World Wide Web pages.
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MICROSOFT EXCEL 2016 [Spreadsheet Software]
6.1 MICROSOFT EXCEL 2016 [Spreadsheet Software] This lesson includes the following sections Spreadsheet Programs and Their Uses The Spreadsheet’s Interface Entering Data in a Worksheet Editing and Formatting a Worksheet Adding Charts Analyzing Data in a Spreadsheet Microsoft Excel is powerful application software designed to process data in columns and rows. It is a useful tool for data analysis and graphical data Computer Studies Guide Book
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presentation.
6.2 Parts of Microsoft excel Workbook Worksheet Charts Workbook – is a file which you work and stores your data because each workbook can contain many sheets which you can organize various kinds of related information in a single file. Worksheet – is called spreadsheet it is the primary document used in Microsoft excel to store and manipulate data a worksheet consist of cells organized into columns and rows and it is always a part of a workbook. The intersection of each column and rows is called a cell which is the basic unit where we store data. Charts – is a graphical representation of worksheet data. 6.2 - Spreadsheet Programs and Their Uses Spreadsheets provide tools for working with numerical data. You can use a spreadsheet program to create budgets, balance sheets, and other types of number-based documents.
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You can display your information in a traditional row-and-column format, or in a chart. 6.3 - The Spreadsheet’s Interface •
In a spreadsheet program, you work in a document called a worksheet. You can collect multiple worksheets into a file called a workbook.
•
Most Windows-based word spreadsheets offer a similar set of tools, including a formula bar, where you can enter and edit data.
•
Data is displayed in cells. A cell is the intersection of a row and column.
•
Each cell has a cell address – the combination of the cell’s column letter and row number.
6.4 - Entering Data in a Worksheet- Types of Data You enter four types of data in a worksheet’s cells: Labels - text or numbers not used in calculations. Values - numbers that can be used in calculations. Dates - a necessary part of most worksheets. Formulas - commands to perform calculations based on numbers or formulas. Computer Studies Guide Book
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Entering Data in a Worksheet- Formulas and Functions If a formula uses a value in another cell, the formula contains a cell reference, or the address of the referred cell. Formulas can refer to entire ranges (or blocks) of continuous cells as well as individual cells. A function is a predefined formula, which the spreadsheet provides to perform a specific type of calculation. You provide basis that tell the function what data to use. Editing and Formatting a Worksheet Spreadsheets provide many of the same editing and formatting tools found in word processors. You can change, copy, move, and delete the data in any cell. Relative and Absolute Cell References If a formula uses a relative cell reference, it automatically dates if (copied or moved), to a different place. An absolute cell reference always refers to the same cell even if the formula is moved to a different place. Adding Charts A chart is a graphical representation of the data in a worksheet. Spreadsheets provide tools that make it easy to create a chart from worksheet data. 78
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You can use many different types of charts, and apply many effects to a chart, to present your data in the most appropriate way
Analyzing Data in a Spreadsheet Three commonly used data-analysis tools are What-if analysis, which lets you test scenarios to see how each affects the result. Goal seeking, which finds values that make the result meet your specifications. Sorting, this lets you arrange the worksheet’s data in various ways.
6.5 - TO APPLY BORDERS, PATTERN OR COLORS TO THE WORKSHEET Highlight cell range you want to add border/pattern/shading. Click format menu click /select cells Format cells screen will appear, click what you want e.g click border >>here select style of border >>border color >>location of border>> When all that is done click OK to return to normal worksheet then observe changes from the screen.
6.6 - ALIGNING WORKSHEET DATA You can align the content of cells left, right center or center aligns across columns you can also rotate or to change text orientation within cells through the following steps:Select the range you want to change alignment by highlighting it. Computer Studies Guide Book
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Click format menu >>click cells Format cell will appear>>click alignment Below orientation >>click orientation you want according to your needs by clicking it once. Make other changes from text alignment >>click down arrow below horizontal/vertical then select alignment you want. When all is done click OK to return to normal worksheet then observe changes
USING REFERENCE OPERATORS Operator
Description
Colon (:)
Defines a range, encompassing the entire cell between and includes the two reference cell.
Comma(,)
Defines a Union, combining multiple reference into one
Single space
Define an intersection, which calculates one result for cell included in both references.
Example =SUM (B3:B7) would sum the range of cells between B3 and B7 = (B3, B4, B5, B6, B5, B6, B7) would sum all cells between and includes B3 and B7
6.7 - ENTERING FORMULA IN A WORKSHEET ADDING Highlight the whole work including one row you want your total to appear in. Click [Auto sum] icon from standard toolbar once, you will get the total or Put the cell pointer where you want the total to appear. Click [Auto sum] icon from the standard toolbar then press enter you will get total. Put the cell pointer where you want the total to appear>> start with equal sign the type a formula accordingly. 80
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Example [=B1+B2+B3+B4+B5] then press enter once or instead of using a formula you apply this [=sum (B1.B5) Press enter key once you will get the total
AVERAGE You can use average to find average>>place cell pointer where you want average to appear. Start with equal sign i.e>> =type total over the number you get the total Example =B5/4press enter key once or Instead of using the total you can apply the formula type =average (B1.B5) presses enter
N/B if you use average and the formula doesn’t appear use =avg (B1.B5) press enter
PERCENTAGE Put cell pointer where you want the result to appear then type the formula Example =b5*15% press enter or Type = b5*15/100 press enter key
MINIMUM AND MAXIMUM Put the cell pointer where you want the result to appear Type formula =max (b1.b5) to find maximum or type= (b1.b5) to fin minimum then press enter Computer Studies Guide Book
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DISTRIBUTION OF SHOES IN SOUTH COAST (KWALE) N/Bdon’t include the totals wen finding maximum or minimum 250 200 150 CHILDREN 100range you want to include in your chart by highlighting it Select the 50 Click chart0 wizard from standard toolbar or pull down insert menuADULTS then click chart
Creating charts
Chart wizard screen will appear with the following features; Standard Type and custom Type Select/click which types of chart you wants either from standard /custom type by clicking it once. Example clicks standard type then click next button
EXAMPLE OF PIE CHART
Chart screen will select want to data. E.g or row to your click next Charts screen with the features Gridlines Labels Tables
CHILDREN AREA
BOYS
GIRLS
MEN
WOMEN
Diani
100
90
110
100
Ukunda
50
45
87
78
Mabungo
75
150
67
79
Lunga-Lunga
130
200
92
101
Harmony
105
99
120
90
Tukutane
48
48
80
120
67
77
Make all Ramisi 65 87 changes cording to when all finish button to return to your normal worksheet EXAMPLE OF COLUMN CHART
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source data appear, here how do you arrange your clicks column according needs then button. options will appear following Tittle, Axes, legend, Data and Data
necessary you want acyour charts done click
DISTRIBUTION OF SHOES IN SOUTH COAST (KWALE) DISTRIBUTION OF SHOES IN SOUTH COAST (KWALE)
250 200 150 100 50 0
250 200 150 100 50 0
CHILDREN ADULTS
CHILDREN ADULTS
EXAMPLE OF PIE CHART
EXAMPLE OF PIE CHART AREA
CHILDREN BOYS
ADULTS
GIRLS
MEN
100 CHILDREN 90 110
Diani Ukunda
50
45
75
150
DianiLunga-Lunga
100 130
Harmony Ukunda
AREA
BOYS
87
WOMEN 100 ADULTS 78
GIRLS
MEN
WOMEN
200
90 92
110 101
100
10550
99
45120
90 87
78
Tukutane
48
48
80
120
Ramisi
65
87
67
77
Mabungo
Mabungo
75
67
150
79
67
79
Lunga-Lunga
130
200
92
101
Harmony
105
99
120
90
48
80
120
Diani 87 18%
67
77
DISTRIBUTION OF SHOES
48 CHILDREN
Ramisi Tukutane 11% AREA Ramisi 0% Tukutane 8%
Harmony 76 | P a g e 18% Lunga‐ Lunga 23%
65
Ukunda 9% Mabungo 13% Computer Studies Guide Book
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LESSON REVIEWS • Define and differentiate the terms worksheet and spreadsheet. • Identify four types of data that can be entered in a worksheet. • Explain how cell addresses are used in spreadsheet programs. • Explain what a formula is and how formulas can be used in spreadsheet programs. • List three types of analytical tools commonly found in spreadsheets. • Create the following spread sheet No. Name Maths English 01 Melissa wanjiku 99 87 02 Duncan otieno 78 88 03 Swabrinnamarzuk 92 98 04 CidjiGogan 77 87 05 Tiffany Nashpay 90 89 06 Philip odanga 92 78 07 Charity shaaban 80 92 08 Emmanuel musau 98 78 09 Brenda wanjiku 80 78 10 Timmkaranja 99 98 a) Find total of each student using the applied formula b) Copy the data in sheet 1 and to sheet 2 c) Sort the total in descending order d) Relay the data in sheet 1 in a bar chart OF PIE e)EXAMPLE Create a pie chart for theCHART name and total in sheet 2 f) Insert a date and time in your sheet
Kiswahili 90 98 87 76 90 98 88 98 90 93
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science 78 90 94 98 92 89 89 90 78 97
SST/RE 87 79 91 78 78 87 90 72 79 89
T/Marks
MICROSOFT ACCESS 2016 LESSON REVIEW •
Define and differentiate the terms worksheet and spreadsheet.
•
Identify four types of data that can be entered in a worksheet.
•
Explain how cell addresses are used in spreadsheet programs.
• Explain what a formula is and how formulas can be used in spreadsheet programs. •
List three types of analytical tools commonly found in spreadsheets.
•
Create the following spread sheet
a)
Find total of each student using the applied formula
b)
Copy the data in sheet 1 and to sheet 2
c)
Sort the total in descending order
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d)
Relay the data in sheet 1 in a bar chart
e)
Create a pie chart for the name and total in sheet 2
f )
Insert a date and time in your sheet
7.1
MICROSOFT ACCESS
Database Management Systems and Enterprise Software This lesson includes the following sections Databases and Management Systems Working with a Database Enterprise Software Databases and Database Management Systems The Difference between Databases and DBMSes Database Basics DBMSes Basics
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Databases and Database Management Systems The Difference between Databases and DBM A database is a repository for collections of related data or facts. A database management system (DBMS) is a software tool that lets users add, view, and work with the data in a database. Large databases and DBMS’ are commonly used by companies, but many productivity applications are built around database concepts Databases and DBMS - Database Basics Databases use three main structures for organizing data: Fields, which store various pieces of data related to a single entity. Recordsor collections of fields relating to an entity. Tables, which are collections of related records The two primary types of databases are flat-file databases (with only one table) and relational databases (with multiple, related tables). PROFESSIONAL ADDRESS BOOK 7.2 - KEYS Fields that are part of the table relationship are called keys. A key usually consist of one field, but may consist of more than threeor two kinds of keys Primary keys – a table can have only one primary key. A primary key consists of one or more field that uniquely identify each record that you store in tables often there’s a unique identification number such as ID number, a serial number or a code that serve as a primary key e.g you might have a customer table where each customer has a unique customer ID customer. The customer ID field is the primary ID field it is usually composed of pre-existing fields that taken together, provide unique values e.g you might use a combination of last name first name and birth date as the primary keys for a table about people. Foreign keys – A table can also have one or more foreign keys. A foreign key contains values that correspond to values in the primary keys of another table. E.g you might have an order table in which each order has a customer ID number that corresponds to order in a customer’s table. The customer ID fields are a foreign key Computer Studies Guide Book
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of the order table. TYPES OF DATA TYPE Numeric /Numbers Examples of numerical values are balance due and average Numeric fields are handy as you can do various types of arithmetic calculations with them. Alphanumeric or string/Text This is the most common type of data type consisting of variety of characters that you find on your keyboard. Examples of Alphanumeric /Text fields are names, addresses, countries phone numbers and comments. This data type can store up to 255 characters in length Date - A field can be specified to hold only time-type values. Ms-Access understands a variety of time format. Time - A field can be specified to hold monetary values and calculations can easily be made up. Up to 15 digits to the left of the decimal point and four digits to the right of the decimal
Yes /No (True/False) A field can be defined to hold only Yes/No (True/False). Type information for example you might define a field number ADULT, which would be used to indicate the age status of each individual in a database. 7.3 - COMPONENTS OF THE DATABASE Table –this is the storage location of data. Looks like an excel worksheet It is the building block for forms and reports. Forms – displays templates used to create forms in access. The forms make data more readable and understanding on the screen. Reports–printing templates used to design reports for output i.e Printouts of the data stored in tables Query – queries extracts data from the table based on user definable criteria Databases and DBMS- DBMS Basics 88
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A DBMS allows users to access and manage the data collected in a database. Data management tasks (all done through the DBMS) can be divided into three categories: Entering data into the database. Sorting (rearranging) the data in the database. Obtaining subsets of the data for use. Working with a Database Creating Database Tables Viewing Records
Sorting Records Querying a Database Generating Reports
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Working With a Database – Creating Database Tables The first step in building a database is to create its tables. This means identifying, naming, and organizing its fields to receive data. Databases can store the following types of fields: Text
Memo
Logical
Binary
Numeric
Date/Time
Counter
Working With a Database – Creating Database Tables You can create forms that let you view and enter data for one record at a time. Database tools such as masks can validate data as it is entered and thus ensure the data is in the correct format.
Working With a Database - Viewing Records A filter is a tool that lets you view records that match a given criteria. Filters are helpful when searching for certain types of information in a large database with many records. A form can work with a filter, but enables you to view information about a single record. 90
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Working With a Database - Sorting Records Sorting means arranging the records in a database. A DBMS enables you to sort records alphabetically, numerically, and chronologically. You can sort records in ascending (A-Z) order or descending (Z-A) order. 7.4 - Working with a Database - Querying a Database A query is a statement you define, which tells the DBMS to find records that match criteria you specify. Modern DMBS software provides built-in querying tools, based on one or more of the following languages: •
SQL
•
Query by Example (QBE)
•
Xbase
Working With a Database - Generating Reports A report is a subset of information from a database, produced in printed form. You can generate the data for a report by using a query, filter, or other tools. Reports can be formatted in a wide variety of ways. Enterprise Software Enterprise software is a large-scale application based on a DBMS, used by a large organization. Enterprise software can meet the needs of many different users in different locations. In an enterprise, different users by have different interfaces to the database, so they can work only with the data they need.
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LESSON REVIEWS 1. Define the terms database and database management system (DBMS). 2. Explain the following terms in relationship with Ms-Excel a. Workbook b. Worksheet c. Chart d. Cell 3. List three tasks that a DBMS enables users to do. 4. Differentiate between flat-file databases and relational databases. 5. List three steps needed to create a database. 6. Explain the purpose of filters and forms. 7. List three examples of query languages 8. By indicating the formula work out the following (4marks) a. Percentage of 56/60 in column C4 and 27/30 in column D4 b. Sum of 80,78,88,77,90 in E2,E3,E4,E5,E6 Respectively
LESSON REVIEWS
9. Use the table below to answer the questions a – c (12marks) CANDIDATE MAT EN COM TOTA KI INSH S NAMES H G P L S A
TO T
SCI E
SS T
CR E
TO T
BRIAN 90 44 30 45 32 79 59 23 O’NEIL 98 37 28 38 31 88 47 29 CORNELL 87 29 32 44 32 98 55 23 TAYLOR 98 40 29 46 34 96 49 25 RICHARD 79 45 33 48 26 89 55 27 MEAN a. Write down an expression for the English total marks for both O’Neil and Richard b. Write down an expression for total marks for both Brian and Taylor Define the terms database and database management system (DBMS). c. Find the mean for math and science using the right procedural formula
2.
Explain the following terms in relationship with Ms-Excel
a. Workbook 92
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MARK S
1.
CHAPTER EIGHT MICROSOFT POWERPOINT 2016 (PRESENTATION PROGRAMS) b. Worksheet c. Chart d. Cell 3.
List three tasks that a DBMS enables users to do.
4.
Differentiate between flat-file databases and relational databases.
5.
List three steps needed to create a database.
6.
Explain the purpose of filters and forms.
7.
List three examples of query languages
8.
By indicating the formula work out the following (4marks)
a.
Percentage of 56/60 in column C4 and 27/30 in column D4
b.
Sum of 80,78,88,77,90 in E2,E3,E4,E5,E6 Respectively
9.
Use the table below to answer the questions a – c (12marks)
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a) Write down an expression for the English total marks for both O’Neil and Richard b) Write down an expression for total marks for both Brian and Taylor c) Find the mean for math and science using the right procedural formula
8.1
MICROSOFT POWERPOINT 2016 (Presentation-Programs)
This lesson includes the following sections: Presentation Program Basics Integrating Multiple Data Sources Presenting Slide Shows
8.2 Presentation Program Basics Presentation Programs and Their Uses The Presentation Program’s Interface Creating a Presentation Formatting Slides Special Features of Presentation Programs FEATURES OF THE APPLICATION Window manipulation - buttons, minimize, maximize, close window Tittle bar – name of the document, extension (pptx) and programmes name Tab name Toolbar – some toolbar have hidden tool they have an arrow in the lower right corner which (When clicked) displays an additional options Field for content – (text) entering, paper here you type insert object etc Insertion point – the position in the document where the cursor is flashing Thumbnail pane – the left side of the slide showing the details of the slide 94
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Field for notes – the slide Status bar – displays information about the current position in the document insertion point and the mode of special functions Rulers – above horizontal and left / vertical ruler of the PowerPoint Text effect tool – contains different text effects such as shadow or reflection. Text highlight colour tool – is used to emphasize the text with color Shading tool- is used to color the background Border tool – is used to set different types of borderline (borders) around the selected text Font color tool – is used to select the color of the text
List tool includes Bullets and numbering To add a new item to the list press the enter key To finish the list double press the enter key Text alignment – offers the following alignments Computer Studies Guide Book
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Align Left (Ctrl +L) Align Center (Ctrl +E) Align Right (Ctrl + R) Align Justify (Ctrl +J) Presentation Program Basics - Presentation Programs and Their Uses Presentation programs are used to create slides–single-screen images that contain text, graphics, charts, and more. A collection of slides is called a presentation. A presentation program lets you create a set of slides and show (present) them to an audience. The Presentation Program’s Interface Presentation programs provide many of the same editing and formatting tools found in word processors and other common application
Creating a Presentation To create a presentation, you can select a predesigned template to create a common look for the slides. Individual slide elements appear inside text boxes and frames. You can easily add text or graphics to a box or frame, and move or resize it as needed. Formatting Slides You can format a slide by choosing different: Fonts and font sizes Colors Backgrounds Borders TRANSITION TAB 96
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Add visual /sound effect defying slide transition Options for the slide transition (on mouse click) or Tool to set transition duration option To apply changes to all slides ANIMATION TAB To animate entrance/exit the motion path of the object on the slide – select an object and chose one of the animation Left mouse click to make the visible animation pane with listed animation SLIDE SHOW TAB From the beginning – to start the view slide show from the beginning (or press key F5) From current slide – to start/view slide show from the current slide (shift +f5) broadcast slides show –a new feature of MS Power point 2010 – application sends the link to the remote users who can see the presentation through the internet browser Custom slide show – customizing the slide show (determining new sequence of
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slide) Hide slide – you can hide a slide making it invisible (not appearing) during full screen slide show. N/B: During the slide show the right mouse button shows us available navigation –shortcut –previous –next go to end show Presentation Program Basics - Special Features Presentation programs provide several special features Outlining—for contents, arrangement and order. Annotations—notes to individual slides.
Animation—moving transitions to parts of a slide. Sound and video—audio or multimedia enhancement. Embedded objects—WWW links. HTML conversion —presentations on the Web. Integrating Multiple Data Sourcesin a Presentation You can add different media types, such as audio or video files, to a slide. If you present your slides from the PC’s disk and have the appropriate output devices, you can present multimedia elements in a slide show. 98
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Presenting Slide Shows You can print slides and present them on a slide or overhead projector. You also can display slides directly from the PC’s disk, with the following advantages: You can present them in any order you like. You can display slides on the PC’s monitor, project them on a screen, or connect the PC to a TV or large monitor. You can move from slide to slide manually, or automate the presentation.
Word of Life Christian Academy lesson on PowerPoint SLIDSHOW presentation in progress
LESSON REVIEWS 1.
Identify four interface elements found in most presentation programs.
2.
Describe the process of creating a presentation.
3. Name three media sources that might be used in a multimedia presentation. 4.
List three ways that slides can be presented from a presentation program.
5.
Create a presentation sowing demographical distribution of Kwal
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MICROSOFT PUBLISHER 2016
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9.1 MICROSOFT PUBLISHER 2016 Is a software application programmes that falls under graphic design or desktop publishing programmes (DPP). It is one of the most powerful desktop publishing programmes. Starting a program or application is the first step toward anything done Purposes of DTP Graphic design Page layout design Printing Types of DTP Graphical based Computer Studies Guide Book
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Layout based Designing a publication
A sample of a brochure made on MS Publisher
The type of documents produced by publishers Wedding cards Business cards Invitation cards Letter heads Logos Calendars Performers Brochures Certificates Signs Banners Loading publisher Click on start button Point to programs Point to Microsoft office Select Microsoft office publisher Open run Type the path
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“Mspub” Click ok or press enter key
Types of publication Publication for print Web site and E-mail Design sets Blank print publication Existing publication Creating business card using blank print publication Open publisher On the catalog window Select blank print publication Set layout of the page
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Select a text box from the insert menu Format it to have the desired design or appearance Arranging layout Click on the arrange menu on the menu bar Select arrange layout guides Set the size or number of columns and rows>>press enter to accept Creating business card using publication for print Open publisher program Select publication for print on the catalog window Select business card Choose the design of the cards Enter the text that fit the card Format it to have the required settings Click on multiple commands that appears on the task pane to duplicate the card N/B: all the other designs are created using the same procedures following each design’s publication
LESSON REVIEW 1)
What is DTP?
2)
What is the purpose of DTP?
3)
Give types of DTP software
4)
Outline examples of publications
5)
Design a significant business card for your own business
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INTERNET/NETWORKING, COMMUNICATION AND E-MAIL
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10.1 Introduction to internet and networking Internet: is the network of computers that can communicate with each other that is the sending and receiving of the information. Networking: is the interlinking of computers within a geographical location for the purpose of sharing data and information.
10.2 Terms frequently used in networking WWW – World Wide Web HTTP – Hyper Text Transfer Protocol HTML – Hyper Text Markup Language IP – internet protocol URL – Uniform Resource Locator ISP – Internet Server Provider WB – Web Brewers is a location where information is secured is searched on the internet e.g Yahoo, Hotmail, Gmail, Web2mail File Transfer Protocol (FTP) Trivial File Transfer Protocol (TFTP) Simple Mail Transfer Protocol (SMTP) TELNET Domain Name System (DNS Is a line or a command in which the information is transferred to the internet from one computer to the other 106
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10.4 Registering an E-mail address Open internet brewers’ icon Type the web browser on the address bar e.gwww.yahoomail.comwww.hotmail. com or www.gmail.com Select sign up if you don’t have an address Answer the relevant information on the page that will be provided. Type the code and select create account
10.5 Reading mails Open internet browser icon Type the web browser you registered to After the page opens type in the ID and the password you used to open the account Select sign in or press enter on the key board Select the inbox and click tittle provided on your messages on the inbox
10.6 Sending a mail When the inbox is active select compose a new Type the mail of the recipient in full Type the tittle or the subject Enter your main message and press send
10.7 Attaching files When the compose or new window is active Computer Studies Guide Book
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Select attach file Click browser to search your new file where you have saved it After selecting the file select open Finally click on attach and give it time to process Send your message to the designated recipient
10.8 Deleting mails Select the messages from any box e.g inbox, sent, attachment, draft and spam to delete your message Click on the small box that appears on your message at the start of your message Click delete and let it finish the process
10.9 Forwarding messages This is the transfer of a message from your inbox to someone else of a new and different mail address Open the inbox >>select the message>>click forward Type the email of the intended recipient in full >>click send 10.10 Using draft mails Draft is used to save message you create before sending to any recipient These messages can be open at another time to be sent to different recipients Open the new or compose window on your mail box Type the subject and the main message or attach the file Click saves to draft.
10.11 Sign out 108
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This takes you out of mail box to avoid clients reading your mails After reading, composing and saving draft messages Click on the sign out command to avoid any other person viewing your details or accessing your mails
10.12 Searching contents on the internets Open the internet browser icon>>type the information you want to search on the address bar >>click go or press enter key on the computer keyboard.
10.13 Using Google Is a search engine that provides all the information searched on the internet. All the contents are displayed clearly with Google Open web browser>>type the path www.google.com on the address bar >>press go or enter key on the computer keyboard.
10.14 Examples of search engines Google. Yahoo. Bing Ask.com AOL.com Baidu DuckDuckGo
10.15 Types of web internet domains Com – communication Computer Studies Guide Book
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Org – Organization Net – Networks
10.16 Examples of browsers Mozilla Firefox Internet explorer
Torch Google chrome Apple safari Opera
10.17 The Uses of a Network A network connects computers so they can communicate, exchange information, and share resources. The main benefits of using a network are: Simultaneous Access Shared Peripheral Devices Personal Communication 110
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Easier Backup Simultaneous Access In organizations, many people may need to use the same data or programs. A network solves this problem. Shared data and programs can be stored on a central network server. A server that stores data files may be called a file server. Managers may assign access rights to users. Some users may only be able to read data, others may be able to make changes to existing files Shared Peripheral Devices Because peripheral (external) devices like printers can be expensive, it is costeffective to connect a device to a network so users can share it. Through a process called spooling, users can send multiple documents (called print jobs) to a networked printer at the same time. The documents are temporarily stored on the serverand printed in turn. Personal Communication One of the most common uses of networks is for electronic mail (e-mail). An e-mail system enables users to exchange written messages (often with data files attached) across the local network or over the Internet. Two other popular network-based communications systems are teleconferencing and videoconferencing
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Networks enable managers to easily back up (make backup copies of ) important data. Administrators commonly back up shared data files stored on the server, but may also use the network to back up files on users’ PCs.
10.18 Networks are structured Local Area Networks (LANs) Wide Area Networks (WANs) Server-Based Networks Client/Server Networks Peer-to-Peer Networks
10.19 Network Media and Hardware In a network, the media are the wires, cables and other means by which data travels from its source to its destination. The most common network media are twisted-pair cable, coaxial cable, fiber-optic cable, and wireless links. Each node uses a special device, called a network interface card (NIC). The card connects to the network media and controls the flow of data. NICs must use a common network technology to communicate. The most popular network technologies for LANs are Ethernet, Fast Ethernet, and Token Ring
10.20 Network Software A network operating system (NOS) is the group of programs that manages the resources on a network. Common network operating systems for PC-based networks include: Novell NetWare Microsoft Windows NT Server 112
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Microsoft Windows 2000 Banyan VINES AppleShare Linux
10.21 Data Communications over Standard Telephone Lines Networks commonly use dedicated media to transmit data. However, the public telephone system can also be used for data communications.
Internal Modem
External Modem
Standard phone lines transmit data much more slowly than network media, but Uses for a Modem devices such as modems make phone lines practical for data transmission over long distances.
Modems are primarily used for file transfer, or sending files to a remote computer
Many people and businesses use modems to exchange data, and to establish Sending a file to another computer is called uploading. connections with office networks
Receiving a file from another computer is called Telephone downloading Lines - Modems Data Communications over Standard Most telephone lines attached to home and businesses are analog, not digital. Using Digital Telephone Lines Because PCs companies transmitareand receivedigital data in digital format, a device called a data modem Telephone now installing telephone lines, which are dedicated to transmitting in digitalis needed to convert digital data to analog format for transmission over phone lines.
format.
When receiving data from another computer, the modem converts it from analog phone lines transmit data at much higher speeds than standard analog phone lines. formatDigital to digital format.
Often, data travels across analog and digitalTelephone lines. In such cases, data- may need to be converted from one format Data Communications overlines Standard Lines Choosing a Modem to another multiple times before reaching its destination.
When choosing a modem, consider the following factors: Computer Studies Guide Book
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•
Transmission speed - the speed at which the modem sends data - which is measured in bits per second.
•
Data compression, the technology the modem uses to shrink data so it can be transmitted faster.
•
Error correction, the method the modem uses to ensure data is sent and received without errors.
•
Internal versus external, which describes whether or not the modem fits inside the PC case.
Uses for a Modem Modems are primarily used for file transfer, or sending files to a remote computer Sending a file to another computer is called uploading. Receiving a file from another computer is called downloading Using Digital Telephone Lines Telephone companies are now installing digital telephone lines, which are dedicated to transmitting data in digital format. Digital phone lines transmit data at much higher speeds than standard analog phone lines. Often, data travels across analog lines and digital lines. In such cases, data may need to be converted from one format to another multiple times before reaching its 114
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destination.
Common Digital Services The most commonly used digital telephone services are: ISDN, T1, and T3 DSL ATM Cable Modem ISDN, T1, and T3 Integrated Services system that replaces digital services.
Digital Network (ISDN) is a analog phone services with
Basic rate ISDN (BRI) phone line: two for transmits data up to
offers three channels on one data and one for control. BRI 128 Kbps.
Primary rate ISDN transmission speeds service.
(PRI) offers 24 channels at up to 1.544 Mbps. This is T1
Using even more channels, T3 service offers up to 672 channels and speeds up to 44.736 Mbps. Using Digital Telephone Lines - DSL Technologies Digital Subscriber Line (DSL) service is outpacing ISDN services. Standard DSL offers speeds of 52 Mbps using standard phone lines. Several are transto 51.84
types of DSL service available, reaching mission speeds up Mbps
ATM Asynchro(ATM) offered as
nous transfer mode digital service is a high-bandwidth, Computer Studies Guide Book
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efficient means for transferring multimedia content, data, and voice over phone lines. Some types of ATM service can reach transmission speeds of 10,000 Mbps.
Cable Modem Connections Cable modems allow users to connect their PCs to the Internet via the local cable television system. Cable companies offer Internet service by combining television and data signals and distributing them over the cable system. 116
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Cable modem service can achieve speeds of 27 Mbps.
10.22 Networks in the Home Because more homes now have multiple computers, home networks are gaining
in popularity. Home networks offer the same advantages to home users as to a business. Home networks are typically based on existing telephone or wireless technologies. Popular PC operating systems, such as Windows and the Mac OS, provide simple networking tools that are adequate for running a home network Internet – is derived from the word inter&net which means international networking. Networking is the sharing of computer resources e.g documents, printers and drivers we can also call internet (cyberspace) 10.23 Types of Communication Networks Communication Networks can be of following 5 types: Computer Studies Guide Book
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Local Area Network (LAN) Metropolitan Area Network (MAN) Wide Area Network (WAN) Wireless Inter Network (InternetLAN – Local area network (covers a range of more than 10KM) 10.24 Local Area Network (LAN) It is also called LAN and designed for small physical areas such as an office, group of buildings or a factory. LANs are used widely as it is easy to design and to troubleshoot. Personal computers and workstations are connected to each other through LANs. We can use different types of topologies through LAN; these are Star, Ring, Bus, Tree etc. LAN can be a simple network like connecting two computers, to share files and network among each other while it can also be as complex as interconnecting an entire building. LAN networks are also widely used to share resources like printers, shared hard-drive etc.
Characteristics of LAN LAN’s are private networks, not subject to tariffs or other regulatory controls. LAN’s operate at relatively high speed when compared to the typical WAN. There are different types of Media Access Control methods in a LAN, the prominent ones are Ethernet, Token ring. It connects computers in a single building, block or campus, i.e. they work in a restricted geographical area. Applications of LAN One of the computers in a network can become a server serving all the remaining computers called clients. Software can be stored on the server and it can be used by the remaining clients. Connecting locally all the workstations in a building to let them communicate with each other locally without any internet access. 118
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Sharing common resources like printers etc. are some common applications of LAN. Advantages of LAN Resource Sharing: Computer resources like printers, modems, DVD-ROM drives and hard disks can be shared with the help of local area networks. This reduces cost and hardware purchases. Software Applications Sharing: It is cheaper to use same software over network instead of purchasing separate licensed software for each client a network. Easy and Cheap Communication: Data and messages can easily be transferred over networked computers. Centralized Data: The data of all network users can be saved on hard disk of the server computer. This will help users to use any workstation in a network to access their data. Because data is not stored on workstations locally. Data Security: Since, data is stored on server computer centrally, it will be easy to manage data at only one place and the data will be more secure too. Internet Sharing: Local Area Network provides the facility to share a single internet connection among all the LAN users. In Net Cafes, single internet connection sharing system keeps the internet expenses cheaper. Disadvantages of LAN High Setup Cost: Although the LAN will save cost over time due to shared computer resources, but the initial setup costs of installing Local Area Networks is high. Privacy Violations: The LAN administrator has the rights to check personal data files of each and every LAN user. Moreover he can check the internet history and computer use history of the LAN user. Data Security Threat: Unauthorized users can access important data of an organization if centralized data repository is not secured properly by the LAN administrator. LAN Maintenance Job: Local Area Network requires a LAN Administrator because, there are problems of software installations or hardware failures or cable disturbances in Local Area Network. A LAN Administrator is needed at this full time job. Covers Limited Area: Local Area Network covers a small area like one office, one building or a group of nearby buildings. 10.25 Metropolitan Area Network (MAN) It was developed in 1980s.It is basically a bigger version of LAN. It is also called MAN Computer Studies Guide Book
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and uses the similar technology as LAN. It is designed to extend over the entire city. It can be means to connecting a number of LANs into a larger network or it can be a single cable. It is mainly hold and operated by single private company or a public company.
Characteristics of MAN It generally covers towns and cities (50 km) Communication medium used for MAN are optical fibers, cables etc. Data rates adequate for distributed computing applications. Advantages of MAN Extremely efficient and provide fast communication via high-speed carriers, such as fibre optic cables. It provides a good back bone for large network and provides greater access to WANs. The dual bus used in MAN helps the transmission of data in both directions simultaneously. A MAN usually encompasses several blocks of a city or an entire city. Disadvantages of MAN More cable required for a MAN connection from one place to another. It is difficult to make the system secure from hackers and industrial espionage (spying) graphical regions. 10.26 Wide Area Network (WAN) It is also called WAN. WAN can be private or it can be public leased network. It is used for the network that covers large distance such as cover states of a country. It 120
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is not easy to design and maintain. Communication medium used by WAN are PSTN or Satellite links. WAN operates on low data rates.
Characteristics of WAN It generally covers large distances (states, countries, continents). Communication medium used are satellite, public telephone networks which are connected by routers. Advantages of WAN Covers a large geographical area so long distance business can connect on the one network. Shares software and resources with connecting workstations. Messages can be sent very quickly to anyone else on the network. These messages can have picture, sounds or data included with them (called attachments). Expensive things (such as printers or phone lines to the internet) can be shared by all the computers on the network without having to buy a different peripheral for each computer. Everyone on the network can use the same data. This avoids problems where some users may have older information than others. Disadvantages of WAN Need a good firewall to restrict outsiders from entering and disrupting the network. Setting up a network can be an expensive, slow and complicated. The bigger the network the more expensive it is. Once set up, maintaining a network is a full-time job which requires network supervisors Computer Studies Guide Book
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and technicians to be employed. Security is a real issue when many different people have the ability to use information from other computers. Protection against hackers and viruses adds more complexity and expense. 10.27 Wireless Network Digital wireless communication is not a new idea. Earlier, Morse code was used to implement wireless networks. Modern digital wireless systems have better performance, but the basic idea is the same. Wireless Networks can be divided into three main categories: System interconnection Wireless LANs Wireless WANs System Interconnection System interconnection is all about interconnecting the components of a computer using short-range radio. Some companies got together to design a short-range wireless network called Bluetooth to connect various components such as monitor, keyboard, mouse and printer, to the main unit, without wires. Bluetooth also allows digital cameras, headsets, scanners and other devices to connect to a computer by merely being brought within range. In simplest form, system interconnection networks use the master-slave concept. The system unit is normally the master, talking to the mouse, keyboard, etc. as slaves. Wireless LANs These are the systems in which every computer has a radio modem and antenna with which it can communicate with other systems. Wireless LANs are becoming increasingly common in small offices and homes, where installing Ethernet is considered too much trouble. There is a standard for wireless LANs called IEEE 802.11, which most systems implement and which is becoming very widespread. Wireless WANs The radio network used for cellular telephones is an example of a low-bandwidth wireless WAN. This system has already gone through three generations. The first generation was analog and for voice only. 122
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The second generation was digital and for voice only. The third generation is digital and is for both voice and data.
Inter Network Inter Network or Internet is a combination of two or more networks. Inter network can be formed by joining two or more individual networks by means of various devices such as routers, gateways and bridges. 10.28 Reference Models in Communication Networks The most important reference models are: OSI reference model. TCP/IP reference model.
Introduction to ISO-OSI Model There are many users who use computer network and are located all over the world. To ensure national and worldwide data communication ISO (ISO stands for International Organization of Standardization.) developed this model. This is called a model for open system interconnection (OSI) and is normally called as OSI model. OSI model architecture consists of seven layers. It defines seven layers or levels in a complete communication system. OSI Reference model is explained in other chapter. Computer Studies Guide Book
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TCP/IP Reference model is explained in details other chhapter.
F Princciples and Layyers 10.30 The OSI Model - Features,
There are n numbers of ussers who use coomputer networrk and are locatted worldwide data communiccation, systemss must be developed which aree co has developped a standard. ISO stands forr Internationall organization of S Open System Interconneection (OSI) annd is commonlyy known as OSII m OSI model is sevven layer archittecture. It definnes seven layerss or The ISO-O They are: 1. Application A Layeer 2. Prresentation Layyer 3. Seession Layer 4. Trransport Layer 5. Network N Reference Layer Model 10.29 Introduction to TCP/IP 6. Data D link Layer TCP/IP is transmission control protocol internet protocol. Protocols are set of 7. Phhysicaland Layer
rules which govern every possible communication over the internet. These protocols describe the movement of data between the host computers or internet and offers Below we h the compllete representatiion of the OSI model, have m showcaasin simple naming and addressing schemes.
with each other. o
TCP/IP Reference model is explained in details other chapter.
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10.30 The OSI Model - Features, Principles and Layers There are n numbers of users who use computer network and are located over the world. So to ensure, national and worldwide data communication, systems must be developed which are compatible to communicate with each other ISO has developed a standard. ISO stands for International organization of Standardization. This is called a model for Open System Iterconnection (OSI) and is commonly known as OSI model. The ISO-OSI model is seven layer architecture. It defines seven layers or levels in a Computer Studies Guide Book
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complete communication system. They are: 1.
Application Layer
2.
Presentation Layer
3.
Session Layer
4.
Transport Layer
5.
Network Layer
6.
Data link Layer
7.
Physical Layer
Below we have the complete representation of the OSI model, showcasing all the layers and how they communicate with each other. In the table below, we have specified the protocols used and the data unit exchanged by each layer of the OSI Model.
Feature of OSI Model Big picture of communication over network is understandable through this OSI model. We see how hardware and software work together. We can understand new technologies as they are developed. Troubleshooting is easier by separate networks. Can be used to compare basic functional relationships on different networks
Principles of OSI Reference Model The OSI reference model has 7 layers. The principles that were applied to arrive at the seven layers can be briefly summarized as follows: 126
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A layer should be created where a different abstraction is needed. Each layer should perform a well-defined function. The function of each layer should be chosen with an eye toward defining internationally standardized protocols. The layer boundaries should be chosen to minimize the information flow across the interfaces. The number of layers should be large enough that distinct functions need not be thrown together in the same layer out of necessity and small enough that architecture does not become unwieldy.
10.31 Functions of Different Layers Following are the functions performed by each layer of the OSI model. This is just an introduction; we will cover each layer in details in the coming tutorials.
OSI Model Layer 1: The Physical Layer Physical Layer is the lowest layer of the OSI Model. It activates, maintains and deactivates the physical connection. It is responsible for transmission and reception of the unstructured raw data over network. Voltages and data rates needed for transmission is defined in the physical layer. It converts the digital/analog bits into electrical signal or optical signals. Data encoding is also done in this layer.
OSI Model Layer 2: Data Link Layer Data link layer synchronizes the information which is to be transmitted over the physical layer. The main function of this layer is to make sure data transfer is error free from one node to another, over the physical layer. Computer Studies Guide Book
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Transmitting and receiving data frames sequentially is managed by this layer. This layer sends and expects acknowledgements for frames received and sent respectively. Resending of non-acknowledgement received frames is also handled by this layer. This layer establishes a logical layer between two nodes and also manages the Frame traffic control over the network. It signals the transmitting node to stop, when the frame buffers are full. OSI Model Layer 3: The Network Layer Network Layer routes the signal through different channels from one node to other. It acts as a network controller. It manages the Subnet traffic. It decides by which route data should take. It divides the outgoing messages into packets and assembles the incoming packets into messages for higher levels.
OSI Model Layer 4: Transport Layer Transport Layer decides if data transmission should be on parallel path or single path. Functions such as Multiplexing, Segmenting or Splitting on the data are done by this layer It receives messages from the Session layer above it, converts the message into smaller units and passes it on to the Network layer. Transport layer can be very complex, depending upon the network requirements. Transport layer breaks the message (data) into small units so that they are handled more efficiently by the network layer.
OSI Model Layer 5: The Session Layer Session Layer manages and synchronizes the conversation between two different applications. Transfer of data from source to destination session layer streams of data are marked and are resynchronized properly, so that the ends of the messages are not cut prematurely 128
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and data loss is avoided.
OSI Model Layer 6: The Presentation Layer Presentation Layer takes care that the data is sent in such a way that the receiver will understand the information (data) and will be able to use the data. While receiving the data, presentation layer transforms the data to be ready for the application layer. Languages (syntax) can be different of the two communicating systems. Under this condition presentation layer plays a role of translator. It performs Data compression, Data encryption, Data conversion etc.
OSI Model Layer 7: Application Layer Application Layer is the topmost layer. Transferring of files disturbing the results to the user is also done in this layer. Mail services, directory services, network resource etc. are services provided by application layer. This layer mainly holds application programs to act upon the received and to be sent data. Merits of OSI reference model Computer Studies Guide Book
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OSI model distinguishes well between the services, interfaces and protocols. Protocols of OSI model are very well hidden. Protocols can be replaced by new protocols as technology changes. Supports connection oriented services as well as connectionless service.
Demerits of OSI reference model Model was devised before the invention of protocols. Fitting of protocols is tedious task. It is just used as a reference model. Physical Layer - OSI Reference Model Physical layer is the lowest layer of the OSI reference model. It is responsible for sending bits from one computer to another. This layer is not concerned with the meaning of the bits and deals with the setup of physical connection to the network and with transmission and reception of signals. Functions of Physical Layer Following are the various functions performed by the Physical layer of the OSI model. Representation of Bits: Data in this layer consists of stream of bits. The bits must be encoded into signals for transmission. It defines the type of encoding i.e. how 0’s and 1’s are changed to signal. 130
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Data Rate: This layer defines the rate of transmission which is the number of bits per second. Synchronization: It deals with the synchronization of the transmitter and receiver. The sender and receiver are synchronized at bit level. Interface: The physical layer defines the transmission interface between devices and transmission medium. Line Configuration: This layer connects devices with the medium: Point to Point configuration and Multipoint configuration. Topologies: Devices must be connected using the following topologies: Mesh, Star, Ring and Bus. Transmission Modes: Physical Layer defines the direction of transmission between two devices: Simplex, Half Duplex, and Full Duplex. Deals with baseband and broadband transmission.
Design Issues with Physical Layer The Physical Layer is concerned with transmitting raw bits over a communication channel. The design issue has to do with making sure that when one side sends a 1 bit, it is received by the other side as a 1 bit and not as a 0
Typical questions here are: How many volts should be used to represent a 1 bit and how many for a 0? How many nanoseconds a bit lasts? Whether transmission may proceed simultaneously in both directions? Whether transmission may proceed simultaneously in both directions? How many pins the network connector has and what each pin is used for? The design issues here largely deal with mechanical, electrical and timing interfaces, and the physical transmission medium, which lies below the physical layer. Data Link Layer - OSI Model Computer Studies Guide Book
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Data link layer performs the most reliable node to node delivery of data. It forms frames from the packets that are received from network layer and gives it to physical layer. It also synchronizes the information which is to be transmitted over the data. Error controlling is easily done. The encoded data are then passed to physical. Error detection bits are used by the data link layer. It also corrects the errors. Outgoing messages are assembled into frames. Then the system waits for the acknowledgements to be received after the transmission. It is reliable to send message. The main task of the data link layer is to transform a raw transmission facility into a line that appears free of undetected transmission errors to the network layer. It accomplishes this task by having the sender break up the input data into data frames (typically a few hundred or few thousand bytes) and transmits the frames sequentially. If the service is reliable, the receiver confirms correct receipt of each frame by send back an acknowledgement frame. Functions of Data Link Layer Framing: Frames are the streams of bits received from the network layer into manageable data units. This division of stream of bits is done by Data Link Layer. Physical Addressing: The Data Link layer adds a header to the frame in order to define physical address of the sender or receiver of the frame, if the frames are to be distributed to different systems on the network. Flow Control: A flow control mechanism to avoid a fast transmitter from running a slow receiver by buffering the extra bit is provided by flow control. This prevents traffic jam at the receiver side. Error Control: Error control is achieved by adding a trailer at the end of the frame. Duplication of frames is also prevented by using this mechanism. Data Link Layers 132
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adds mechanism to prevent duplication of frames. Access Control: Protocols of this layer determine which of the devices has control over the link at any given time, when two or more devices are connected to the same link.
Design Issues with Data Link Layer The issue that arises in the data link layer (and most of the higher layers as well) is how to keep a fast transmitter from drowning a slow receiver in data. Some traffic regulation mechanism is often needed to let the transmitter know how much buffer space the receiver has at the moment. Frequently, the flow regulation and the error handling are integrated. Broadcast networks have an additional issue in the data link layer: How to control access to the shared channel. A special sub layer of the data link layer, the Medium Access Control (MAC) sub layer, deals with this problem. Network Layer - OSI Model The network Layer controls the operation of the subnet. The main aim of this layer is to deliver packets from source to destination across multiple links (networks). If two computers (system) are connected on the same link, then there is no need for a network layer. It routes the signal through different channels to the other end and acts as a network controller. Computer Studies Guide Book
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It also divides the outgoing messages into packets and to assemble incoming packets into messages for higher levels. In broadcast networks, the routing problem is simple, so the network layer is often thin or even non-existent.
Functions of Network Layer It translates logical network address into physical address. Concerned with circuit, message or packet switching. Routers and gateways operate in the network layer. Mechanism is provided by Network Layer for routing the packets to final destination. Connection services are provided including network layer flow control, network layer error control and packet sequence control. Breaks larger packets into small packets. Design Issues with Network Layer A key design issue is determining how packets are routed from source to destination. Routes can be based on static tables that are wired into the network and rarely changed. They can also be highly dynamic, being determined anew for each packet, to reflect the current network load. If too many packets are present in the subnet at the same time, they will get into one another’s way, forming bottlenecks. The control of such congestion also belongs to the network layer. Moreover, the quality of service provided (delay, transmit time, jitter, etc.) is also a network layer issue. When a packet has to travel from one network to another to get to its destination, many problems can arise such as: The addressing used by the second network may be different from the first one. The second one may not accept the packet at all because it is too large. The protocols may differ, and so on. 134
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It is up to the network layer to overcome all these problems to allow heterogeneous networks to be interconnected.
Transport Layer - OSI Model
The basic function of the Transport layer is to accept data from the layer above, split it up into smaller units, pass these data units to the Network layer, and ensure that all the pieces arrive correctly at the other end. Furthermore, all this must be done efficiently and in a way that isolates the upper layers from the inevitable changes in the hardware technology. The Transport layer also determines what type of service to provide to the Session layer, and, ultimately, to the users of the network. The most popular type of transport connection is an error-free point-to-point channel that delivers messages or bytes in the order in which they were sent. The Transport layer is a true end-to-end layer, all the way from the source to the destination. In other words, a program on the source machine carries on a conversation with a similar program on the destination machine, using the message headers and control messages. Functions of Transport Layer Service Point Addressing: Transport Layer header includes service point address which is port address. This layer gets the message to the correct process on the computer unlike Network Layer, which gets each packet to the correct computer. Segmentation and Reassembling: A message is divided into segments; each segment contains sequence number, which enables this layer in reassembling the Computer Studies Guide Book
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message. Message is reassembled correctly upon arrival at the destination and replaces packets which were lost in transmission. Connection Control: It includes 2 types: Connectionless Transport Layer: Each segment is considered as an independent packet and delivered to the transport layer at the destination machine. Connection Oriented Transport Layer: Before delivering packets, connection is made with transport layer at the destination machine. Flow Control: In this layer, flow control is performed end to end. Error Control: Error Control is performed end to end in this layer to ensure that the complete message arrives at the receiving transport layer without any error. Error
Correction is done through retransmission.
Design Issues with Transport Layer Accepting data from Session layer split it into segments and send to the network layer. Ensure correct delivery of data with efficiency. Isolate upper layers from the technological changes. Error control and flow control. 136
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Session Layer - OSI Model The Session Layer allows users on different machines to establish active communication sessions between them. Its main aim is to establish, maintain and synchronize the interaction between communicating systems. Session layer manages and synchronize the conversation between two different applications. In Session layer, streams of data are marked and are resynchronized properly, so that the ends of the messages are not cut prematurely and data loss is avoided.
Functions of Session Layer Dialog Control: This layer allows two systems to start communication with each other in half-duplex or full-duplex. Token Management: This layer prevents two parties from attempting the same critical operation at the same time. Synchronization: This layer allows a process to add checkpoints which are considered as synchronization points into stream of data. Example: If a system is sending a file of 800 pages, adding checkpoints after every 50 pages is recommended. This ensures that 50 page unit is successfully received and acknowledged. This is beneficial at the time of crash as if a crash happens at page number 110; there is no need to retransmit 1 to100 pages. Design Issues with Session Layer To allow machines to establish sessions between them in a seamless fashion.
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Provide enhanced services to the user. To manage dialog control. To provide services such as Token management and Synchronization.
Presentation Layer - OSI Model The primary goal of this layer is to take care of the syntax and semantics of the information exchanged between two communicating systems. Presentation layer takes care that the data is sent in such a way that the receiver will understand the information (data) and will be able to use the data. Languages (syntax) can be different of the two communicating systems. Under this condition presentation layer plays a role translator. In order to make it possible for computers with different data representations to communicate, the data structures to be exchanged can be defined in an abstract way. The presentation layer manages these abstract data structures and allows higher-level data structures (eg: banking records), to be defined and exchanged.
Functions of Presentation Layer Translation: Before being transmitted, information in the form of characters and numbers should be changed to bit streams. The presentation layer is responsible for interoperability between encoding methods as different computers use different encoding methods. It translates data between the formats the network requires and the format the computer. Encryption: It carries out encryption at the transmitter and decryption at the receiver. Compression: It carries out data compression to reduce the bandwidth of the data to be transmitted. The primary role of Data compression is to reduce the number of bits to be 0transmitted. It is important in transmitting multimedia such as audio, video, text etc.
Design Issues with Presentation Layer 138
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To manage and maintain the Syntax and Semantics of the information transmitted.
Encoding data in a standard agreed upon way. Eg: String, double, date, etc. Perform Standard Encoding on wire.
Application Layer - OSI Model It is the top most layer of OSI Model. Manipulation of data (information) in various ways is done in this layer which enables user or software to get access to the network. Some services provided by this layer includes: E-Mail, transferring files, distributing the results to user, directory services, network resources, etc. The Application Layer contains a variety of protocols that are commonly needed by users. One widely-used application protocol is HTTP(Hypertext Transfer Protocol), which is the basis for the World Wide Web. When a browser wants a web page, it sends the name of the page it wants to the server using HTTP. The server then sends the page back. Other Application protocols that are used are: File Transfer Protocol (FTP), Trivial File Transfer Protocol (TFTP), Simple Mail Transfer Protocol(SMTP), TELNET, Domain Name System(DNS) etc.
Functions of Application Layer Mail Services: This layer provides the basis for E-mail forwarding and storage. Computer Studies Guide Book
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Network Virtual Terminal: It allows a user to log on to a remote host. The application creates software emulation of a terminal at the remote host. User’s computer talks to the software terminal which in turn talks to the host and vice versa. Then the remote host believes it is communicating with one of its own terminals and allows
user to log on. Directory Services: This layer provides access for global information about various services. File Transfer, Access and Management (FTAM): It is a standard mechanism to access files and manages it. Users can access files in a remote computer and manage it. 140
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They can also retrieve files from a remote computer.
Design Issues with Application Layer There are commonly reoccurring problems that occur in the design and implementation of Application Layer protocols and can be addressed by patterns from several different pattern languages: Pattern Language for Application-level Communication Protocols Service Design Patterns Patterns of Enterprise Application Architecture Pattern-Oriented Software Architecture
The TCP/IP Reference Model TCP/IP means Transmission Control Protocol and Internet Protocol. It is the network model used in the current Internet architecture as well. Protocols are set of rules which govern every possible communication over a network. These protocols describe the movement of data between the source and destination or the internet. They also offer simple naming and addressing schemes.
Protocols and networks in the TCP/IP model:
Overview of TCP/IP reference model TCP/IP that is Transmission Control Protocol and Internet Protocol was developed by Department of Defence’s Project Research Agency (ARPA, later DARPA) as a part of a research project of network interconnection to connect remote machines. The features that stood out during the research, which led to making the TCP/IP reference model were: Computer Studies Guide Book
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Support for a flexible architecture. Adding more machines to a network was easy. The network was robust, and connections remained intact until the source and destination machines were functioning. The overall idea was to allow one application on one computer to talk to(send data packets) another application running on different computer.
Different Layers of TCP/IP Reference Model Below we have discussed the 4 layers that form the TCP/IP reference model: Layer 1: Host-to-network Layer Lowest layer of the all. Protocol is used to connect to the host, so that the packets can be sent over it. Varies from host to host and network to network. Layer 2: Internet layer Selection of a packet switching network which is based on a connectionless internetwork layer is called a internet layer. It is the layer which holds the whole architecture together. It helps the packet to travel independently to the destination. Order in which packets are received is different from the way they are sent. IP (Internet Protocol) is used in this layer. The various functions performed by the Internet Layer are: Delivering IP packets Performing routing Avoiding congestion Layer 3: Transport Layer It decides if data transmission should be on parallel path or single path. Functions such as multiplexing, segmenting or splitting on the data is done by 142
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transport layer. The applications can read and write to the transport layer. Transport layer adds header information to the data. Transport layer breaks the message (data) into small units so that they are handled more efficiently by the network layer. Transport layer also arrange the packets to be sent, in sequence. Layer 4: Application Layer The TCP/IP specifications described a lot of applications that were at the top of the protocol stack. Some of them were TELNET, FTP, SMTP, DNS etc. TELNET is a two-way communication protocol which allows connecting to a remote machine and run applications on it. FTP (File Transfer Protocol) is a protocol that allows File transfer amongst computer users connected over a network. It is reliable, simple and efficient. SMTP (Simple Mail Transport Protocol) is a protocol, which is used to transport electronic mail between a source and destination, directed via a route. DNS (Domain Name Server) resolves an IP address into a textual address for Hosts connected over a network. It allows peer entities to carry conversation. It defines two end-to-end protocols: TCP and UDP TCP (Transmission Control Protocol): It is a reliable connection-oriented protocol which handles byte-stream from source to destination without error and flow control. UDP (User-Datagram Protocol): It is an unreliable connection-less protocol that do not want TCPs, sequencing and flow control. Eg: One-shot request-reply kind of service.
Merits of TCP/IP model It operated independently. It is scalable. Computer Studies Guide Book
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10.32 Difference between OSI and TCP/IP Reference Model Following are some major differences between OSI Reference Model and TCP/IP Reference Model, with diagrammatic comparison below. Client/server architecture. OSI(Open System Interconnection) 1. OSI is a generic, protocol independent standard, acting as a communication gateway between the network and end user. 2. In OSI model the transport layer guarantees the delivery of packets. 3. Follows vertical approach. 4. OSI model has a separate Presentation layer and Session layer. 5. Transport Layer is Connection Oriented. 6. Network Layer is both Connection Oriented and Connection less. 7. OSI is a reference model around which the networks are built. Generally it is used as a guidance tool. 8. Network layer of OSI model provides both connection oriented and connectionless service. 9. OSI model has a problem of fitting the protocols into the model.
10. Protocools are hidden inn OSI model annd are easily replaced y changes. 130 | Pasas the g etechnology 11. OSI moodel defines serrvices, interfacees and protocols very v clearly andd makes clear diistinction between them. It is protoccol independentt. 12. It has 7 layers
TCP/IP(Transmission Control Protocol / Internet Protocol) 1. TCP/IP model is based on standard protocols around which the Internet has developed. It is a communication protocol, which allows connection of hosts over a network. 2. In TCP/IP model the transport layer does not guarantees delivery of packets. Still the TCP/IP model is more reliable. 3. Follows horizontal approach. 4. TCP/IP does not have a separate Presentation layer or Session layer. 5. Transport Layer is both Connection Oriented and Connection less. 6. Network Layer is Connection less. 7. TCP/IP model is, in a way implementation of the OSI model. 8. The Network layer in TCP/IP model provides connectionless service. 9. TCP/IP model does not fit any protocol
10. In TCP/IP reeplacing protocol is not easy. s interfaaces and protocools are not cleaarly 11. In TCP/IP, services, a protocol deependent. seeparated. It is also 12. It has 4 layerrs
Supports a number ofsonrouting Diagramm matic Comparis between protocols. O Reference Model and TC OSI CP/IP Referencce Model Can be used to establish a connection between two computers.
Demerits of TCP/IP In this, the transport layer does not guarantee delivery of packets. The model cannot be used in any other application. 144
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Replacing protocol is not easy. It has not clearly separated its services, interfaces and protocols. Comparison of OSI and TCP/IP Reference Model Now it’s time to compare both the reference model that we have learned till now. Let’s start by addressing the similarities that both of these models have. Following are some similarities between OSI Reference Model and TCP/IP Reference Model. Both have layered architecture. Layers provide similar functionalities.
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Both are protocol stack. Both are reference models.
10.32 Difference between OSI and TCP/IP Reference Model Following are some major differences between OSI Reference Model and TCP/IP Reference Model, with diagrammatic comparison below. OSI(Open System Interconnection) - TCP/IP(Transmission Control Protocol / Internet Protocol)
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10.33 KEY TERMS in Computer Networks Following are some important terms, which are frequently used in context of Computer Networks. Terms
Definition
1. ISO
The OSI model is a product of the Open Systems Interconnection project at the International Organization for Standardization. ISO is a voluntary organization.
2. OSI Model Open System Interconnection is a model consisting of seven logical layers.
3. TCP/IP Model Transmission Control Protocol and Internet Protocol Model is based on four layer model which is based on Protocols. 4. UTP
Unshielded Twisted Pair cable is a Wired/Guided media which consists of two conductors usually copper, each with its own colour plastic insulator
5. STP
Shielded Twisted Pair cable is a Wired/Guided media has a metal foil or braided-mesh covering which encases each pair of insulated conductors. Shielding also eliminates crosstalk
6. PPP
Point-to-Point connection is a protocol which is used as a communication link between two devices.
7. LAN
Local Area Network is designed for small areas such as an office, group of building or a factory.
8. WAN
Wide Area Network is used for the network that covers large distance such as cover states of a country
9. MAN
Metropolitan Area Network uses the similar technology as LAN. It is designed to extend over the entire city.
10. Crosstalk
Undesired effect of one circuit on another circuit. It can occur when one line picks up some signals travelling down another line. Example: telephone conversation when one can hear background conversations. It can be eliminated by shielding each pair of twisted pair cable.
11. PSTN
Public Switched Telephone Network consists of telephone lines, cellular networks, satellites for communication, fiber optic cables Computer Studies Guide Book
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etc. It is the combination of world’s (national, local and regional) circuit switched telephone network.
12. File Transfer, Access and Management (FTAM) Standard mechanism to access files and manages it. Users can access files in a remote computer and manage it. 13. Analog Transmission The signal is continuously variable in amplitude and frequency. Power requirement is high when compared with Digital Transmission. 14. Digital Transmission It is a sequence of voltage pulses. It is basically a series of discrete pulses. Security is better than Analog Transmission. 15. Asymmetric digital subscriber line(ADSL) - A data communications technology that enables faster data transmission over copper telephone lines than a conventional voice band modem can provide. 16. Access Point Alternatively referred to as a base station and wireless router, an access point is a wireless receiver which enables a user to connect wirelessly to a network or the Internet. This term can refer to both Wi-Fi and Bluetooth devices. 17. Acknowledgement (ACK) Short for acknowledgement, ACK is an answer given by another computer or network device indicating to another computer that it acknowledged the SYN/ACK or other request sent to it. Note: If the signal is not properly received an NAK is sent. 18. Active Topology
The term active topology describes a network topology in which the signal is amplified at each step as it passes from one computer to the next.
19. Aloha
Protocol for satellite and terrestrial radio transmissions. In pure Aloha, a user can communicate at any time, but risks collisions with other users’ messages. Slotted Aloha reduces the chance of collisions by dividing the channel into time slots and requiring that the user send only at the beginning of a time slot.
20. Address Resolution Protocol(ARP) ARP is a used with the IP for mapping a 32-bit Internet Protocol address to a MAC address that is recognized in the local network specified in RFC 826. 148
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10.34 Computer Networks Modern world scenario is ever changing. Data Communication and network have changed the way business and other daily affair works. Now, they highly rely on computer networks and internetwork. A set of devices often mentioned as nodes connected by media link is called a Network. A node can be a device which is capable of sending or receiving data generated by other nodes on the network like a computer, printer etc. These links connecting the devices are called Communication channels. Computer network is a telecommunication channel using which we can share data with other computers or devices, connected to the same network. It is also called
Data Network. The best example of computer network is Internet. Computer network does not mean a system with one Control Unit connected to multiple other systems as its slave. That is Distributed system, not Computer Network. A network must be able to meet certain criteria, these are mentioned below: Performance Reliability Scalability Computer Networks: Performance It can be measured in the following ways: Transit time: It is the time taken to travel a message from one device to another. Response time: It is defined as the time elapsed between enquiry and response. Other ways to measure performance are: Efficiency of software Computer Studies Guide Book
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Number of users Capability of connected hardware Computer Networks: Reliability It decides the frequency at which network failure take place. More the failures are, less is the network’s reliability. Computer Networks: Security It refers to the protection of data from any unauthorized user or access. While travelling through network, data passes many layers of network, and data can be traced if attempted. Hence security is also a very important characteristic for Networks. Properties of a Good Network Interpersonal Communication: We can communicate with each other efficiently and easily. Example: emails, chat rooms, video conferencing etc., all of these are possible because of computer networks. Resources can be shared: We can share physical resources by making them available on a network such as printers, scanners etc. Sharing files, data: Authorized users are allowed to share the files on the network. Basic Communication Model A Communication model is used to exchange data between two parties. For example: communication between a computer, server and telephone (through modem).
Communication Model: Source Data to be transmitted is generated by this device, example: telephones, personal computers etc. Communication Model: Transmitter The data generated by the source system is not directly transmitted in the form its generated. The transmitter transforms and encodes the data in such a form to produce electromagnetic waves or signals. Communication Model: Transmission System A transmission system can be a single transmission line or a complex network connecting source and destination. 150
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Communication Model: Receiver Receiver accepts the signal from the transmission system and converts it into a form which is easily managed by the destination device. Communication Model: Destination Destination receives the incoming data from the receiver. Data Communication The exchange of data between two devices through a transmission medium is called Data Communication. The data is exchanged in the form of 0’s and 1’s. The transmission medium used is wire cable. For data communication to occur, the communication device must be a part of a communication system. Data Communication has two types - Local and Remote which are discussed below: Data Communication: Local Local communication takes place when the communicating devices are in the same geographical area, same building, or face-to-face etc. Data Communication: Remote Remote communication takes place over a distance i.e. the devices are farther. The effectiveness of a data communication can be measured through the following features: Delivery: Delivery should be done to the correct destination. Timeliness: Delivery should be on time. Accuracy: Data delivered should be accurate.
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Message: It is the information to be delivered. Sender: Sender is the person who is sending the message. Receiver: Receiver is the person to whom the message is being sent to. Medium: It is the medium through which the message is sent. For example: A Modem. Protocol: These are some set of rules which govern data communication. Uses of Computer Networks Had it not been of high importance, nobody would have bothered connecting computers over a network. Let’s start exploring the uses of Computer Networks with some traditional use cases at companies and for individuals and then move on to the recent developments in the area of mobile users and home networking. Computer Networks: Business Applications Following are some business applications of computer networks: Resource Sharing: The goal is to make all programs, equipment’s (like printers etc.), and especially data, available to anyone on the network without regard to the physical location of the resource and the user. Server-Client model:
One can imagine a company’s information system as consisting of one or more databases and some employees who need to access it remotely. In this model, the data is stored on powerful computers called Servers. Often these are centrally housed and maintained by a system administrator. In contrast, the employees have simple machines, called Clients, on their desks, using which they access remote data. Communication Medium: 152
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A computer network can provide a powerful communication medium among employees. Virtually every company that has two or more computers now has e-mail (electronic mail), which employees generally use for a great deal of daily communication
E-Commerce: A goal that is starting to become more important in businesses is doing business with consumers over the Internet. Airlines, bookstores and music vendors have discovered that many customers like the convenience of shopping from home. This sector is expected to grow quickly in the future.
The most popular forms are listed in the below figure:
Computer Networks: Home Applications Some of the most important uses of the Internet for home users are as follows: Access to remote information Person-to-person communication Interactive entertainment Electronic commerce Computer Studies Guide Book
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Computer Networks: Mobile Users
Mobile computers, such as notebook computers and Mobile phones, are one of the fastest-growing segments of the entire computer industry. Although wireless networking and mobile computing are often related, they are not identical, as the below figure shows. Line Configuration in Computer Networks A Network is nothing but a connection made through connection links between two or more devices. Devices can be a computer, printer or any other device that is capable to send and receive data. There are two ways to connect the devices: Point-to-Point connection Multipoint connection
Point-To-Point Connection It is a protocol which is used as a communication link between two devices. It is simple to establish. The most common example for Point-to-Point connection (PPP) is a computer connected by telephone line. We can connect the two devices by means of a pair of wires or using a microwave or satellite link. 154
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Example: Point-to-Point connection between remote control and Television for changing the channels.
Multipoint Connection It is also called Multi-drop configuration. In this connection two or more devices share a single link. There are two kinds of Multipoint Connections: If the links are used simultaneously between many devices, then it is spatially shared line configuration. If user takes turns while using the link, then it is time shared (temporal) line configuration.
10.35 Types of Network Topology Network Topology is the schematic description of a network arrangement, connecting various nodes(sender and receiver) through lines of connection. BUS Topology Bus topology is a network type in which every computer and network device is connected to single cable. When it has exactly two endpoints, then it is called Linear Bus topology.
Features of Bus Topology It transmits data only in one direction. Every device is connected to a single cable
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Advantages of Bus Topology It is cost effective. Cable required is least compared to other network topology. Used in small networks. It is easy to understand. Easy to expand joining two cables together.
Disadvantages of Bus Topology Cables fails then whole network fails. If network traffic is heavy or nodes are more the performance of the network decreases. Cable has a limited length. It is slower than the ring topology. RING Topology It is called ring topology because it forms a ring as each computer is connected to another computer, with the last one connected to the first. Exactly two neighbors for each device.
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Features of Ring Topology A number of repeaters are used for Ring topology with large number of nodes, because if someone wants to send some data to the last node in the ring topology with 100 nodes, then the data will have to pass through 99 nodes to reach the 100th node. Hence to prevent data loss repeaters are used in the network. The transmission is unidirectional, but it can be made bidirectional by having 2 connections between each Network Node, it is called Dual Ring Topology. In Dual Ring Topology, two ring networks are formed, and data flow is in opposite direction in them. Also, if one ring fails, the second ring can act as a backup, to keep the network up. Data is transferred in a sequential manner that is bit by bit. Data transmitted, has to pass through each node of the network, till the destination node.
Advantages of Ring Topology Transmitting network is not affected by high traffic or by adding more nodes, as only the nodes having tokens can transmit data. Cheap to install and expand
Disadvantages of Ring Topology Troubleshooting is difficult in ring topology. Adding or deleting the computers disturbs the network activity. Failure of one computer disturbs the whole network.
STAR Topology In this type of topology all the computers are connected to a single hub through a cable. This hub is the central node and all others nodes are connected to the central node.
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Features of Star Topology Every node has its own dedicated connection to the hub. Hub acts as a repeater for data flow. Can be used with twisted pair, Optical Fiber or coaxial cable.
Advantages of Star Topology
Fast performance with few nodes and low network traffic. 158
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Hub can be upgraded easily. Easy to troubleshoot. Easy to setup and modify. Only that node is affected which has failed, rest of the nodes can work smoothly.
Disadvantages of Star Topology Cost of installation is high. Expensive to use. If the hub fails then the whole network is stopped because all the nodes depend on the hub. Performance is based on the hub that is it depends on its capacity MESH Topology It is a point-to-point connection to other nodes or devices. All the network nodes are connected to each other. Mesh has n(n-1)/2 physical channels to link n devices. There are two techniques to transmit data over the Mesh topology, they are: Routing Flooding
MESH Topology: Routing In routing, the nodes have a routing logic, as per the network requirements. Like routing logic to direct the data to reach the destination using the shortest distance. Or, routing logic which has information about the broken links, and it avoids those nodes etc. We can even have routing logic, to re-configure the failed nodes. MESH Topology: Flooding In flooding, the same data is transmitted to all the network nodes; hence no routing logic is required. The network is robust, and the it’s very unlikely to lose the data. But it leads to unwanted load over the network.
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Types of Mesh Topology Partial Mesh Topology:In this topology some of the systems are connected in the same fashion as mesh topology but some devices are only connected to two or three devices. Full Mesh Topology:Each and every nodes or devices are connected to each other. Features of Mesh Topology •
Fully connected.
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Robust.
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Not flexible.
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Advantages of Mesh Topology
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Each connection can carry its own data load.
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It is robust.
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Fault is diagnosed easily.
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Provides security and privacy.
Disadvantages of Mesh Topology Installation and configuration is difficult. Cabling cost is more. 160
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Bulk wiring is required. TREE Topology It has a root node and all other nodes are connected to it forming a hierarchy. It is also called hierarchical topology. It should at least have three levels to the hierarchy.
Features of Tree Topology Ideal if workstations are located in groups. Used in Wide Area Network.
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Advantages of Tree Topology Extension of bus and star topologies. Expansion of nodes is possible and easy. Easily managed and maintained. Error detection is easily done.
Disadvantages of Tree Topology Heavily cabled. Costly. If more nodes are added maintenance is difficult. Central hub fails, network fails.
HYBRID Topology It is two different types of topologies which is a mixture of two or more topologies. For example if in an office in one department ring topology is used and in another star topology is used, connecting these topologies will result in Hybrid Topology (ring topology and star topology). Features of Hybrid Topology It is a combination of two or topologies Inherits the advantages and disadvantages of the topologies included 162
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Advantages of Hybrid Topology Reliable as Error detecting and trouble shooting is easy. Effective. Scalable as size can be increased easily. Flexible. Disadvantages of Hybrid Topology Complex in design. Costly.
10.36 Transmission Modes in Computer Networks Transmission mode refers to the mechanism of transferring of data between two devices connected over a network. It is also called Communication Mode. These modes direct the direction of flow of information. There are three types of transmission modes. They are: Simplex Mode Half duplex Mode Computer Studies Guide Book
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Full duplex Mode
SIMPLEX Mode In this type of transmission mode, data can be sent only in one direction i.e. communication is unidirectional. We cannot send a message back to the sender. Unidirectional communication is done in Simplex Systems where we just need to send a command/ signal, and do not expect any response back. Examples of simplex Mode are loudspeakers, television broadcasting, television and remote, keyboard and monitor etc.
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HALF DUPLEX Mode Half-duplex data transmission means that data can be transmitted in both directions on a signal carrier, but not at the same time. For example, on a local area network using a technology that has half-duplex transmission, one workstation can send data on the line and then immediately receive data on the line from the same direction in which data was just transmitted. Hence half-duplex transmission implies a bidirectional line (one that can carry data in both directions) but data can be sent in only one direction at a time. Example of half duplex is a walkie- talkie in which message is sent one at a time but messages are sent in both the directions.
FULL DUPLEX Mode In full duplex system we can send data in both the directions as it is bidirectional at the same time in other words, data can be sent in both directions simultaneously. Example of Full Duplex is a Telephone Network in which there is communication between two persons by a telephone line, using which both can talk and listen at the same time.
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10.37 Transmission Mediums in Computer Networks Data is represented by computers and other telecommunication devices using signals. Signals are transmitted in the form of electromagnetic energy from one device to another. Electromagnetic signals travel through vacuum, air or other transmission mediums to move from one point to another (from sender to receiver). Electromagnetic energy (includes electrical and magnetic fields) consists of power, voice, visible light, radio waves, ultraviolet light, gamma rays etc. Transmission medium is the means through which we send our data from one place to another. The first layer (physical layer) of Communication Networks OSI Seven layer model is dedicated to the transmission media, we will study the OSI Model later. Computer Studies Guide Book
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Factors to be considered while selecting a Transmission Medium Transmission Rate Cost and Ease of Installation
Resistance to Environmental Conditions Distances Bounded or Guided Transmission Media Guided media, which are those that provide a conduit from one device to another, include Twisted-Pair Cable, Coaxial Cable, and Fibre-Optic Cable. A signal travelling along any of these media is directed and contained by the physical limits of the medium. Twisted-pair and coaxial cable use metallic (copper) conductors that accept and transport signals in the form of electric current. Optical fibre is a cable that accepts and transports signals in the form of light. Twisted Pair Cable This cable is the most commonly used and is cheaper than others. It is lightweight, cheap, can be installed easily, and they support many different types of network. Some important points: Its frequency range is 0 to 3.5 kHz. 166
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Typical attenuation is 0.2 dB/Km @ 1 kHz. Typical delay is 50 Âľs/km.
Repeater spacing is 2km. A twisted pair consists of two conductors (normally copper), each with its own plastic insulation, twisted together. One of these wires is used to carry signals to the receiver, and the other is used only as ground reference. The receiver uses the difference between the two. In addition to the signal sent by the sender on one of the wires, interference (noise) and crosstalk may affect both wires and create unwanted signals. If the two wires are parallel, the effect of these unwanted signals is not the same in both wires because they are at different locations relative to the noise or crosstalk sources. This results in a difference at the receiver. Twisted Pair is of two types: Unshielded Twisted Pair (UTP) Shielded Twisted Pair (STP) Unshielded Twisted Pair Cable It is the most common type of telecommunication when compared with Shielded Twisted Pair Cable which consists of two conductors usually copper, each with its own colour plastic insulator. Identification is the reason behind coloured plastic insulation. UTP cables consist of 2 or 4 pairs of twisted cable. Cable with 2 pair use RJ-11 connector and 4 pair cable use RJ-45 connector. Advantages of Unshielded Twisted Pair Cable Computer Studies Guide Book
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Installation is easy Flexible Cheap It has high speed capacity, 100 meter limit Higher grades of UTP are used in LAN technologies like Ethernet. It consists of two insulating copper wires (1mm thick). The wires are twisted together in a helical form to reduce electrical interference from similar pair. Disadvantages of Unshielded Twisted Pair Cable Bandwidth is low when compared with Coaxial Cable Provides less protection from interference. Shielded Twisted Pair Cable This cable has a metal foil or braided-mesh covering which encases each pair of insulated conductors. Electromagnetic noise penetration is prevented by metal casing. Shielding also eliminates crosstalk (explained in KEY TERMS Chapter). It has same attenuation as unshielded twisted pair. It is faster the unshielded and
coaxial cable. It is more expensive than coaxial and unshielded twisted pair. Advantages of Shielded Twisted Pair Cable Easy to install Performance is adequate Can be used for Analog or Digital transmission 168
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Increases the signaling rate Higher capacity than unshielded twisted pair Eliminates crosstalk
Disadvantages of Shielded Twisted Pair Cable Difficult to manufacture
Heavy
Performance of Shielded Twisted Pair Cable One way to measure the performance of twisted-pair cable is to compare attenuation versus frequency and distance. As shown in the below figure, a twisted-pair cable can pass a wide range of frequencies. However, with increasing frequency, the attenuation, measured in decibels per kilometer (dB/km), sharply increases with frequencies above 100 kHz. Note that gauge is a measure of the thickness of the wire.
Applications of Shielded Twisted Pair Cable In telephone lines to provide voice and data channels. The DSL lines that are used by the telephone companies to provide high-data-rate connections also use the high-bandwidth capability of unshielded twisted-pair cables. Local Area Network, such as 10Base-T and 100Base-T, also use twisted-pair cables.
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Coaxial is called by this name because it contains two conductors that are parallel to each other. Copper is used in this as centre conductor which can be a solid wire or a standard one. It is surrounded by PVC installation, a sheath which is encased in an outer conductor of metal foil, barid or both. Outer metallic wrapping is used as a shield against noise and as the second conductor which completes the circuit. The outer conductor is also encased in an insulating sheath. The outermost part is the plastic cover which protects the whole cable.
Coaxial Cable Standards Coaxial cables are categorized by their Radio Government (RG) ratings. Each RG number denotes a unique set of physical specifications, including the wire gauge of the inner conductor, the thickness and the type of the inner insulator, the construction of the shield, and the size and type of the outer casing. Each cable defined by an RG rating is adapted for a specialized function, as shown in the table below:
Coaxial Cable Connectors To connect coaxial cable to devices, we need coaxial connectors. The most common type of connector used today is the Bayonet Neill-Concelman (BNC) connector. The below figure shows 3 popular types of these connectors: the BNC Connector, the BNC T connector and the BNC terminator.
The BNC connector is used to connect the end of the cable to the device, such as a TV set. The BNC T connector is used in Ethernet networks to branch out to a connection to a computer or other device. The BNC terminator is used at the end of the cable to prevent the reflection of the signal.
There are two types of Coaxial cables: Base-Band This is a 50 ohm (ℌ) coaxial cable which is used for digital transmission. It is mostly used for LAN’s. Baseband transmits a single signal at a time with very high speed. The major drawback is that it needs amplification after every 1000 feet. 170
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Broad-Band This uses analog transmission on standard cable television cabling. It transmits several simultaneous signal using different frequencies. It covers large area when compared with Baseband Coaxial Cable.
Advantages of Coaxial Cable •
Bandwidth is high
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Used in long distance telephone lines.
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Transmits digital signals at a very high rate of 10Mbps.
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Much higher noise immunity
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Data transmission without distortion.
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The can span to longer distance at higher speeds as they have better shielding when compared to twisted pair cable
Disadvantages of Coaxial Cable Single cable failure can fail the entire network. Difficult to install and expensive when compared with twisted pair. If the shield is imperfect, it can lead to grounded loop. Computer Studies Guide Book
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Performance of Coaxial Cable We can measure the performance of a coaxial cable in same way as that of Twisted Pair Cables. From the below figure, it can be seen that the attenuation is much higher in coaxial cable than in twisted-pair cable. In other words, although coaxial cable has a much higher bandwidth, the signal weakens rapidly and requires the frequent use of repeaters.
Applications of Coaxial Cable Coaxial cable was widely used in analog telephone networks, where a single coaxial network could carry 10,000 voice signals. Cable TV networks also use coaxial cables. In the traditional cable TV network, the entire network used coaxial cable. Cable TV uses RG-59 coaxial cable. In traditional Ethernet LANs. Because of it high bandwidth, and consequence high data rate, coaxial cable was chosen for digital transmission in early Ethernet LANs. The 10Base-2, or Thin Ethernet, uses RG-58 coaxial cable with BNC connectors to transmit data at 10Mbps with a range of 185 m.
Fiber Optic Cable A fibre-optic cable is made of glass or plastic and transmits signals in the form of 172
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light. For better understanding we first need to explore several aspects of the nature of light. Light travels in a straight line as long as it is mobbing through a single uniform substance. If ray of light travelling through one substance suddenly enters another substance (of a different density), the ray changes direction.
Propagation Modes of Fiber Optic Cable Current technology supports two modes (Multimode and Single mode) for propagating light along optical channels, each requiring fibre with different physical characteristics. Multimode can be implemented in two forms: Step-index and Graded-index.
Multimode Propagation Mode Multimode is so named because multiple beams from a light source move through the core in different paths. How these beams move within the cable depends on the structure of the core as shown in the below figure. In multimode step-index fibre, the density of the core remains constant from the centre to the edges. A beam of light moves through this constant density in a straight line until it reaches the interface of the core and the cladding.
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The term step-index refers to the suddenness of this change, which contributes to the distortion of the signal as it passes through the fibre. In multimode graded-index fibre, this distortion gets decreases through the cable. The word index here refers to the index of refraction. This index of refraction is related to the density. A graded-index fibre, therefore, is one with varying densities. Density is highest at the centre of the core and decreases gradually to its lowest at the edge.
Single Mode Single mode uses step-index fibre and a highly focused source of light that limits beams to a small range of angles, all close to the horizontal. The single-mode fibre itself is manufactured with a much smaller diameter than that of multimode fibre, and with substantially lower density. The decrease in density results in a critical angle that is close enough to 90 degree to make the propagation of beams almost horizontal.
Fibre Sizes for Fiber Optic Cable Optical fibres are defined by the ratio of the diameter or their core to the diameter of their cladding, both expressed in micrometers. The common sizes are shown in the figure below: Fiber Optic Cable Connectors There are three types of connectors for fibre-optic cables, as shown in the figure below. The Subscriber Channel (SC) connector is used for cable TV. It uses push/pull locking system. The Straight-Tip (ST) connector is used for connecting cable to the networking devices. MT-RJ is a connector that is the same size as RJ45.
Advantages of Fibre Optic Cable •
Fibre optic has several advantages over metallic cable:
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Higher bandwidth
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Less signal attenuation
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Immunity to electromagnetic interference
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Resistance to corrosive materials
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Light weight
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Greater immunity to tapping
Disadvantages of Fiber Optic Cable •
There are some disadvantages in the use of optical fibre:
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Installation and maintenance
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Unidirectional light propagation
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High Cost
Performance of Fibre Optic Cable Attenuation is flatter than in the case of twisted-pair cable and coaxial cable. The
performance is such that we need fewer (actually one tenth as many) repeaters when we use the fibre-optic cable.
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Applications of Fibre Optic Cable •
Often found in backbone networks because its wide bandwidth is cost-effective.
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Some cable TV companies use a combination of optical fibre and coaxial cable thus creating a hybrid network.
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Local-area Networks such as 100Base-FX network and 1000Base-X also use fibre-optic cable.
Un-Bounded or Un-Guided Transmission Media Unguided medium transport electromagnetic waves without using a physical conductor. This type of communication is often referred to as wireless communication. Signals are normally broadcast through free space and thus are available to anyone who has a device capable of receiving them. The below figure shows the part of the electromagnetic spectrum, ranging from 3 kHz to 900 THz, used for wireless communication. We can divide wireless transmission into three broad groups: •
Radio waves
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Micro waves
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Infrared wave
Radio Waves Electromagnetic waves ranging in frequencies between 3 KHz and 1 GHz are normally called radio waves.Radio waves are omnidirectional. When an antenna transmits radio waves, they are propagated in all directions. This means that the sending and receiving antennas do not have to be aligned. A sending antenna sends waves that can be received by any receiving antenna. The omnidirectional property has disadvantage, too. The radio waves transmitted by one antenna are susceptible to interference by another antenna that may send signal suing the same frequency or band. Radio waves, particularly with those of low and medium frequencies, can penetrate walls. This characteristic can be both an advantage and a disadvantage. It is an advantage because; an AM radio can receive signals inside a building. It is a disadvantage because we cannot isolate a communication to just inside or outside a building. 176
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Omnidirectional Antenna for Radio Waves Radio waves use omnidirectional antennas that send out signals in all directions.
Applications of Radio Waves The omnidirectional characteristics of radio waves make them useful for multicasting in which there is one sender but many receivers. AM and FM radio, television, maritime radio, cordless phones, and paging are examples of multicasting.
Micro Waves Electromagnetic waves having frequencies between 1 and 300 GHz are called micro waves. Micro waves are unidirectional. When an antenna transmits microwaves, they can be narrowly focused. This means that the sending and receiving antennas need to be aligned. The unidirectional property has an obvious advantage. A pair of antennas can be aligned without interfering with another pair of aligned antennas.
The following describes some characteristics of microwaves propagation: •
Microwave propagation is line-of-sight. Since the towers with the mounted antennas need to be in direct sight of each other, towers that are far apart need Computer Studies Guide Book
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to be very tall. •
Very high-frequency microwaves cannot penetrate walls. This characteristic can be a disadvantage if receivers are inside the buildings.
•
The microwave band is relatively wide, almost 299 GHz. Therefore, wider sub-bands can be assigned and a high date rate is possible.
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Use of certain portions of the band requires permission from authorities.
Unidirectional Antenna for Micro Waves Microwaves need unidirectional antennas that send out signals in one direction. Two types of antennas are used for microwave communications: Parabolic Dish and Horn. A parabolic antenna works as a funnel, catching a wide range of waves and directing
them to a common point. In this way, more of the signal is recovered than would be possible with a single-point receiver. A horn antenna looks like a gigantic scoop. Outgoing transmissions are broadcast up a stem and deflected outward in a series of narrow parallel beams by the curved 178
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head. Received transmissions are collected by the scooped shape of the horn, in a manner similar to the parabolic dish, and are deflected down into the stem.
Applications of Micro Waves Microwaves, due to their unidirectional properties, are very useful when unicast (one-to-one) communication is needed between the sender and the receiver. They are used in cellular phones, satellite networks and wireless LANs. There are 2 types of Microwave Transmission: •
Terrestrial Microwave
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Satellite Microwave
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•
Used for long distance telephone communication
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Carries 1000’s of voice channels at the same time
Disadvantages of Microwave Transmission •
It is very costly
Terrestrial Microwave For increasing the distance served by terrestrial microwave, repeaters can be installed with each antenna .The signal received by an antenna can be converted into transmittable form and relayed to next antenna as shown in below figure. It is an example of telephone systems all over the world
There are two types of antennas used for terrestrial microwave communication: Parabolic Dish Antenna In this every line parallel to the line of symmetry reflects off the curve at angles in a way that they intersect at a common point called focus. This antenna is based on geometry of parabola. Horn Antenna It is a like gigantic scoop. The outgoing transmissions are broadcast up a stem and deflected outward in a series of narrow parallel beams by curved head.
Satellite Microwave This is a microwave relay station which is placed in outer space. The satellites are launched either by rockets or space shuttles carry them. These are positioned 36000 Km above the equator with an orbit speed that exactly matches the rotation speed of the earth. As the satellite is positioned in a geo-synchronous orbit, it is stationery relative to earth and always stays over the same point on the ground. This is usually done to allow ground stations to aim antenna at a fixed point in the sky. 180
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Features of Satellite Microwave •
Bandwidth capacity depends on the frequency used.
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Satellite microwave deployment for orbiting satellite is difficult.
Advantages of Satellite Microwave •
Transmitting station can receive back its own transmission and check whether the satellite has transmitted information correctly.
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A single microwave relay station which is visible from any point.
Disadvantages of Satellite Microwave •
Satellite manufacturing cost is very high
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Cost of launching satellite is very expensive
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Infrared Waves Infrared waves, with frequencies from 300 GHz to 400 THz, can be used for short-range communication. Infrared waves, having high frequencies, cannot penetrate walls. This advantageous characteristic prevents interference between one system and another, a short-range communication system in on room cannot be affected by another system in the next room.
When we use infrared remote control, we do not interfere with the use of the remote by our neighbours. However, this same characteristic makes infrared signals useless for long-range communication. In addition, we cannot use infrared waves outside a building because the sun’s rays contain infrared waves that can interfere with the communication.
Applications of Infrared Waves The infrared band, almost 400 THz, has an excellent potential for data transmission.
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Such a wide bandwidth can be used to transmit digital data with a very high data rate. The Infrared Data Association (IrDA), an association for sponsoring the use of infrared waves, has established standards for using these signals for communication between devices such as keyboards, mouse, PCs and printers. Infrared signals can be used for short-range communication in a closed area using line-of-sight propagation.
10.38 Network Devices
Repeaters The number of nodes on a network and the length of cable used Influence the quality of communication on the network Attenuation– The degradation of signal clarity Repeaters Work against attenuation by repeating signals that they receive on a
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Network Typically cleaning and regenerating the digital transmission in the process
Note that on analog networks, devices that boost the signal are called Amplifiers These devices do not have the same signal regeneration capabilities as repeaters– Because they must maintain the shape of the received signal Repeaters work in the Physical layer (layer 1) - On optical networks, signal amplification is handled by optical repeaters some repeaters can be used to connect two physically different types of Cabling Hubs
Hub– Generic connection device used to tie several networking cables together to create a link between different stations on a network Active hubs– Amplify or repeat signals that pass through them Passive hub– Merely connects cables on a network and provides no signal regeneration Topology refers to the physical layout of network cable and devices Advantages of Hub Can extend a network’s total distance Do not seriously affect network performance 184
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Certain repeaters can connect networks using different physical media Disadvantages of Hub Cannot connect different network architectures, such as Token Ring and Ethernet Do not reduce network traffic
They repeat everything they receive Do not segment the network Do not reformat data structures Cannot connect networks that require different types of frames Wireless access points Provide cell-based areas where wireless clients such as laptops and PDAs can connect to the network By associating with the access point Operate at the Physical and Data Link layers of the OSI model– In most respects, a wireless access point functions exactly like a hub Wireless Connectivity Access points typically broadcast their network name The Service Set Identifier (SSID) The network name When wireless clients are powered on, they begin scanning the air space for available access points Computer Studies Guide Book
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They detect the broadcasted SSID of the various access points in the area Attempt to associate with the one that has the highest signal level and the lowest error rate
If the system is open, the client is accepted by the access point and begins communications When SSID is not broadcasted– Wireless clients must already be configured with the correct SSID The client will send out a probe request with– Configured SSID – Access point with 186
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that SSID configured will allow the client to associate
Wireless Security Measures While security is always necessary in WLANs due to the broadcast nature of the medium These devices are not designed to handle the most complex and highest levels of security The most important reason to implement security on your WLAN at home Others in your neighborhood do not use your bandwidth for free Bridges Operate at the Data Link layer of the OSI model Filter traffic between network segments by examining the destination MAC address Based on the destination MAC address, the bridge either forwards or discards the frame Reduce network traffic by keeping local traffic on the local segment Broadcast Frame destined for all computers on the network
Transparent Bridges Also called learning bridges– Because they build a table of MAC addresses as they receive frames They “learn” which addresses are on which segments Computer Studies Guide Book
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The bridge uses the source MAC addresses to determine which addresses are on which segments
By determining a frame’s origin, the bridge knows where to send frames in the future Ethernet networks mainly use transparent bridges
Advantages •
Can extend a network by acting as a repeater
•
Can reduce network traffic on a segment by subdividing network communications
•
Increase the available bandwidth to individual nodes because fewer nodes share a collision domain
•
Reduce collisions
•
Some bridges connect networks using different media types and architectures
Disadvantages •
Slower than repeaters and hubs
•
Extra processing by viewing MAC addresses
•
Forward broadcast frames indiscriminately, so they do not filter broadcast traffic
•
More expensive than repeaters and hubs
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•
Broadcast storm
•
When two or more stations engage in the transmission of excessive broadcast traffic
Switches Operate at the Data Link layer of the OSI model Increase network performance by reducing the number of frames transmitted to the rest of the network Switch opens a virtual circuit between the source and the destination Prevents communications between just two computers from being broadcast to every computer on the network or segment Called micro segmentation When two machines have a virtual circuit They do not have to share the bandwidth with any other computers Multiple virtual circuits can be in use at the same time, each with its own full bandwidth Called “switched bandwidth” When machines must share a wire and compete for available bandwidth with other machines, they experience contention. Computer Studies Guide Book
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Advantages of the switch •
Switches increase available network bandwidth
•
Switches reduce the workload on individual computers
•
Switches increase network performance
•
Networks that include switches experience fewer frame collisions because switches create collision domains for each connection (a process called micro segmentation)
•
Switches connect directly to workstations
Disadvantages of the switch Switches are significantly more expensive than bridges Network connectivity problems can be difficult to trace through a switch 190
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Broadcast traffic may be troublesome.
Routers
Routers Operate at the Network layer of the OSI model Provide filtering and network traffic control on LANs and WANs Can connect multiple segments and multiple networks Internetworks– Networks connected by multiple routers Similar to switches and bridges in that they segment a network and filtertraffic Routers use the logical address
Advantages of the router •
Can connect different network architectures, such as Ethernet and Token Ring
•
Can choose the best path across an internetwork using dynamic routing techniques
•
Reduce network traffic by creating collision domains
•
Reduce network traffic by creating broadcast domains Computer Studies Guide Book
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Disadvantages of the router •
Routers work only with routable network protocols; most but not all protocols are routable
•
Routers are more expensive than other devices
•
Dynamic router communications (inter-router communication) cause additional network overhead, which results in less bandwidth for user data
•
Routers are slower than other devices because they must analyze a data transmission from the Physical through the Network layer
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•
Hybrid device
•
Functions as both a bridge for non-routable protocols and a router for routable protocols
•
Provides the best attributes of both a bridge and a router
•
Operates at both the Data Link and Network layers and can replace separate bridges and routers
Gateway •
Usually a combination of hardware and software
•
Translates between different protocol suites
•
Has the most negative effect on network performance Packets must be rebuilt not just at the lower levels but at thevery upper levels
•
So that actual data content can be converted into a format the destination can process
•
Creates the most latency
Ethernet Operations Ethernet - A network access method (or media access method) originated by the University of Hawaii Later adopted by Xerox Corporation, and standardized as IEEE 802.3 in the early 1980s Today, Ethernet is the most commonly implemented media access method in new LANs CSMA/CD Carrier Sense Multiple Access with Collision Detection (CSMA/CD) Used by Ethernet to prevent data packets from colliding on the network Allows any station connected to a network to transmit anytime there is not already a transmission on the wire After each transmitted signal, each station must wait a minimum of 9.6 microsecComputer Studies Guide Book
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onds before transmitting another frame Called the inter frame gap (IFG), or inter packet gap (IPG)
LESSON REVIEW 1.
What is an internet?
2.
Give examples of browsers
3.
List the domain types
4.
Outline the search engines
5.
Give the meaning of the following
- LAN - WAN - MAN - WI-FI 6.
Outline the following by giving the full meaning
- HTTP - HTML - ISP - IP - URL 7.
Explain how computer data travels over telephone lines.
8.
Explain a modem’s function.
9.
Describe the types of network topologies with their characteristics
10.
List four features you should consider when evaluating modems.
11.
Differentiate four types of digital telephone services.
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Samplee Test PaperO One
1. W What is a compuuter? (4marks) (A A) It is a technoology (B B) It is an electtronic device ussed to process data d to producee information (C C) Is a machinee used by learners to play gam mes (D D) Is a machinee used as a televvision 2. Leeila a class six pupil wanted too start a compuuter, what couldd have been the ideal procedurres to start the coomputer? (4markks) (A A) Socket screen u.p.sc.p.uu c.p.u screen (B B) U.p.s socket screenn (C C) U.p.sc.p.u (D D) Screen c.p.u u.p..s soccket 3. Which W of the following is NOT T a good environnmental conditiion for the com mputers?(4markks) (A A) Ventilation (B B) Fan (C C) Air Conditiooners (D D) Dust 4. How H many buttoons are there onn a computer moouse? (4markks) (A A) Two (B B) Three (C C) Four (D D) Five 5. Name N the follow wing computer hardware h parts (12maarks)
.......................................
…………………………………………………
…… ………………… ………………… …………….
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……………………………………… ………………
6. W Which of the following computter programmess are used for tyyping (A A) Paint (B B) Ms. Excel (C C) Ms. PowerPPoint (D D) Type faster 7. How H many keys are there on the computer keyyboard (A A) 106 (B B) 204 (C C) 104 (D D) 404 1. Which W one of thee following keyys is the longestt key on the com mputer keyboarrd (A A) Spacebar keey (B B) Enter key (C C) Delete key (D D) Tab key
12.
Describe one potential use for a home network
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(4markks)
(4markks)
(4MARKS)
SampleTest PaperTwo 1. What is a computer? (4marks) …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… ……………………………………………………………………………………………… 2. Which are the desktop features? (6marks) i. ii. iii. 3. What are the mouse techniques (10marks) I. ………………………………………………………………………………………………………… ………………………………………………………………………………………………………… II. ………………………………………………………………………………………………………… ………………………………………………………………………………………………………… III. ………………………………………………………………………………………………………… ………………………………………………………………………………………………………… IV. ………………………………………………………………………………………………………… ………………………………………………………………………………………………………… V. ………………………………………………………………………………………………………… ………………………………………………………………………………………………………… 4. In the space provided below draw, name and give the functions of the computer hardware parts (24marks) Image
Image
Name………………………………………..
Name……………………………………….
Function…………………………………………..
Function …………………………………………..
Image
Image
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Name ……………………………………… Function……………………………………. 197
5. W What are the goood environmenttal conditions for fo the computeers? I. II. I III. I IV.
(88marks)
1. Define D the follow wing terms as used u in computeer studies
(99marks)
i.
Compuuter ……… ………………… ………………… ………………… ………………… ………………… ………………… …… ……… ………………… ………………… ………………… ………………… ………………… ………………… …… ……… ………………… ………………… ………………… ………………… ………………… ………………… ……
ii.
Softwarre ……… ………………… ………………… ………………… ………………… ………………… ………………… …… ……… ………………… ………………… ………………… ………………… ………………… ………………… …… ……… ………………… ………………… ………………… ………………… ………………… ………………… ……
iii.
Hardwaare ……… ………………… ………………… ………………… ………………… ………………… ………………… …… ……… ………………… ………………… ………………… ………………… ………………… ………………… …… ……… ………………… ………………… ………………… ………………… ………………… ………………… …… N the follow wing mouse partts (6markks) 6. Name
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SampleTest Paper Three 7. What is a computer? (4marks) …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… 8. Which are the desktop features? (6marks) iv. v. vi. 9. What are the mouse techniques (10marks) VI. ………………………………………………………………………………………………………… ………………………………………………………………………………………………………… VII. ………………………………………………………………………………………………………… ………………………………………………………………………………………………………… VIII. ………………………………………………………………………………………………………… ………………………………………………………………………………………………………… IX. ………………………………………………………………………………………………………… ………………………………………………………………………………………………………… X. ………………………………………………………………………………………………………… ………………………………………………………………………………………………………… 10. List the FIVE keyboard arrangement groups (5marks) i. ii. iii. iv. v. 11. Name FOUR good environmental conditions for computers (4marks) i. ii. iii. iv. 12. What are the functions of the following keys (15 marks) i. Spacebar key ………………………………………………………………………………………………………… ………………………………………………………………………………………………………… ii. Backspace key ………………………………………………………………………………………………………… ………………………………………………………………………………………………………… 174 | P a g e Computer Studies Guide Book
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iii.
Caps lock key ………………………………………………………………………………………………………… …………………………………………………………………………………………………………
iv.
Enter key ………………………………………………………………………………………………………… ………………………………………………………………………………………………………… v. Tab key ………………………………………………………………………………………………………… ………………………………………………………………………………………………………… 13. In the table below List and give the functions of the computer hardware parts (10marks) No. Hardware Function i. ii. iii. Iv v. 14. List FIVE categories of computers i. ii. iii. iv. 15. List some of the software programmes used in the computer system I. II. III. IV. V.
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(5marks)
(5marks)
SampleTest Paper Four 1. What is a computer?
(4marks)
……………………………………………………………………………………………………………………………… ……………………………………………………………………………………………………………………………… ……………………………………………………………………………………………………………………………… 2. What are the mouse techniques (10marks) XI. ………………………………………………………………………………………………………… ………………………………………………………………………………………………………… XII. ………………………………………………………………………………………………………… ………………………………………………………………………………………………………… XIII. ………………………………………………………………………………………………………… ………………………………………………………………………………………………………… XIV. ………………………………………………………………………………………………………… ………………………………………………………………………………………………………… XV. ………………………………………………………………………………………………………… ………………………………………………………………………………………………………… 3. List the FIVE keyboard arrangement groups (5marks) vi. vii. viii. ix. x. 4. Name FOUR good environmental conditions for computers (4marks) v. vi. vii. viii. 5. What are the functions of the following keys (15 marks) vi. Spacebar key ………………………………………………………………………………………………………… ………………………………………………………………………………………………………… vii. Backspace key ………………………………………………………………………………………………………… ………………………………………………………………………………………………………… viii. Caps lock key ………………………………………………………………………………………………………… ………………………………………………………………………………………………………… 176 | P a g e Computer Studies Guide Book
201
ix.
Enter key ………………………………………………………………………………………………………… ………………………………………………………………………………………………………… x. Tab key ………………………………………………………………………………………………………… ………………………………………………………………………………………………………… 6. Define the following terms as used in computer studies (9marks) iv.
Computer ………………………………………………………………………………………………………… …………………………………………………………………………………………………………
v.
Software ………………………………………………………………………………………………………… …………………………………………………………………………………………………………
vi.
Hardware ………………………………………………………………………………………………………… ………………………………………………………………………………………………………… 7. Define and give FOUR examples of each of the following in the table below ( 10marks) i. Input ………………………………………………………………………………………………………… ………………………………………………………………………………………………………… ii. Output ………………………………………………………………………………………………………… ………………………………………………………………………………………………………… 8. Which are the desktop features? (3marks) vii. viii. ix.
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SampleTest Paper Five 2. Define the following terms as used in computer studies
(10marks)
vii.
Computer ………………………………………………………………………………………………………… …………………………………………………………………………………………………………
viii.
Software ………………………………………………………………………………………………………… …………………………………………………………………………………………………………
ix.
Hardware ………………………………………………………………………………………………………… …………………………………………………………………………………………………………
x.
Information ………………………………………………………………………………………………………… …………………………………………………………………………………………………………
xi.
Data ………………………………………………………………………………………………………… …………………………………………………………………………………………………………
3. Define and give FOUR examples of each of the following in the table below ( 10marks) iii. Input ………………………………………………………………………………………………………… ………………………………………………………………………………………………………… iv. Output ………………………………………………………………………………………………………… ………………………………………………………………………………………………………… No. 1. 2. 3. 4.
Input devices
No. 1. 2. 3. 4.
Output devices
4. Give the functions of the following shortcut keys (6marks) i. CTRL +S……………………………………………………………………………………………… ii. CTRL +E……………………………………………………………………………………………… iii. CTRL + L……………………………………………………………………………………………… iv. CTRL +H……………………………………………………………………………………………… v. CTRL+ V……………………………………………………………………………………………… vi. CTRL+ O……………………………………………………………………………………………… 178 | P a g e Computer Studies Guide Book
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5. List FIVE categories of computers v. vi. vii. viii. ix.
(5marks)
6. List the FIVE keyboard arrangement groups xi. xii. xiii. xiv. xv.
(5marks)
7. Enumerate FIVE importance of computers in our society today i. ii. iii. iv. v.
(5 marks)
8. Enumerate how one can tell the symptoms of a virus in a computer i. ii. iii. iv. v.
(5marks)
9. What are some of the computer application packages? i. ii. iii. iv. v. vi. vii.
(7marks)
204
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Sample Test Paper Six
1. Enumerate FIVE importance of computers in our society today a. b. c. d. e. 2. List and explain the FIVE mouse techniques i. ii. iii. iv. v. 3. What are the functions of Operating system? i. ii. iii. iv. 4. Enumerate how one can tell the symptoms of a virus in a computer vi. vii. viii. ix. x. 5. How can one treat computer virus from the computer system? i. ii. iii. iv. 6. What are some of the computer application packages? I. II. III. IV. V.
(5 marks)
(5marks)
(5marks)
(5marks)
(4marks)
(4marks)
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Sample Test Paper Seven
1. Define the following terms as used in computer studies
(10marks)
xii.
Computer ………………………………………………………………………………………………………… …………………………………………………………………………………………………………
xiii.
Software ………………………………………………………………………………………………………… …………………………………………………………………………………………………………
xiv.
Hardware ………………………………………………………………………………………………………… …………………………………………………………………………………………………………
xv.
Virus ………………………………………………………………………………………………………… …………………………………………………………………………………………………………
xvi.
Anti-Virus ………………………………………………………………………………………………………… ………………………………………………………………………………………………………… 2. Enumerate FIVE importance of computers in our society today (5 marks) vi. vii. viii. ix. x. 3. Give the functions of the following shortcut keys (6marks) vii. ALT +F4 ………………………………………………………………………………………………………… viii. CTRL +E ………………………………………………………………………………………………………… ix. CTRL + L………………………………………………………………………………………………………… x. CTRL +H ………………………………………………………………………………………………………… xi. CTRL+ V……………………………………………………………………………………………… xii. CTRL+ X……………………………………………………………………………………………… 4. Enumerate how one can tell the symptoms of a virus in a computer (5marks) xi. xii. xiii. 181 | P a g e 206
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5.
6.
7.
8.
9.
xiv. xv. How can one treat computer virus from the computer system? (4marks) v. vi. vii. viii. What are some of the computer application packages? (4marks) viii. ix. x. xi. Distinguish between system software and application software (4marks) …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… Explain the following terms in relationship with Ms-Excel e. Workbook…………………………………………………………………………………………………… ……………………………………………………………………………………………………………… f. Worksheet…………………………………………………………………………………………………… ……………………………………………………………………………………………………………… g. Chart………………………………………………………………………………………………………… ……………………………………………………………………………………………………………… h. Cell…………………………………………………………………………………………………………… ……………………………………………………………………………………………………………… Define and give FOUR examples of each of the following in the table below ( 12marks) v. Input ………………………………………………………………………………………………………… vi. Output ………………………………………………………………………………………………………… No. 1. 2. 3. 4.
Input devices
No. 1. 2. 3. 4.
10. What are the functions of Operating system?
Output devices
(5marks)
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v. vi. vii. viii. ix. 11. Use the table below to answer the questions a – c (12marks) CANDIDATE MAT EN COM TOTA KI INSH S NAMES H G P L S A
TO T
SCI E
SS T
CR E
BRIAN 90 44 30 45 32 79 59 O’NEIL 98 37 28 38 31 88 47 CORNELL 87 29 32 44 32 98 55 TAYLOR 98 40 29 46 34 96 49 RICHARD 79 45 33 48 26 89 55 MEAN d. Write down an expression for the English total marks for both O’Neil and Richard e. Write down an expression for total marks for both Brian and Taylor f. Find the mean for math and science using the right procedural formula
23 29 23 25 27
10. What are the areas where this programme Excels can be applicable? (5marks i. ii. iii. iv. v.
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TO T
MARK S
ICT CERTIFICATE LEVEL 2 ½ HOURS SECTION A(30marks) 1. Define the following terms as used in related course (5marks) i. Data ii. Computer iii. Bandwidth iv. Broadband v. topology vi. Information vii. Virus viii. Software ix. Wi‐Fi x. Data communication 2. List some of the basic computer component(5marks) 3. Differentiate between application software and system software (4marks) 4. Highlight importance of a computer in a society today (5marks) 5. Using a table show show the difference between RAM and ROM (6marks) 6. Give the functions of the following keys (4marks) i. CTRL + SHIT+ P ii. CTRL+ SHIFT + F iii. CTRL +Z iv. CTRL + N 7. What are the factors considered when classifying a monitor (3marks) SECTION B (40marks) 8. Illustrate how the following can be troubleshoot (6 marks) i. HDD ii. Power supply iii. Motherboard 9. Outline some of the major motherboard failures (6marks) 10. Outline the procedures of booting process (8marks) 11. Highlight the functions of OS(8marks) 12. Outline FOUR types of networking (4marks) 13. Explain four main techniques used for backup (4 marks 14. Briefly describe types of installation (4marks) 184 | P a g e
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SECTION C (30marks) 1. By help of diagrams explain the FOUR network topologies (20 marks) 2. A friend is having a problem with his pc which he started experiencing since a week ago and he explain in short, due to his ignorance in computers, he says “my computer system is running slow”. State what could be the possible cause and how to solve it? 3. Give the quotation on setting up a mini‐cyber by giving appropriate network devices and how they will be connected and operate. SECTIONS
ESTIMATED SCORES
STUDENTS’ SCORE
SECTION A
30 MARKS
SECTION B
40 MARKS
SECTION C
30 MARKS
TOTAL
100 MARKS
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