ICSE E-World 7.Indd

Contents

1. Computer—Hardware components 1 Adjusting Row Height and Column Width in a Data and Information Worksheet Hardware and Software Formatting—Numerical Data, Text, Working of a Computer Aligning, Borders, Background Colour and External Hardware Patterns Storage Devices AutoFill Internal Hardware 6. Database and DBMS—An Introduction 66 2. Number System—An Introduction 16 Database and DBMS Number System File-oriented and database approach Ltd Decimal Number System Characteristics of database approach Binary Number System Uses of database Octal Number System Starting Microsoft Access Hexadecimal Number System Creating Database Pvt. Conversion between Number System Components of Microsoft Access 2010 window Conversion between Decimal Fractions and Objects and Tables in Access Binary Query 3. Computer Virus 24 7. More on HTML 86 Computer Virus Lists Malware Tables Types, Traits and Symptoms of Virus Forms Services Computer security Image Antivirus Software Hyperlinks 4. Ethics and Safety Measures in Computing 34 8. Looping statements in QBasic 108 Computing Ethics Introduction to Loops Unethical Practices Parts of a Loop Preventine Measures Types of Loops: Counter Method, Firewell FOR-NEXT Loop, WHILE-WEND Loop, Parental Control Education DO Loop Digital Footprints Exiting Loops 5. Spreadsheets—An Introduction 42 9. Programming in Qbasic Graphics Spreadsheets and Sound 129 Components of Microsoft Excel 2010 Various commands used to draw different shapes Window India Commands to generate sound Basic Operations—Creating, Saving, Exiting, Play music using QBASIC code Opening a Workbook Sample projects Printing, Navigating, Renaming, Adding and Removing a Worksheet Activities and Projects 146 Entering Data in a Worksheet Sample Test Paper 149 Editing—Selecting, Changing, Deleting, Copying,Pearson Moving, Inserting and Deleting Data© in a Worksheet

ICSE_E-World 7_Prelim.indd 6 14/02/2017 06:18:57 AM 1 Computer—Hardware Components

Ltd The former chairman of IBM Thomas Chapter Focus Watson in 1943 was reported to have said, "I ✓ Data and Information think there is a world market for maybe ✓ Hardware and Software Pvt. FIVE computers!" Today, most of us have ✓ Working of a Computer ✓ External Hardware about fi ve computers with us, in some form ✓ Storage Devices or other including laptops, netbooks, ✓ Internal Hardware cellphones, iPads, tablet PCs and what not! Nowadays, computers are an integral part of our lives. Services A computer system is an electronic device that accepts data as input (through input devices like keyboard and mouse), processes the input data by performing mathematical and logical operations (through the CPU) and gives the desired output (through output devices like monitor and printer). The computer also stores large amounts of data and information either temporarily or permanently in memory devices. The concept of generating output informationEducation from the input data is also referred to as Input-Process-Output (IPO) concept (Fig. 1.1).

Data and Information INPUT InstructionsIndia PROCESS OUTPUT Fig. 1.1 IPO concept

DATA AND INFORMATION A computer is a data-processing machine. Data refers to the raw facts and fi gures which are processedPearson logically by sets of instructions known as programs. The data is supplied to the computer by input devices. Information, on the other hand, is the logically processed data that is meaningful© and timely. The same data can be processed with different algorithms to cater to different information needs.

ICSE_E-World 7.indd 1 14/02/2017 07:40:13 AM For example, the marks submitted by the teachers to the report generation system may be considered as data, whereas the report card that is generated by the system is the information (Fig. 1.2).

Data Processing Information

Fig. 1.2 Relationship between data and information HARDWARE AND SOFTWARE The computer system has two very important components—hardware and software. Ltd Hardware Memory Unit Hardware refers to the tangible components or the Pvt. machinery that makes up a Central Processing Unit (CPU) computer. Hardware Control Unit (CU) components accept the data Input Device Output Device and instructions, process it Arithmetic and generate the desired and Logic Unit (ALU) outputs. All input, output, Services processing devices, logical Fig. 1.3 Functional units of a computer circuits, chips and so on are examples of hardware. Figure 1.3 shows the basic diagram of the functional units of a computer system.

Software Software refers to a collection of programs.Education It is a set of instructions that tells the computer about the tasks to be performed and how these tasks are to be performed. Operating systems, applications, utilities and so on are examples of software. Let us now take a look into theIndia working of a computer. WORKING OF A COMPUTER A computer accepts data, processes data, generates output and stores data. The computer system accepts input through input devices. The input in the form of data and instructions is processed by the Central Processing Unit (CPU). The memory unit stores the data, instructions and intermediatePearson results temporarily or permanently. Finally, the result is generated through the output© unit. We will learn more about hardware in this chapter. Hardware: External and Internal Hardware The hardware of a computer can be external hardware or internal hardware.

ICSE_E-World 7.indd 2 14/02/2017 07:40:14 AM Table 1.1 External and Internal Hardware External Hardware Internal Hardware External hardware are the devices that are attached to Internal hardware are the components that are within the computer box into one of the ports of the computer. the computer box. They are built-in, attached or added as expansion cards to the motherboard of the computer. Some of the external hardware components are as Some of the internal hardware components are as follows: follows: • Input devices—Keyboard, Mouse, Light Pen, • Motherboard Barcode Reader, Optical Character Recognition • Power supply (OCR), Magnetic Ink Character Reader (OMR), • Fan Ltd Smart card, Touchscreen, Scanner, Joystick, • Processor Digitising tablet, Web Camera, Digital Camera, • Primary Memory—RAM and ROM Biometric Devices, • Disk drives • Output devices—Monitor, Speaker, Printer, • Ports Pvt. Projector, Plotter, • Storage devices—Compact Disc, Digital Versatile Disc, USB fl ash drive, Modem, Memory card

EXTERNAl HARDWARE The external hardware devices are discussed below. ServicesInfo Hub Programs have to be loaded The Input Devices into the main memory ﬁ rst The input devices accepts information from the users. Some of to be executed. Register is a special location within the the popular input devices are listed here. CPU that is used to hold Keyboard: A computer keyboard (Fig. 1.4) is the most common data and addresses required during processing. and standard input device. It is anEducation electromechanical device designed to transmit specialised electronic codes when a key is pressed. Keyboards have standard typewriter keys, function keys, cursor movement keys, numericIndia keys and special purpose keys like Ctrl (Control), Del (Delete), Ins (Insert) and Alt (Alternate). Keyboards are generally wired but nowadays wireless keyboards are also common. Fig. 1.4 Keyboard Mouse: The mouse (Fig. 1.5) is an important input device. A mouse allows control of an on- screen pointer called a cursor, which commonly looks like an arrow. When the arrow is properly Pearsonpositioned, it can be used to perform various tasks by pressing buttons on the © mouse. A mouse is generally an optical mouse. An optical mouse has a small light (usually red) under it and works on the principle of refl ection of light. A wireless mouse is not attached to the computer through a wire. It communicates with the computer using signals. Fig. 1.5 Mouse

ICSE_E-World 7.indd 3 14/02/2017 07:40:17 AM Light Pen: Light pen (Fig. 1.6) resembles ordinary pens and is used to indicate locations on a computer screen. There is a light-sensitive detector on the tip of the light pen. The detector identifi es the location of the pen on the screen, when the light pen touches the screen. It is connected to the VDU (Visual Display Unit). There is a light-sensitive detector on the tip of the light pen. The detector identifi es the location of the pen on the screen, where the light pen touches the screen. It is used to draw images on screen and instruct the computer to change the Fig. 1.6 Light pen shape, size, position and colour of sections of a screen. Barcode Reader: A barcode is a pattern printed in lines of different thicknesses that can be seen on many products. A barcode Ltd reader is used to scan the barcode of a product, thereby eliminating chances of any typing errors. It also helps to make Pvt. transactions faster. Figure 1.7(a) shows a barcode reader and Figure 1.7(b) shows (a) Barcode reader (b) Sample barcode a sample barcode. Fig. 1.7 Optical Character Recognition (OCR): An OCR reader (Fig.1.8) is a device that analyses the scanned character,Services recognises it and produces electronic or digital copy. It is widely used to convert books and documents into electronic fi les.

Fig. 1.8 OCR reader Optical Mark Recognition (OMR): An OMR is used widely for evaluating multiple-choice questionnaires. The device has a high- intensity light inside that is directed in the form of a beam at the sheets Education of papers being fed through it. The beam scans the number and location of the pencil marks on the sheet of paper. The data is then convertedIndia into signals for the computer. Figure (a) OMR sheet (b) OMR 1.9 shows a part of an OMR sheet. Fig. 1.9 Magnetic Ink Character Recognition (MICR): An MICR (Fig. 1.10) is primarily used for verifying cheques. This recognition can identify and interpret numbers and few special symbols Pearson printed with magnetic ink on a © cheque. The input is then stored for processing. It decreases the chances of errors, makes SPECIMEN transactions faster, automatic and more secure. (a) MICR (b) MICR cheque Fig. 1.10

ICSE_E-World 7.indd 4 15/02/2017 08:37:10 AM Smart Card: A smart card (Fig. 1.11) is used to buy products or to avail any special service. It is a multipurpose card input device. These cards have microchips that keep users’ records updated each time the card is used. The transactions are updated in the user’s bank account. Fig. 1.11 Smart card Touchscreen: The user enters the choice provided on the screen by just touching the screen (Fig. 1.12). The software determines the kind of choice the user has entered. Many kiosks that offer self-help use this technology such as ATM, theatres and airports. Touchpads and Fig. 1.12 Touchscreen gamepads are also examples of similar input devices. Ltd A touchpad is usually found on a laptop where it is used in place of a mouse. Scanner: A scanner is an electronic device that scans images, printed or handwritten text documents or a particular object to convert them into a digital ﬁ le formatPvt. (Fig. 1.13). The common types of scanners are ﬂ atbed scanners, handheld scanners and sheet-fed scanners. Joystick: Joysticks were initially used as control devices for aircraft (Fig. 1.14). It is a movable stick with buttons attached to a base that helps control and record the movements into a software. Trackball is an advanced kind of joystick. Joysticks are commonly used for playing video games. Services Digitising Tablet: This is mainly used by artists and architects. Also known as a graphic tablet, it is an input device that enables to draw and sketch directly into a computer. It consists of an electronic tablet and a cursor or a pen (called a stylus) (Fig. 1.15). Electronic whiteboards which are used in several classrooms are also an example of a digitising tablet. Education

India

Fig. 1.13 Scanner Fig. 1.14 Joystick Fig. 1.15 Digitising tablet

Web Camera: It can capture full motion video images. The images are digitised. Web camera or webcam (Fig. 1.16) is connected to the computerPearson on the USB port. Webcam allows user to record their video. It is© placed on the computer above the screen to capture the images. Laptops come with in-built webcam. Fig. 1.16 Web camera Digital Camera: A digital camera (Fig. 1.17(a)) captures still images. The images are digitised and can be brought into the computer and stored. A digital camera is also used to read QR (Quick Response) code. A QR code (Fig. 1.17(b)) is an array of black and white squares. It (a) Digital camera (b) QR code stores information about link of websites, phone number or Fig. 1.17 5

ICSE_E-World 7.indd 5 15/02/2017 09:37:33 AM SMS text. QR code can store more information than a barcode. QR code are used in products, in visiting cards and for advertising.

Biometric Devices Biometric devices (Fig. 1.18) measure human traits for authentication. This can include fi ngerprints, eye retina and iris, voice patterns, facial patterns and hand measurements for authentication. For example, PCs nowadays include a fi ngerprint scanner where you can place your index fi nger. The computer analyses the fi ngerprint to determine your identity. Biometric devices are used at various places for different purposes—for marking Ltd attendance in offi ces, recognising passengers in airports, accessing bank Fig. 1.18 Biometric devices lockers and unlocking a smartphone. Pvt. Info Hub Webcam, image scanner, digital camera, ﬁ ngerprint scanner, 3D scanner and laser rangeﬁ nder are some more examples of input devices. Audio inputs may be taken through microphone and Musical Instrument Digital Interface (MIDI) keyboard. Input devices used for medical imaging include Magnetic Resonance Imaging (MRI), Computerised Axial Tomography (CAT scan), PositronServices Emission Tomography (PET) and ultrasonography.

Power Glove: Data gloves, 3D trackers and body suits are considered as modern day interface to sense any bend in the human body. An inexpensive input glove is the Power Glove by Mattel, designed as an input device for the Nintendo Entertainment System (video game). Computers are also capable of recognising gestures as input. A music artist can use gestures for generating creative musical notation.Education Speech recognition is also another type of input for the computer. Many touch technologies, such as the use of stylus or touchscreen sense pressure, are being used to perform the ‘select’ operations on computers. India Output Devices Output devices present the information from the computers. Some of the popular output devices are listed here. Monitor: The standard output device of a computer system is the monitor or the computer screen. The Pearsonmonitor creates a visual display from processed data that users can view. It is also known ©as the VDU (Visual Display Unit). Monitors come in a variety of screen sizes and visual resolutions. There are two types of computer monitors—Thin Film Transistor (TFT) monitors (Fig. 1.19) usually use LCD or plasma to create output. Flat Panel Light Emitting Diode (LED) Fig. 1.19 TFT monitor are latest type of monitors. They produce images with high contrast, emit less heat and are environment friendly.

ICSE_E-World 7.indd 6 14/02/2017 07:40:30 AM Be a Techie! You can change your monitor’s screen resolution settings by following the mentioned steps. Step 1: Click on Start Control Panel. Step 2: Click on the Display icon. Step 3: The Display Properties window opens up. Step 4: Click on the Settings tab. Step 5: Drag the sliding bar under Screen Resolution to the left (for less) or right (for more) till it reads 1024x768. Step 6: Click on Apply OK to save the chosen screen resolution settings. Ltd Speakers: Speakers (Fig. 1.20) provide output in audio format. Headphones are also considered to be a variation of speakers. Pvt. Printer: A printer (Fig. 1.21) produces a hard copy of the processed data such as documents and photographs. The computer sends the image data to the printer, which then physically recreates the image on a paper. Printers are mainly of two types—Impact and Non-impact printers. Fig. 1.20 Speakers Impact Printer: In this type of printer, the print head strikesServices the paper taking with it the ink ribbon to create a text or an image. It is quite slow and noisy in nature. Examples of this type include dot-matrix, line and daisy wheel printers. Fig. 1.21 Printer Non-impact Printer: These printers produce text or images on paper without striking the paper physically. These emit less sound when compared to impact printers. Examples of this type include thermalEducation printers, laser printers and inkjet printers. Save paper, Save trees! Think... before you print! Projector: A projector (Fig. 1.22) is an output device that projects an imageIndia onto a surface, commonly a projection screen. The computer sends the image data to the video card which then sends the video image to the projector. They are typically used for teaching, giving presentations to an Fig. 1.22 Projector audience or for viewing videos. Plotter: A plotter (Fig. 1.23) creates a hard copy of a digitally rendered design. ThePearson design is sent to the plotter via a graphics card and it creates the design© using a pen. Generally used in engineering applications, plotters basically draw an image using a series of straight lines. Fig. 1.23 Plotter

ICSE_E-World 7.indd 7 14/02/2017 07:40:35 AM Modem A modem (short for modulator-demodulator) is an electronic device (Fig. 1.24) that converts digital signals of a computer into analog form so that they can travel over a phone line. At the destination, the receiving modem converts the analog signals back into their digital form so that the destination computer understands Fig. 1.24 Modem them. Figure 1.25 shows the working mechanism of a modem.

Ltd

Sender Receiver Fig. 1.25 Transmission of signals through modem Pvt.

CPU of computer Modems are used for connecting computers to the Internet. Modems are connected to a computer and a Modem telephone line. Figure 1.26 shows the connection of a modem with a computer and a telephone line. Services

Info Hub • Modems can be external or internal. External modems generally contain indicators which help Telephone in understanding the functioning of the modem. EducationAlso an external modem can be moved from one Fig. 1.26 Connection of a modem computer to another. Hub • On technical basis, hubs can be categorised into passive hubs, intelligent hubs, and switching A hub is a device (Fig. 1.27) that is used hubs. to connect computers in a network.India Hubs are commonly used to connect segments of a Port for connecting modem LAN. A hub contains multiple ports. Small Ports for connecting or additional hub (typically hubs network 4 to 5 computers. Larger hubs computers labelled Link or Out) contain 8, 12, 16 and even 24 ports. In a hub, whenPearson one computer sends data on the network, the hub© simply forwards the packets to all the other computers connected to it. Each computer is responsible for determining which packets are destined for it and ignoring the others.

Fig. 1.27 A hub having four ports

ICSE_E-World 7.indd 8 14/02/2017 07:40:36 AM STORAGE DEVICES The external memory devices store data permanently. Some popular storage devices are discussed below (Fig. 1.28). Compact Disc: Previously compact disc (CD) was used only for recording and storing audio fi les. Subsequently along with audio and video, other data can also be stored on them. The data is stored on the CDs in optical format. About 700 MB of data can be stored on a CD. CDs can be of two types—CD-R (Recordable CD) and CD-RW (Rewritable CD). Digital Versatile Disc: The format of storing data in a digital versatile disc (DVD) is similar to that of a compact disc. A DVD can store data six times more than a CD. A single-sidedLtd DVD can store about 4.7 GB of data while a double-sided disc can store data upto 9 GB. Like CDs, DVDs are also used as backup devices. Pvt. CDs and DVDs have a lifetime of few decades before they get spoilt. Scientists are now working upon prolonging the lifetime of data storage, as high as 3 × 1020 years at room temperature that will lead to eternal data storage. Blu-ray Disc: A blu-ray disc (BD) is used for high-defi nition video storage. It is often used by gamers. Blu-ray discs are similar to CDs and DVDs in their looks but can store about fi ve times more data than a single-side. These can store up toServices 25 GB of data per layer. A blu-ray disc is also an optical storage device.

Education

(a) CD (b) DVD (c) Blu-ray disc India Fig. 1.28 USB Flash Drive: Popularly known as pen drive or thumb drive (Fig. 1.29), it can store data upto 64 GB. It has an integrated Universal Serial Bus (USB) interface. It is non-volatile and data can be rewritten Fig. 1.29 USB Flash drive on it.

MemoryPearson Card: Data is stored in digital format on the memory card (Fig.© 1.30 ). It can be used in various electronic devices from handheld computers, mobile phones, cameras and so on. It is also a rewritable device. Although it is small in size, it can store large amount of data.

Fig. 1.30 Memory cards

ICSE_E-World 7.indd 9 14/02/2017 07:40:37 AM Internal Hardware

Power Supply

Processor with fan Ltd Motherboard DVD drive Pvt. Hard disk drive

Ribbon cables

Services Expansion slots

Fig. 1.31 Components inside a CPU

The internal hardware components are present inside the CPU box. Figure 1.31 shows the components inside a CPU. Education Let us discuss the internal hardware components in detail. Motherboard India The computer is built up around a motherboard. The motherboard (Fig. 1.32) is most important part in the PC. It is a large Printed Circuit Board (PCB). The motherboard is used to connect all the essential components of a computer. It contains the processor, sockets and interface to plug RAM, hard drive, disk drives and optical drives. The BIOS (Basic Input Output System) and CMOS (Complementary Metal-Oxide Semiconductor) are present on the motherboard. BIOS is usedPearson as an interface between the operating system and the motherboard. It is stored in ROM. CMOS© chip saves some system information, such as time and system date. CMOS is kept powered by a button battery on the motherboard.

ICSE_E-World 7.indd 10 14/02/2017 07:40:38 AM BIOS on motherboard Battery for CMOS chip motherboard

Fig. 1.32 Motherboard Ltd

Info Hub Pvt. The computer is switched off and then switched on; the computer displays the correct date and time. Ever wonder how? Because of CMOS. The CMOS chip is on even when the computer power is switched off.

SMPS Services Switched Mode Power Supply (SMPS) (Fig. 1.33) provides power to all internal components of the computer. When the computer is turned on, the power supply converts the incoming AC voltage into low voltage DC supply. The SMPS also protects the computer from sudden surge and spikes in the power. Fig. 1.33 Power Supply

Fan Education Fan (Fig. 1.34) is inside the computer cabinet. It prevents the internal components from overheating. It maintains the fl ow of air inside the case. The fanIndia can push the warm air outside, pull air from outside and also move the air inside to cool the parts. Fig. 1.34 Fan Ports Ports are the inlets on the rear side of computer case where you can plug various devices such as mouse, keyboard or printer. The ports are connected to the motherboard inside the computer case. TherePearson are different kinds of ports. Some© ports used earlier but not much nowadays are: • Serial Port—to connect old peripherals. • Parallel Port—to connect old printers. • PS/2 Port to connect mouse and keyboard into PC. • VGA connector for connecting to a monitor.

ICSE_E-World 7.indd 11 14/02/2017 07:40:39 AM • SCSI Port for connecting the hard disk drives and network connectors. Some popular ports are: • USB Ports—to connect camera, scanner and printer, keyboard, pen drives, external hard disk drive • LAN port to connect the computer to a network. • Audio plugs (Line-In, Line-Out and microphone) for connecting sound speakers and microphone. • HDMI Port to connect projector Ltd Mouse Parallel port USB Port Line-in LAN port Pvt.

Services Keyboard Serial Port Video Microphone Line-out Fig. 1.36 Backside of Graphics computer cabinet with the Array different ports (VGA port) Fig. 1.35 Ports Primary Memory: The primary memory is also known as the main memory or internal memory. Some of the characteristics of Educationthe primary memory are: ✓ The primary memory can be directly accessed by the CPU. ✓ This kind of memory is fast but expensive. ✓ Any process to be executedIndia has to be first loaded into the primary memory. The primary memory is of two types—RAM and ROM. RAM: This stands for Random Access Memory. This memory (Fig. 1.37) holds the data, intermediate results and all system and user processes duringPearson the running of the system. The data and instructions are fetched by the control unit from the RAM. It is volatile since all the data gets erased© as soon as the power is switched off. Nowadays, computer generally have 2 GB RAM to 32 GB RAM. RAM may be static (SRAM) Fig. 1.37 RAM or dynamic (DRAM) or a combination of both (SDRAM). DRAM is mostly used in computer as it is small and SRAM is used for cache memory. ROM: This stands for Read Only Memory. ROM (Fig. 1.38) comes programmed from the manufacturer. Data can be real from ROM. ROM is when the power is switched off. ROM is

ICSE_E-World 7.indd 12 14/02/2017 07:40:40 AM used for storing BIOS. ROM contains instructions that help during the start-up of the computer. There are different types of ROM. ✓ ROM—Read Only Memory. It is non-programmable and non-erasable. ✓ PROM—Programmable ROM. The user can write the data once into PROM. Erasing of data is not possible in PROM. ✓ EPROM—Erasable PROM. The data written on EPROM can be erased. ✓ EEPROM—Electrically EPROM. The data written on EEPROM can be overwritten electrically, thus making it the most popular one, for example, Memory Card. Fig. 1.38 ROMLtd A disk drive is inside the computer case that holds the non-seasonable disk. The disk can be a hard disk drive for hard disk, CD drive for CD-ROM and DVD drive for DVD. Hard Disk: A hard disk (Fig. 1.39) is one of the most important Pvt. secondary memory devices. Data is stored on the hard disk in the digital format. It has a rotating magnetic disk protected by a hard cover. It is divided into a number of tracks and sectors that store data. Hard disks can store large amount of data. Fig. 1.39 Hard disk

Processor Services The processor or the CPU (Fig. 1.40) is the main component of the computer. It is a chip inside the computer. It performs the tasks that allow the computer to function properly. It receives input, controls the different actions to be performed and sends the output. Pentium Pro, Pentium 2 and Pentium 4 are some of the processors. Fig. 1.40 Processor Education

India ASSESSMENT ZONE

A. Choose the correct answer. 1. Which of the following is not an internal hardware device? (a) Light pen (b) SMPS (c) Motherboard (d) Fan 2. WhichPearson of the following is an Input device? (a) Monitor (b) Processor (c) Memory card (d) Smart card 3.© Which of the following is a type of impact printers? (a) Dot-matrix (b) Laser (c) Thermal (d) Inkjet 4. Which of the following is not a secondary storage device? (a) ROM (b) CD (c) DVD (d) Hard disk 5. Which of the following input devices is used by artists to draw pictures on a computer? (a) Scanner (b) Plotter (c) Digitising tablet (d) Microphone

ICSE_E-World 7.indd 13 14/02/2017 07:40:43 AM B. State whether the following statements are True or False. 1. An input device converts binary data into a form that we can read. 2. A DVD can store more data than a Blu-ray disc. 3. ROM is a type of primary memory. 4. Light pen identifi es the location of the pen on the screen. 5. A TFT monitor occupies more space than a CRT monitor. C. Fill in the blanks using the words given in the box.

Input Inkjet Touchpad Joystick RAM Laser OMR 1. ______is used as control devices for aircraft. Ltd 2. A joystick is an example of an ______device. 3. ______is an example of primary memory. 4. An ______is used for reading and evaluating multiple-choice answers. Pvt. 5. A ______is an input device usually found on a laptop where it is used in place of a mouse. 6. Two examples of non-impact printers are ______printer and ______printer. D. Answer the following questions. 1. Defi ne the functional units of a computer using a structural diagram only. 2. Differentiate between different types of hardware components. 3. Differentiate between data and information, with an example. Services 4. What is an input devices? Briefl y describe any three input devices. 5. Defi ne an output devices. Describe any three output devices briefl y. 6. Differentiate between: (a) RAM and ROM, (b) Primary and Secondary memory. 7. Explain different types of storage devices. 8. Briefl y explain the difference between internal and external hardware, with suitable examples. 9. Describe any three internal hardware components.Education 10. Write a short note on Modem and hub. 11. Write short notes on: (a) MICR, (b) OMR. E. Solve the crossword using theIndia given clues. Crossword Zone 1 ACROSS 3. It provides output in audio formats. 2 4. An electronic device that scans images, printed or 3 handwritten text documents.

Pearson DOWN 1. A pattern printed in lines of different thickness that © can be seen on many products.

2. The tangible components or the machinery that makes up a computer. 4 5 5. A type of non-volatile memory.

ICSE_E-World 7.indd 14 14/02/2017 07:40:44 AM 1. Find the latest input, output and memory devices. Z one o

2. List the latest type of internal and hardware components and their features. n e 3. Find out more about software by listing the differences between hardware and software.

e Stu ag dy m I Ltd Identify the devices given below. Categorise them as input, output and memory devices. Also mention in which generation of computers these devices were invented. Pvt. 1. 2. 3. 4. 5.

6. 7. 8. Services 9. 10.

Education

India

Pearson ©

ICSE_E-World 7.indd 15 14/02/2017 07:40:57 AM 2 Number System—An Introduction Ltd

Number system is a set of fi xed values that Chapter Focus are used to represent different quantities. ✓ Number System Pvt. Normally, the decimal number system is the ✓ Decimal Number System most extensively used number system used ✓ Binary Number System ✓ Octal Number System by humans all over the globe. This system ✓ Hexadecimal Number System was the fi rst popular, globally accepted ✓ Conversion between Number System number system. Services All the number systems used before it for counting were dependent on external resources. But, the decimal number system became popular because everyone could use their fi ngers for counting instead of external resources as we have 10 fi ngers in our hands. There were several other added advantages of this number system because of the power of multiplication and division by 10. But, when electronics was invented, microEducation miniature switches were used to design integrated circuits. These switches had two states—on and off. So it was necessary for another number system to be invented, so that these circuits could be used. This would have drastically reduced the size of the computers. So, the two state devices or the digital computers started using this new number system called theIndia binary number system. The digital computers can store all kinds of data and information including text, numbers, audio, video and graphics, but all of these are stored either as 0 or 1.

Let us look into the number systems. NUMBER PearsonSYSTEM A number© system (numeral system) is a writing system for expressing numbers with a given set of mathematical symbols used in a consistent manner. The number system helps to represent a set of numbers in a unique or standard manner. A number system in base r uses unique symbols for r digits. One or more digits are combined to get a number. The base of a number decides the valid digits that are used to make a number. The position of digits in a number

ICSE_E-World 7.indd 16 14/02/2017 07:40:58 AM starts from the right-hand side of the number. The rightmost digit has position 0, the next digit on its left has position 1 and so on. The digits of a number have two kinds of values:

✓ Face value ✓ Position value The face value of a digit is the digit located at that position. For example, in decimal number 87, face value at position 0 is 7 and face value at position 1 is 8. The position value of a digit is (baseposition). For example, in the decimal number 87, the position value of the digit 7 is 100 and the position value of digit 8 is 101. Decimal numbers have a base of 10. The number is calculated as the sum of, face value * baseposition, of each of the digits.Ltd For the decimal number 87, the number can be represented as 8*101 + 7*100 = 80 + 7 = 87. In computers, there are mainly four kinds of number systems that require attention. Pvt. ✓ Decimal number system — Base 10 ✓ Binary number system — Base 2 ✓ Octal number system — Base 8 ✓ Hexadecimal number system — Base 16

The Decimal Number System (or Denary Number System) This is the most popular positional number system. ‘Deci’Services means 10, so this system has a base of 10 and its range is from 0 to 9. Thus, a number seven hundred thirty-six is formed by placing the digits according to their proper place as shown below. 7 hundreds 3 tens 6 units = 7 × 100 + 3 × 10 + 6 × 1 = 7 × 102 + 3 × 101 + 6 × 100 = 736

The Binary Number System (or Dyadic Number System) The word ‘binary’ comes from ‘bi’ meaningEducation two. The binary numeral system is a way to write numbers using only two digits—0 and 1, thus having a base of 2. A single binary digit (like ‘0’ or ‘1’) is called a ‘bit’. These are used in computers as a series of ‘OFF’ and ‘ON’ switches. In binary, each digit’s place value is double than that of the next digit to the right; the place value of the rightmost digit beingIndia 1. For many years, mathematicians saw base two as a primitive system and overlooked the potential of the binary system as a tool for developing computer science and many electrical devices. Binary number system has been used in almost every electronic gadgets/devices; from calculators to supercomputers. Machine codes are binary digits. The binary system works well for Pearsoncomputers because the mechanical and electronic circuits recognise only two states of operation,© such as ON/OFF or CLOSED/OPEN. The Octal Number System The octal numbering system was adopted in computer systems because it can represent bits in a compact way. One octal digit can represent three bits. It provided an easier way to work with binary numbers. The octal number system consists of eight digits—0 to 7. This number system has a base of 8.

ICSE_E-World 7.indd 17 14/02/2017 07:40:58 AM The Hexadecimal Number System The hexadecimal number system replaced the octal number system because the hexadecimal system needs only two digits to show the information in one byte of data. The hexadecimal numbers system consists of sixteen digits—0 to 9 and A to F, where A stands for 10, B for 11, C for 12, D for 13, E for 14 and F for 15. This number system has a base of 16. Both octal and hexadecimal number systems help in compression of binary data. Each octal digit represents 3 binary digits and each hexadecimal representation represents 4 binary digits. Table 2.1 Number System Base of number system Digits used Ltd Binary 2 0, 1 Octal 8 0, 1, 2, 3, 4, 5, 6, 7 Decimal 10 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 Pvt. Hexadecimal 16 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, A, B, C, D, E, F

where, A stands for 10, B for 11, C for 12, D for 13, E for 14 and F for 15.

CONVERSION BETWEEN NUMBER SYSTEMS Services Although conversion of numbers between various number systems is possible, in this book, we will study about conversion from decimal to binary and vice versa.

Conversion from Decimal to Binary Number System To convert a number from decimal to binary number system, the number has to be divided with the base (here, 2) repeatedly till theEducation quotient is greater than or equal to the base. The remainder of this integer division is also noted down. While displaying, the result has to be written in the reverse order of the remainder along with the target base. Examples: India

Convert from decimal to binary: 57(10) = ?(2) Convert from decimal to binary: 425(10) = ?(2) Remainder 2 425 2212 1 Remainder 2106 0 2 57 2530 2281 Pearson 2261 2140 2130 © 27 0 26 1 23 1 23 0 11 11

So, (57)10 = (111001)2 So, (425)10 = (110101001)2

ICSE_E-World 7.indd 18 14/02/2017 07:40:58 AM Conversion from Binary to Decimal Number System To convert a number from binary to decimal number system, each digit of the number has to be added, starting from right to left, to the product of the place and the face value. The face value is the digit itself and the place value can be found by raising the current base with the increasing values starting from 0. Examples: Be a Techie! Convert from binary to decimal: 111101(2) = ?(10)

111101 Try out interconversions between number 0 1 2 3 4 5 = 1 × 2 + 0 × 2 + 1 × 2 + 1 × 2 + 1 × 2 + 1 × 2 systems involving decimal, octal Ltdand = 1 + 0 + 4 + 8 + 16 + 32 hexadecimal. Remember that decimal has a base of 10, octal has a base of 8 and = 61 (10) hexadecimal has a basePvt. of 16.

Convert from binary to decimal: 100111(2) = ?(10) 100111 = 1 × 20 + 1 × 21+ 1 × 22 + 0 × 23 + 0 × 24 + 1 × 25 = 1 + 2 + 4 + 0 + 0 + 32 Services = 39(10)

Example: Convert (1234)10 to binary. 2 1234 2 617 0 2 308 1 2 154 0 Education 2 77 0 2 38 1 2 19 0 India 2 9 1 2 4 1 2 2 0 1 0 = (10011010010) Pearson2

Example:© Convert (1011011110)2 to decimal. = 0 × 20 + 1 × 21 + 1 × 22 + 1 × 23 + 1 × 24 + 0 × 25 + 1 × 26 + 1 × 27+ 0 × 28 + 1 × 29. = 0 + 2 + 4 + 8 + 16 + 0 + 64 + 128 + 0 + 512. = (734)10

ICSE_E-World 7.indd 19 14/02/2017 07:41:00 AM Conversion of Decimal Fractions into Binary To convert decimal fractions into binary, multiply the fraction by the target base. The result now has two parts: a whole number and the fractional component. Note the whole number and repeat the multiplication of the fractional number till the desired number of digits or till the fractional component becomes zero. Now display the result in the usual order from top to bottom.

For example (i) Convert (0.875)10 to binary. 0.875 × 2 = 1.75 1 0.75 × 2 = 1.50 1 Ltd 0.50 × 2 = 1.00 1 = (0.111) 2 Pvt. Conversion of Binary Fractions Into Decimal To convert binary fractions into decimal fractions, multiply the face value of the bit with the place value of the bit starting from the first digit after the decimal point and going towards the right. The place value of the first place after the decimal point is 2–1. Now add up each term to get the final decimal value. Services

For example, (0.1101)2 to decimal. = 1 × 2–1 + 1 × 2–2 + 0 × 2–3 + 1 × 2–4 1 1 1 = + + 0 + 2 4 16 = 0.5 + 0.25 + 0.0625 Education = (0.8125)10 India Convert (83.33)10 to binary The whole number component is 83.

2 83 2 41 1 2 20 Pearson1 2 10 0 2© 5 0 2 2 1 1 0

= (1010011)2 The fractional component is 0.33.

ICSE_E-World 7.indd 20 14/02/2017 07:41:00 AM 0.33 × 2 = 0.66 0 0.66 × 2 = 1.32 1 0.32 × 2 = 0.64 0 0.64 × 2 = 1.28 1 0.28 × 2 = 0.56 0

= (0.01010)2 upto 5 places

Thus, (83.33)10 = (1010011.01010)2 upto 5 places after the decimal point. Ltd ⇒ Convert (11011101.0110111)2 to decimal The whole number component is (11011101) 2 Pvt. = 1 × 20 + 0 × 21 + 1 × 22 + 1 × 23 + 1 × 24 + 0 × 25 + 1 × 26 + 1 × 27 = 1 + 0 + 4 + 8 + 16 + 38 + 64 + 128

= (221)10 The fractional component is (0.110111) 2 Services = 1 × 2–1 + 1 + 2–2 + 0 × 2–3 + 1 + 2–4 + 1 × 2–5 + 1 × 2–6 1 1 1 1 1 = + + 0 + + + 2 4 16 32 64 = 0.5 + 0.25 + 0.0625 + 0.03125 + 0.015625 = (0.859375) 10 Education 10 So, (11011101.0110111)2 = (221.859375) IndiaTable 2.2 Number representation Decimal Binary Octal Hexadecimal 0 0 0 0 1 1 1 1 2 10 2 2 3 11 3 3 Pearson4 100 4 4 © 5 101 5 5 6 110 6 6 7 111 7 7 8 1000 10 8 9 1001 11 9 10 1010 12 A 11 1011 13 B

ICSE_E-World 7.indd 21 14/02/2017 07:41:00 AM Decimal Binary Octal Hexadecimal 12 1100 14 C 13 1101 15 D 14 1110 16 E 15 1111 17 F

Tech Bytes

• Number system: A writing system used • Face value: The face value of a digit is the for expressing numbers with a given set of digit located at that position. mathematical symbols used in a consistent • Position value: The position value of a digitLtd manner. is (baseposition). Pvt. Bits to Remember  A number system (numeral system) is a writing system for expressing numbers with a given set of mathematical symbols used in a consistent manner.  Decimal, binary, octal and hexadecimal are four kinds of number systems.  ‘Deci’ means 10, so this system has a base of 10 and its range is fromServices 0 to 9.  The binary numeral system is a way to write numbers using only two digits—0 and 1—thus having a base of 2.  The octal number system consists of eight digits—0 to 7.  The hexadecimal numbers system consists of sixteen digits—0 to 9 and A to F. Education ASSESSMENT ZONE India A. Choose the correct answer. 1. The range of an octal number system is ______. (a) 0–9 (b) 0–8 (c) 0–7 (d) 0–1 2. To convert a number from decimal to binary number system, divide it by ______(a) 9 (b) 2 (c) 3 (d) 0 3. The hexadecimalPearson number system consist of ______digits. (a)© 10 (b) 6 (c) 16 (d) 1 4. The binary number system consist of ______and ______digits. (a) 1 and 2 (b) 0 and 1 (c) 4 and 3 (d) 0 and 7 5. In binary number system, the mechanical circuits recognise only two states ______and ______. (a) ON and OFF (b) Yes or NO (c) True or False (d) None

ICSE_E-World 7.indd 22 14/02/2017 07:41:02 AM B. State whether the following statements are True or False. 1. Number system is a set of different values that are used to represent different quantities. 2. Decimal number system has a base of 16. 3. You can convert decimal fractions into binary and vice versa. 4. The position value of a digit is the digit located at that position. 5. The binary number system works well for computers because the mechanical and electronic circuits recognise only two states of operation. C. Answer the following questions. 1. Convert the following decimal numbers into their binary equivalents: (a) 15 (b) 24 (c) 13 (d) 532 Ltd (e) 34 (f) 100 (g) 87 (h) 50 2. Convert the following binary numbers into their decimal equivalents: Pvt. (a) 101101001 (b) 110101101 (c) 1010010001 (d) 100111 (e) 10101010 (f) 1110110 (g) 100001 (h) 111000 3. Differentiate between binary and decimal number systems. 4. Defi ne the following terms: (a) Face value (b) Position value D. Crossword zone. Services Crossword Zone 1

2 ACROSS 2. Base 8 3 Education4. Digit located at that position 4 5. Two digits 0 and 1

DOWN India 1. Base 10 3. Base 16

Pearson ©

Prepare a PowerPoint presentation on the topic ‘Number System’ in a computer. Z one o

You can work in groups of fi ve and restrict the number of slides to fi fteen with verbal n presentation to 10 minutes per group. e

ICSE_E-World 7.indd 23 14/02/2017 07:41:04 AM 3

Computer Virus

Ltd Security is one of the major concerns of any computer system. The information systems are becoming increasingly important and unavoidable in all spheres globally. Almost all major global activities are dependent on computer systems. Thus potential threats toPvt. the computer systems are also increasing. The biggest asset and challenge of a computer system is the security and integrity of data and its processed information. Nowadays acts of malware attacks and cyber terrorism are becoming very common. One must ensure the integrity of data that: • comes into the system, Services • is stored in the system, • is processed into information and • is shared further. The following points ensure the data integrity of any system. • No one must be able to alter the data without proper permissions.Education • No external programs must be able to access the data unless allowed. • The vital information must be secured from programs or persons with malicious intent. • The personal information of any person must not be given out under any India circumstances. Any software causing or having the potential to cause damage to data/information or prevent the usual functioning of the system without the intent of the user is classifi ed as a perverse software. These are potentially unwanted programs that can alter data, damage data and behave in an unpredictablePearson way. Files can be shared between the computers on the network. This makes a© computer vulnerable to attacks by viruses, worms, Trojan horses and so on, which can easily spread because of the underlying network. Malware or malicious software is a term used to describe software that is included to damage the computer such as computer viruses, worms, Trojan horses and spyware. It uses different ways to harm the system. Virus, Trojan horses and worms are examples of malicious software.

ICSE_E-World 7.indd 24 14/02/2017 07:41:06 AM The devices that support Internet connectivity like mobiles, laptops and other gadgets are also major targets of malware attacks. Let us discuss a few common types of malware. 1. Virus: A computer virus is a software program that is destructive in nature and spreads itself from normal operations of a computer. It damages the fi les and data. It can delete information and may even change the fi le extensions to remove the associations. It attaches with healthy programs and replicates itself and can spread across a network. Viruses can attach themselves to any type of fi le (host) and spread when these infected fi les are copied to other computers. People unknowingly spread a computer virus by Ltd sharing infected fi les or sending emails with viruses as attachments, and also through secondary memory devices like pen drives. They can also spread easily through download on the Internet. Some examples of viruses are ‘melissa’ andPvt. ‘I Love You’.

Info Hub Some notable computer viruses are: Creeper (1971), Elk Cloner (1982), Jerusalem (1987) and Melissa (1999), ILOVEYOU (2000), Code Red (2001), Nimda (2001)Services and Blaster (2003). 2. Bomb: It is a software that is intentionally attached to a computer system. It starts its activity on the occurrence of a predefi ned event. These can’t move or infect other programs and damages only specifi c targets. Friday the 13th and Happy Birthday 30th are two such examples. 3. Worm: It is a software that uses network to replicate itself. So they travel from one node in a network to any otherEducation node within or outside the network. It has that code that can copy itself. They replicate themselves by making their own copies again and again on the local drive and on any other machine via network. They can spread worldwide via the Internet. CodeIndia Red, Scalper and Nimda are some examples of worms. A worm is different from virus. It does not harm any fi le or data but its copies consume the computer resources and make them slow. Virus is more dangerous than a computer worm as it makes changes to the fi les and deletes them.

4. Trojan: It is a destructive program that disguises itself as a useful program. The name ‘Trojan horse’ is from wooden horse of Troy in Greek mythology. The users install Trojan horses thinking that it is a useful program such as a game or a screensaver. The software may look normal but contains programs that corrupt the data or damage the

ICSE_E-World 7.indd 25 14/02/2017 07:41:07 AM fi les. A Trojan Banker steals online banking credit card information. Another Trojan Mailfi nder can get email addresses from the computer address book. Backdoor and Nuker are other examples of Trojans. Unlike viruses and worms, Trojan horses do not replicate themselves and do not copy themselves into other fi les. They get activated only when it is executed by the user.

Info Hub Trojan horse: The Greek soldiers reached the city of Troy by hiding themselves inside a large wooden horse. The people of Troy pulled the horse inside their city. They did not know that the Greek soldiers were Ltdhiding inside the horse.

5. Spywares: Spyware is program that spies on the computer system of thePvt. user. It gets installed on the computer with or without permission of the user. It collects information about the user activities on the computer. It can record keystrokes. So it can record the password, and credit card numbers the user enters in the computer. It sends the collected information back to the creator, so that they can use the user’s information. Spyware is used to steal information. SpyAnytime and GATOR are some spywares. Windows 7 offers a built-in antispyware that detects andServices removes the spywares in the system, known as the Windows Defender (Fig. 3.1). To start Windows Defender click on Windows Defender from the Control Panel. You have to turn this service on before using it. Click on Scan to detect and remove spywares from the system.

Education

India

Pearson ©

Fig. 3.1 Windows Defender

6. Sweeper: It is a malicious program used by hackers. It sweeps (deletes) all data from your computer system. It gets downloaded when you are connected with the Internet.

ICSE_E-World 7.indd 26 14/02/2017 07:41:09 AM Hacking is an unauthorised intrusion into another computer system to perform tasks without the consent of the owner.

Info Hub Ethical hackers or White hat hackers generally intrude into the other systems without any harmful intent. Generally, they test the security of the organisation and identify the ﬂ aws and loopholes of the system.

7 Zombies: Zombies are similar to spywares except that they do not steal information. They install themselves on the target machines and wait for the hackers to giveLtd instructions to them. 8. Adware: It is an advertisement displaying software that downloads andPvt. installs itself such that it keeps on displaying unwanted advertisement downloaded from the Internet. It generally is bundled with sharewares or freewares. The advertisements are generally displayed as pop-up messages and might be hosts for viruses occasionally. 9. Hijack: It is a malware that changes the settings of the browser and displays advertisements as pop-up. These generally modify the Internet settings of the browser and changes the home page, search page and even theServices system pages like the error page. Types of Virus The virus can damage the computer system by damaging the programs or reformatting the disk. There are three main kinds of virus—boot sector virus, program fi le virus and bimodal or bipartite virus. • Boot sector exists on a storageEducation media like hard drive. A computer needs the boot sector to load the operating system. During booting process, the boot sector program is loaded. Boot sector virus infects the boot sector program and replaces it with its corrupted version. During booting when the computer reads the disk, the boot virus loads into computer memory and infects the system. Form, Disk KillerIndia , Brain, Stoned and Michelangelo are some boot viruses. Nowadays, the operating systems include safeguard from boot viruses. Boot virus is very rare now. • Program or File virus infects the executable program fi les like .exe, .com and .bin. When the program fi les are executed, the program fi le virus gets loaded in memory. WhenPearson memory gets infected, any program that executes in memory also gets infected. Jerusalem, Sunday, Cleevix and Cascade are some program viruses. © A few types of these viruses are described below: i. Companion Virus: While executing the programs, the operating system maintains a hierarchy of the extensions of the programs. So the program name with the higher priority extension, for example .com is executed before the program name with the lower priority extension, for example .exe. This feature is exploited by the companion virus. The virus names itself after any existing program but with a

ICSE_E-World 7.indd 27 14/02/2017 07:41:10 AM higher priority extension. So whenever the user executes the program, the virus is executed instead of the original program. ii. Macro Virus or Document Virus: A macro is a named single instruction that in turn contains a group of instructions that have to be executed sequentially as a batch. They are generally used in some applications like MS Word to program certain steps. Macro viruses use this feature of macro and execute themselves by disguising themselves as authorised macros for the application. Melissa and Bablas are examples of this virus. iii. Polymorphic Virus: Poly means many and morph means form. This type of virus has the ability to change its form each and every time it is replicated. SoLtd it becomes difficult to detect this type of virus. iv. Stealth Virus: It manipulates the virus detection software and authenticates itself as a normal program. Thus it has the ability to hide itself and avoid Pvt.detection and removal. Whale and Zer Bug are examples of this virus. v. Cluster Virus: It changes the file system and directories of the disk so that although the virus is located in a single place running any program runs the virus first. vi. Email Virus: It is transmitted along with email attachmentsServices like documents or programs. When the recipient runs the attachment, the virus gets installed in the system. vii. Multipartite or Hybrid Virus: It infects both the hard disk drives and the program files. These are difficult to identify and disinfect because of their complex logic. Natas, Tequilla and Emperor are examples of this virus. • Bimodal or bipartite virus are typesEducation of virus that are capable of affecting the boot sector as well as the program files Traits of a Virus 1. It can replicate (copy) itself.India 2. It may spread by infected devices, via networks, emails or by internet downloads. 3. It is auto executable. 4. It may be executed even before the operating system starts. 5. It may even damage the operating system. 6. It mayPearson wipe off user data. 7. It© may alter data in a file. 8. It may change file extensions. 9. It may delay or prevent the booting process. 10. It may corrupt the software. 11. It may attempt to avoid detection and removal. 12. It may even damage the hardware and make the memory unusable.

ICSE_E-World 7.indd 28 14/02/2017 07:41:10 AM Symptoms of a Computer Virus A virus can affect a computer in different ways. However, the following problems are commonly noticed when a computer is infected with a virus.

✓ The computer runs slower than usual and takes longer time to load programs. ✓ The programs behave erratically and the computer stops responding or hangs frequently. ✓ The computer crashes and restarts every few minutes. ✓ New fi les keep appearing on the system. Files having strange names appear on the system. ✓ You are unable to access fi les or the contents of the fi les get deleted. ✓ You notice unusual and strange error messages such as ‘Your PC is stoned’. Ltd ✓ New icons appear on the desktop. Strange graphics are displayed on the monitor. ✓ The free space of the computer decreases. Pvt. ✓ The fi le sizes or the number of fi les increase. COMPUTER SECURITY Proper security measures must be undertaken for the prevention, identifi cation and treatment of viruses in a computer system or any other device (like mobile phones) that have a possibility of virus attack. Some of the measures include - Services 1. Scan and clean secondary storage devices such as CD, pen drives and hard disk before use. 2. Delete unwanted fi les in the system. 3. Check all email attachments and Internet downloads before installation and execution. 4. Backup important data on to externalEducation disk drives, or online cloud services like OneDrive or Dropbox, so that it may be recovered if data is deleted by the virus. 5. Do not install pirated software in the system. 6. In a large network, properIndia authentication must be done before the user is allowed to use the computer system. Granting access by a password, biometric authentication (like fi ngerprint , retina, face or voice recognition) makes the system less vulnerable. 7. Install antivirus software. Update regularly so that it may have the database updated for new viruses. 8. Antivirus apps must be installed in mobile phones and tablets, and any new app that is installedPearson must be scanned before use. 9. © Install Internet security software like fi rewalls.

Info Hub ‘Install from unknown sources’ option must be deselected in mobile phones to prevent installation of unknown apps.

ICSE_E-World 7.indd 29 14/02/2017 07:41:11 AM Antivirus Software Antivirus software is a utility software that has the counter logic for scanning, detection, identification and treatment of viruses. In case the software is not able to remove a virus, it is neutralised. The antivirus keeps a watch on the functioning of the computer system. If a virus is found it may alert the user, mark the infected program or kill the virus. Every computer on the computer network must have antivirus software that is updated on a regular basis so that newly discovered virus information and removal code can be made available to the antivirus. Antivirus software can be used to protect the computer from various types of malware. Antivirus software can detect viruses, worms and so on, and warn you of their presence in your computer. It can also deactivate and clean the computer of different types of malicious software.Ltd Antivirus software may disinfect the system in one or more of the following ways: • Delete: Remove the effected file by deleting it. Pvt. • Fix: Remove that part of the code from the infected file which has the virus definition and thus repair the file. • Quarantine: Move the virus to a vault to ensure that the virus cannot execute and further affect the system. There are various types of antivirus software such as AVG, ServicesAvira, Norton, Kaspersky, Quick Heal and McAfee. Firewall: A firewall is used to prevent unauthorised access to the network. A firewall can be implemented as a software, hardware or a combination of both. All data or messages entering or leaving the network pass through the firewall. Firewall examines each message and blocks those that do not meet the specified security criteria. Thus it can stop or prevent a lotof network intrusions and attacks. Education Windows 7 offers a built-in firewall. To start it (Fig. 3.2), click on Windows Firewall from the Control Panel. Turn on the firewall to activate online protection from intruders and hackers. India

Pearson ©

ICSE_E-World 7.indd 30 21/02/2017 10:27:02 PM Ltd

Pvt.

Services

Fig. 3.2 Windows Firewall Education Tech Bytes

• Boot sector virus: It infects the boot sector • Trojan: a program inserted into a system program and replacesIndia it with its corrupted by a hacker that will perform a harmless version. function while copying information held in • Program virus: It infects the executable a classifi ed fi le into a fi le with a low priority, program fi les like .exe, .com and .bin. which the hacker can then access without • Malware: It is short for malicious software. the authorised user’s knowledge It is used for software that is harmful for the • Antivirus: a software program that looks for computer and disturbs its normal operations. virus software on a computer and destroys it Pearson• Virus: a program which adds itself to an before it can damage data or fi les © executable fi le and copies itself to other • Firewall: a hardware or software security executable fi les each time an infected fi le is system between a server and the intranet or run the Internet that allows information to pass out to the Internet but checks any incoming • Worm: a program which replicates itself data before passing it on to the private server over a computer network and usually performs malicious actions

ICSE_E-World 7.indd 31 21/02/2017 10:27:16 PM Bits to Remember  A computer virus spreads itself from one computer to another and interferes with the normal operations of a computer.  There are two main kinds of virus—boot sector virus and program fi le virus.  Boot sector virus infects the boot sector program and replaces it with its corrupted version.  Program virus infects the executable program fi les like, .exe, .com and .bin.  Forms of virus attack (malware, worm, spyware, trojan horse, sweeper)  Antivirus software can detect viruses, worms and so on, and warn you of their presence in your computer. Ltd

Pvt. ASSESSMENT ZONE

A. Choose the correct answer. 1. Which virus infects program fi les like having an .exe extension? (a) Program Virus (b) Trojan Horse (c) Spyware (d) Malware 2. ______poses as useful programs. Services (a) Malware (b) Trojan (c) Virus (d) Sweeper 3. ______malicious program used by hackers. (a) Sweeper (b) Spyware (c) Trojan (d) Worm 4. ______is program that spies on the user. (a) Trojan (b) Spyware (c) Sweeper (d) Virus 5. ______exists on a storageEducation media like hard disk. (a) Boot sector (b) Program Virus (c) Sweeper (d) None B. State whether the following statements are True or False. 1. A bomb can travel from one node of network to any other node within or outside the network. India ______2. Antivirus software is a utility software that has the counter logic for scanning, detection, identifi cation and treatment of viruses. ______3. Melissa is a type of a worm. ______4. Trojan is a destructive program that disguises itself as a useful program. ______5. Stealth virus changes the fi le system and directories of the disk. Pearson ______C. Answer the following questions. 1. Defi ne the term Virus.© 2. Defi ne malware. Explain different types of malware. 3. Describe the traits and symptoms of a computer virus. 4. Differentiate between boot sector and program virus. 5. How can you know if your computer is affected by a virus? 6. What are different forms of virus attack?

ICSE_E-World 7.indd 32 14/02/2017 07:41:13 AM 7. Defi ne the term ‘antivirus’. 8. What do you understand by fi rewall? 9. What are program viruses? Explain different types of program virus. D. Solve the crossword using the clues. Crossword Zone 1 ACROSS 2 3 2. device used for connecting 5. pre-agreed signals Ltd 4 6. replicates itself 5 DOWN Pvt. 1. one who breaks into a computer system 3. various elements in a network

4. Digital to Analog 6

Services Find out: a) the latest antivirus software available. b) the latest type of virus present. Zone Z c) the ways to prevent the computer from any kind of malware.

e Stu Education ag dy m I

Identify the different typesIndia of malware by the pictures given below. Write a short note on each type of virus.

1. 2. 3. 4.

Pearson ©

ICSE_E-World 7.indd 33 14/02/2017 07:41:20 AM