RS3668_COMPUTER-SCIENCE-GRADE-9 (1).pdf

Computer Science Grade 9 Government of Nepal Ministry of Education, Science and Technology Curriculum Development Centre Sanothimi, Bhaktapur Computer Science Grade 9 Government of Nepal Ministry of Education, Science and Technology Curriculum Development Centre Sanothimi, Bhaktapur 2076 Publisher: Government of Nepal Ministry of Education, Science and Technology Curriculum Development Centre Sanothimi, Bhaktapur © Publisher Edition: 2076 BS (2020 AD) Printing: Janak Shikshya Samagri Kendra Limited Sanothimi, Bhaktapur Preface The curriculum and curricular materials are developed and revised on a regular basis with the aim of making education objective-oriented, practical, relevant and job oriented. It is necessary to instill the feelings of nationalism, national integrity and democratic spirit in students and equip them with morality, discipline and self-reliance, creativity and thoughtfulness. It is essential to develop in them the linguistic and mathematical skills, knowledge of science, information and communication technology, environment, health and population and life skills. It is also necessary to bring in them the feeling of preserving and promoting arts and aesthetics, humanistic norms, values and ideals. It has become the need of the present time to make them aware of respect for ethnicity, gender, disabilities, languages, religions, cultures, regional diversity, human rights and social values so as to make them capable of playing the role of responsible citizens. This textbook for grade nine students as an optional Computer Science has been developed in line with the Secondary Level Optional Computer Science Curriculum, 2074 so as to strengthen knowledge, Skills and competencies on computer literacy. It is finalized by incorporating the recommendations and feedback obtained through workshops, seminars and interaction programmes. The textbook is written by Mr. Sunil Kumar Gharti, Mr. Sushil Upreti and Mr. Bimal Thapa. In Bringing out the textbook in this form, the contribution of the Director General of CDC Dr. Lekha Nath Poudel is highly acknowledged. Similarly, the contribution of Prof. Dr. Shashidhar Ram Joshi, Dr. Dipendra Gurung, Ms. Pramila Bakhati, Mr. Nabaraj Paudel, Mr. Jagadish Bhatta, Mr. Dibakar Durdarshi is also remarkable. The content was edited by Mr. Yubraj Adhikari and Mr. Khil Narayan Shrestha. The language of this book was edited by Mr. Shankar Adhikari and Mr. Nabin Kumar Khadka. The layout of this book was designed by Mr. Khados Sunuwar. CDC extends sincere thanks to all those who have contributed in developing this textbook. Efforts have been made to make this textbook activity-oriented, interesting and learner centered Curriculum Development Centre welcomes constructive feedback. 2076 Curriculum Development Centre Sanothimi, Bhaktapur Contents S.N. Page No Unit 1.1 Computer Fundamentals 1 Unit 1.2 Types of Computer 12 Unit 1.3 Basic Architecture of Computer 22 Unit 1.4 Computer Hardware 29 Unit 1.5 Computer Software 57 Unit 2.1 Computer Graphics 77 Unit 3.1 Internet Technology 99 Unit 3.2 HTML (Hypertext Markup Language) 113 Unit 3.3 Cascading Style Sheets (CSS) 157 Unit 4.1 Computer Programming 174 Unit 4.2 Programming in QBASIC 186 Unit 1.1 Computer Fundamentals Introduction to Computer The modern world is called the age of science and technology. We cannot imagine life without science and technology. The modern world of advanced technology could not have been established without the development of computer technology. There is rapid development in computer. Computer is used in many different fields for varieties of tasks. It is used all over the world, no matter whether a country it is developed, developing or underdeveloped. Computer is also used in Nepal various fields like: business, bank, education, entertainment, scientific research, law, airlines, traffic control, etc. So, the computer is now affecting every sphere of human activities and leading to many changes. It has brought enormous changes in the world. Introduction The word "Computer" is derived from the Latin word "Computare" which means 'to calculate'. Nowadays, computer has become an indispensable part of our life. Computer is used in various places like: home, school, college, offices etc. Computer can perform complex mathematical calculations accurately in a short period of time. The modern computer has lots of capabilities like creating documents, videos, games, music presentation, etc. It can use AI (Artificial Intelligence) for understanding natural language, taking self-decision capabilities, analysing graphs and patterns, etc. Data is raw facts, concepts, or instructions in a formalized manner, which should be suitable for communication, interpretation, or processing by computer. Data is represented with the help of characters such as alphabets (A-Z, a-z), digits (0-9) or special characters (+,-,/,*,,= ) Information is organized or classified data, which has some meaningful results for the receiver. Information is the processed data or meaningful results on which decisions and actions are based. 1 Computer Science : Grade 9 A computer is an electronic device that accepts raw data and instructions from users; processes it according to the given set of instructions, stores and gives meaningful information. Computer Working Principle of a Computer Computer is an electronic device that converts raw data into meaningful information carrying out various processes as instructed by the programme. Every computer has the ability to: a. Input: Enter raw data into the computer. b. Process: Process according to the given set of instructions to produce the required result. c. Output: Get meaningful information from the computer. d. Storage: Store data and information for future use. Characteristics of a Computer A computer is powerful and useful in all areas. The use of computer is increasing with time. The main features or characteristics of computer are described below: i. Automatic A computer is an automatic device. It can do tasks automatically as instructed by software. It can automatically control various devices attached with computer system. 2 Computer Science : Grade 9 ii. Speed A computer performs tasks accurately. The operations on data in computer are performed through electronic circuit according to given instructions. Computer can perform millions and billions of operations on data within a second. The speed of computer is measured in MegaHertz (MHz) or GigaHertz (GHz). The time taken to perform a task is measured in fraction of second. The smaller units of second are given below: Power of Unit of Time Meaning Part of Second 10 Millisecond (ms) One thousandth of second 1/1000 10-3sec. Microsecond(us) One millionth of second 1/1,000,000 10-6sec. Nanosecond(ns) One billionth of second 1/1,000,000,000 10-9sec. Picosecond (ps) One trillionth of second 1/1,000,000,000,000 10-12sec. Femtosecond (fs) One quadrillionth of second 1/1,000,000,000,000,000 10-15sec. iii. Accuracy A computer performs t4asks accurately. If data and instructions given to the computer are correct then it gives an accurate output. It means output totally depends on the given instructions and input data. If input data is incorrect then the output will be incorrect which is called GIGO (Garbage in Garbage out). iv. Storage Computer system consists of data storage unit. A computer has main storage and secondary storage. A large amount of data can be stored in secondary storage like hard disk, pen drive, CD/DVD, etc. for future use. The main memory (RAM) stores currently used data. Computer stores data in term of 0 and 1. The different units of storage in computer are given below: S.No. Memory Unit Description 1 Bit 1 Bit = 0 or 1 2 Nibble 1 Nibble = 4 Bits 3 Byte 1 Byte = 8 Bits Computer Science : Grade 9 3 4 Kilobyte (KB) 1 Kilobyte (KB) = 1024 Bytes 5 Megabyte (MB) 1 Megabyte (MB) = 1024 KB 6 Gigabyte (GB) 1 Gigabyte (GB) = 1024 MB 7 Terabyte (TB) 1 Terabyte (TB)= 1024 GB 8 Petabyte (PB) 1 Petabyte (PB) = 1024 TB 9 Exabyte (EB) 1 Exabyte (EB) = 1024 PB v. Diligence A computer can continuously work for a long time without losing its speed and accuracy. So it is called diligent device. It doesn’t get tired or bored or lazy while working. vi. Versatile A computer is a versatile device which means it is flexible. It has capability of performing different types of tasks like drawing paints, playing games, music, calculations, sending an e-mail, desktop publishing work, etc. in different field efficiently. So it is used in different fields to perform varieties of tasks. Application of Computer A computer is given great importance in every field of work. Nowadays, it is impossible to find where computer are not used. Computer and its technology are used in education, agriculture, industries, banking, engineering, scientific research and many more. The main applications of computer are described below: i. Education Nowadays, computer and Internet technology have changed the present education system. Computer technology can be used for visual illustration like smart classroom and distance learning education system. Today, school and colleges use computer in computer lab and multimedia to teach students. A teacher can teach by using computer- based presentations. Students can study various subject and complete assignment by using Internet. 4 Computer Science : Grade 9 Computer in Education ii. Communication A computer plays a key role in the field of communication. The Internet and computer are used to send and receive information. A computer uses various communication services like e-mail, video conferencing, net phone, chatting, Facebook, Twitter, Instagram, etc. Computer in Communication iii. Banking Sector A computer has brought revolution in the banking sector. The different services like accounting, customer records to update, bank statement etc. are performed by using computer in banking sector. ATM (Automated Teller Machine) allows 24 hours banking services to their customers so that they can withdraw money at any time. Computer Science : Grade 9 5 Computer in Banking Sector iv. Medicine A computer is used in scanning and diagnosing of various diseases through CT scan (Computed Tomography scan), ultrasounds, ECG (Electro Cardio Graph) etc. It is also used in hospitals to keep records of patients and medicines. Nowadays, computer is used in surgery too. Doctors use computer and Internet services to provide telemedicine services to remote areas of our country, Nepal. Computer in Medicine v. Entertainment A computer is used to entertain people. It is used to play games, listen to music, watch videos, movies and cartoon etc. It is used to watch online movies and play online games 6 Computer Science : Grade 9 by using Internet. Computer in Entertainment vi. Scientific Research A computer is used in all types of scientific research. Scientists collect the latest information by using internet all over the world. It is used in weather forecasting, space research, complex research in various scientific fields etc. Computer in Scientific Research vii. Agriculture Computer has not only made changes in modern occupation but also made changes in the traditional occupation sector like agriculture. Through the social networking site, farmers can get connect with other experts and exchange their views and other details when they have internet connected computers. Farmers can get information on different agricultural issues through internet surfing. Farmers can get connect with foreign customer which can help to improve their product and increase their production capacity. Farmers can use the computer to keep financial record, production record, online banking, online sales, onlne purchased the required resources through the internet. The amount of water sprinkled in a balanced quantity can also computerized. Computer Science : Grade 9 7 Computer in Agriculture Summary  The word "Computer" is derived from the Latin word "Computare" which means to calculate.  A computer is an electronic device that accepts the raw data and instructions from the user; processes raw data according to the given set of instructions, stores and gives meaningful information.  The speed of computer is measured in MegaHertz (MHz) or GigaHertz (GHz).  A large amount of data is stored in secondary storage like hard disk, pen drive, CD/DVD, etc. for future use.  Computer and its technology are used in education, medicine, banking sector, entertainment, scientific research and agriculture. Technical Terms Computer : An electronic device that processes raw data to give information. Input : Enter raw data and instruction into the computer. Output : Display meaningful information from the computer. Process : Computation according to given set of instructions to produce required result. 8 Computer Science : Grade 9 Storage : Keeping data and information for future use. GIGO : If inputted data is incorrect then output will be incorrect. Byte : The combination of eight bits. Exercises 1. Answer the following questions. a) Define Computer and list its capabilities. b) Write the limitations of computer. c) What is GIGO? d) Explain working principles of computer with block diagram. e) List any four features of computer. f) Why is computer called diligence machine? g) Describe the use of computer in education field. h) Mention any four uses of computer. i) State different units of storage in computer. 2. State 'True' or 'False'. a) Computer is an electrical machine which can perform a task. b) Computer processes raw data according to the given set of instructions. c) The speed of computer is measured in MegaHertz (MHz). d) A large amount of data is stored in secondary storage. e) Computer is a versatile device which has the capability of performing different types of tasks. f) The combination of 1025 Megabyte is equal to one Gigabyte. Computer Science : Grade 9 9 3. Match the following. Group 'A' Group 'B' i) Microsecond a) Raw facts or figures ii) Data b) Application of computer iii) GIGO c) One millionth of second iv) Education d) Error due to wrong input f) RAM 4. Choose the best answer from the list. a. The measurement of second equal to one-millionth of a second is called... i) millisecond ii) microsecond iii) nanosecond iv) picosecond b. When the input is wrong, then the output will also be wrong, it is termed as i) FIFO ii) LIFO iii) GIGO iv) None of above c. How many kilobytes make one megabyte? i) 1030 ii) 1000 iii) 1048 iv) 1024 d. Repeatedly working capability of computer is known as i) storage ii) speed iii) diligence iv) versatility 5. Fill in the blanks with appropriate words: a) The word "Computer" is derived from the Latin word……… b) The speed of computer is measured in………….. c) Nowadays, computer and……… technology has changed the present education system. d) ……allows 24 hours banking services to their customers to withdraw money at any time. 10 Computer Science : Grade 9 6. Write the full form of. i) GIGO ii) GB iii) TB iv) PB v) EB vi) KB vii) AI viii) MHz ix) GHz x) ATM xi) ECG xii) RAM xiii) CT scan 7. Write a short note on the following. a) Application of computer b) Use of computer in Scientific Research c) Computer in banking Sector d) Storage e) Speed Project Work 1. Draw a computer and its parts on a chart paper and display it in your classroom. 2. Divide a class into various groups and conduct a presentation on the following topics: a) Features of computer b) Main application area of computer 3. During the course of a normal day, keep a list of your encounters with computer of various kinds. Your list should include the and the time of the encounter, the type of interaction you had with the technology and the result of the interaction. Share your list with the class. 4. Conduct a speech competition on the topic 'Role of computer in education and entertainment'. Computer Science : Grade 9 11 Unit 1.2 Types of Computer Nowadays, various types of computer are available. These computers are different from each other on the basis of their purpose, capacity, size, working principle, brand etc. Computer can be categorized into three types according to the working principle (data type they operate). They are: i. Analog computer ii. Digital computer iii. Hybrid computer On the basis of working principle Analog Computer Digital Computer Hybrid Computer On the basis of On the basis of size purpose Special purpose General purpose Mainframe Micro computer Mini computer Super computer computer Classification of Computer 12 Computer Science : Grade 9 Analog Computer Analog computers are special-purpose computers which can measure continuously changing data such as pressure, temperature, voltage, etc. It can perform a single task. For example, speedometer which displays speed of vehicles, voltmeter, analog watch, seismograph, etc. The features of analog computer are given below:  cheaper than other device.  on continuous data.  storage capacity is low.  works in real-time.  gives output in the form of graph and signals. Analog computer Digital Computer Digital computers are general-purpose computers which solve problems by computing discrete data. It works on digital values, binary digits (0 or 1). It can perform many tasks according to user requirements. Computer in school, home and office are examples of digital computer. Feature of digital computer  works on discontinuous.  highly accurate and reliable.  used for general purpose. Computer Science : Grade 9 13  based on discrete data (digit 0 and 1). Digital Computer On the basis of purpose, digital computers are classified into two types. i. Special Purpose Digital Computer These types of digital computer are designed to perform a single specific task. The program is loaded during manufacturing time in this type of digital computer which cannot be changed by user. Digital thermometer, digital watch, self-driven vehicle, washing machine, digital television, etc. are the example of special-purpose digital computers. ii. General Purpose Digital Computer These types of digital computer are designed to perform more than one task. The user can load programs into the computer as per requirement to perform a different task. Desktop computer, laptop, notebook, etc. are the example of general-purpose digital computers. On the basis of size, digital computers are classified into four types. They are i. Microcomputer ii. Minicomputer iii. Mainframe computer and iv. Supercomputer i. Microcomputer Microcomputer is also called PC (Personal Computer) because it is used by a single person at a time. Microprocessor is used as main processing unit (CPU). IBM-PC was 14 Computer Science : Grade 9 the first microcomputer designed by IBM (International Business Machine) company. Microcomputers are used in the home, school, college, hospital, offices, etc. for data processing purpose. These microcomputers are further divided into the following categories:  Desktop computer  Laptop computer  Palmtop computer  Notebook computer  Tablet computer Notebook Computer ii. Minicomputer Minicomputer Minicomputer is more powerful and expensive than microcomputer but less powerful and costly than mainframe computer. So, the capabilities of a minicomputer are in between microcomputer and mainframe computer. Minicomputer is used in scientific research, banking system, telephone switch, etc. These computers work on multiprocessing system and about two hundred of PCs can be connected to the network. PDI-1 was the first minicomputer designed by DEC (Digital Equipment Crop) company in 1960. Computer Science : Grade 9 15 Time-sharing, batch processing, online processing, etc. are the services provided by minicomputer. IBM-System/3, Honeywell 200, etc. are some examples of minicomputer. iii. Mainframe Computer Mainframe Computer Mainframe computers are more powerful, have large storage capacity and more expensive than minicomputer but less powerful and costly than supercomputer. These computers allows multi-user and have multi-processor and support more than 200 PCs. These computers are used as a server on WWW (World Wide Web) and also used in large organizations such as a bank, telecommunication, airlines and universities for large data processing. IBM is the major manufacturer of mainframe computer. IBM 1401 mainframe computer was brought to Nepal for the first time to process census data in year. IBM-2 series, system 210 servers, CDC (Control Data Cyber) 6600 etc. are the popular examples of mainframe computer. iv. Supercomputer Sunway Taihulight Supercomputers are the most powerful, most expensive and have the highest processing speed most than other computers. It has parallel processing for performing any task. These computers are mainly used in weather forecasting, nuclear energy research, national security, space-related research, etc. 16 Computer Science : Grade 9 Nowadays, most powerful supercomputer is Sunway Taihulight from National Super Computing Centre, Wuxi, China. Supercomputer can perform more than one trillion calculations per second. Piz Daint, Tianhe-z, Titan, Seq voie, Cori, ETA-10, etc. are the popular examples of supercomputer. Hybrid Computer Hybrid Computer The computer-designed with combined features of analog computer and the digital computer is called a hybrid computer. These computers are designed for a special purpose. They are used in hospital for Ultra Sound, ECG (Electro Cardio Graph), CT scan (Computed Tomography scan), etc., in aeroplanes for air pressure, temperature, speed, weight, in scientific lab, in ships, large industries etc. Feature of hybrid computer  expensive  designed for special purpose  works on both has continuous and discrete value  more complex and limited storage Computer Science : Grade 9 17 Summary  Computers are different from each other on the basis of their purpose, capacity, size, working principle, brand etc.  Analog computers are special purpose computer which can measure continuously changing data such as pressure, temperature, voltage, etc.  Digital computers are general-purpose computers which solve problems by discrete data.  IBM-PC was the first microcomputer designed by IBM (International Business Machine) company.  Desktop computer, laptop, notebook, etc. are the examples of general-purpose digital computers.  On the basis of size, digital computers are classified into four types: Microcomputer, Minicomputer, Mainframe computer and Supercomputer  Supercomputer is the most powerful and expensive and has the highest processing speed than other computers.  The computer-designed with combined feature of analog computer and digital computer is called a hybrid computer. Technical Terms Analog computer : Measures continuously changing data such as pressure, temperature. Digital computer : Solves problems by discrete data. Minicomputer : More powerful and more expensive than a microcomputer. Mainframe computer : More powerful and has large storage and more expensive than minicomputer. Super computer : The most powerful, the most has expensive and with the highest processing speed than others. Hybrid computer : A computer with the combination of features of both analog computer and digital computer. 18 Computer Science : Grade 9 Exercises 1. Answer the following questions. a) How are computers classified into different types? b) What is analog computer? Where is it used? c) Define digital computer. What are the types of digital computers? d) Differentiate between general-purpose computers and special purpose computers. e) Classify a computer on the basis of size. f) What is mainframe computer and what are its typical applications? g) What are supercomputers? Write their application. h) What is microcomputer? Write its types. i) Define hybrid computer? How is it used in hospitals. 2. State 'True' or 'False'. a) Analog computer solves problems by discrete data. b) Laptop computers are portable computers. c) Hybrid computer has the features of analog and digital computer. d) Minicomputer is more powerful and more expensive than mainframe computer e) Desktop computer is an example of general-purpose digital computers. 3. Match the following. Group 'A' Group 'B' a) i) Analog computer a) about 200 users ii) Digital computer b) used in hospital iii) Hybrid computer c) deals with 0 or 1 iv) Minicomputer d) measures continuously changing data e) about 5000 users Computer Science : Grade 9 19 Group 'A' Group 'B' b) i) Mainframe computer a) PC ii) Super computer b) PDP-1 iii) Microcomputer c) IBM1401 iv) Minicomputer d) Sunway Taihulight e) IBM 2040 4. Choose the correct answer. a. The most powerful, expensive and largest processing computer is... i) Microcomputer ii) Supercomputer iii) Mainframe computer iv) Minicomputer b. CT- Scan is an example of ……… computer. i) Analog ii) Micro iii) Hybrid iv) None of above c. ….. is the mainframe computer brought to Nepal for the first time to process census data in 2028 BS. i) IBM 1400 ii) IBM1401 iii) IBM1402 iv) IBM1403 d. Nowadays, the most powerful supercomputer is Sunway taihulight from ………. i) India ii) Germany iii) China iv) America e. Minicomputer is more powerful and expensive than ……….. computer. i) Micro ii) Super iii) Mainframe iv) None of them 5. Fill in the blanks with appropriate. i) ……… computers are special-purpose computers which can measure continuously changing data. ii) ………….. was the first microcomputer designed by IBM. iii) ……….. computer is more powerful and expensive than microcomputer but less powerful and costly than mainframe computer. 20 Computer Science : Grade 9 iv) ……… computers are used as server on WWW. v) …… computers are general-purpose computers which solve problems by computing discrete data. vi) ……….. has parallel processing for performing any task. vii) ……… computer is used in hospital for UltraSound. 6. Write the full form of the following. i) IBM ii) CPU iii) PC iv) DEC v) WWW vi) CDC vii) ECG 7. Write short notes on the following. a) Mainframe computer b) Supercomputer c) Desktop computer d) Hybrid computer e) Analog computer Project Work 1. Draw on a chart paper the types of computer on the basis of working principle and paste in your classroom. 2. Collect some examples of analog, digital and hybrid computers. 3. Prepare a presentation about the use and purpose of hybrid and supercomputer in different sectors and present to your class as a group work. 4. Divide a class into various groups and conduct a presentation on the following topics: a. Type of computer on the basis of purpose. b. Type of computer on the basis of size. c. Type of computer on the basis of work. Computer Science : Grade 9 21 Unit 1.3 Basic Architecture of Computer A combination of related units that have common purpose of achieving some objectives is called a system. For example, there are different units in the hospital system like doctor, nurse, surgery room, medical, etc. Likewise, there are different units in computer system that work together to perform varieties of tasks. So, computer system is a group of hardware and software which work together to process data according to the instructions given by user to produce information. Basic Architecture of Computer The main components of computer system are defined below: a. Data: Data is the main part of computer system. It can be processed to get desired 22 Computer Science : Grade 9 output as information. b. Software: A set of programs are called software which instructs the hardware to perform a task. For example MS Windows, MS Word, MS Excel, etc. c. User: The person who operates computer system is called a user. d. Hardware: The physical parts of a computer which can be touched, seen and felt are called computer hardware. For example Keyboard, mouse, monitor, etc. The computer hardware is further divided into four units: a. Input unit b. Process unit c. Output unit and d. Storage unit a. Input Unit This unit enters data into the computer. An input unit consists of input devices like keyboard, mouse, microphone, joystick, etc. These devices are used to enter data and instructions or commands into computer system. Input unit acts as a communication channel between user and computer. The input devices translate the information into a form understandable by the computer. Input Device b. Processing Unit A processing unit consists of processing devices like CPU (Central Processing Unit). CPU is the main processing unit of a computer system. It is also known as the brain of computer system. It receives data from input unit, processes it as instructed by the user and produces information as output. Computer Science : Grade 9 23 CPU (Central Processing Unit) The speed of CPU is measured in hertz. Hertz is also called CPU clock rate or CPU clock speed. Nowadays, CPU speed is measured in Gigahertz (GHz). 1 GHz = 1000 MHz (MegaHertz). = 1,000,000 KHz (Kilo Hertz). = 1,000,000,000 Hz (Hertz). So, one GigaHertz is equal to one billion hertz. The CPU speed of 2.1 GHz is equal to 2.1 *1,000,000,000 Hertz. The CPU consists of the three main parts. i. CU (Control Unit), ii. ALU (Arithmetic Logic Unit) and iii. MU (Memory Unit- Register Array) i. Control Unit Control Unit is a part of the CPU that controls and coordinates activities of other units of computer system. It acts as a nervous system of computer. It controls the execution of instructions given to system. It coordinates the flow of data in or out of ALU, memory and various input or output devices. ii. Arithmetic Logic Unit Arithmetic logic unit is a part of CPU that can perform arithmetic operation like addition, subtraction, multiplication and division. It also performs logical comparison like equal to, greater than, less than, etc. to compare between two numbers. 24 Computer Science : Grade 9 iii. MU (Memory Unit- Register Array) Memory unit is also a part of CPU but not the part of main memory that store currently executing task. It is located inside the microprocessor and has very limited storage. It is used to store very active data and instructions temporarily during processing. c. Output Unit An output unit consists of output devices like monitor, printer, speaker, etc. These devices are used to display information after processing raw data from the processing unit. Output devices d. Storage Unit A storage unit consists of primary and secondary storages. The primary storage or main storage stores raw data and instruction. RAM (Random Access Memory) and ROM (Read Only Memory) are the examples of storage unit.The functions of the storage unit are below.  It stores intermediate results of processing.  It stores all the data and the instructions required for processing.  It stores the final results of processing before these results are released to an output device. The secondary storage stores processed or unprocessed data or information for future use. Hard disk, pen drive, CD, DVD, etc. are the examples of the storage unit. Storage devices Computer Science : Grade 9 25 Summary  A combination of related units that have common purpose of achieving some objectives is called computer system.  A processing unit consists of Control Unit, Arithmetic logic unit and Memory unit.  The speed of CPU is measured in hertz. Hertz is also called CPU clock rate or CPU clock speed.  An output unit consists of output devices like monitor, printer, speaker, etc.  A storage unit consists of primary and secondary storages. Technical Terms Computer system : A combination of hardware and software to produce information. Hardware : The physical parts of computer which can be touched, seen and felt. Software : A set of programs which instruct hardware to perform a task. User : The person who operates a computer system. Data : Raw facts or figures which do not have a clear meaning. Input unit : To enter data and instructions or commands into the computer system. Processing unit : Processes raw data as instructed by the user and produce output. Arithmetic unit : Performs arithmetic operation like addition, subtraction, etc. Logic unit : Performs logical operations like equal to, greater than, less than, etc. Exercises 1. Answer the following questions. a) What is the computer system? b) Write down the main units of the computer system. 26 Computer Science : Grade 9 c) Draw a block diagram of the computer system. d) Mention the functions performed by ALU. e) Define CPU with two major sections of it. f) Differentiate between input unit and output unit. 2. State 'True' or 'False'. a) The main units of computer system are input, process, output and storage. b) The user enters data and instruction by using input device and it is called input. c) The processing unit display results from computer. d) A scanner is the device of the memory unit. e) The CPU speed of 3.1 GHz is equal to 3.1 x1,000 Hertz. 3. Match the following words. Group 'A' Group 'B' i) Input unit a) Process raw data to produce output ii) Output unit b) store currently executing task iii) Processing unit c) To enter data and commands iv) Memory unit d) Produce information e) Fraction of second 4. Choose the best answer. a. How many units are there in a computer system? i) 2 ii) 3 iii) 4 iv) 5 b. Which device does not belong to input unit? i) Microphone ii) Keyboard iii) Printer iv) Mouse c. ……. is also known as the brain of the computer system. i) Input unit ii) Processing unit iii) Output unit iv) Memory unit Computer Science : Grade 9 27 d. The nerve centre of computer is ………. i) ALU ii) main memory iii) control unit iv) all of the above e. Monitor, printer, plotter and speaker are the examples of ……….. device. i) input ii) output iii) processing iv) none of them 5. Fill in the blanks with appropriate word. a) computer system is a combination of……… and software. b) ………….. unit consists of input devices. c) ……… is a part of CPU that controls and co-ordinates. d) …… can perform arithmetic operation as well as logical operation. e) ……….. is a part of CPU that stores currently executing task. f) ……… consists of output devices. 6. Write the full form of: i) CPU ii) ALU iii) Hz iv) MHz v) GHz vi) MU vii) CU viii)RAM ix)ROM x) KHz 7. Write short notes on: a. ALU b. Storage Unit c. Components of computer system d. Output unit Project Work 1. Describe computer system and its main unit by using power point presentation and demonstrate in your class as a group work. 2. Prepare a presentation about "CPU is also known as the brain of computer system" and demonstrate in your class. 28 Computer Science : Grade 9 Unit 1.4 Computer Hardware The physical parts of a computer which can be seen, felt and touched are called computer hardware. Computer hardware is important component of computer system. The user can perform a task by using a set of instructions through the computer hardware. So, the combination of computer hardware and software makes up a full functioning computer system that performs specific task. Motherboard, microprocessor, RAM, ROM, hard disk, pen drive, keyboard, scanner, monitor, etc. are the examples of computer hardware. a. Motherboard Motherboard is called PCB (Printed Circuit Board) or system board or main circuit board. All parts of computer system like microprocessor, slots, ports etc. are mounted on motherboard. So, it is also called backbone of computer system. It also connects important chips like ROM chip, Network chip, sound card, etc. Motherboard Function of motherboard a. There are different slot which joins modem, TV card, etc. in motherboard. b. Motherboard helps in data communication among different hardware. c. BIOS (Basic Input Output System) programs are stored in ROM and ROM is Computer Science : Grade 9 29 attached to motherboard to boot the system. b. Microprocessor Microprocessor is an important part of computer hardware. Computer cannot perform the task without a microprocessor. So, it is also called the brain of a computer. Microprocessor gets data and instructions from various hardware and processes it with the help of software to produce information as an output to the user. It can do arithmetic calculation and logical comparison between two numbers. Nowadays, a trillion of instructions can be processed within a second. Microprocessor Working of Microprocessor i. Fetch The user can give data and instructions which is stored in RAM. Microprocessor receives data and instruction according to necessity and requirement which is known as fetch. So, fetch means get instruction from memory. ii. Decode The main function of microprocessor is to change fetched instruction into decoded instruction. The given instruction is separated for arithmetic or logical calculation. So decode means to decide what the instruction means. iii. Execute Microprocessor can perform the main task in this unit. For example, ALU is used for mathematical calculation. So, execute means to carry out the instruction into action. iv. Write back 30 Computer Science : Grade 9 Microprocessor processes the instructions and produces result which is transferred to memory for storage. This is called to write back. The complete cycle of four units as fetch, decode, execute and write back of microprocessor for processing the instruction is called the instruction cycle. c. Memory The physical part of a computer that store data, information and software temporarily or permanently is called memory or storage. Storage device or memory device is used to store data and information. The three types of memory are as follows i. Primary memory, ii. Secondary memory and iii. Cache memory. Register High cost Cache memory Low cost Fast access time High disk storage Low storage capacity Main memory capacity Slow access time Magnetic Disks Magnetic Tapes Memory Hierarchy i. Primary memory The main memory is called primary memory. Primary memory stores data temporarily or permanently. It stores information during the processing of raw data. The two types of primary memory are: RAM (Random Access Memory) ROM (Read Only Memory) Computer Science : Grade 9 31 RAM (Random Access Memory) RAM is the main memory of computer system. It is volatile or temporary memory. Volatile memory means that RAM loses its information when the computer is switched off or faces power failure. So, it needs constant power supply to hold currently running program. It is also called semiconductor memory. It is read/write memory. There are two types of RAM. They are SRAM and DRAM. SRAM: SRAM stands for Static Random Access Memory. It does not need periodic refreshing to preserve the information. It is faster and expensive than DRAM. Characteristic of Static RAM  Long life and no need to refresh  Faster and used as cache memory  Large size and expensive  Expensive and high power consumption DRAM: DRAM stands for Dynamic Random Access Memory. It needs a periodic refreshing to preserve the information. It is slower and cheaper than SRAM. Characteristics of Dynamic RAM  Short data lifetime and needs to be refreshed continuously  Slower as compared to SRAM and used as RAM  Smaller in size and less expensive  Less power consumption RAM ROM (Read Only Memory) ROM is a non-volatile or permanent memory. Non-volatile means never loses data in ROM. It stores data permanently even when the computer is switched off or power failure. It is read-only memory because the programs in ROM are stored at the time of 32 Computer Science : Grade 9 manufacture of the computer. It is fixed on motherboard. The three types of ROM are PROM, EPROM and EEPROM. PROM PROM stands for Programmable Read Only Memory. Once a program has been written onto the PROM, it remains there forever and can't be updated and deleted. EPROM EPROM stands for Erasable Programmable Read Only Memory. It can be erased by ultraviolet light and reprogramming. EEPROM EPROM stands for Electrical Erasable Programmable Read Only Memory. It is called flash ROM. It can be erased by exposing it to an electrical charge and reprogramming. It is also called hybrid memory with a combined feature of RAM and ROM. ROM Firmware Firmware is software that's embedded in a piece of hardware. So, the firmware is software for hardware. CPU Register CPU Register is a small storage memory, located inside the microprocessor and has a high speed data transfer rate. It stores data and instructions used by the microprocessor. Cache Memory Cache memory is also like CPU Register, located inside the microprocessor but has high storage capacity than CPU Register and high-speed data access rate. It also stores the data and instruction used by the microprocessor. So, it stores very active data and instructions temporarily during processing. If required data and instruction are not found in cache memory then the searching is done in primary memory. Computer Science : Grade 9 33 ii. Secondary Memory Secondary memory is also called auxiliary memory or backup memory. These memories are used to store data and instructions permanently for future use. CD/DVD, pen drive, hard disk, etc. store data and instruction for future. The various types of secondary memory are Magnetic Tape, Hard disk, SSD (Solid State Drive), Optical Storage Disc, Pen drive, etc. a. Magnetic Storage Computer systems need to store data in digital format. One of the most widely used types of digital data storage is magnetic storage. This refers to any type of data storage using a magnetized medium. Several types of magnetized media are used in computer systems, including magnetic tape, floppy disks, Super disks, hard disks, etc. Magnetic Tape Magnetic Tape is a usable secondary storage device to store and retain a large volume of data. It is made up of a plastic strip of which one surface is coated with magnetic ink. Analog and digital data are stored in magnetic tape. Normally, minicomputer, mainframe computer, large scale business organization server, etc. uses magnetic tape for backup data and information. Magnetic tape driver are used to store and retrieve the data and information from magnetic tape. The main important function of magnetic tape is to store data safely for a long period of time. Magnetic Tape and Tape Drive Hard Disk Hard disk is commonly used storage device. It stores large amount of data and information permanently. It is also called fixed disk. It is made of aluminium materials 34 Computer Science : Grade 9 and the surface is coated with the ferromagnetic element. Circular metal discs also called platters to rotate while writing or reading the data and information into them. It stores a large amount of data on hard disk. The speed of the hard disk is measured in rpm (revolutions per minute). The hard disks with 5400 rpm or 7200 rpm are generally used in present-day computer system. Hard disk capacity Hard disk must be formatted before use. There are thousands of track on the surface of hard disk. So, each track is divided into various sectors. Each sector stores 512 bytes. Header is used to read and write on hard disk. The storage capacity of hard disk is determined from number of disk or platter it contains and their density. Hard Disk Track and Sector SSD (Solid State Drive) Hard disk can be replaced and upgraded by SSD (Solid State Drive) as new technology. Semiconductor chips are used to store data in SSD. The speed to read and write data is greater than hard disk. So its price is more expensive than hard disk. Laptop, notebook, ultra book, etc. uses SSD as storage device. Its storage capacity is about 4 TB but various companies are trying to develop SSD with high storage capacity. It is more costly than HDD (Hard Disk Drive). Computer Science : Grade 9 35 Solid State Drive Differences between SSD and Hard disk S.N. Hard disk SSD 1 It is heavier than SSD. It is lighter than hard disk. Its storage capacity is 500 GB to 2 Its storage capacity is 1 TB to 4 TB. 100 TB. 3 It is cheaper than SSD. It is more expensive than hard disk. 4 It takes 6-7 watt electricity. It takes 2-3 watt electricity. The file writing speed is 50-120 The file writing speed is 200-550 MB/S 5 MB/S (megabyte per second) (megabyte per second) 6 It is made up of aluminium material. It is made up of semiconductor microchip. External Hard Drive The working principle of hard disk is similar to that of internal hard drive but it is not placed inside CPU casing. It can be externally connected with a USB (Universal Serial Bus) port. It is portable and easy to carry. It is used to transfer data, information and software from one computer to another. External Hard Drive 36 Computer Science : Grade 9 Pen drive Pen drive is a popular flash storage device. It is also called flash memory. It is connected through the USB ports. It is a small size and portable device. It can be carried in a pocket like pen. So it got its name as a pen drive. It is used to transfer data, information and software from one computer to another. It is made up of semiconductor chip which is EEPROM technology. The writing speed of pen drive of USB 3.0 is up to 60 MB/S and data reading speed up to 120 MB/S. Pen drive b. Optical Storage Disc The disc that uses laser light technology to store and retrieve data is called optical storage disc. The most commonly used optical storage discs are CD, DVD, Blu-ray disk, etc. CD (Compact Disc) In 1980, Philips Company of Netherland developed first CD or optical disk which was 12cm in diameter and had 72 minutes audio/video storage capacity. The laser ray technology is used to retrieve and store the data. The information on the optical disk is stored in the form of pits. The pits are tiny reflective bump. CD has the diameter of 12 cm. It's weight is 18gm and width 1mm (millimetre). The data can be written on a CD only once. CD is made up of poly carbon and both surfaces are coated with aluminium. Nowadays, CDs are commonly used in microcomputer. It can be used to transfer data from one computer to another. The storage capacity of a CD is 700MB. The three types of optical storage devices are:  CD-ROM → Compact Disc – Read Only Memory  WORM → Write Once Read Many  CD-RW → Compact Disc – Rewritable Computer Science : Grade 9 37 a. CD-ROM stores data or programs like video, music, software, etc. for selling purpose developed by different company. The information stored on it is read-only. b. WORM is an optical storage media which is purchased as blank media and data can be written only once but can be read many times. c. CD-RW (Compact Disc - Rewritable) means read and write in it multiple time. It is similar to pen drive as information can be read from and written to the disk many times. CD (Compact Disk) DVD (Digital Versatile Disc) DVD stands for Digital Versatile Disc or Digital Video Disc. Its storage capacity is higher than CD. It stores multiple layers of data. The various DVD storage capacities are  Single Side Layer- 4.7 GB  Single Side Double Layer-8.5 GB  Double Layer Single Side- 9.4 GB  Double Layer Double Side-17.08 GB Philips, Sony, Toshiba/ Panasonic companies developed first DVD in 1995. DVD Drive is used to read/write the data on DVD. DVD 38 Computer Science : Grade 9 Differences between CD and DVD S.N. CD DVD 1 Its storage capacity is 700MB. Its storage capacity is up to 20GB. 2 It is cheaper. It is more expensive. It is used to store audio and 3 It is used to store video and software. software. 4 Its types are CD-R, CD-RW, etc. Its types are: DVD-RW, DVD+RW, etc. It was developed by Philips and It was developed by Philips, Sony, Toshiba, 5 Sony. Panasonic etc. Blue-ray Disc It is an optical data storage device. Its storage capacity is up to 200GB. It is mainly used to store high-quality audio and movie data. It is scratch resistant discs. Differences between Primary memory and Secondary memory: S.N. Primary memory Secondary memory It is also called main memory or It is also called auxiliary memory or 1 internal memory. backup memory. 2 It is volatile and non-volatile memory. It is non-volatile memory. 3 The storage capacity is less. The storage capacity is more. 4 Its types are RAM, ROM, etc. Its types are: Hard disk, CD/DVD, etc. It is made up of magnetic materials, poly 5 It is made up of semiconductor. carbon, etc. The data is directly accessed by the The data cannot be directly accessed by 6 processing unit. the processing unit. iii. Units of memory measurement The smallest unit of memory measurement is bit (binary digit- 0 or 1). The data stored in a computer is a binary digit, byte, kilobyte, megabyte, gigabyte, terabyte, etc. Bit Bit stands for Binary digit. The value of the binary digit is 0 or 1. Computer Science : Grade 9 39 Nibble Nibble is the combination of 4 bits. Byte Byte is the combination of 8 bits. The units of memory measurements are as follows: S.N. Memory Unit Description 1 Bit 1 Bit = 0 or 1 2 Nibble 1 Nibble = 4 Bits 3 Byte 1 Byte = 8 Bits 4 Kilobyte (KB) 1 Kilobyte (KB) = 1024 Bytes 5 Megabyte (MB) 1 Megabyte (MB) = 1024 KB 6 Gigabyte (GB) 1 Gigabyte (GB) = 1024 MB 7 Terabyte (TB) 1 Terabyte (TB)= 1024 GB 8 Petabyte (PB) 1 Petabyte (PB) = 1024 TB d. Input Device The devices through which raw data and instructions are entered into the computer system are called input devices. The user gives raw data into the computer for processing through the input devices. Keyboard, mouse, joystick, microphone, etc. are examples of an input device. i. Keyboard Keyboard is a common input device. The data is entered into the computer by typing through the keyboard. The most common layout of the keyboard is "QWERTY" keyboard. The different keys present in the keyboard are:  Alphabet keys – A-Z  Numeric Keys – 0-9  Function Keys – F1, F2 ….. F12  Special Purpose Keys – Shift, Delete, Alt, Enter, Ctrl 40 Computer Science : Grade 9  Arrow keys →, ↓, ←, ↑ The keyboard which is connected to a computer without wire is called wireless keyboard. Multimedia keyboard contains additional multimedia keys. The different types of keyboard are multimedia keyboard, AT-keyboard, Enhanced Keyboard, XT-keyboard, etc. Keyboard ii. Mouse The mouse is a pointing input device. It is used to point object, give command, draw paint, etc. into the computer. The common three buttons of a mouse are: i. Left Button ii. Right Button iii. Scroll Button Mouse The user uses buttons for clicking, double clicking, right-clicking, dragging, scrolling, etc. to give command into the computer. The mouse was developed by Douglas Engelbart in 1964 that was of wood. Apple Macintosh was the first computer to use mouse. Mechanical mouse, optical mouse and wireless mouse are different types of mouse. iii. Joystick Joystick is an input device which is used to play video games. There are different types of joystick available for various video games. It has more buttons that help in playing and controlling objects in Joystick games. iv. Track Ball Track ball is a pointing input device. It consists of a movable small ball in a socket. Computer Science : Grade 9 41 The pointer moves on screen when the ball rolls with our fingertips. Track ball are mostly used on a laptop, palmtop, notebook etc. It is also called upside-down mouse as it contains ball on the top of the device. It is fixed and requires less space for operation. v. Touchpad Track Ball Touchpad is a touch-sensitive pad that is used as a pointing device in a laptop computer. It is also known as Glide pad, Glide point, pressure-sensitive tablet or track pad etc. Touchpad has two buttons (left and right) like a mouse. Touch Pad vi. Scanner Scanner is an input device which scans drawing or document and enters into computer in digital format. The photocopy machine gives the facility of the scanner. Scanner converts Scanner hardcopy into soft copy. vii. BCR (Bar Code Reader) BCR is a hand-held or stationary input device used to capture and read the information contained in a bar code. A BCR merely captures and translates the barcode into numbers or letters. The data must be sent to a computer so that a software application can make sense of the data. Barcode scanners can be connected to a computer through serial ports, keyboard port, or an interface device called a wedge. A BCR works by directing a beam of light across the bar code and measuring the amount of light that reflects back. The scanner converts the light energy, which is then converted into data by the decoder and forwarded to a computer. 42 Computer Science : Grade 9 Bar Code Reader Bar Code viii. QR Code Scanner It stands for Quick Response Code. The advanced form of Bar Code Reader is QR Code Scanner. A QR code is a pattern of black and white squares. The QR code of any product gives information about the website address. A QR code can be read and processed by a smartphone QR Code or a cell phone with the help of Apps or Applications. ix. Microphone Microphone is a sound input device. It helps to input sound or music into the computer in a digital format. It is used in audio chatting and video conferencing through Skype, Viber, Facebook, messenger etc. Microphone x. Digital Camera Digital Camera is an input device that takes photographs or video and enters them into the computer system in digital format. It stores the file in SD card. The data from the SD card then get transferred into the computer through a cable. Mobile phone camera is also an example of digital camera. Digital Camera xi. Graphic Digitizer Graphic Digitizer is an input device. It is a device used to convert hand sketch image or signature into digital format to the computer. It is also called digital tablet. Stylus (electronic pen) helps to draw an image onto the flat surface and send to the Graphic Digitizer Computer Science : Grade 9 43 computer for digital store. Graphic Digitizer is mainly used by designer and engineer. xii. Touch Screen Touch Screen is a touch-sensitive display panel covering the screen. It is mostly used in smartphone. Nowadays, laptop, notebook, palmtop and desktop computer use touch screen as their display unit. The user touches on the screen with their finger to select an object on the screen and give command to the computer system. Touch Screen e. Output Device The device which displays meaningful information from the computer is called an output device. So, an output is the result produced by processing unit. The common output devices are monitor and printer. Some other output devices are: plotter, speaker, headphone, etc. Monitor Monitor is the most common output device. It is also called VDU (Visual Display Unit) in computer system. The output displayed on monitor's screen in the form of text, videos and graphics is called soft copy output. On the basis of colour the monitors are of two types: i. Monochrome monitor and ii. Colour monitor Monochrome monitor The monitor which display output in one colour like green, white, black, blue, etc. is called monochrome monitor. 44 Computer Science : Grade 9 Colour monitor The monitor which displays output in different colours more than sixteen is called colour monitor. The information displayed on the screen is made of combination of small tiny dots. The small tiny dots are called pixel. The clear screen consists of three terms as screen resolution, dot pitch and refreshes rate. i. Screen Resolution It represents the number of horizontal and vertical pixels. The clear screen is due to the high resolution of the monitor. The common resolution ranges are 640 ˟ 480, 1024˟768, 1600˟1200 etc. ii. Dot Pitch The dot pitch is a measure of how close the pixels or dots are to create an image on the monitor. So, it is measured in millimetre. The clear screen is due to the low dot pitch of the monitor. iii. Refresh Rate The refresh rate is the rate due to each pixel on screen re-drawn. A low refresh rate results in a poor image on the screen. It is measured in hertz. So, the clear image is due to the high refresh rate. On the basis of technology, monitors are classified into three types as: i. CRT Monitor CRT stands for Cathode Ray Tube. It operates in the following ways:  The electron gun emits a beam of electrons cathode rays.  The electron beam passes through focusing and deflection systems that direct it towards specified positions on the phosphor-coated screen.  When the beam hits the screen, the phosphor emits a small spot of light at each position contacted by the electron beam.  It redraws the picture by directing the electron beam back over the same screen points quickly. Computer Science : Grade 9 45 CRT Monitor There are two ways Random scan and Raster scan by which we can display an object on to the screen. ii. LCD Monitor LCD stands for Liquid Crystal Display. It is very light, thin and consumes less power than CRT monitor. The two-layer in this monitor which consists of liquid crystal form an image. It is used in laptop, notebook, digital watch, desktop computer, etc. It is more expensive than CRT monitor and produces a high quality image on the screen. The fluorescent lamps are used for backlighting in LCD monitor for displaying image on the screen. LCD Monitor iii. LED Monitor LED stands for Light Emitting Diode. It is very lighter and thinner than LCD and CRT monitors. It consumes less power than CRT and LCD monitors. Its working power is higher than others. So its lifetime is more and can be used for long-time-work. The quality of image on the screen is higher than that of other monitors. The diodes are used for backlighting in LED monitor for displaying the image on the screen. LCD and LED monitors are called flat panel displays. 46 Computer Science : Grade 9 LED Monitor ii. Printer Printer is a hard copy output device. It prints text & graphics on paper. There are many different types of printers available in market. Its speed is measured by CPS (Character per second), LPM (Line per minute) and PPM (Page per minute). The printers are classified in two types on the basis of printing quality. They are:  Impact printer  Non-impact printer Impact Printer An impact printer is a type of printer that operates by striking a metal or plastic head against an ink ribbon. Its structure is like a typewriter. It uses small pin-like objects or hammers that strike on the inked ribbon and characters are formed on the paper. These printers are slow and noisy. These printers use black or blue or red colour. The printing quality of impact printer is lower than non-impact printer. The three main types of impact printer are following: i. Dot Matrix Printer Dot-matrix printer is a type of impact printer. The printer head contains a number of pins. The printer head strikes on the inked ribbon, the striking forms dotted characters on the paper. The speed of Dot-matrix printers ranges from 50 to 400 CPS (Character Per Second). Computer Science : Grade 9 47 Dot Matrix Printer ii. Daisy Wheel Printer Daisy wheel printer is a type of impact printer. It uses hammer-like object to hit on the ink ribbon and a character is formed on the paper. The hammer contains letter face and is arranged in wheel like form and motor spins the wheel at a rapid rate. When desired characters spin to the correct position, a printer hammer strikes on the ribbon and output is formed on the paper. The speed of the daisy wheel printer ranges from 25 to 55 CPS (Character Per Second). Print Head of Daisy Wheel iii. Line Printer Line printer is a type of impact printer. Its printing quality is better than that of Daisy wheel printer and Dot- matrix printer. It prints text line by line. So, it is called a line printer. The three types of line printer are: Drum printer: In this type, there is a cylindrical drum which continuously rotates over the paper surface and causes characters rise and hits on the ribbon. Chain Printer: In the chain printer, high-speed print chain is used. This chain contains different types of characters. 48 Computer Science : Grade 9 Drum Printer Band Printer: In this line printer, steel print band is used to print one line printout on paper at a time. Non-Impact Printer The non-impact printer does not use the printing head to strike against ribbon and paper. Instead, small drops of ink are sprayed onto the paper. So non- impact printers are faster and are of high quality than impact printer. It does not produce sound while printing. Inkjet printer, laser printer, 3D printer are the popular types of non- impact printer. i. Ink-jet Printer Inkjet printer prints text and graphics on paper by spraying small drops of ink into paper. The speed of inkjet printer is generally 1 to 4 pages per minute. It uses an A4 size paper. The liquid colour-filled cartridge is used instead of ink ribbon. Colour inkjet printer uses black colour. Four colour-CMYK (Cyan, Magenta, Yellow, Black) cartridges are used for colour printout. Inkjet Printer ii. Laser Printer A laser printer is a type of printer which makes use of a laser beam to produce an Computer Science : Grade 9 49 image on the drum or you can say that it is a printer that makes use of a focused beam of light to transfer text and images onto paper. It was first developed by Gary Starkweather at Xerox PARC in 1971. Laser printer makes use of laser technology for the printing of copies onto the paper. Its printout technology is like a photocopy machine. It uses colour powdered toner to print text and graphics on paper. Its printing quality is high. Laser Printer iii. 3D – Three Dimensional Printer Impact printer & non-impact printer prints text on paper but 3D printer prints an object. For example, any playing toys or any machinery parts are printed through the 3D printer. 3D printing builds parts out of plastic, metal and other materials directly from CAD (Computer-Aided Design) drawings that have been cross-sectioned into thousands of layers. This technology helps to build a 3D object by modelling. This technology is called additive manufacturing. 3D Printer iii. Graphic Plotter The graphic plotter is a hard copy output device which is used for good quality print or drawing like charts, map, engineering design, etc. Figures or maps are printed on 50 Computer Science : Grade 9 graph paper placed on square board. The graphic plotter is used to print large size figure or map. It gets instruction from computer and draws a clear image by using pen. The different types of plotters are given below. Pen plotter: Pen plotter contains one or more pen. It prints colour drawing with shade. Electrostatic plotter: Electrostatic plotter does not contain any type of pen. It prints like laser printer. Dot-matrix plotter: Dot matrix plotter prints drawing like impact printer. Print head strikes on ink ribbon and prints images on paper. Graphic Plotter iv. Speaker Speaker is a common audio output device. It is used to receive sound or music from computer system. It is used to covert digital data into audio analog data which user can understand. The quality of sound output depends on the speaker's quality. For example, loud speakers, sub woofers, in- wall/ceiling speaker, outdoor speaker, etc. are the different types of speakers. Speaker Computer Science : Grade 9 51 Summary  The physical parts of computer which can be seen, felt and touched are called computer hardware.  The complete cycle of four units as fetch, decode, execute and write back of microprocessor for processing the instruction is called instruction cycle.  Motherboard helps in data communication between different hardwarea.  Microprocessor gets data and instruction from various hardwarea and processes it with the help of software to produce information as an output to user  The physical parts of a computer that store data, information and software temporarily or permanently is called memory or storage.  Hard disk stores large amount of data and information permanently and made up of aluminium materials and surface is coated with the ferromagnetic element.  The most commonly used optical storage discs are: CD ROM, DVD, Blu-Ray Disk, etc.  The devices which ae used to enter raw data and instructions into the computer system are called input devices.  The devices which display meaningful information from the computer is called an output device. Technical Terms Hardware : the physical parts of a computer which can be touched, seen and felt. Fetch : get an instruction from memory. Decode : decides what the instruction means. Write back : microprocessor processes the instructions and produces result. Primary memory : stores data temporarily or permanently. Cache memory : the high-speed execution memory. Secondary memory : stores data and instruction permanently for future use. Magnetic Tape : store and retains a large volumes of data. 52 Computer Science : Grade 9 Input device : the devices which are used to enter raw data and instructions Output device : the device which displays meaningful information Screen Resolution : represents the number of horizontal and vertical pixels. Refresh Rate : rate where each pixel on the screen is re-drawn. Speaker : a devoce to receive sound or music from computer system. Exercises 1. Answer the following questions. a) Define computer hardware with its importance in computer system. b) What is a microprocessor? How does it work? Explain. c) What is computer memory? Write its major classification. d) Why is secondary memory used for future storage? Explain with its types. e) What is a motherboard? What does it contain? f) How does a computer mouse work? Who developed it? 2. Differentiate. a) RAM and ROM b) Primary and Secondary memory c) Input and Output devices d) Magnetic storage disk and Optical storage e) Hard disk drive and Solid state drive f) Impact and nonimpact printers 3. State 'True' or 'False'. a) Motherboard connects all parts of computer. b) Volatile memory saves information even when the computer is switched off. c) Secondary memory stores information permanently. d) Mouse is a pointing input device. Computer Science : Grade 9 53 e) Magnetic tapes are made up of plastic. f) Pen drive is more popular than an optical storage device. g) Google Company provides cloud storage services through Google Drive. h) LED is very heavier and thicker than LCD and CRT monitors. i) Line printer is a type of non-impact printers. j) Graphic plotter is a hard copy output device which is used to produce a good quality print. 4. Match the following. Group 'A' Group 'B' a) i) Input device a) Memory losses its information when the power isfailure. ii) Output device b) a device to store data and information. iii) Storage device c) a device to enter data and commands. iv) Volatile memory d) a device to produce information. e) a device to process data. Group 'A' Group 'B' b) i) CRT monitor a) CAD drawings ii) LCD monitor b) Diode iii) LED monitor c) Phosphorus iv) 3D printer d) Florescent Lamp e) Carbon 5. Choose the correct answer. a. ………… is also called a brain of computer. i) Motherboard ii) Microprocessor iii) RAM iv) Monitor 54 Computer Science : Grade 9 b. Which is not an output device? i) Printer ii) Speaker iii) Plotter iv) QR Code Scanner c. ……. can be erased by ultraviolet light and reprogrammed. i) PROM ii) EPROM iii) EEPROM iv) RAM d. ………. is a memory inside the microprocessor. i) RAM ii) Cache iii) ROM iv) Secondary e. Hard disk can be replaced and upgraded by ………... i) pen drive ii) magnetic disk iii) SSD iv) magnetic tape f. The speed of hard disk is measured in ………… i) mgh ii) kHz iii) rpm iv) rcm g. ………. represents the number of horizontal and vertical pixels. i) Size of monitor ii) Screen resolution iii) Dot pitch iv) Refresh rate h. ………... is an example of impact printer. i) 3D printer ii) Inkjet printer iii) Laser printer iv) Line printer 6. Fill in the blanks with appropriate word. a) Microprocessor gets data and instructions from various ………… and processes it. b) ………….. is called PCB (Printed Circuit Board). c) ……… devices are used to store data and information. d) …… is volatile or temporary memory. e) ……….. is a non-volatile or permanent memory. f) ……… stores data and instruction used by the microprocessor. g) Secondary memory is also called …………. memory. h) Hard disk can be replaced and upgraded by …………. i) The storage of data on online server by using internet is ……… Computer Science : Grade 9 55 7. Write the full form of: i) CPU ii) RAM iii) ROM iv) PCB v) BIOS vi) SRAM vii) DRAM viii) PROM ix)EPROM x) EEPROM xi) CD xii) DVD xiii) SSD xiv) rpm xv) USB xvi) BCR xvii) QR xviii) VDU xix) CRT xx) LCD xxi) LED xxii) CPS xxiii) LPM xxiv) PPM xxv) CMYK xxvi) 3D 8. Write short note. a) Motherboard b) 3D printer c) QR Code d) SSD e) LED monitor Project Work 1. Prepare a presentation about different hardwares found in computer lab and demonstrate in your class as a group discussion. 2. Draw a chart paper about different types of computer hardware with name and paste in your classroom. 3. Consult your computer teacher to follow the steps 'how to store information in cloud storage' and demonstrate in a sheet of chart paper. 4. Visit IT solution offices such as computer maintenance centre and sales, and collect information on the latest devices. 56 Computer Science : Grade 9 Unit 1.5 Computer Software The combination of hardware and software to perform a task is called computer system. The set of instructions or programs written by using a programming language to solve a problem is called computer software. So, software controls and operates computer hardware to perform a task. The set of instruction or command is called program. The set of program to perform a specific task is called software. Generally, computer software is classified into two types. a. System software b. Application software a. System Software The software that manages controls and supports computer system is called system software. So, system software creates link between computer and user. It is a platform for running application software. It manages files and folders. It can be sub-divided into the operating system, utility software, device driver software, language processing software, etc. i. Operating System An operating system is the system software that manages and controls the overall operation of computer. It coordinates, controls and manages computer hardware. The operating system is installed in C: drive of hard Operating system disk. It is the first software that is loaded into computer memory (RAM). The popular operating system are Windows XP, Windows 7, Windows 8, Windows 10, Linux based fedora, UNIX, MS-DOS etc. Android KitKat, Android Marshmallow, Android Oreo are the popular operating system of Android smartphone and IOS is the operating system of Apple iPhone. Computer Science : Grade 9 57 The main functions of the operating system are explained below: a. Memory Management: Operating system performs the task of allocation and de-allocation of RAM-memory space needed to run programs and other resources. b. Processor Management Operating system must allocate resources to processes and enable processes to share and exchange information. c. Device management Operating system co-ordinates with all devices like keyboard, printer, monitor, mouse etc. So, the operating system helps to manage input, process and output devices. d. File Management Operating system manages all files in computer. It keeps records of filename, type, size, location, etc. e. Security Operating system provides a security mechanism while using a computer. For example, password is used in a system to prevent unauthorized access. The operating system can be classified into two types based on the mode of the user as: Single User Operating System It is designed to manage the computer so that one user can effectively do one thing at a time. The Palm Operating System for palm handheld computers is a good example of a modern single-user, single-task operating system. This is the most common type of operating system used on a home computer as well as on computer in offices and other work environments. Single User Operating system is designed to manage computer so that only one user can work on it at a time. MS-DOS, Windows 8/10 etc. are the examples of single-user operating system. Multi-User Operating System Multi-user operating system is designed to manage computer so that many users can 58 Computer Science : Grade 9 work on it at a time. Many computers are connected to network through one operating system. So operating system coordinates and controls all computers connected to network. Mainframe computer uses multiuser operating system. UNIX, VMS (Vertical Memory System), Windows Server 2016, MVS (Multiple Virtual Storage), etc. are examples of multi-user operating system. The operating system can be classified into two types based on the user interface as: CUI (Character User Interface) In this type of operating system, user gives command or character to perform tasks. The keyboard is used to give command in this operating system. It is less user-friendly in comparison to other operating system. DOS, UNIX, Novel Netware, etc. are examples of character user interface-based operating system. DOS Screen GUI (Graphical User Interface) In this type of operating system, the user gives command to perform the tasks by clicking on icons, buttons and menus using a mouse. It uses keyboard as well as mouse and it is user-friendly in comparison to CUI operating system. MS Windows 7/8/10, Linux, etc. are the examples of GUI. Nowadays, Microsoft Corporation develops GUI based operating system. Windows operating system users have increased. Windows is a GUI based operating system that controls all activities of computer system. In this operating system, the user uses different application program and document display on window. So it is named as Windows. Mouse is used to open file, shut down computer and perform different commands in windows operating system. The user does not need to remember long commands to perform task. Nowadays, Windows10 is the latest operating system. Computer Science : Grade 9 59 ii. Language Processor A computer is an electronic machine. So it understands machine level language (binary language: 0 or 1). A computer program is a set of instructions to perform tasks. System software that converts different programming language into machine level language is called language processor. So language processor converts high-level language or assembly language into machine level language and vice versa. The three types of language processor are explained below: a. Assemblers An assembler is a type of language processor which converts program code written in assembly language into machine language. Machine level language uses binary digit, 0 or 1 to write a program which is difficult. So a programmer writes programs using assembly language. Mnemonic Code is used for writing program in assembly language. The source program is an input of assembler that contains assembly language instructions. The output generated by the assembler is the object code or machine code understandable by the computer. Source Code Assembler Object Code (Assembly Language) (Machine Language) Assembler b. Compilers The high-level programming language is developed for the improvement of assembly language. A compiler is a type of language processor which converts the program written in high-level language into machine level language at once. The equivalent machine code obtained after translation is called object code. So the process of converting source code into object code is known as compilation. The compiler specifies the errors at the end of compilation with line numbers when there are any errors in the source code. The errors must be removed before the compiler can successfully recompile the source code again. C, C#, C++, Java, PHP, etc. are compiler-based programming languages. 60 Computer Science : Grade 9 Source Code Compiler Object Code (High Level Language) (Machine Language) Compiler c. Interpreter Interpreter is a type of language processor which converts the program written in high- level language into machine level language line by line. If there is any error in the middle of the program then program is interrupted in between. So, after removing the error, the program needs to run again from the beginning. LOGO, QBASIC, BASICA, Perl, Python, etc. are interpreter based language. iii. Utility Software Utility software is also called service program. A set of programs that perform task related to the maintenance of computer software and hardware is called utility software. The main objective of utility software is the smooth functioning of computer system. The examples of utility software are:  Antivirus software (Kaspersky, Norton Antivirus)  Backup Software (Nova BACKUP Professional, Ashampoo Backup Pro)  Encryption Tools (Versacrypt, Bitcocker)  File Compression Tools (Winzip, WinRAR)  Disk Utilities (Disk Defrag, WinDirstat) iv. Device Drivers Software Operating system often provides programs for working with special devices such as printers. These programs are called drivers because they allow the operating system and another program to activate and use the hardware device. Most new software you buy will work with your printer, monitor and other equipment without requiring you to install any special driver because the device driver for common peripherals are already included in the operating system. Computer Science : Grade 9 61 b. Application Software Application software is designed to fulfil the requirement of user. A set of programs designed to do specific tasks is called application software. The application software is used to type e-mail, edit photos, prepare presentation, listen to music, design engineering work, edit videos, produce bills etc. The popular two types of application software are given below. i. Packaged/General Purpose Application Software The software developed for all general users to perform their generalized tasks is called general-purpose application software. It cannot be modified as per user requirement. It is costlier and easily available in market. The examples of general-purpose application software are:  MS Office Package (MS-Word, MS-Excel, Microsoft office MS-PowerPoint)  Adobe Photoshop  Auto CAD  SPSS (Statistical Package for the Social Sciences)  Autodesk Maya. ii. Customized/Tailored Software The software which is designed to fulfil the specific requirement of an individual or office or organization is called customized/tailored software. It can be modified as per user's requirement. It can be used in school, college, hotel, travel agency, airlines, hospital, insurance, etc. for performing different tasks like account, administration, store, ticket booking, etc. There are different softwares in many offices and they are expensive. Desktop Once the computer is started, user name and password is typed and a screen opens up that is called desktop. The background area of the Windows screen is desktop. Desktop contains icons, taskbar, start button, etc. which is opened by clicking with 62 Computer Science : Grade 9 mouse. Desktop element differs according to versions of Windows like Windows XP and Windows10. The user can add/remove icons on desktop. Windows 10 Desktop Windows XP Desktop Icon Icons are the small picture buttons that represent file, folder, programs, etc. Mouse is used to click on icon to perform a task. Icon is the main component of GUI operating system. Windows 10 desktop elements i. This PC This PC is an important system folder on desktop. This PC is a gateway to user to see contents of storage device like hard disk, DVD, pen drive, network computer, etc. by double-clicking on it. ii. Recycle Bin This PC Recycle Bin is a system folder which contains deleted file and folders. It is very useful for recovering the files and folders which are accidentally deleted. Select the file and press delete button to transfer to recycle bin. But pressing shift + delete button on selection will permanently delete selected file from hard disk. The file and folder can be restored from Recycle Bin recycle bin to their original location if needed for use in future. Documents Document is a system folder of desktop. It is created while installing Windows operating system. The user stores the document in document folder. Documents Computer Science : Grade 9 63 Addition of Windows 10 Desktop icon The user can add/remove the icons according to their requirement in Windows10. The following steps show how to add/remove the icon. Step 1. Right-click on an empty area of desktop and click personalize. Step 2. Select setting and click on Themes. Step 3. Click on Desktop Icon setting which is located on left top part of setting window. Step 4. Now Desktop Icon setting appears. Step 5. Click on checkbox of different desktop icons as your requirement for adding/ removing icons. The user gives command by clicking mouse for different purposes. The actions of mouse and their uses are as follows: Word Meaning Point To put mouse pointer on icon or item. Click Once click left button of mouse and release it. Right Click Once click right button of mouse and release it. Double Click Click left mouse button of in quick succession and release it. Point and click the item or icon by left button and drag into the new Drag and Drop location or place and drop it. Dialog Box It is also called a communication box. It appears to perform a task or command like file save, document print, etc. to user in Windows operating system. The dialog box contains option like ok button or cancel button. Here, press Ok button if it is satisfied to send the command to the computer and press cancel button if unsatisfied. So the user can choose different option by means of GUI control Font Dialog Box 64 Computer Science : Grade 9 and perform the tasks. GUI Control of Dialog Box a. Radio Button A radio button is the main GUI control used in window dialog box. It allows a user to select only one option at a time. A round dark bullet is marked in the selected button. Radio Button b. CheckBox A small square box which allows a user to select the available option or multiple selections is called checkbox. Check Box c. List Box The series of options displays on the box is called list box. The option of list box can be viewed by clicking on item. d. Text Box List Box The rectangular box which allows a user to input or types text on it is called a text box. It contains default text or blank space. Text Box Command Button e. Command Button A small rectangular box that activates an action is called command button. 'Ok' and 'Cancel' the common command buttons. Management of Files and Folders in Windows File A file is a set of related data and information stored on a computer system. File names are divided into two parts as illustrated in figure below: Computer Science : Grade 9 65 Extension gives information about the file types. Some popular extensions of files are: data.txt Filename Extension  Media file (Video File) -.mp4,.mpeg,.avi,.flv,.wmv  Audio file (Audio File) -.mp3,.wav,.aac  Picture file (Image File) -.jpg,.gif,.png,.ico  Office Document -.doc,.docx  E-Book File -.pdf  Spread sheet file(Excel File) -.xls,.xlsx Folder Folder is a container which stores file, program and subfolder. It is also known as directory in DOS. Subfolder is located inside the folder and store data and information. a. This PC opening file and folder This PC  Double click on This PC icon on desktop.  There appears This PC window which contains system folder like Desktop, phone, videos, documents, etc. and drive C:, D:, E:, etc.  Double click on required file store in any drive.  To close the open window, click on close (ˣ) button located on top left side of window. b. File Explorer  Click on Search Windows icon and type file explorer near to start button on desktop.  Then click on the File Explorer menu.  There appears File Explorer window and as a requirement of the user, click on file located on drive or folder. File Explorer 66 Computer Science : Grade 9 Creating a new folder  Double click on This PC.  Double click on drive or folder where you wish to create a new folder.  Right-click on an empty area of the of window.  There appears temporary Floating Menu.  Select "New" and click "Folder" and type folder name and press "Enter" key on the keyboard. Creating new folder Rename File or Folder  Right-click on file or folder to be renamed.  There appears temporary Floating Menu and click on rename option. 

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