Flipp Book Class-8 new1

Project -1 1. Bisakha has designed the following web page, now as Bisakha you are asked to design. Smart Computer Science Book-8 295

12Data Communication & Network CHAPTER Juna : I get surprised. How is it possible to communicate This chapter includes: around the globe using phone, chat, video call, • Data Communication etc. ? • Signals of Data Commu- Muna : Yes, it is the contribution nication of network of communi- • Communication Media cation channel . • Networking • Classification of Com- puter Network • Network Devices Juna : How is it possible to trans- fer our sound, video, text message? Muna : It's by Using the communication media, software and some other device. Juna : Is it using wire ? Muna : Wire as well as signals transmitted through air. Let's study about this in this chapter. DATA COMMUNICATION The transmission of data and information from one electronic device to an- other over a communication medium is known as data communication. In data communication , two or more computers are connected with a cable or without cable. The data communication is also called data transmission. Example of Data communication system are: 296 Data Communication & Network

a. Communication on telephone and mobile phone. b. Radio and television broadcasting. c. Sending data from one computer to another (Such as e-mail, chatting, video conference. d. Transferring data using blue tooth in Mobile phone and Laptop computer, etc. Advantages of Data Communication Data communication is the most essential technology due to the following: a. Data communication makes the fastest and cost effective communication for long distance geographical area. b. Data communication provides information to people all over the world in- stantly. Such as news broadcasting. c. You can send or receive messages or documents to any part of the world instantly with the help of data communication. d. Due to the data communication, you can do live talk with looking each other to your friends or relatives staying in any part of the world. SIGNALS OF DATA COMMUNICATION In the data communication system, data are transmitted in the form of signals which is known as the physical form of transmitted data. There are two types of data transmission signals: Smart Computer Science Book-8 297

a. Analog Signal b. Digital Signal Analog Signal : The analog signal is one that goes continue with respect to time, and may have any value within a given range. In analog signals, the transmission of data is in continues wave form as voltage varies with the time. Transmission of data (sound, picture, etc) over a telephone line is an ex- ample of analog signals. Digital Signal : A digital signal may have only two possible values that is zero (0)and one (1) which represent on and off of the electricity pulses. Transmission data among the computers are example of digital signal. COMMUNICATION MEDIA The signal of data transmission through the communication channel is known as the data transmission media. It is a path of data trans- mission to transmit source sender device to receiver device vice versa. Some of the common data transmission media are as follows: a. Guided media b. Unguided media Guided Media : The guided media is known as the wired media. In this media, data are transmitted through the wire which includes twisted pair cable, coaxial cable, fiber-optic cable, etc. Unguided Media: The unguided media is known as the wireless media. In this media, rapidly different types of new technology are coming. It is more flexible and cost effective media so it is also more popular. Radio signals, infrared signals and Micro Wave are used to transmit the data in this technology. The com- 298 Data Communication & Network

mon unguided communication technology are satellite connection, blue tooth technology, Wi-Fi (Wireless Fidelity) technology, etc. COMPUTER NETWORK Computer network is a group of computers and peripherals, connected by communication different medium. It is capable of sharing data, information, files, software and hardware resources such as printer, drives, etc among the many users. Banking cash deposit and withdraw, Automatic Teller Machine (ATM) of the bank work on the basis of computer network. Airlines ticketing system also run by computer network. Advantages of Computer Network Computer network has a lot of benefits. Some of the common advantage are as follow: a. Computer network allows to communicate among the people instantly. b. It allows to share data and information, files, software among the people at a time. c. User can share hardware resources such as printer, scanner, disk, etc. d. It allows to take backup of important data and information. Network Components Computer network is a system. It is integrated with different hardware devices swell as software devices to establish the communication among the comput- ers. Generally,Network components are two types: a. Hardware Components b. Software Components HARDWARE COMPONENTS Networking hardware, also known as network equipment or computer net- working devices, are physical devices which are required for communication Smart Computer Science Book-8 299

and interaction between devices on a computer network. Specifically, they mediate data in a computer network. Server Computer: The server computer is the main computer which provides ser- vices to the other computers in the computer network. It is also called host computer. Network operating system is installed in this computer. All the other computers are connected to the Serv- er computer. Client computer: The Computer which is connected with the main server is called client computer. It is also called work station where user run the application. It is less powerful and less storage capacity than the user computer. The Client computer is also called workstation where common user works. The client computer always takes the services from the server computer. NIC : (Network Interface Card): NIC card is a device which is used to connect computer and network cable in the Computer Network. It always coordinates to transfer of data among the computers connected to a network. It is installed in an expansion slots or in built in motherboard. It helps to trans transfer of data and information. Every NIC is as- signed a unique address called MAC (Media Access Address) which is also called physical address. This MAC address is stored in the ROM (Read Only Memory). Hub : Hub is a device that connects individual devices on a network so that they can communicate with one another. It makes sim- ple physical connection gather the signal from individual net- work devices, amplifying the signals, and then sending them onto all other connected devices. It is also used to split the network segment. It's major disadvantages are: 300 Data Communication & Network

a. It can't filter network traffic. b. It imposes limitation to the number of computer that can be connected. Switch : Like a hub, switch too connects individual devices on a network so that they can com- municate with one another. Switches are more logical than hub. Unlike a hub, network switches are capable of inspecting the data packets as they are received, determining the sources and destination device of that packet, and forwarding that packet appropriately. Repeater : Repeater is a device which is installed on the link of network. It receives signal, regenerates it and sends the refresh copy back to the link. Router : Router is a connection device which is the most intelligent device. It is used to connect two or more dissimilar network, like LAN and internet. It's main function is to find out the best path (route) for data transmission in network. It has the best traffic management capacity. So, it re- duces the amount of data traffic during the transmission. SOFTWARE COMPONENTS: Network software is an extremely broad term for a range of software aimed at the de- sign and implementation of modern networks. Various types of network software sup- port the creation, calibration and operation of networks. Specially, Network software gives life to all the hardware components of Network and control and execute them. Network Operating System (NOS): Network operating system is a set of group of program which is responsible to man- age the overall computer network and its hardware as well as software resources. Commonly Network operating system is known as server software. It is installed in the server computer. Some of the common Network operating system are Windows Smart Computer Science Book-8 301

NT, Windows 2000, Windows Server 2019, Novel Netware, UNIX, LINUX, etc. Network Protocols Network protocols are the set of rules which are followed by computer network during the data transmission. Protocols manges the system to receive and send the data among the devices connected to the network. Some of the common protocols are used in a common network are: a. TCP/IP (Transmission Control Protocol/Internet Protocol) b. NetBEUI(Net BIOS Extended User Interface) c. HHTP (Hyper Text Transfer Protocol) d. IPX/SPX (Internet Packet Exchange/Sequenced Packet Exchange) e. POP (Post Office Protocol) CLASSIFICATION OF COMPUTER NETWORK Basically Computer network is classified into different categories on the basis of following : a. Area covered by Network b. Architecture of the Network. c. Based on Topology d. Transmission medium used Based on area covered The Computer network based on area covered can be classified into three types: LAN (Local Area Network), MAN(Metropolitan Area Network) and WAN (Wide Area Network). Personal Area Network (PAN): A personal area network (PAN), is a comput- er network used for communication among computer and different technological devices close to one or two people, usually at home. For example Computer, Printer, Scanner, Gaming Consoles, Cell phone, PDA. 302 Data Communication & Network

Local Area Network(LAN) As a name, Local Area Network (LAN) connects several comput- ers within a small geographical area such as a room, building or school. Coaxial Cables are usu- ally used to connect the computers in LAN. Fiber optic cable also can be used for fast data transmission but it is expensive. Basically LANs are based on Ethernet technology. Network in your school, Bank are example of LAN. Home Network: A Home network is very similar to LAN, but this LAN has a primary use residentially. A Home network is used to connect devices in a home, such as a wireless printer that is attached to a computer and mobile device to print or scan wirelessly anywhere in the home. The source of sharing is through DSL (Digital Subscriber Line) provider. Usually, a smaller number of devices can be connected to this type of network Storage Area Network: Storage Area Network (SAN), Unlike other net- works, this network allows a user to access and store data. SAN's are primarily used to make storage devices such as Disk arrays, and they are connected to the server giving an impression as if they are connected. Smart Computer Science Book-8 303

Campus Area Network: A Campus area network also known as Corporate area network is just an interconnection of multiple Lo- cal Area Network (LAN). A CAN or campus area network spans over a shorter distance than Wide Area Net- work (WAN) and Metropolitan Area Network (MAN) Metropolitan Area Network (MAN) The Metropolitan Area Network is confined to a city or a metropolitan area. Two or more than two LANs are connected and form the MAN. ATM network of Bank is a good example Metropolitan area network. Wide Area Network (WAN) Wide Area Network (WAN) connects user across large distance, often cross- ing the geographical boundaries of cit- ies. This network uses transmission facilities provided by the telephone companies and ISP (Internet Service Providers) to transmit the data across the large geographical area. Network of Bank with e-banking, network of multi- national companies, internet are the ex- ample of WAN. Based on Architecture The Network architecture could be defined as the structure and organization of the computer's hardware and software. Based on the architecture, network 304 Data Communication & Network

can be classified into two types: b. Peer to Peer (P2P) Network a. Client/Server Networks Client/Server Network Client/Server model is the most effi- cient network model. It is also known as the distributed application struc- ture. In this network, there is a cen- tralised powerful computer known as server and all other computers or nodes or workstations which are con- nected to this server are known as cli- ents. A server machine is a host that is running one or more server programs which share their resources with clients. A client does not share any of its resources, but requests a server's contents. Therefore, this type of network is totally controlled by server. It is expensive to setup. Peer to Peer (P2P) Network In this architecture, there is not any dedi- cated server machine. Instead, there is a direct connection between the nodes. All of the computers are equal and therefore known as peers. Normally each computer serves as client/server and there is no one responsible for the entire network. This architecture is better for smaller organiza- tions's network. It is inexpensive to setup. Based on the Topology of the network Topology means the arrangement of computers in a network. Five basic to- pologies are used for arranging the computers in a network. Such as Star, Ring, Bus Mesh or Tree Topology. Smart Computer Science Book-8 305

Bus Topology In bus topology, a single cable also known as backbone carries all the data. All the computers and other peripherals devices are connected to this backbone cable. This kind of topology is used for small networks. The amount of cabling is also very less. The entire network is dependent on the single backbone cable. Star Topology In star topology, all the computers are connected to one single central device known as a Hub. The hub could be a computer hub or sometimes just a switch. The hub controls the function of this net- work. Any information, which has to be transferred from one computer to another has to pass through the central hub. This type of network is easy to setup, but if central connection point fails, the entire network stops working. But when there is a failure in cable then only computer might get effected and not the entire network. Ring Topology A ring topology is a network topology or an arrangement in which each network device or computer is attached along the same signal path to two other devices, forming a path in the shape of ring. Each device in the network handles every message that flows through the ring. Each device in the ring has unique ad- 306 Data Communication & Network

dress. Since in a ring topology there is only one pathway, ring networks are generally disrupted by the failure of a single link. Tree Topology Among all the network to- pologies, the tree topology is said to be a combination of the bus and the star to- pology. The tree like struc- ture allows us to have may servers on network and we can branch out the network in many ways. A tree structure suits best when the network is widely spread and vastly divided into many branches. A tree network may not suit small net- works as it may be a waste of cable. Mesh Topology Mesh topology works on the concept of route. In mesh topology, message sent to the destination can take any possible shortest, easiest route to reach its destination. Unlike topolo- gies like star and bus, messages are usually broadcasted to every comput- er. Similarly, in the ring topology mes- sage can travel in only one direction. Internet uses the mesh topology and the message finds its route to its destination. Based on Transmission Media Transmission media refers to the way data is transferred from one node to other node on a network. The computers or devices can be linked to each other on a network Smart Computer Science Book-8 307

through cables and satellites. For the short distance Network, Caballing is used which is called wired Network but long distance Network, caballing is not possible, there fore satellite is used to transmit data through radio waves and microwave. Such network is called, Wireless Network. So, based on transmission media wired and wireless network are existing. Points to Know • The transmission of data and information from one electronic device to another over a communication medium is known as data communication. • The Computer Network is basically referred to as a group of computers and de- vices connected to each other with different communication channel. • The purpose of computer network is to communicate among users and also allow them to share the information, data and resources. • The advantages of computer Network are communication and enable sharing of data hardware resources, files, data, information and software. • Network Components are broadly divided into two types: Hardware component and Software Component • The server computer is the main computer which provides services to the other computers. • The Computer which is connected with the main server where user works. • NIC card is a device which is used to connect computer and network cable in the Computer Network. • Hub makes physical connection with individual devices on a network so that they can communicate with one another. • Switch can determine the source and destination node of similar network. • Repeater receives signal, regenerates it and sends the refresh copy back to the next link. • Router is the most intelligent device It is used to connect two or more dissimilar network, like LAN and internet. • Router's main function is to find out the best path for data transmission in network. • Network operating system is a set of group of program which is responsible to im- age the overall computer network and its hardware as well as software resources. • Network protocols are the set of rules which are followed by computer network during the data transmission. 308 Data Communication & Network

• Computer Networks are classified into the following different categories: a. Area covered by the Network b. Network Architecture c. Network Topology d. Based on transmission media • Based on the area covered by any network, they are classified into LAN, MAN and WAN. • LAN is a network covering a small geographical area like home or office. • MAN is a network connects two or more LANs together but does not extend beyond the boundaries of an area. • WAN is a network that covers a broad geographical area. • Network Architecture could be defined as the structure and organization of the com- puter's hardware and software. • Based on the architecture involved for creating a network, it is divided into two main categories: a. Client/Server Network b. Peer to Peer Network • Client/Server Networks have a centralised computer known as Server while all other are known as a Client. • In Peer-to Peer network, all the machines are interconnected and each machine behaves as a server and a client. • Topology means the arrangement of computers in a network. • There are five basic topologies used for creating a network. a. Bus Topology b. Star Topology c. Ring Topology d. Tree Topology e. Mesh Topology • Various mediums are used for networking, cables are used for small distance and radio waves and microwaves are used for long distances. • Cables used for networking are twisted pair cable or coaxial cable or fiber optic cable. • Radio waves and microwaves can be transmitted through satellite. Smart Computer Science Book-8 309

Terms to Know Wave : Disturbance or variation of energy hen travels through a me- dium. Wireless : Connection without using wire Radio Signal : Type of electromagnetic radiation best-known for their use in communication technologies, such as television, mobile phones and radios. Infared Signal : A means of using light to transmit a signal over distance. Micro Wave : Microwave is a line of sight wireless communication technology that uses high frequency MAC Address : A hardware identification number that uniquely identifies each device on a network. Network Traffic : Amount of data moving across a network at a given point of time. Logical : Sense according to the rules of logic Data PAcket : A unit of data made into a single package that travels along a given network path. Ethernet : A computer network architecture consisting of various specified local-area network protocols, devices, and connection methods. Node : A connection point that can receive, create, store or send data along distributed network routes. Peripheral Device : Devices connects to a computer system to add functionality. Worksheet Objective Questions 1. Fill in the blanks: a. The ........................ is formed by the network of millions of computers all over the world. b. The transmission of data and information from one electronic device to another over a communication medium is known as ............... ....................................... 310 Data Communication & Network

c. The ....................... .............................. is one that goes to continue with respect to time, and may have any value within a given range. d. A digital signal may have only two possible values that is ................................. ................and one ..................................... e. ..................................... ....................................... is a path of data transmission to transmit source sender device to receiver device vice versa. f. ............................. .............................. is capable of sharing data, information, files, software and hardware resources. g. The ..................................... computer is a main computer which provides ser- vices to the other computers. h. Based on area covered by network are........................., ............................ and ................................. i. A .................................network is limited within the room or building. j. A .................................network is limited to a town or city. k. Star topology uses the device called ............................ to connect to all the computers. l. Client/Server network is a centralised powerful computer known as.................. ................................ m. In bus topology, a single cable also known as ........................... . n. ....................... ............................. is said to be a combination of the bus and the star topology. o. ...................... topology works on the concept of route of routes. p. Based on transmission media ........................... and ....................... network are existing. q. The Computer which is connected with the main server is called ...................... ............ computer. 2. State wether the following statements are true or false: a. Data is transmitted over a telephone cable in the form of digital sig- nal. Smart Computer Science Book-8 311

b. Transmission data among the computers are example of analog signal. c. Server computer is a host computer. d. Windows NT is a example of network operating system. e. Internet is a example of Wide Area Network. f. Bank ATM is an example MAN. g. School Computer Lab is a perfect example of LAN. h. In star topology, if the hub fails the entire network is disabled. i. Mesh topology message can travel in only one direction. j. Internet is an example of Mesh topology. 3. Match the following: Message takes shortest route to reach a. LAN destination. b. MAN Hub c. WAN Networking Interface Card d. NIC Centralised powerful computer. e. Networking device Transmit radiowaves and microwaves f. Server Wide Area Network g. Bus Topology Metropolitan Area Network h. Tree Topology Local Area Network i. Mesh topology Single backbone cable j. Satellites Combination of bus and star topologies. 4. Write the full forms of: a. Wi-Fi .................................................. b. ATM...................................................... c. NIC ................................................... d. NIC ....................................................... e. MAC.................................................. f. ROM .................................................... g. LAN ................................................ h. NOS..................................................... 312 Data Communication & Network

i. TCP/IP .............................................................................................................. j. POP................................................... k. MAN..................................................... l. WAN ................................................. m. ISP........................................................ n. P2P ............................................... o. NetBEUI............................................... 4. Choose the correct option: a. Transmission of data over a Telephone Line is i) Analog ii) Digital iii) Hybrid iv) All of these b. Which one is guided media? ii) Twisted Pair i) Co-exal Cable iii) Fiber Optic iv) All of these c. Network Operating System is installed in : i) Host Computer ii) Client Computer iii) Work station iv) All of these d. Which is not protocol? ii) IPX/HPX i) TCP/IP iv) UNIX iii) Net/BEUI e. Which is unguided media? ii) Micro Waves i) Radio Waves iv) All of these iii) Infrared f. Network Operating System is installed in : i) Host Computer ii) Client Computer iii) Work station iv) All of these g. Client-Server Network is based on : i) Transmission Media ii) Architecture iii) Topology iv) Area Covered Smart Computer Science Book-8 313

Descriptive Questions 1. Answer the Following questions: a. What is data communication? Give one example. b. Why do you need data communication? c. Differentiate between analog and digital signal. d. What do you mean by transmission media? Name four common data transmission media. e. What is computer network? Give one example. f. Write any four advantages of computer network. g. Write the common network hardware components. h. What is Network Interface Card? i. Differentiate between hub and switch. j. What is router? k. What is protocol? Give any two example. l. Differentiate between LAN and MAN. m. What is WAN? Give one example. n. Differentiate between client/Server network and P2P network. o. What do you mean by topology? Write the name of five topologies. p. What is ring topology? Analytical Case Study Questions: 1. Dalima Trading Pvt. Ltd. is planing to connect all together 20 computers in the corporate office building. Now, on the basis of this relation, answer the following questions: a. Which type of Network will be formed after connecting these computers? b. Recommend the most economical cable with a high data transfer speed that can be used to connect these computers. c. List out the device required to establish this network ? 2. Shree Kanata Chaudhary has a laptop, printer, mobile phone, tablet. He is willing to connect all these devices: a. Which type of Network will be formed ? b. Which type of media will be used to transfer data from one device to another ? c. List out the device required to establish this Network ? 314 Data Communication & Network

3. All the 25 computers in an organization are connected on a network so that they can use one printer and access the internet through the same modem. Now, Answer the following questions in the basis of this relation: a. Why is it good idea to connect all the computers on a network ? b. Which type of Network will be established ? c. List out the device required to establish this Network . 4. Identify the devices used for each of the following: a. Hardware component used to connect computers on a network . b. Every compute has a network component should have this card . c. Eight wire connector that is commonly used to connect the network interface card with the hub. 5. Mr. Sherpa wants to connect his computer with the main computer of each department on his office. He has asked his assistant to find out about the following: a. Which type of Network Technology will be used? b. Which type of network will be formed ? c. Illustrate the network with diagram. Activities Based Questions: 1. The computer teacher has asked the students to make a presentation on the following topic. a. Types of network b. Wired and Wireless network technology Using the suitable presentation software Prepare the presentation with relevant picture, video clip and information Smart Computer Science Book-8 315

13Basic Concept of Programming CHAPTER Juna : Without life how does computer is working ? This chapter includes: Muna : Due to computer pro- • Computer Program and gram, it works . Programming. Juna : What is written in the pro- • Program development gram ? technique. • Program Design Tools • Knowing symbols used in Flowchart. Muna : Clear set of instruction is written in program. Juna : How is it written such program ? Muna : Before writing program, it needs a complete design well mentioned how does it work. It is designed with some tools such as algorithm & flowchart . Juna : How to design it ? Is it engineering ? Muna : Yes, it is ! Clearly flow of work is defined with symbols in flow chart and stepwise flow of instruction are written in the algorithm. Let's discuss in detail ! COMPUTER PROGRAM Computer is a machine which can not perform any task itself. It needs set of our clear instructions to perform a task. So, we have to write a set of instruc- tions what and how should our computer perform a task. Such a written set of instruction is known as the computer program. To write a computer program, 316 Basic Concept of Programming

we must maintain and follow the certain process is called programming. PROGRAM DEVELOPMENT TECHNIQUE There are certain technique or logic and process to develop a computer pro- gram such as understating the problem, designing with program design tools, coding, testing, debugging and implementation, which is known as program- ming. The programming is done by computer programmer using the high level computer language. PROGRAM DESIGNING Program designing refers to find the steps to solve the existing problem. Plan- ning shows the direction of flow of working process, calculation, decision mak- ing and other additional information in the program. It gives clear idea and logic to the programmer to solve the problem. It is also called program plan- ning. There are some program designing tools Some of the most commonly used planning tools are a. Algorithm b. Flowchart. c. Pseudo Code Algorithm Algorithm is a set of rules and sequential steps that define how a problem can be solved in a finite and ordered sequence is known as algorithm. In an ordered sequence, the next instruction follows automatically. It is written in simple language. An algorithm should have following properties: a. The steps of an algorithm should be written clear. b. The steps of algorithm should be executable by the computer. c. The number of steps involved should be finite. d. Input should be in ready before operation. e. Algorithm should give output after executing the number of steps. Flowchart A flowchart is a pictorial representation of the problem solving process. Differ- Smart Computer Science Book-8 317

ent Geometrical symbols are used to show the various operations and deci- sions making to solve a problem. The flowchart symbols are connected by arrows to show the sequence of operations. The following table shows a set of symbols which are used while drawing flowcharts. Advantages of Flowchart 1. Flowcharts are used as a visual display for communicating the logic. 2. A flowchart can be used as model of a program. The study of the flowcharts gives new ideas to solve the problems. 3. A long procedure can be shown in the form of a small flowchart. 4. Flowcharts serve as proper program documentation. A programmer who has designed it can be able to tell his approaches to a new programmer through a flowchart. New programmer can understand it easily in absence of main programmer. 5. Once the flowchart is completed, it acts as a guideline and makes easy to write the program. Limitation of the Flowchart 1. Flowcharts are sometimes difficult to translate into programming language. 2. There is no uniform practice for drawing a flowchart for the same problem. 3. It is a time consuming task. 4. Program can be modified but is not possible to modify the flowchart. It should be redrawn, which becomes costly. 5. When there are complex branches and loops, the flowchart becomes more complicated. Rules for Flowcharting 1. The direction of flow in flowchart is from top to bottom or from left to right. 2. Arrowheads are used to show the flow of information or sequence of actions. 3. Use only one ‘Start’ and one ‘Stop’ point. 4. The terms used in the flowchart should be cleared. 5. Flowchart should be cleared. 318 Basic Concept of Programming

6. Avoid using computer language in the flowchart. Symbols used in the Flowchart Geometrical Symbol Name of the Symbol Purpose Start/Stop Symbol. Shows start and end of task. Input/output Symbol. Shows the input output opera- tion of program. Processing Symbol. Shows the process or action in the program. Logical/Decision mak- Shows the decision making or ing Symbol. choice in the flowchart. Flow Lines. Show the flow of the operation. Connector symbol It is used, if flowchart is not fit on single page to show the connec- tion of different pages. Structure of Algorithm and Flowchart Basically,the following common control structures are required for writing an al- gorithm Sequential : The algorithm is written in sequential steps i.e. step 1, step 2, …. , step n within Start and End structure. Selection : For the purpose of selection, If else structure can be used. Looping : Looping is used for repetitive execution. Worked out Examples of Flowchart Sequential Structure 1. Nabil Bank has decided to calculate the simple interest @ 10% for their custom- ers. Write algorithm and flowchart for this case. Smart Computer Science Book-8 319

Algorithm Flowchart Step-1 : START Step-2 : Read principal amount, time and rate START Step-3 : Calculate simple interest Read P, T, R Step-4 : Display result. SI=(P*T*R)/100 Step-5 : STOP PRINT SI STOP 2. Bikrant has given a task to solve the problem of finding out sum, product and dif- ference of any two numbers. Flowchart Algorithm Start Step-1 : START Step-2 : Read any two numbers. Read A, B Step-3 : Find the sum, product and difference. S=A+B Step-4 : Display result. D=A-B Step-5 : STOP P=A*B PRINT S PRINT D PRINT P Selection Structure STOP 1. Jacky and her group has given a class work to draw a flow chart to find out smaller number out of any two number. Algorithm START Step-1 : Start Read A , B Step-2 : Ask two different numbers. Step-3 : Compare both number to find greater. No IS A<B ? Yes If first number is greater, print it. PRINT B PRINT A If second number is greater, print it. Step-4 : Stop STOP 320 Basic Concept of Programming

2. Bidhu and his group are assigned a work in the class to write an algorithm and draw a flowchart to find out greatest number out of three numbers. Algorithm START Step-1 : Start Step-2 : Ask three different numbers. Read A , B, C Step-3 : Compare three numbers with Yes No each other. IS A>B ? - If first number is greatest, print it. IS A>C ? No No Yes IS B>C ? - If second number is greatest, print it. Yes - if third number is greatest, print it PRINT A PRINT C PRINT B Step-4 : Stop STOP 3. School has conducted a examina- tion and decided the grading system in the basis of following condition. Average Grade >80 ‘A+’ >60 ‘A’ START >50 ‘B+’ >40 ‘B’ Read P <=40 C+ Yes PRINT A+ Now, write algorithm and draw flowchart . IS P>80 ? PRINT A Algorithm No Step-1 : Start Step-2 : Ask percentage marks. Yes IS P>60 ? Step-3 : Compare the percentage marks. No - If percentage is above 80, print A+. Yes PRINT B+ IS P>50 ? - If percentage is above 60, print A No - If percentage is above 50, print B+. Yes PRINT B - If percentage is above 40, print B. IS P>40 ? - If percentage is below 50, print B+. Step-4 : Stop No PRINT C+ STOP Smart Computer Science Book-8 321

Loop Structure 1. Ravi Chandra Maharjan’s group is given a task to write an algorithm and draw a flowchart to print a name of a student 10 times. Flowchart Algorithm S TART Step-1 : START Read Name Step-2 : Start to Count (Count=1) Step-3 : Read a name Count=1 Step-4 : Display your name Print Name Step-5 : Count one more (Count=Count+1) Step-6 : Is Count <=10 ? Count=Count+1 - if yes, repeat step-3 Yes Step-7 : STOP Is Count <=10 ? No STOP Pseudocode Pseudocode is a kind of program design tool. It is written in step by step what does your program do. It is written in our language almost as we do in the pro- gramming language. Commonly, it is used to give more focus on programming logic and technique. Examples: 1. Write a Pseudocode to input any two number and find the sum. Start INPUT First number INPUT second number Calculate sum of these two numbers Display the sum Stop 2. Write a pseudocode to find the greater number out of any two input numbers: START INPUT First number INPUT second number 322 Basic Concept of Programming

IF First number is greater than the Second number PRINT \"First number is greater\" ELSE PRINT \"Second Number is greater\" END IF STOP 3. Write a pseudocode to print your name 10 times. START INPUT Enter your name Initialize I to 1 WHILE I less than or equal to 10 PRINT name Increase value of I by 1 as I=I+1 WEND STOP Points to Know • The transmission of data and information from one electronic device to another over a communication medium is known as data communication. • Computer program is a set of instructions which orders to the computer to perform the task. • There are certain steps and process which are followed to write a computer pro- gram is called programming. • The tools which are used to design the program is called program design tools. Algorithm,Flowchart, Pseudo code are program design Tools. • Algorithm is a set of rules and sequential steps that define how particular problem can be solved in a finite and ordered sequence is known as algorithm. • A flowchart is a pictorial representation of the problem solving process. Different Geometrical symbols are used to show the various operations and decisions mak- ing to solve a problem. Smart Computer Science Book-8 323

Terms to Know Program : Set of instruction to tell to the computer. Programming : Precesses involved to write a program. Logic : Idea to write a program. Coding : Write instructions to a computer program. Bugs : Errors in the program. Debugging : Finding and removing errors in the programs. Looping : Repetition of task. Worksheet Objective Questions 1. Fill in the blanks: a. The programming is done by computer ........................................ b. ............................... is a set of rules and sequential steps. c. The number of steps involved should be finite. d. ................................... is a pictorial representation of the problem solving pro- cess. e. The flowchart symbols are connected arrows to show the sequence of opera- tion. f. ............................... is used to repetitive execution. g. ............................... is used to give more focus in programming logic and tech- nique. 2. State whether the following statements are true of false: a. Computer can perform the task itself. b. Computer does not work unless it is given correct instruction. c. Algorithm should give output after executing the number of steps. 324 Basic Concept of Programming

d. Flowchart is a program writing tool. e. Flowchart can be used as model of a program. f. Flowcharts are used as a visual aid for communicating logic. g. Arrow heads are used to show the sequence of action. h. You can use many 'Start' and 'Stop' point. Descriptive Questions 1. Answer the following questions: a. What is computer program? b. Write the program development technique. c. What do you mean by programming? d. What do you mean by program designing? e. What is Algorithm? f. Write any three properties of Algorithm. g. What is Flowchart? h. Write any three advantages of Flowchart. i. Write the any three advantages of Flowchart. j. Write some rules of flowchart. k. What is pseudocode? 2. Write an algorithm, pseudo code and draw a flowchart : a. To read marks in science, maths and computer in variable S, M and C respec- tively and find the total and average marks. T=S+M+C and AV=(S+M+C)/3 b. To read principal amount, time and rate in variable P, T and R and find out simple interest. Hint: SI=(P*T*R)/100. c. To read the length and breadth of a rectangle in variable L and B and calculate perimeter and area. Hint: P=2*(L+B) and A=L*B. 3. To read a age of a person in variable A and find wether he is senior citizen of na- tion or not. If his age is above 60, senior citizen otherwise he is not senior citizen. Smart Computer Science Book-8 325

4. To read the age of a person and find age status in the basis of following conditions: Age Status of Age <5 Baby <10 Child <18 Teenager <40 Old <60 Adult >=80 Old 5. To read 10 numbers in a N variable and find their sum. S=S+N 6. To read a number and display multiples up to 10th terms. 7. To display first 10 natural numbers (1 to 10) with their sum. 8. To read two numbers in variable NU and DENO. Divided the number NU by DENO and print the quotient, provided the variable DENO is not equal zero (0). If DENO is zero (0), Print the error message \"You can not divided by zero\". 326 Basic Concept of Programming

Programming in Q-basic CHAPTER Juna : How to write computer This chapter includes: 14 program, ma'am? • Introduction of Qbasic Muna : Using the high level pro- • Elements of Qbasic gramming language, • Start the program cod- we have to write clear ing, saving and run the program. instruction according to program design . Juna : Ma'am, Which high level language we use, ? Muna : There are different types of High-level Language. Here, we use Q-BASIC. Juna : Is here any rules to write program ? Muna : Yes, There are certain keywords, Using these key words, we write clear instruction followed by rules. Lets go ahead in detail for writing computer program . INTRODUCTION QBASIC is a high level programming language which stands for Quick Begin- ners All Purpose Symbolic Instruction Code. It is developed by Microsoft Cor- poration in USA. QBASIC was released with the operating system MS-DOS (Microsoft Disk Operating System) in 1985. It provides user friendly environ- ment with pull down menus, which makes user easier to work. Smart Computer Science Book-8 327

FEATURES OF QBASIC a. Smart Editor b. Simple and easy to understand c. Supports modular programming d. Supports graphical user interface e. It provides user friendly environment. f. It supports line number and line label. g. It supports versatile Looping and decision making LOADING THE QBASIC To load from the Windows environment, follow the following steps: Step-1 : Find the QBASIC folder. Step-2 : Open the folder. Step-3 : Double click on QBASIC.EXE file. Now, You get the welcome Screen of QBASIC. You should press the 'Enter Key' to clear the welcome screen. Title Bar Menu Bar View Window Immediate Window Status Bar COMPONENTS OF Q-BASIC WINDOW The Q-BASIC windows is consisted of menu bar, title bar, status bar, view window, immediate window. 328 Programming in Q-basic

View Window : It is upper part of the window which allows to write series of instructions. Actual program is written in this window. To get the output result of set of instructions, you should give run command. Immediate Window : It is lower part of the window which allows to write only one instruction at time. After typing instruction and pressing En- ter key, you get the output result. CODING Coding is the process of writing programs using commands to solve a prob- lem. The coding is done in view window. If any error comes, editing can be done in the same window. Type the following programs as given below and run it. Sample Program REM : Testing QBASIC Program CLS PRINT “Hello Programming World!!!” PRITNT PRINT “It is my First Program.” END RUN A PROGRAM To get the output result of the above coded programs, you must run the pro- gram. To run a program, follow the following steps: Step 1 : Select ‘Start’ option from ‘Run’ menu. Now program starts to run. You get the following output. Output Hello Programming World!!! It is my First Program. Trick & TIPS • You can press Shift+F5 to run a program firm beginning and F5 keep continue the ‘Run’ command from the current position previous execution. Smart Computer Science Book-8 329

SAVE A PROGRAM Save a program is to store a program under a file name in the disk permanent- ly for the future use. When you save you program file, QBASC automatically add .BAS extension. To save a program, follow the these steps: Steps to Follow: Step-1 : Press Alt+F to ac- cess the File menu. Step-2 : Select Save or Save As option and press Enter key. Step-3 : Now, Save dialog box appears as giv- en. Step-4 : Select the location and type the file name. Step-5 : Now, press the Enter key or click the 'Ok' button. OPEN A SAVED PROGRAM The ‘Open’ command is used to load an already saved program from the disk into the memory. To perform this task, do the following: Steps to Follow: Step-1 : Select the ‘Open’ op- tion of the ‘File’ menu. Step-2 : The ‘Open’ dialog box appears. Step-3 : Select the file name from list of files by moving the cursor us- ing arrow or directional key. Step-4 : Select the file and press enter key. 330 Programming in Q-basic

Now, you will get the program on the view window. STARTING NEW PROGRAM The ‘New’ command is used to start new program. To use this command do the following: Steps to Follow: Step-1 : Select ‘New’ form the ‘File’ menu. It displays the dialog box, if existing program file is not saved. Step-2 : Select ‘Yes’ to save or ‘No’ to clear the screen without saving. EXIT FROM QBASIC The ‘Exit’ command is used to exit from the QBASIC program. To perform this task, do the following: Step-1 : Select ‘Exit’ from the ‘File’ menu. If the file is not saved it displays the message box to alert you to save file. Trick & TIPS • You can press ‘Alt+F’ to activate the ‘File’ menu. Then using pull down menu and select required command. ELEMENTS OF QBASIC The programming language is consisted by different types of elements. Each element has own common function in the programming which are most useful to develop the computer program. Some of the common elements of QBASIC are: a. Character set b. Constant c. Variable d. Data e. Operators f. Statement Smart Computer Science Book-8 331

Character Set All the characters or symbols which are accepted by QBASIC are called char- acter set. The character set includes the alpha character A to Z or a to z, num- ber 0 to 9 and special symbols: + - * / \\ ^ \" ' , ; : = > < ( ) . ? $ % & ! # space. Constant Constant refers to the data item whose values do not change during the ex- ecution of program. Such as “Ramu”, “Kathmandu”, 50, 10, etc . There are two types of constant: a. Numeric Constant b. String Constant Numeric Constant: Numeric constant may positive or negative numbers which performs the mathematical operations such as addition, subtraction, multiplication, etc. Rules for numeric constants • Comma is not allowed in the numeric constants. 1,000 is invalid but 1000 is valid. • Blank space is not allowed in a numeric constant. 5 000 is in valid but 5000 is valid • Alpha character is not used in the Numeric constant. Rs. 25 is invalid but 25 is valid • Minus sign ‘ – ‘ is used to represent a negative number and ‘+’ sign is used to represent positive number. But + sign positive value takes by default. It is not necessary to write. +25 or 25 represents positive number and -25 represents negative number. Sample Program CLS QP = 500 RP = 10 TA = QP * RP D = 10 * TA / 100 NT = TA - D PRINT \"Total Amount=\"; TA PRINT \"Discount=\"; D 332 Programming in Q-basic

PRINT \"Net Total=\", NT END • In this program, 500 and 10 are the numeric constants. String Constant : String constant is the combination of alphabets, numbers and special symbols written within quotation marks. String constant or string constant can not be used for the mathematical operations. Rules for string constant • String constant must be written within double quotation marks. For example RAMU is an invalid string constant but “RAMU” is a valid string constant. • Space can be given in a string constant. “Rahul Mandal” is a valid string constant. • Number, special characters, roman number can be included in the string con- stant. For example: “Maitidevi- 33” Sample Program CLS N$ = \"Rahul Mandal\" AD$ = \"Shiraha, Lahan-5.\" PH$ = \"033-2550607.\" PRINT N$ PRINT AD$ PRINT PH$ END • In this program Rahul Mandal\", \"Shiraha, Lahan-5.\" and “033-2550607.\" are string constant. Variable Variable is a character or group of character which represents reference or name to any data for the computer memory. The value of variable may be changed during the execution of the program. For example A, N$, ROLL, R!, Q#, X& are some valid variables. There are two types of variables: a. String variable b. Numeric variable String Variable: A variable which stores string type of data or value is called string variable. For Smart Computer Science Book-8 333

example: “Ram”, “Maitidevi-33” “Class –IV” etc. N$, AD$, CL$ are valid string variables. $ dollar sign is used in the end of string variable. Numeric Variable: A variable which stores numeric type of data or value is called string variable. Numeric type of data may negative of positive. For example: 50, 500,400, etc. there are four types of numeric variables: a. Integer Variable b. Long Integer Variable c. Single Precision Variable d. Double Precision Variable Integer Variable: Integer variable stores integer number which my negative or posi- tive whole number. Percentage (%) sign is used in the end of integer variable. Integer variable supports the range of value -32768 to 32767. For example: A%=50, A% is an integer variable and 50 is the whole number. Long Integer Variable: Long integer variable stores long range of integer number. It can support the range of data -2,147,483,648 to 2,147,483,647. Ampersand (&) symbol is used in the end of long integer variable. For example: N&=234, N& is a long integer variable and 234 is a whole number. Single Precision Variable: The single precision variable can store the number with up to seven digits accuracy. It is a default variable. It consumes 4 bytes memory space. Exclamation ( ! ) symbol is used in the end of single precision variable name. For example: A!=50.50,here A! is a single precision variable and 50.50 is a fraction value. Double Precision Variable: Double Precision variable stores long range of fraction- al value. It gives up to 15 digits accuracy to store data. It reserves 8 bytes memory space. Hash symbol ( # ) is used in the end of double precision variable. For example: N#=789.45, here N# is a double precision variable and 789.45 is a fractional value. Rules for Naming a Variable • Variable name starts with alpha character (A to Z or a to z). For example N$, N% are valid variable name. 334 Programming in Q-basic

• Variable name may be given up to 40 characters long. • Blank space is not allowed in the variable name. For example: ROLL NO is not valid but ROLLNO is valid variable name • Keywords or reserve words of QBASIC are not allowed as a variable name. IN- PUT!, LET% are invalid variable name. Sample Program CLS LET N$ = \"Rabin Gupta\" LET AD$ = \"Rajbiraj- Campus Road, Saptari\" LET PH# = 9848116626 PRINT N$ PRINT AD$ PRINT PH# END • In the Above program N$ and AD$ is a string variables, and PH# is a double precision variable. Because the number assigned in the variable is more than 7 digits. If you are try to assign in others variable it displays error. Sample Program CLS A! = 25456.55 B% = 600 P# = A! * B% PRINT P# END • In the above program A! is single precision variable where seven digits fractional value is assigned, B% integer where whole number is assigned and P# is a double precision variable where output will be more than in seven digits in fraction. Trick & TIPS • Precision variable can store whole number as well as fraction values. Smart Computer Science Book-8 335

Points to Know • QBASIC is a high level programming language. It is used to develop application program. • Actual program is written in the view window of the QBASIC. • Immediate window is used to run the single instruction. • Coding is the process of writing programs using commands to solve a problem. • Characters or symbols which are accepted by QBASIC are called character set. • The elements of QBASIC consist of the character set, constants, variables, opera- tors and the statements. • Constant refers to the data item whose values do not change during the execution of program. There are two types of constant string and numeric constant. • Variable is a character or group of character which represents reference or name to any data for the computer memory. • The value of variable may be changed during the execution of the program. • Variable is classified into two common group string and numeric variable. • Numeric variables are four types which are Integer Variable, Long Integer Vari- able, Single Precision Variable, Double Precision Variable. Terms to Know Variable : Reference or name to any data for the computer memo- ry. Constant : Data item whose values do not change during the execution of program. String : A data type used in programming to represent text rather than numbers. Precision : Refers to the closeness of two or more measurements to each other. Integer : Number which may negative or positive whole number. 336 Programming in Q-basic

Worksheet Objective Questions 1. Fill in the blanks: a. QBASIC is a ................................. level programming language. b. Actual program is written in............................. window. c. ................................ is the process of writing program. d. .............................. is used to keep continue the previous run command. e. QBASIC was released in........................ f. ............................... constant is quoted with quotation mark. g. ................................. is a name to any data for the computer memory. h. .......................... variable is always followed by dollar sign. i. Double precision gives up to ............................ digits accuracy. j. Single precision gives up to .............................. digits accuracy. k. Variable name may be up to ............................... characters long. 2. State wether the following statements are true of false: a. Computer can perform the task itself. b. Immediate window is used to run a multiple instructions at a time. c. Constant value does not change during the program execution. d. 1, 000 is a valid numeric constant. e. Blank space is not allowed in numeric constant. f. Value of variable may be change during the program execution. g. Precession variable does not store fractional value. h. Integer is a default variable. i. String variable is always followed by dollar sign. Smart Computer Science Book-8 337

3. Match the Following a. Single precession % F5 b. Double precession ! $ c. Long integer Shift +F5 # d. Integer & e. String f. Keep continue previous run command g. Run from initial phase Descriptive Questions 1. Answer the following questions: a. What is QBASIC ? b. Write any four features of QBASIC. c. Differentiate between view window and immediate window. d. What do you mean by coding? e. Write the name of common type of QBASIC elements. f. What does character set include? g. What do you mean by constant? h. Write the rules for numeric constant. i. Write the rules for string constant. j. What do you mean by variable? k. Write the rules for name a variable. l. What is numeric variable? Write the type of numeric variable. m. What do you mean by precession variable? Write their types. n. What do you mean by integer variable? 338 Programming in Q-basic

15Operator, Operand & Expression CHAPTER Juna : Wow, programming is so fun! What we learn in this This chapter includes: chapter Ma'am? • Introduction of opera- Muna : To form a clear instruc- tors operand and ex- tions, keyword is not pression enough, it needs some el- ements . • Types of Operators and Expression • Hierarchy of Arithmetic operation. • Hierarchy of Arithmetic operation. Juna : Oh, interesting ! Let's go ahead. Muna : Combination of keyword, operators and operand forms clear instruction also called expression. On the basis of such instruction, computer works. Juna : How do operators work ? Muna : Operators help to perform the operation, such as add, subtract, combine text, etc. OPERATORS Operators are special symbols which come with expression to perform the operation during the program execution. Such as mathematical operation, logical operation, string operation and relational operation. QBASIC supports four types of operators: Smart Computer Science Book-8 339

a. Arithmetic Operators b. Relational Operators c. Logical Operators d. String Operators Arithmetic Operators The symbols which are used to perform the mathematical operation is called arithmetic operators. Arithmetic operators always operate on numeric con- stant and variable. The result prepared by arithmetic operators will be dis- played on the screen or assigned in the variable. QBASIC supports different types of arithmetic operators, shown in the table. Operators Function Example + - Addition A+B * / Subtraction A-20 \\ ^ Multiplication 20*5 MOD Real division A/B Integer Division A\\B Exponential A^2 Modulo Arithmetic (Return re- A MOD B mainder of division calculation.) Hierarchy of Arithmetic Operator If arithmetic expression contains more than one operator, then operators are operated one after another in the basis of their priority. The order of opera- tional priority is called hierarchy of operation. The hierarchy table is shown as follows: Arithmetic Operators Symbol Priority Exponential ^ 1st Multiplication and division *and / 2nd Integer division / 3rd Modulo Arithmetic MOD 4th Addition and subtraction + and - 5th 340 Operator, Operand & Expression

Example: 10 + 20 / 4 * 5 - 2 ^ 2 Priority Operation Output 1st 2^2 10+20/4*5-4 2nd 20/4 10+5*5-4 3rd 5*5 10+25-4 4th 10+25 35-4 5th 35-4 31 (Final Result) Trick & TIPS • If expression is inside a bracket ( ), then it is operated first. If an expression contains the same order of priority of operators, the operations are done from left to right. Lab Activities 1. Class VIII students have been as- signed a task fter completing the class to type the following expression and note down the result. Expression Result PRINT 7+10*5 PRINT 5^3+4*2 PRINT 10 MOD 3 + 5 PRINT 9/6\\4 PRINT (5+10 *15/3) PRINT (10+2)^2 PRINT (4+2)/(2+1) Smart Computer Science Book-8 341

Relational Operators The symbols which are used to compare two values is called relational op- erators. Relational operators are used in logical expression which returns the value true (-1) or false (0) called Boolean value. QBASIC supports the follow- ing relational operators: Operators Name of Operator Example > Greater A>B < Smaller A<B >= Greater than or Equal to A>=B <= Smaller than or Equal to A<=B = Equal A=B <> Not equal to A <> B Logical Operators Logical operators are used to combine two or more relational expressions or conditions and returns single value true (-1) or false (0). So, Logical operators are also called conjunction operators. QBASIC supports different types of logi- cal operators. Some of the common operators are: a. AND b. OR c. NOT AND operator AND is a logical operator which returns true value (-1), if all the conditions are satisfied, otherwise returns false value ( 0 ). Syntax: first condition AND Second Condition ……….. Examples: PRINT 10>5 AND 10> 8 It returns true value (-1) because all the conditions are satisfied PRINT 10>5 AND 10>20 It returns false value ( 0 ) because only first condition is satisfied but second condition is not satisfied. 342 Operator, Operand & Expression

The truth table of AND operator Condition AND operator Condition Result TRUE (-1) AND TRUE (-1) TRUE (-1) TRUE (-1) AND FALSE ( 0 ) FALSE ( 0 ) FALSE ( 0 ) AND TRUE (-1) FALSE ( 0 ) FALSE ( 0 ) AND FALSE ( 0 ) FALSE ( 0 ) OR operator OR is a logical operator returns true values (-), if any one or all the conditions are satisfied otherwise returns false values (0) Syntax: first condition OR Second Condition ……….. Examples: PRINT 10>5 OR 10> 8 It returns true value (-1) because both conditions are satisfied PRINT 10>5 AND 10>20 It returns false value (-1 ) because first condition is satisfied but second condition is not satis- fied. PRINT 10>5 OR 10>8 It returns false value (0), because both conditions are not satisfied. The truth table of OR operator Condition AND operator Condition Result TRUE (-1) OR TRUE (-1) TRUE (-1) TRUE (-1) OR FALSE ( 0 ) TRUE (-1 ) FALSE ( 0 ) OR TRUE (-1) TRUE ( -1 ) FALSE ( 0 ) OR FALSE ( 0 ) FALSE (-1 ) NOT operator NOT is a logical operator which operates only one condition. It logically reverse an outcome making a true condition false or a false condition true. Syntax : NOT (condition) Smart Computer Science Book-8 343

Examples: PRINT NOT (20>30) It returns true value (-1) because conditions is not satisfied but NOT operator reverse and returns the result. PRINT NOT (30>20) It returns the false value ( 0 ) because conditions is not satisfied but NOT operator reverse and returns the result. The truth table of OR operator Condition Result TRUE (-1) FALSE ( 0 ) FALSE (0) TRUE (-1) Lab Activities 1. Anamika Yadv and her friends have been assigned a practical work to test the following conditions in the immedi- ate window and note down the output result. Now, what result will be noted in the output and True or False col- umn. Conditions Output True or False PRINT 2>4 AND 4>2 PRINT 2>4 OR 4>2 PRINT 4>1 AND 4>2 PRINT 2>1 AND 1>2 PRINT 2>4 OR 1>2 PRINT 2>1 OR 1>2 PRINT NOT(2>4) PRINT NOT (4>2) PRINT NOT(2>4 OR 2>5) PRINT NOT(2>4 OR 5>3) PRINT NOT(2>4 AND 2>5) PRINT NOT(2>4 AND 5>3) 344 Operator, Operand & Expression