BCA113 Internet Computing and Ethics

BACHELOR OF COMPUTER APPLICATIONS INTERNET COMPUTING AND ETHICS BCA113 Prof. Kiran Gurbani

CHANDIGARH UNIVERSITY Institute of Distance and Online Learning Course Development Committee Chairman Prof. (Dr.) R.S. Bawa Vice Chancellor, Chandigarh University, Punjab Advisors Prof. (Dr.) Bharat Bhushan, Director, IGNOU Prof. (Dr.) Majulika Srivastava, Director, CIQA, IGNOU Programme Coordinators & Editing Team Master of Business Administration (MBA) Bachelor of Business Administration (BBA) Co-ordinator - Prof. Pragya Sharma Co-ordinator - Dr. Rupali Arora Master of Computer Applications (MCA) Bachelor of Computer Applications (BCA) Co-ordinator - Dr. Deepti Rani Sindhu Co-ordinator - Dr. Raju Kumar Master of Commerce (M.Com.) Bachelor of Commerce (B.Com.) Co-ordinator - Dr. Shashi Singhal Co-ordinator - Dr. Minakshi Garg Master of Arts (Psychology) Bachelor of Science (Travel & TourismManagement) Co-ordinator - Dr. Samerjeet Kaur Co-ordinator - Dr. Shikha Sharma Master of Arts (English) Bachelor of Arts (General) Co-ordinator - Dr. Ashita Chadha Co-ordinator - Ms. Neeraj Gohlan Master of Arts (Mass Communication and Bachelor of Arts (Mass Communication and Journalism) Journalism) Co-ordinator - Dr. Chanchal Sachdeva Suri Co-ordinator - Dr. Kamaljit Kaur Academic and Administrative Management Prof. (Dr.) Pranveer Singh Satvat Prof. (Dr.) S.S. Sehgal Pro VC (Academic) Registrar Prof. (Dr.) H. Nagaraja Udupa Prof. (Dr.) Shiv Kumar Tripathi Director – (IDOL) Executive Director – USB © No part of this publication should be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, photocopying, recording and/or otherwise without the prior written permission of the author and the publisher. SLM SPECIALLY PREPARED FOR CU IDOL STUDENTS Printed and Published by: Himalaya Publishing House Pvt. Ltd., E-mail: [email protected], Website: www.himpub.com For: CHANDIGARH UNIVERSITY Institute of Distance and Online Learning CU IDOL SELF LEARNING MATERIAL (SLM)

Internet Computing and Ethics Course Code: BCA113 Credits: 3 Course Objectives:  To enrich the knowledge of students about computer basics and internet.  To make them aware about the practical implications of electronic commerce.  To illustrate the practicality of open source software licenses and open source project structure. Syllabus Unit 1 - Computer Basics and Internet: Computer Classifications, Storage Organization, Network Devices and Mobile Generations. Unit 2 - Internet and Its Use: Internet Connectivity, Internet Protocols: FTP, HTTP, Telnet, TCP/IP, SMTP, Virtual Reality, Cookies and Sessions. Unit 3 - Cloud Computing: Characteristics, Types, Service Models, Deployment Models, Applications and Challenges. Big Data: Characteristics, Types, Approach and Challenges. Unit 4 - Internet Security: Concept, Privacy versus Security, Ethical Issues, Cyber Crime, Types of Cyber Crimes, Cyber Law, Virus: Introduction, Types of Virus, Detection and Malware. Unit 5 - E-commerce Fundamentals: Introduction, The E-commerce Environment, Benefits, Limitations of E-commerce, Applications of E-commerce. Unit 6 - E-commerce Fundamentals: E-commerce Marketplace, E-portals, E-auctions and Business Models for E-commerce. Unit 7 - Electronic Payment Systems: Introduction, Types of Electronic Payment Systems, Digital Token-based Electronic Payment Systems, Smart Cards and Electronic Payment Systems, Credit Card-based Electronic Payment Systems, Risk and Electronic Payment Systems, E-cash, Electronic Cheque and Elements of Electronic Payments. CU IDOL SELF LEARNING MATERIAL (SLM)

Unit 8 - Introduction to Open Source Software 1: Open Source Software Examples: The GNU Projects, The Operating System GNU/Linux, Apache Web Server. Unit 9 - Introduction to Open Source Software 2: Strengths of Open Source Software – Open Source Software Assessment, Open Source Challenges. Open Source Community and Contribution. Unit 10 - Introduction to Standards: Types of Standard, Lifecycle of Standard, Importance of Standards Adoption of Open Source. Web Server, Apache Software Foundation (ASF), and Contribute to Open Source Project and Drivers for Open Source Adoption. Unit 11 - Adoption Methods and Process: Examples of Open Standard Adoptions in the World and Open Source Challenges. Text Books: 1. Raymond Greenlaw and Ellen Hepp. (2001) Fundamentals of the Internet and the World Wide Web, New Delhi: Tata McGraw Hill. 2. Kalakota R. and Whinston A.B. (1997) Readings in Electronic Commerce, India: Addison Wesley. 3. Rajkumar B., James B. and Andrzej M. Goscinski (2011), Cloud Computing: Principles and Paradigms, US: Wiley. Reference Books: 1. Deitel & Nieto (2000), Internet and World Wide Programming, New Delhi: Pearson Education. 2. Joseph, S.J. (2012), E-Commerce: An Indian Perspective (Second Edition), New Delhi: Prentice-Hall of India. 3. Kamlesh K. Bajaj and Debjani Nag (2005), E-commerce: The Cutting Edge of Business, Second Edition. New Delhi: Tata McGraw Hill Publication. 4. Hissam and Karim, R. (2005), Perspectives on Free and Open Source Software, Lakhani (eds), New Delhi: The MIT Press. 5. Bill, F. (2013), Taming the Big Data Tidal Wave: Finding Opportunities in Huge Data Streams with Advanced Analytics, US: Wiley. CU IDOL SELF LEARNING MATERIAL (SLM)

CONTENTS 1 - 44 45 - 68 Unit 1: Computer Basics and Internet 69 - 103 Unit 2: Internet and Its Use 104 - 122 Unit 3: Cloud Computing 123 - 137 Unit 4: Internet Security 138 - 146 Unit 5: E-commerce Fundamentals - 1 147 - 162 Unit 6: E-commerce Fundamentals - 2 163 - 178 Unit 7: Electronic Payment Systems 179 - 201 Unit 8: Introduction to Open Source Software - 1 202 - 222 Unit 9: Introduction to Open Source Software - 2 223 - 236 Unit 10: Introduction to Standards Unit 11: Adoption Methods and Process CU IDOL SELF LEARNING MATERIAL (SLM)

Computer Basics and Internet 1 UNIT 1 COMPUTER BASICS AND INTERNET Structure: 1.0 Learning Objectives 1.1 Introduction 1.2 Computer Classifications 1.3 Storage Organization 1.4 Network Devices and Mobile Generations 1.5 Summary 1.6 Key Words/Abbreviations 1.7 Learning Activity 1.8 Unit End Questions (MCQ and Descriptive) 1.9 References 1.0 Learning Objectives After studying this unit, you will be able to:  Describe various classifications of computers w.r.t. generations, Data Processing, Purpose, Size and Capacity  Explain the hierarchy of storage devices  Elaborate various network devices and their roles  Explain various mobile generations CU IDOL SELF LEARNING MATERIAL (SLM)

2 Internet Computing and Ethics 1.1 Introduction Computers are such an integral part of our everyday life now most people take them and what they have added to life totally for granted. Digital data storage is essentially the recording of digital information in a storage medium, typically by electronic means. The storage device usually enables a user to store large amounts of data in a relatively small physical space, and makes sharing that information with others easy. The device may be capable of holding the data either temporarily or permanently. Network devices, or networking hardware, are physical devices that are required for communication and interaction between hardware on a computer network. 1.2 Computer Classifications Classifications of Computers On the basis of On the basis of On the basis of On the basis of Generation Data Processed Size and Capacity Purpose First Analog Super Special Generation Digital Computers Purpose Hybrid Second Mainframe General Generation Computers Purpose Third Mini Generation Computers Fourth Micro Generation Computers Fifth Generation Fig. 1.1: Classifications of Computers CU IDOL SELF LEARNING MATERIAL (SLM)

Computer Basics and Internet 3 I. Classification of Computer Based Generation Computers are such an integral part of our everyday life now most people take them and what they have added to life totally for granted. Even more so the generation who have grown from infancy within the global desktop and laptop revolution since the 1980s. The history of the computer goes back several decades however and there are five definable generations of computers. Each generation is defined by a significant technological development that changes fundamentally how computers operate – leading to more compact, less expensive, but more powerful, efficient and robust machines. 1940 – 1956: First Generation – Vacuum Tubes These early computers used vacuum tubes as circuitry and magnetic drums for memory. As a result, they were enormous, literally taking up entire rooms and costing a fortune to run. These were inefficient materials which generated a lot of heat, sucked huge electricity and subsequently generated a lot of heat which caused ongoing breakdowns. These first generation computers relied on ‘machine language’ (which is the most basic programming language that can be understood by computers). These computers were limited to solving one problem at a time. Input was based on punched cards and paper tape. Output came out on printouts. The first computer systems used vacuum tubes for circuitry and magnetic drums for memory, and were often enormous, taking up entire rooms. These computers were very expensive to operate and in addition to using a great deal of electricity, the first computers generated a lot of heat, which was often the cause of malfunctions. First generation computers relied on machine language, the lowest-level programming language understood by computers, to perform operations, and they could only solve one problem at a time. It would take operators days or even weeks to set-up a new problem. Input was based on punched cards and paper tape, and output was displayed on printouts. CU IDOL SELF LEARNING MATERIAL (SLM)

4 Internet Computing and Ethics The UNIVAC and ENIAC computers are examples of first-generation computing devices. The UNIVAC was the first commercial computer delivered to a business client, the U.S. Census Bureau in 1951. An analog computer or analogue computer is a type of computer that uses the continuously changeable aspects of physical phenomena. Digital computer is any of a class of devices capable of solving problems by processing information in discrete form. It operates on data, including magnitudes, letters, and symbols, that are expressed in binary code, i.e., using only the two digits 0 and 1. UNIVAC and ENIAC computers are digital computers. These computer are special purpose computers. Speed of these types of Computers are measured in Milli-seconds. These were very big in size, weight was about 30 tonnes. Key points of First Generation: (1) Technology used: Vacuum tube. (2) Operating speed: Milli-second range. (3) Programming language used: Machine language. (4) Memory used: Primary memory: Magnetic core memory Secondary memory: Magnetic drum, Magnetic tape. (5) I/O device: Punched card as input device, Printing device as output device. (6) Use: Simple mathematical calculation. (7) Computers were extremely large in size, and they required special cooling system, e.g., ENIVAC, EDVAC, UNIVAC, etc. CU IDOL SELF LEARNING MATERIAL (SLM)

Computer Basics and Internet 5 1956 – 1963: Second Generation – Transistors The replacement of vacuum tubes by transistors saw the advent of the second generation of computing. Although first invented in 1947, transistors weren’t used significantly in computers until the end of the 1950s. They were a big improvement over the vacuum tube, despite still subjecting computers to damaging levels of heat. However, they were hugely superior to the vacuum tubes, making computers smaller, faster, cheaper and less heavy on electricity use. They still relied on punched card for input/printouts. The language evolved from cryptic binary language to symbolic (‘assembly’) languages. These meant programmers could create instructions in words. About the same time high level programming languages were being developed (early versions of COBOL and FORTRAN). Transistor-driven machines were the first computers to store instructions into their memories – moving from magnetic drum to magnetic core ‘technology’. The early versions of these machines were developed for the atomic energy industry. The world would see transistors replace vacuum tubes in the second generation of computers. The transistor was invented at Bell Labs in 1947 but did not see widespread use in computers until the late 1950s. The transistor was far superior to the vacuum tube, allowing computers to become smaller, faster, cheaper, more energy-efficient and more reliable than their first-generation predecessors. Though the transistor still generated a great deal of heat that subjected the computer to damage, it was a vast improvement over the vacuum tube. Second generation computers still relied on punched cards for input and printouts for output. From Binary to Assembly: Second generation computers moved from cryptic binary machine language to symbolic, or assembly, languages, which allowed programmers to specify instructions in words. High-level programming languages were also being developed at this time, such as early versions of COBOL and FORTRAN. These were also the first computers that stored their instructions in their memory, which moved from a magnetic drum to magnetic core technology. CU IDOL SELF LEARNING MATERIAL (SLM)

6 Internet Computing and Ethics In second generation, analog as well as digital computers are available. These computers are special purpose computers. Speed of these types of computers are measured in Micro-seconds. Due to the presence of transistors, it reduces the size of a computer as compared to first generation computers. Key Points of Second Generation: (1) Technology used: Transistor. (2) Operation speed: Micro-second range (10-6 sec). (3) Programming language used: Assembly language. (4) Memory used: Primary memory: Magnetic core memory. Secondary memory: Magnetic drum, Magnetic tape. (5) I/O: Punched card as input device, Printer as output device. (6) Use: Computers were used for complex scientific calculations. (7) The size, cost, power requirement, heat generation decreased compared to previous generation. (8) Processing speed, storage capacity, use of the computer increased compared to previous generation, e.g., IBM 1620, IBM 7094, LEO MARK III, etc. 1964 – 1971: Third Generation – Integrated Circuits By this phase, transistors were now being miniaturized and put on silicon chips (called semiconductors). This led to a massive increase in speed and efficiency of these machines. These were the first computers where users interacted using keyboards and monitors which interfaced with an operating system, a significant leap up from the punch cards and printouts. This enabled these machines to run several applications at once using a central program which functioned to monitor memory. CU IDOL SELF LEARNING MATERIAL (SLM)

Computer Basics and Internet 7 The development of the integrated circuit was the hallmark of the third generation of computers. Transistors were miniaturized and placed on silicon chips, called semiconductors, which drastically increased the speed and efficiency of computers. Instead of punched cards and printouts, users interacted with third generation computers through keyboards and monitors and interfaced with an operating system, which allowed the device to run many different applications at one time with a central program that monitored the memory. Computers for the first time became accessible to a mass audience because they were smaller and cheaper than their predecessors. As a result of these, advances which again made machines cheaper and smaller, a new mass market of users emerged during the 60s. Third generation microcomputers are digital computers. These computers will able to process data in binary form. These computer are general purpose computers. Speed of these types of computers are measured in Nano-seconds. In this generation, use of Integrated Chips in the computer provides the small size of the computer. Key Points of Third Generation:- (i) Technology used: IC (Integrated Circuit). (ii) Operating speed: Nano-second range (10-9 sec). (iii) Programming language used: HLL (High Level Language) like FORTAN, COBOL, PASCAL, C, C++, etc. (iv) Memory used: Primary memory: Semiconductor memory (silicon) Secondary memory: Magnetic tape, Magnetic disk like floppy disk, hard disk, etc. (v) I/O device: Keyboard as input device, monitor as output device. (vi) Use: Computers were used for managing population census, bank, insurance company, etc. CU IDOL SELF LEARNING MATERIAL (SLM)

8 Internet Computing and Ethics (vii) Concept of database was developed and used. (viii) Size, cost, power requirement and heat generation decreased compared to previous generations. (ix) Processing speed, storage capacity and use of the computer increased compared to previous generations, e.g., IBM 360 series, ICL 900 series, Honeywell 200 series, etc. 1972 – 2010: Fourth Generation – Microprocessors This revolution can be summed in one word: Intel. The chip-maker developed the Intel 4004 chip in 1971, which positioned all computer components (CPU, memory, input/output controls) onto a single chip. What filled a room in the 1940s now fit in the palm of the hand. The Intel chip housed thousands of integrated circuits. The year 1981 saw the first ever computer (IBM) specifically designed for home use and 1984 saw the Macintosh introduced by Apple. Microprocessors even moved beyond the realm of computers and into an increasing number of everyday products. The microprocessor brought the fourth generation of computers, as thousands of integrated circuits were built onto a single silicon chip. What in the first generation filled an entire room could now fit in the palm of the hand. The Intel 4004 chip, developed in 1971, located all the components of the computer—from the central processing unit and memory to input/output controls—on a single chip. Microprocessors also moved out of the realm of desktop computers and into many areas of life as more and more everyday products began to use microprocessors. As these small computers became more powerful, they could be linked together to form networks, which eventually led to the development of the Internet. Fourth generation computers also saw the development of GUIs, the mouse and handheld devices. The increased power of these small computers meant they could be linked, creating networks, which ultimately led to the development, birth and rapid evolution of the Internet. Other major advances during this period have been the Graphical user interface (GUI), the mouse and more recently the astounding advances in laptop capability and handheld devices. CU IDOL SELF LEARNING MATERIAL (SLM)

Computer Basics and Internet 9 Fourth generation Minicomputer and Macintosh are digital computers. These computers will be able to process data in binary form. Fourth generation computers are special purpose as well as general purpose computers. Speed of these types of computers are measured in Pico-seconds. In this generation, because of Microprocessor, still small in size as compared to previous generation computers. Key Points of Fourth Generation:- (1) Technology used: VLSI (or Microprocessor). (2) Operating speed: Pico-second range. (3) Programming language used: 4GL (Problem Oriented Language). (4) Memory used: Primary: Semi-conductor memory Secondary: Magnetic tape, Magnetic disk, Optical memory (CD/DVD/ Blu ray), Flash memory (pen drive, memory card). (5) I/O device: Advanced I/O devices like mouse, touch screen, scanner, LCD, LED, color printer, etc. are developed. (6) Use: Computers are used for different tasks in different areas like education, business, hospital, transportation, military, etc. (7) Microcomputers like desktop PC, laptop, notebook, etc. are developed. (8) The popular communication media like internet, email, mobile communication, etc. were developed. (9) Advanced, user-friendly, web based software, etc. are developed. (10) Size, cost, power requirement, heat generation decreased compared to previous generation. (11) Operating speed, storage capacity and use of the computer increased compared to previous generation, e.g., IBM desktop PC, HP laptop, Acer notebook, Mac book, etc. CU IDOL SELF LEARNING MATERIAL (SLM)

10 Internet Computing and Ethics 2010 Onwards: Fifth Generation – Artificial Intelligence Computer devices with artificial intelligence are still in development, but some of these technologies are beginning to emerge and be used such as voice recognition. AI is a reality made possible by using parallel processing and superconductors. Leaning to the future, computers will be radically transformed again by quantum computation, molecular and nano technology. The essence of fifth generation will be using these technologies to ultimately create machines which can process and respond to natural language, and have capability to learn and organize themselves. Fifth generation computing devices, based on artificial intelligence, are still in development, though there are some applications, such as voice recognition, that are being used today. The use of parallel processing and superconductors is helping to make artificial intelligence a reality. Quantum computation and molecular and nanotechnology will radically change the face of computers in years to come. The goal of fifth-generation computing is to develop devices that respond to natural language input and are capable of learning and self-organization. Fifth generation mainframe and supercomputers are digital computers. In fifth generation, computers will support to analog as well as digital form of data. Fifth generation computers are special purpose as well as general purpose computers. Speed of these types of computers are measured in more than Femto-second. This generation is based on Artificial Intelligence. Hence, it is available in different sizes and unique features. Key Points of Fifth Generation: (1) Technology to be used: Bio-chip. (2) Operating speed: Femto-second range (10-15 second)/TIPS (3) Programming language to be used: Natural language. (4) The computers will have AI. CU IDOL SELF LEARNING MATERIAL (SLM)

Computer Basics and Internet 11 (5) The computers will be used in complex calculation where intelligence of the computer is required. (6) The computers will have parallel processing in full fledge. (7) The computers will be based on KIPS (Knowledge based Information Processing System). Table 1.1: Classification of Generations of Computer Technology First Second Third Four Fifth used Generation Generation Generation Generation Generation Programming Vacuum Translator IC VSLSI Bio-chip Languages tube microprocessor Speed Assembly High Level 4 GL (Problem Natural Machine Language Language Language Primary Language oriented) More than Memory Micro- Nano- Pico- Femto-seconds Milli- seconds seconds seconds Magnetic Semiconductor seconds – memory Semiconductor Magnetic core – core memory memory Magnetic tape, memory Magnetic magnetic disk – Secondary Magnetic Magnetic tape, – Memory tape, tape, (hard disk, magnetic disk magnetic floppy disk) (CD, DVD, BD) Not known Input Device magnetic Keyboard Flash Memory Much higher Output Device drum drum Mouse scanner Punch card Monitor Touch screen, Mainframe Cost, Size Punch card computer and Speed, Printing Printing Low printer device device Moderate Very low Super Capability Very high High Computer Types of Very less Less Microcomputers High Computer UNIVAC Transistor Minicomputer and ENIAC computer and Macintosh II. Classification of Computer Based on Data Processed Computer systems may be classified according to the data they are designed to process or they may be classified according to their size and capabilities. CU IDOL SELF LEARNING MATERIAL (SLM)

12 Internet Computing and Ethics The data required for processing may be obtained either as a result of counting or through some measuring device. Data obtained through counting is known as discrete data, while that obtained through measuring instruments is known as continuous data. There are three types of computer under this category. They are: 1. Analog Computer 2. Digital Computer 3. Hybrid Computer 1. Analog Computer Analog computer, any of a class of devices in which continuously variable physical quantities such as electrical potential, fluid pressure, or mechanical motion are represented in a way analogous to the corresponding quantities in the problem to be solved. The analog system is set up according to initial conditions and then allowed to change freely. These are computers that measure the continuous physical Fig. 1.2: Analog magnitude or electrical states. For example, pressure, temperature, Computer voltage, volume, etc. For instance, a petrol pump at the filling station uses an analog device to measure the quantity of petrol to the nearest Naira/Kobo and the quantity of the pumped fuel to the nearest one- tenth of a liter. A speedometer in a vehicle is another example of analog computer. Analog computers are used for scientific, engineering and process control purposes. Since they deal with quantities that are continuously varying in nature, they give only approximate result, i.e., not accurate results as in digital computer. Other examples are the thermometer, volume control of a TV set meter, etc. 2. Digital Computers The Digital computer is the most commonly used type of computer and is used to process information with quantities using digits, usually using the binary number system. CU IDOL SELF LEARNING MATERIAL (SLM)

Computer Basics and Internet 13 These are computer designed to processed data in Fig. 1.3: Digital Computer discrete numerical form which are represented by discrete signal using binary code, numbers, letters and symbols are represented by codes based on the binary number system consisting of two digits, i.e., 1 and 0. The digital computer must convert all data to binary form. Generally, results from digital computer are more than the results from analog computers. They are used for counting and calculating numbers. Examples are calculator, adding machine, counting machine, etc. 3. Hybrid Computers (Analog + Digital) Hybrid computers are computers that exhibit features of analog computers and digital computers. The digital component normally serves as the controller, and provides logical and numerical operations, while the analog component often serves as a solver of differential equations and other Fig. 1.4: Hybrid Computer mathematically complex equations. A hybrid computing system is one in which desirable characteristics of both the analog and digital computers are integrated. In an intensive care unit, analog computers may measure the patient’s heart rate, temperature, etc. The measurements may then be converted into numbers and supplied to the digital part of the system which will thereafter regulate the flow of certain medications. They can be used for both counting and measuring. In fact, they are very useful in the control of manufacturing and processing. CU IDOL SELF LEARNING MATERIAL (SLM)

14 Internet Computing and Ethics III. Classification of Computer Based on Size and Capability Classification of computers are based on their architecture, speed of executing commands or instructions, peripheral used and also their uses. Microcomputers are usually used in home and offices and only a single user can perform the task using a microcomputer. Its storage and data handling capacity are limited as per the requirement for home and office work. The another type of computer is called minicomputer which has usually larger storage and can handle multi-user at a time. This chapter includes the classification of computers. Computer's Classification Computers are classified on different parameters, such as, storage capacity, processing speed and component (CPU) used in computers. Depending upon the components used and features of different computers, they are classified into four groups, Microcomputers, Minicomputers, Mainframe computers and Supercomputers. 1. Microcomputers A microcomputer is a small, relatively inexpensive computer with a microprocessor as its central processing unit (CPU). It includes a microprocessor, memory and minimal input/output (I/O) circuitry mounted on a single printed circuit board (PCB). Microcomputer is a computer whose CPU Fig. 1.5: Microcomputer (Central Processing Unit) is a microprocessor. All the components of a microprocessor are on a single integrated circuit chip. Microcomputer can be categorized as the desktop, programmable and workstation. The microprocessor based computers are called third generation computers. They are the backbone of the modern computer era. The first and second generation computers are based on vacuum tubes and bipolar junction transistors. CU IDOL SELF LEARNING MATERIAL (SLM)

Computer Basics and Internet 15 Fig. 1.6: Architecture of Microcomputer Desktop Computers: A desktop computer is a personal computer that fits on or under a desk. It has a monitor or another display, keyboard, mouse, and either a horizontal or vertical (tower) form factor. Unlike a laptop, which is portable, a desktop computer is meant to stay at one location. Desktop computer is a type of microcomputer. A desktop computer has a keyboard for input data, a LCD or CRT monitor to display information and Central Processing Unit tower contains storage, memory, different types of drives, such as, CD drive, hard drive, etc. A desktop computer is mainly used at home and office applications. Desktop Computer (System Unit) Flat-panel Display (Output Device) Speaker (Output Device) Keyboard (Input Device) Mouse (Input Device) Fig. 1.7: Desktop Computer CU IDOL SELF LEARNING MATERIAL (SLM)

16 Internet Computing and Ethics Programmable Computers (PDA): Personal digital assistance is a type of handheld programmable digital computer. It is used as notepads, address books and can connect to world wide web wave to share information. A PDA is equipped with mobile phone, hence called smallest computer. Short for personal digital assistant, a handheld device that combines computing, telephone/fax, Internet and networking features. A typical PDA can function as a cellular phone, fax sender, web browser and personal organizer. PDAs may also be referred to as a palmtop, handheld computer or pocket computer. Fig. 1.8: PDA Device Workstation: A workstation computer has greater memory capability and more extensive mathematical abilities. It is connected with other workstation computers or personal computer to exchange data, and mostly used for scientific applications. It also supports multi-tasking applications. 2. Minicomputers Minicomputers were introduced in early 1960s. They were faster than microcomputers. Basically, these computers were mainly multi-user systems, where many users work on the systems. Generally, these types of computers had larger memories and greater storage capacity. They had large instruction set and address field. These kinds of computers have Fig. 1.9: Minicomputer efficient storage for handling of text, in comparison to lower bit machines. Due to more efficient processor, speed and memory size, minicomputer was used in variety of applications and could support business applications along with the scientific applications. Minicomputer was a multi-user system which means more than one user could use this system simultaneously. CU IDOL SELF LEARNING MATERIAL (SLM)

Computer Basics and Internet 17 Table 1.2: Comparison of Microcomputers and Minicomputers Features Microcomputer Minicomputer Primary memory Shall memory Larger memory Word length Small word length Larger word length Cost low Low High Processor Low High 3. Mainframe Computers Display Card Mainframe computers are large and EPP Reader expensive machines. The word length of CPU mainframe computers may be 48, 60 or 64 bits, memory capacity being in some megabytes and Cash Cartridge storage capacity in some terabytes. Generally, they handle huge volumes of information and Cash Cartridge data. In terms of speed, they are having significant processing capacity. They are used in Cash Cartridge research organizations, large industries and airlines reservation where a large database has to Cash Cartridge be maintained. Cash Handling Mechanism Vault Housing Fig. 1.10: Mainframe Computers 3. Super Computers Super Computers are the fastest computer in current era. The processing capabilities of super computer lies in the range of GIPS2, word length 64-128 or may be in 256 or so. The memory capacity of super computer is in some gigabytes or in terabytes. The storage capacity of this type of computer is in exabytes. CU IDOL SELF LEARNING MATERIAL (SLM)

18 Internet Computing and Ethics Fig. 1.11: Scalable Node Controller The parallel processing of a super computer makes it very fast because it contains number of CPU that operates parallel. They are used at some research centers and government agencies involving sophisticated scientific and engineering tasks. Super computers are used for the following: 1. Weapons research and development 2. Nuclear and plasma physics 3. Rocket research and development 4. Atomic research 5. Aerodynamics CU IDOL SELF LEARNING MATERIAL (SLM)

Computer Basics and Internet 19 Units for Measuring Word Length, Data and Storage Capacity of a Computer Computers are classified on the basis of their data processing speed better known as clock speed and the word length. The word length that is processed by a CUP at a time is one of the important features of that CPU. The following are the units for the measurement of data volume: Table 1.3: Units for the Measurement of Data Volume Bit Bit 0 or 1 Byte B 8 bite Kibibit Kibit 1024 bits Kilobit Kbit 1000 bits Kibibyte (binary) KiB 1024 bytes Kilobyte (decimal) kB 1000 bytes Megabit Mbit 1000 kilobits Mebibyte (binary) MiB 1024 kibibytes Megabyte (decimal) MB 1000 kilobytes Gigabit Gbit 1000 megabits Gibibyte (binary) Gibbs 1024 mebibytes Gigabyte (decimal) GB 1000 megabytes Terabit Tbit 1000 gigabits Tebibyte (binary) TIB 1024 gibibytes Terabyte (decimal) TB 1000 gigabyte Petabit Pbit 1000 terabyte Pebibyte (binary) PiB 1024 tebibytes Petabyte (decimal) PB 1000 terabytes Exabit Ebit 1000 petabits Exbibyte (binary) EiB 1024 pebibytes Exabyte (decimal) EB 1000 petabytes III. Classification of Computer Based on Purpose Purpose-wise, computers can be classified into two types: 1. General Purpose Computer 2. Special Purpose Computer CU IDOL SELF LEARNING MATERIAL (SLM)

20 Internet Computing and Ethics 1. General Purpose Computer These computers can store different programs and can thus be used in countless application. A General Purpose Computer can perform any kind of jobs with equal efficiency simply by changing the application program stored in main memory. Most computers in use today are General Purpose Fig. 1.12: General Purpose computers — those built for a great variety of processing jobs. Computer Simply by using a general purpose computer and different software, various tasks can be accomplished, including writing and editing (word processing), manipulating facts in a database, tracking manufacturing inventory, making scientific calculations, or even controlling organization’s security system, electricity consumption, and building temperature. General purpose computers are designed to perform a wide variety of functions and operations. 2. Special Purpose Computer Special Purpose Computers describe and compares them to general purpose computers in terms of speed and cost. Examples of computers that were designed for the efficient solution of long established algorithms are given, including Navier-Stokes hydrodynamic solvers, classical molecular dynamic machines, and Ising model computers Fig. 1.13: Special Purpose Computers A Special Purpose Computer is the one that is designed to perform only one special task. The program or instructions set is permanently stored in such a machine. It does its single task very quickly and it cannot be used for any other purpose. These computers are often used to perform specific function such as controlling a manufacturing process or directing communications. CU IDOL SELF LEARNING MATERIAL (SLM)

Computer Basics and Internet 21 1.3 Storage Organization What is Digital Data Storage? Digital data storage is essentially the recording of digital information in a storage medium, typically by electronic means. The storage device usually enables a user to store large amounts of data in a relatively small physical space, and makes sharing that information with others easy. The device may be capable of holding the data either temporarily or permanently. Digital data storage devices have many uses. For example, computers usually depend upon information storage to function. Storage media can also be used to back up important information (storing digital data can involve durability and reliability issues, so making independent copies of the information is normally a wise precaution). Some storage devices are also portable, meaning that they can be used to transfer information from one computer to another. Digital data storage media generally fall into one of five categories: magnetic storage devices, optical storage devices, flash memory devices, online/cloud storage, and paper storage. I will give one or more examples of each category below. Digital Data Storage Devices: 1. Hard Drive Disk 2. Floppy Disk 3. Tape 4. Compact Disc (CD) 5. DVD and Blu-ray Discs 6. USB Flash Drive 7. Secure Digital Card (SD Card) 8. Solid State Drive (SSD) 9. Cloud Storage 10. Punch Card 11. RAM 12. ROM CU IDOL SELF LEARNING MATERIAL (SLM)

22 Internet Computing and Ethics 1. Hard Disk Drive Fig. 1.14: Hard Disk Drive A hard disk drive (also known as a hard drive, HD, or Fig. 1.15: Floppy Disk HDD) can be found installed in almost every desktop computer and laptop. It stores files for the operating system and software programs, as well as user documents, such as photographs, text files, and audio. The hard drive uses magnetic storage to record and retrieve digital information to and from one or more fast-spinning disks. 2. Floppy Disk Also known as a diskette, floppy, or FD, the floppy disk is another type of storage medium that uses magnetic storage technology to store information. Floppy disks were once a common storage device for computers and lasted from the mid-1970s through to the start of the 21st century. The earliest floppies were 8-inch (203 mm) in size, but these were replaced by 5 1⁄4-inch (133 mm) disk drives, and finally a 3 1⁄2 inch (90 mm) version. 3. Tape Fig. 1.16: Tape In the past, magnetic tape was often used for digital data storage, because of its low cost and ability to store large amounts of data. The technology essentially consisted of a magnetically thin coated piece of plastic wrapped around wheels. Its relative slowness and unreliability compared to other data storage solutions has resulted in it now being largely abandoned as a media. CU IDOL SELF LEARNING MATERIAL (SLM)

Computer Basics and Internet 23 4. Compact Disc (CD) Fig. 1.17: Compact Disc The compact disc, known for short as a CD, is a form of optical storage, a technology which employs lasers and lights to read and write data. Initially compact discs were used purely for music audio, but in the late 1980s they began to be also used for computer data storage. Initially, the compact discs that were introduced were CD-ROMs (read only), but this was followed by CD-Rs (writable compact discs) and CD-RWs (re-writable compact discs). 5. DVD and Blu-ray Discs The DVD (digital versatile disc) and Blu-ray disc (BD) are formats of digital optical disc data storage which have superseded compact discs, mainly because of their much greater storage capacity. A Blu-ray disc, for example, can store 25 GB (gigabytes) of data on a single-layer disc and Fig. 1.18: DVD and Blu-ray Discs 50 GB on a dual-layer disc. In comparison, a standard CD is the same physical size, but only holds 700 MB (megabytes) of digital data. 6. USB Flash Drive Fig. 1.19: USB Flash Drive Also known as a thumb drive, pen drive, flash-drive, memory stick, jump drive, and USB stick, the USB flash drive is a flash memory data storage device that incorporates an integrated USB interface. Flash memory is generally more efficient and reliable than optical media, being smaller, faster, and possessing much greater storage capacity, as well as being more durable due to a lack of moving parts. CU IDOL SELF LEARNING MATERIAL (SLM)

24 Internet Computing and Ethics 7. Secure Digital Card (SD Card) Common types of memory card, SD cards are used in multiple electronic devices, including digital cameras and mobile phones. Although there are different sizes, classes, and capacities available, they all use a rectangular design with one side “chipped off” to prevent the card from being inserted into the camera or other device the wrong way. Fig. 1.20: Secure Digital Card 8. Solid State Drive (SSD) Fig. 1.21: Solid State Drive A solid state drive uses flash memory to store data and is sometimes used in devices such as notebooks, laptop, and desktop computers instead of a traditional hard disk drive. The advantages of an SSD over a HDD include a faster read/write speed, noiseless operation, greater reliability, and lower power consumption. The biggest downside is cost, with an SSD offering lower capacity than an equivalently priced HDD. 9. Cloud Storage Fig. 1.22: Cloud Storage With users increasingly operating multiple devices in multiple places, many are turning to online and cloud computing solutions. Cloud computing basically involves accessing services over a network via a collection of remote servers. Although the idea of a “cloud of computers” may sound abstract to those unfamiliar with this metaphorical concept, in practice it can provide tremendous storage solutions for devices that are connected to the internet. CU IDOL SELF LEARNING MATERIAL (SLM)

Computer Basics and Internet 25 10. Punch Card Fig. 1.23: Punch Card Punch cards (or punched cards) were a common method of data storage used in the early computers. Basically, they consisted of a paper card with punched or perforated holes that have been created by hand or machine. The cards were entered into the computer to enable the storage and accessing of information. This form of data storage media pretty much disappeared as new and better technologies were developed. 11. RAM RAM is an acronym for random access memory, a type of computer memory that can be accessed randomly; that is, any byte of memory can be accessed without touching the preceding bytes. RAM alternatively referred to Fig. 1.24: RAM as main memory, primary memory, or system memory, RAM (random-access memory) is a hardware device that allows information to be stored and retrieved on a computer. RAM is usually associated with DRAM, which is a type of memory module. Because information is accessed randomly instead of sequentially like it is on a CD or hard drive, access times are much faster. However, unlike ROM, RAM is a volatile memory and requires power to keep the data accessible. If the computer is turned off, all data contained in RAM is lost. 12. ROM Fig. 1.25: ROM Read-only memory (ROM) is a type of storage medium that permanently stores data on personal computers (PCs) and other electronic devices. It contains the programming needed to start a PC, which is essential for boot-up; it performs major input/output tasks and holds programs or software instructions. CU IDOL SELF LEARNING MATERIAL (SLM)

26 Internet Computing and Ethics Because ROM is read-only, it cannot be changed; it is permanent and non-volatile, meaning it also holds its memory even when power is removed. By contrast, random access memory (RAM) is volatile; it is lost when power is removed. There are numerous ROM chips located on the motherboard and a few on expansion boards. The chips are essential for the basic input/output system (BIOS), boot up, reading and writing to peripheral devices, basic data management and the software for basic processes for certain utilities. 1.4 Network Devices and Mobile Generations Network Types  LAN: A local area network (LAN) is a group of computers and peripheral devices that share a common communications line or wireless link to a server within a distinct geographic area. A local area network may serve as few as two or three users in a home- office or several hundred users in a corporation’s central office. Home owners and information technology (IT) administrators set up LANs so that network nodes can share resources such as printers or network storage. LAN networking requires cables, switches, routers and other components that let users connect to internal servers, websites and other LANs that belong to the same wide area network (WAN). Ethernet and Wi-Fi are the two primary ways to enable LAN connections. Ethernet is a specification that enables computers to communicate with each other. Wi-Fi uses radio waves to connect computers to the LAN.  WAN: A wide area network (WAN) is a geographically distributed private telecommunications network that interconnects multiple local area networks (LANs). A LAN is a group of computers and network devices which are all connected to each other, typically from within a short relative geographical distance. In an enterprise or business, a WAN may consist of connections to a company’s headquarters, branch offices, colocation facilities, cloud services and other facilities. Typically, a router or other multifunction device is used to connect a LAN to a WAN. Enterprise WANs allow users CU IDOL SELF LEARNING MATERIAL (SLM)

Computer Basics and Internet 27 to share access to applications, services and other centrally located resources. This eliminates the need to install the same application server, firewall or other resources in multiple locations, for example. WANs are not restricted to the same geographical location as a LAN would be. A LAN can be set up in any number of geographical areas and be connected to a WAN—meaning a WAN is not constrained to one specific location.  MAN: A metropolitan area network (MAN) is a network that interconnects users with computer resources in a geographic area or region larger than that covered by even a large local area network (LAN) but smaller than the area covered by a wide area network (WAN). The term is applied to the interconnection of networks in a city into a single larger network (which may then also offer efficient connection to a wide area network). It is also used to mean the interconnection of several local area networks by bridging them with backbone lines. The latter usage is also sometimes referred to as a campus network. What are network devices? Network devices, or networking hardware, are physical devices that are required for communication and interaction between hardware on a computer network. Connecting Devices We use connecting devices to connect hosts together to make a network or to connect networks together to make an internet. Connecting devices can operate in different layers of the Internet model. We discuss mainly three kinds of connecting devices: hubs, link-layer switches, and routers. Hubs today operate in the first layer of the Internet model. Link-layer switches operate in the first two layers. Routers operate in the first three layers. CU IDOL SELF LEARNING MATERIAL (SLM)

28 Internet Computing and Ethics Application Gateway Application Transport Transport Network Router or Network Data link three-layer switch Data link Physical Physical Bridge or two-layer switch Repeater or hub Passive hub Fig. 1.26: Courtesy: pinoybix.org Types of Connecting Devices Here is the common network device list:  Hub  Switch  Router  Bridge  Gateway  Modem  Repeater  Access Point Hub Fig. 1.27: Hub CU IDOL SELF LEARNING MATERIAL (SLM)

Computer Basics and Internet 29 Hubs connect multiple computer networking devices together. A hub also acts as a repeater in that it amplifies signals that deteriorate after travelling long distances over connecting cables. A hub is the simplest in the family of network connecting devices because it connects LAN components with identical protocols. A hub can be used with both digital and analog data, provided its settings have been configured to prepare for the formatting of the incoming data. For example, if the incoming data is in digital format, the hub must pass it on as packets; however, if the incoming data is analog, then the hub passes it on in signal form. Hubs do not perform packet filtering or addressing functions; they just send data packets to all connected devices. Hubs operate at the Physical layer of the Open Systems Interconnection (OSI) model. There are two types of hubs: simple and multiple port. Hub Falls in Two Categories Active Hub: They are smarter than the passive hubs. They not only provide the path for the data signals in fact they regenerate, concentrate and strengthen the signals before sending them to their destinations. Active hubs are also termed as ‘repeaters’. Passive Hub: They are more like point contact for the wires to built in the physical network. They have nothing to do with modifying the signals. Ethernet Hubs It is a device connecting multiple Ethernet devices together and makes them perform the functions as a single unit. They vary in speed in terms of data transfer rate. Ether utilizes Carrier Sense Multiple Access with Collision Detect (CSMA/CD) to control Media access. Ethernet hub communicates in half-duplex mode where the chances of data collision are inevitable at most of the times. CU IDOL SELF LEARNING MATERIAL (SLM)

30 Internet Computing and Ethics Switch Router Switch Fig. 1.28: Switch Switches generally have a more intelligent role than hubs. A switch is a multiport device that improves network efficiency. The switch maintains limited routing information about nodes in the internal network, and it allows connections to systems like hubs or routers. Strands of LANs are usually connected using switches. Generally, switches can read the hardware addresses of incoming packets to transmit them to the appropriate destination. Using switches improves network efficiency over hubs or routers because of the virtual circuit capability. Switches also improve network security because the virtual circuits are more difficult to examine with network monitors. You can think of a switch as a device that has some of the best capabilities of routers and hubs combined. A switch can work at either the Data Link layer or the Network layer of the OSI model. A multilayer switch is one that can operate at both layers, which means that it can operate as both a switch and a router. A multilayer switch is a high-performance device that supports the same routing protocols as routers. Switches can be subject to distributed denial of service (DDoS) attacks; flood guards are used to prevent malicious traffic from bringing the switch to a halt. Switch port security is important so be sure to secure switches: Disable all unused ports and use DHCP snooping, ARP inspection and MAC address filtering. CU IDOL SELF LEARNING MATERIAL (SLM)

Computer Basics and Internet 31 The following method will elucidate further how data transmission takes place via switches:  Cut-through transmission: It allows the packets to be forwarded as soon as they are received. The method is prompt and quick but the possibility of error checking gets overlooked in such kind of packet data transmission.  Store and forward: In this switching environment the entire packet are received and ‘checked’ before being forwarded ahead. The errors are thus eliminated before being propagated further. The downside of this process is that error checking takes relatively longer time consequently making it a bit slower in processing and delivering.  Fragment Free: In a fragment free switching environment, a greater part of the packet is examined so that the switch can determine whether the packet has been caught up in a collision. After the collision status is determined, the packet is forwarded. Router File Remote Client Server Network Switch WAN Link Hub Media Router Media Client Client Fig. 1.29: Router A router is three-layer device; physical, data link and network layer. As a physical layer device it can regenerates bit, as data link layer device the router can check the physical addresses contained in a packet and as a network layer device it can check the network layer addresses (addresses in IP layer). Routers are inter-networking devices as it can connects LAN-LAN, LAN-WAN, WAN- WAN. CU IDOL SELF LEARNING MATERIAL (SLM)

32 Internet Computing and Ethics Routers can change the physical addresses of a packet. For example, considering a packet is getting sent from LAN 1 to LAN 2 as in the above given figure. At this moment the source address is of the sender’s address and the destination address is of a host of the LAN 2. Now when the packet reaches the router, the router changes the source address of the packet to its own address and then send the packet to the destination address. Router are also used to divide internal networks into two or more subnetworks. Routers can also be connected internally to other routers, creating zones that operate independently. Routers establish communication by maintaining tables about destinations and local connections. A router contains information about the systems connected to it and where to send requests if the destination isn’t known. Routers usually communicate routing and other information using one of three standard protocols: Routing Information Protocol (RIP), Border Gateway Protocol (BGP) or Open Shortest Path First (OSPF). Routers are your first line of defense, and they must be configured to pass only traffic that is authorized by network administrators. The routes themselves can be configured as static or dynamic. If they are static, they can only be configured manually and stay that way until changed. If they are dynamic, they learn of other routers around them and use information about those routers to build their routing tables. Routers are general-purpose devices that interconnect two or more heterogeneous networks. They are usually dedicated to special-purpose computers, with separate input and output network interfaces for each connected network. Because routers and gateways are the backbone of large computer networks like the internet, they have special features that give them the flexibility and the ability to cope with varying network addressing schemes and frame sizes through segmentation of big packets into smaller sizes that fit the new network components. Each router interface has its own Address Resolution Protocol (ARP) module, its own LAN address (network card address) and its own Internet Protocol (IP) address. The router, with the help of a routing table, has knowledge of routes a packet could take from its source to its destination. The routing table, like in the bridge and switch, grows dynamically. Upon receipt of a packet, the router removes the packet headers and trailers and analyses the IP header by determining the source and destination addresses and data type, and noting the arrival time. It also updates the router table CU IDOL SELF LEARNING MATERIAL (SLM)

Computer Basics and Internet 33 with new addresses not already in the table. The IP header and arrival time information is entered in the routing table. Routers normally work at the Network layer of the OSI model. Functionality: When a router receives the data, it determines the destination address by reading the header of the packet. Once the address is determined, it searches in its routing table to get know how to reach the destination and then forwards the packet to the higher hop on the route. The hop could be the final destination or another router. Routing tables play a very pivotal role in letting the router makes a decision. Thus a routing table is ought to be updated and complete. The two ways through which a router can receive information are:  Static Routing: In static routing, the routing information is fed into the routing tables manually. It does not only become a time-taking task but gets prone to errors as well. The manual updating is also required in case of statically configured routers when change in the topology of the network or in the layout takes place. Thus static routing is feasible for thinnest environments with minimum of one or two routers.  Dynamic Routing: For larger environment dynamic routing proves to be the practical solution. The process involves use of peculiar routing protocols to hold communication. The purpose of these protocols is to enable the other routers to transfer information about to other routers, so that the other routers can build their own routing tables. Bridge Bridge Fig. 1.30: Bridge A bridge operates in both physical layer and data link layer. As a physical layer device, it can regenerate bits and as a data link layer device it can check the physical addresses contained in the CU IDOL SELF LEARNING MATERIAL (SLM)

34 Internet Computing and Ethics frame. Bits can be carried to any distance by using properly spaced repeaters but the collision domain will not allow this and that’s why brides are required. Bridges are used to connect two or more hosts or network segments together. The basic role of bridges in network architecture is storing and forwarding frames between the different segments that the bridge connects. They use hardware Media Access Control (MAC) addresses for transferring frames. By looking at the MAC address of the devices connected to each segment, bridges can forward the data or block it from crossing. Bridges can also be used to connect two physical LANs into a larger logical LAN. Bridges work only at the Physical and Data Link layers of the OSI model. Bridges are used to divide larger networks into smaller sections by sitting between two physical network segments and managing the flow of data between the two. Bridges are like hubs in many respects, including the fact that they connect LAN components with identical protocols. However, bridges filter incoming data packets, known as frames, for addresses before they are forwarded. As it filters the data packets, the bridge makes no modifications to the format or content of the incoming data. The bridge filters and forwards frames on the network with the help of a dynamic bridge table. The bridge table, which is initially empty, maintains the LAN addresses for each computer in the LAN and the addresses of each bridge interface that connects the LAN to other LANs. Bridges, like hubs, can be either simple or multiple port. Apart from building up larger networks, bridges are also used to segment larger networks into smaller portions. The bridge does so by placing itself between the two portions of two physical networks and controlling the flow of the data between them. Bridges nominate to forward the data after inspecting into the MAC address of the devices connected to every segment. The forwarding of the data is dependent on the acknowledgement of the fact that the destination address resides on some other interface. It has the capacity to block the incoming flow of data as well. Today Learning bridges have been introduced that build a list of the MAC addresses on the interface by observing the traffic on the network. This is a leap in the development field of manually recording of MAC addresses. CU IDOL SELF LEARNING MATERIAL (SLM)

Computer Basics and Internet 35 Types of Bridges: There are mainly three types in which bridges can be characterized:  Transparent Bridge: As the name signifies, it appears to be transparent for the other devices on the network. The other devices are ignorant of its existence. It only blocks or forwards the data as per the MAC address.  Source Route Bridge: It derives its name from the fact that the path which packet takes through the network is implanted within the packet. It is mainly used in Token ring networks.  Translational Bridge: The process of conversion takes place via Translational Bridge. It converts the data format of one networking to another. For instance Token ring to Ethernet and vice versa. Gateway Host A Network Host B Gateway Host C Fig. 1.31: Gateway Gateways normally work at the Transport and Session layers of the OSI model. At the Transport layer and above, there are numerous protocols and standards from different vendors; gateways are used to deal with them. Gateways provide translation between networking technologies such as Open System Interconnection (OSI) and Transmission Control Protocol/Internet Protocol (TCP/IP). Because of this, gateways connect two or more autonomous CU IDOL SELF LEARNING MATERIAL (SLM)

36 Internet Computing and Ethics networks, each with its own routing algorithms, protocols, topology, domain name service, and network administration procedures and policies. Gateways perform all of the functions of routers and more. In fact, a router with added translation functionality is a gateway. The function that does the translation between different network technologies is called a protocol converter. Modem Internet Modem Router Computer Computer Phone Fig. 1.32: Modem Modems (modulators-demodulators) are used to transmit digital signals over analog telephone lines. Thus, digital signals are converted by the modem into analog signals of different frequencies and transmitted to a modem at the receiving location. The receiving modem performs the reverse transformation and provides a digital output to a device connected to a modem, usually a computer. The digital data is usually transferred to or from the modem over a serial line through an industry standard interface, RS-232. Many telephone companies offer DSL services, and many cable operators use modems as end terminals for identification and recognition of home and personal users. Modems work on both the Physical and Data Link layers. CU IDOL SELF LEARNING MATERIAL (SLM)

Computer Basics and Internet 37 Modem is a device which converts the computer-generated digital signals of a computer into analog signals to enable their travelling via phone lines. The ‘modulator-demodulator’ or modem can be used as a dial up for LAN or to connect to an ISP. Modems can be both external, as in the device which connects to the USB or the serial port of a computer, or proprietary devices for handheld gadgets and other devices, as well as internal; in the form of add-in expansion cards for computers and PCMCIA cards for laptops. Configuration of a modem differs for both the external and internal modem. For internal modems, IRQ – Interrupt request is used to configure the modem along with I/O, which is a memory address. Typically before the installation of built-in modem, integrated serial interfaces are disabled, simultaneously assigning them the COM2 resources. For external connection of a modem, the modem assigns and uses the resources itself. This is especially useful for the USB port and laptop users as the non-complex and simpler nature of the process renders it far much more beneficial for daily usage. Upon installation, the second step to ensure the proper working of a modem is the installation of drivers. The modem working speed and processing is dependent on two factors:  Speed of UART – Universal Asynchronous Receiver or Transmitter chip (installed in the computer to which the modem connection is made)  Speed of the modem itself Repeater Repeater Weak inbound Strong outbound digital signal digital signal Fig. 1.33: Repeater A repeater is an electronic device that amplifies the signal it receives. You can think of repeater as a device which receives a signal and retransmits it at a higher level or higher power so CU IDOL SELF LEARNING MATERIAL (SLM)

38 Internet Computing and Ethics that the signal can cover longer distances, more than 100 meters for standard LAN cables. Repeaters work on the Physical layer. Access Point Access Point (Root Unit) TP-LINK Fig. 1.34: Access Point While an access point (AP) can technically involve either a wired or wireless connection, it commonly means a wireless device. An AP works at the second OSI layer, the Data Link layer, and it can operate either as a bridge connecting a standard wired network to wireless devices or as a router passing data transmissions from one access point to another. Wireless access points (WAPs) consist of a transmitter and receiver (transceiver) device used to create a wireless LAN (WLAN). Access points typically are separate network devices with a built-in antenna, transmitter and adapter. APs use the wireless infrastructure network mode to provide a connection point between WLANs and a wired Ethernet LAN. They also have several ports, giving you a way to expand the network to support additional clients. Depending on the size of the network, one or more APs might be required to provide full coverage. Additional APs are used to allow access to more wireless clients and to expand the range of the wireless network. Each AP is limited by its transmission range — the distance a client can be from an AP and still obtain a usable signal and data process speed. The actual distance depends on the wireless standard, the obstructions and environmental conditions between the client and the AP. Higher CU IDOL SELF LEARNING MATERIAL (SLM)

Computer Basics and Internet 39 end APs have high-powered antennas, enabling them to extend how far the wireless signal can travel. APs might also provide many ports that can be used to increase the network’s size, firewall capabilities and Dynamic Host Configuration Protocol (DHCP) service. Therefore, we get APs that are a switch, DHCP server, router and firewall. To connect to a wireless AP, you need a service set identifier (SSID) name. 802.11 wireless networks use the SSID to identify all systems belonging to the same network, and client stations must be configured with the SSID to be authenticated to the AP. The AP might broadcast the SSID, allowing all wireless clients in the area to see the AP’s SSID. However, for security reasons, APs can be configured not to broadcast the SSID, which means that an administrator needs to give client systems the SSID instead of allowing it to be discovered automatically. Wireless devices ship with default SSIDs, security settings, channels, passwords and usernames. Generations of Mobile Networks First Generation (1G): First generation mobile networks were reliant upon analog radio systems which meant that users could only make phone calls, they couldn’t send or receive text messages. The 1G network was first introduced in Japan in 1979 before it was rolled out in other countries such as the USA in 1980. In order to make it work, cell towers were built around the country which meant that signal coverage could be obtained from greater distances. However, the network was unreliable and had some security issues. For instance, cell coverage would often drop, it would experience interference by other radio signals and due to a lack of encryption, it could easily be hacked. This means that with a few tools, conversations could be heard and recorded. Second Generation (2G): The 1G network was not perfect, but it remained until remained until 1991 when it was replaced with 2G. This new mobile network ran on digital signal, not analog, which vastly improved its security but also its capacity. On 2G, users could send SMS and MMS messages (although slowly and often without success) and when GPRS was introduced in 1997, users could receive and send emails on the move. CU IDOL SELF LEARNING MATERIAL (SLM)

40 Internet Computing and Ethics Third Generation (3G): Third generation mobile networks are still in use today, but normally when the superior 4G signal fails. 3G revolutionized mobile connectivity and the capabilities of cell-phones. In comparison to 2G, 3G was much faster and could transmit greater amounts of data. This means that users could video call, share files, surf the internet, watch TV online and play online games on their mobiles for the first time. Under 3G, cell-phones where no longer just about calling and texting, they were the hub of social connectivity. Fourth Generation (4G): The introduction of 4G went one step further than the revolutionary 3G. It’s five times faster than the 3G network – and can in theory provide speeds of up to 100 Mbps. All mobile models released from 2013 onwards should support this network, which can offer connectivity for tablets and laptops as well as smart phones. Under 4G, users can experience better latency (less buffering), higher voice quality, easy access to instant messaging services and social media, quality streaming and make faster downloads. Fifth Generation (5G): The 5G network is yet to be released but is widely anticipated by the mobile industry. Many experts claim that the network will change not just how we use our mobiles, but how we connect our devices to the internet. The improved speed and capacity of the network will signal new IoT trends, such as connected cars, smart cities and IoT in the home and office. Mobile network operators claim that 5G will be available by 2020 but nothing is certain just yet. 1.5 Summary While computers trace their lineage back several hundred years, most of the advances that led to modern computers have taken place since the late 1940s. Most people think of computers as large cabinets with spinning tapes and blinking lights, which are locked behind security doors. This describes mainframe units—the large machines that process high volumes of information for businesses and governments. Since the invention of the microchip (very small transistors), a new generation of computers has become available. Known as personal or microcomputers, these machines have taken the same computing power that once required an entire room, and placed it in units that can sit on top of a desk or in a person’s lap. CU IDOL SELF LEARNING MATERIAL (SLM)

Computer Basics and Internet 41 Whether large mainframe units or the small micros, all computers operate in basically the same fashion. Alternatively referred to as digital satorage, storage, storage media, or storage medium, a storage device is any hardware capable of holding information either temporarily or permanently. The picture shows an example of a Drobo, an external secondary storage device. There are two types of storage devices used with computers: a primary storage device, such as RAM, and a secondary storage device, such as a hard drive. Secondary storage can be removable, internal, or external. A twenty page whitepaper about Networking Devices, their uses and features. Covers informatory articles on Routers, Switches, Hubs, Bridges etc. 1.6 Key Words/Abbreviations  Hard Drive: The hard drive is what stores all your data. It houses the hard disk, where all your files and folders are physically located  Floppy Disk: A floppy disk is a magnetic storage medium for computer systems. The floppy disk is composed of a thin, flexible magnetic disk sealed in a square plastic carrier. In order to read and write data from a floppy disk, a computer system must have a floppy disk drive (FDD).  Cloud Storage: Cloud storage is a service model in which data is maintained, managed, backed up remotely and made available to users over a network (typically the Internet)  Hub: A network hub is a device that allows multiple computers to communicate with each other over a network. It has several Ethernet ports that are used to connect two or more network devices together. Each computer or device connected to the hub can communicate with any other device connected to one of the hub’s Ethernet ports.  Switch: A switch, in the context of networking is a high-speed device that receives incoming data packets and redirects them to their destination on a local area network (LAN). A LAN switch operates at the data link layer (Layer 2) or the network layer of the OSI Model and, as such it can support all types of packet protocols. CU IDOL SELF LEARNING MATERIAL (SLM)

42 Internet Computing and Ethics  Router: A router is a device like a switch that routes data packets based on their IP addresses. Router is mainly a Network Layer device. Routers normally connect LANs and WANs together and have a dynamically updating routing table based on which they make decisions on routing the data packets. Router divide broadcast domains of hosts connected through it.  Bridge: A bridge is a type of computer network device that provides interconnection with other bridge networks that use the same protocol.  Gateway: A gateway is a hardware device that acts as a “gate” between two networks. It may be a router, firewall, server, or other device that enables traffic to flow in and out of the network.  Modem: Modem is short for “Modulator-Demodulator.” It is a hardware component that allows a computer or another device, such as a router or switch, to connect to the Internet. It converts or “modulates” an analog signal from a telephone or cable wire to digital data (1s and 0s) that a computer can recognize.  Repeater: A repeater operates at the physical layer. Its job is to regenerate the signal over the same network before the signal becomes too weak or corrupted so as to extend the length to which the signal can be transmitted over the same network. An important point to be noted about repeaters is that they do not amplify the signal. When the signal becomes weak, they copy the signal bit by bit and regenerate it at the original strength. It is a 2 port device. 1.7 Learning Activity 1. Describe generations of computer? ----------------------------------------------------------------------------------------------------------- ----------------------------------------------------------------------------------------------------------- 2. Describe generation of mobile? ----------------------------------------------------------------------------------------------------------- ----------------------------------------------------------------------------------------------------------- CU IDOL SELF LEARNING MATERIAL (SLM)

Computer Basics and Internet 43 3. What do you mean by network device? ----------------------------------------------------------------------------------------------------------- ----------------------------------------------------------------------------------------------------------- 4. Write short note on storage devices? ----------------------------------------------------------------------------------------------------------- ----------------------------------------------------------------------------------------------------------- 1.8 Unit End Questions (MCQ and Descriptive) A. Descriptive Types Questions 1. Explain various generations of computer. 2. What is Digital Data Storage? 3. Explain different storage devices for storage organization. 4. Differentiate between bridge and router 5. Explain different network devices available. 6. Explain various generations of mobile network. 7. What are different connecting devices state them and describe in short? 8. Explain difference between Hub and Switch. 9. Explain difference between Bridge and Gateway. 10. Explain Router in detail and state what is static and Dynamic Routing. 11. Explain different types of Bridges. 12. Explain Modem. 13. Explain Use of Repeater. 14. Differentiate between volatile and non-volatile memory. 15. Illustrate the functionality of computer with diagram. 16. Enlighten the scenarios where the different types of network devices can be used 17. With examples elucidate the various network types. CU IDOL SELF LEARNING MATERIAL (SLM)

44 Internet Computing and Ethics B. Multiple Choice/Objective Type Questions 1. The replacement of vacuum tubes is ___________. (a) Intel (b) Transistors (c) Artificial Intelligence (d) Microprocessors 2. Floppy Disk is also known as __________. (a) Diskette (b) Floppy tape (c) Smart Disk (d) USB Disk 3. Active hubs are also termed as _________. (a) Passive hubs (b) Ethernet Hubs (c) Repeaters (d) Half duplex 4. A router is __________ layer device. (a) Four (b) Two (c) Five (d) Three 5. ____________ device converts the computer-generated digital signals of a computer into analog signals to enable their travelling via phone lines. (a) Gateway (b) Modem (c) Bridge (d) Repeater Answers 1. (b), 2. (a), 3. (c), 4. (d), 5. (b) 1.9 References 1. https://www.scribd.com/document/147399873/Networking-Devices-Introductory-Summary 2. https://www.computerhope.com/jargon/s/stordevi.htm 3. http://computerknowledge2011.blogspot.com/2012/02/summary-of-computers.html 4. “Computer Fundamentals and Internet Basic” by Rohit Khurana. CU IDOL SELF LEARNING MATERIAL (SLM)