CSC101 2024 Introduction to Computer Science PDF
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Federal University of Health Sciences, Benue State
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This document provides an introduction to computer science, focusing on the Von Neumann computer architecture. It details the basic components and functions of a computer, including the CPU and its units, and the concept of stored program computers.
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FEDERAL UNIVERSITY OF HEALTH SCIENCES, OTUKPO BENUE STATE COURSE TITLE: INTRODUCTION TO COMPUTER SCIENCE COURSE CODE: CSC 101 VON-NEUMANN COMPUTER ARCHITECTURE Von-Neumann computer architecture design was p...
FEDERAL UNIVERSITY OF HEALTH SCIENCES, OTUKPO BENUE STATE COURSE TITLE: INTRODUCTION TO COMPUTER SCIENCE COURSE CODE: CSC 101 VON-NEUMANN COMPUTER ARCHITECTURE Von-Neumann computer architecture design was proposed in 1945.It was later known as Von- Neumann architecture. Historically there have been 2 types of Computers: 1. Fixed Program Computers – Their function is very specific and they couldn‟t be reprogrammed, e.g. Calculators. 2. Stored Program Computers – These can be programmed to carry out many different tasks, applications are stored on them, hence the name. Modern computers are based on a stored-program concept introduced by John Von Neumann. In this stored-program concept, programs and data are stored in the same memory. This novel idea meant that a computer built with this architecture would be much easier to reprogram. The basic structure is like this, It is also known as ISA (Instruction set architecture) computer and is having three basic units: The Central Processing Unit (CPU) The Main Memory Unit The Input/Output Unit 1. Central Processing Unit: The central processing unit is defined as the electric circuit used for the executing the instruction of computer program. It has following major components: Control Unit – A control unit (CU) handles all processor control signals. It directs all input and output flow, fetches code for instructions, and controls how data moves around the system. Arithmetic and Logic Unit (ALU) – The arithmetic logic unit is that part of the CPU that handles all the calculations the CPU may need, e.g. Addition, Subtraction, Comparisons. It performs Logical Operations, Bit Shifting Operations, and Arithmetic operations. Registers – Registers refer to high-speed storage areas in the CPU. The data processed by the CPU are fetched from the registers. There are different types of registers used in architecture :- 1. Accumulator: Stores the results of calculations made by ALU. It holds the intermediate of arithmetic and logical operations. it acts as a temporary storage location or device. 2. Program Counter (PC): Keeps track of the memory location of the next instructions to be dealt with. The PC then passes this next address to the Memory Address Register (MAR). 3. Memory Address Register (MAR): It stores the memory locations of instructions that need to be fetched from memory or stored in memory. 4. Memory Data Register (MDR): It stores instructions fetched from memory or any data that is to be transferred to, and stored in, memory. 5. Current Instruction Register (CIR): It stores the most recently fetched instructions while it is waiting to be coded and executed. 6. Instruction Buffer Register (IBR): The instruction that is not to be executed immediately is placed in the instruction buffer register IBR. Buses – Data is transmitted from one part of a computer to another, connecting all major internal components to the CPU and memory, by the means of Buses. Types: 1. Data Bus: It carries data among the memory unit, the I/O devices, and the processor. 2. Address Bus: It carries the address of data (not the actual data) between memory and processor. 3. Control Bus: It carries control commands from the CPU (and status signals from other devices) in order to control and coordinate all the activities within the computer. Input/Output Devices – Program or data is read into main memory from the input device or secondary storage under the control of CPU input instruction. Output devices are used to output information from a computer. If some results are evaluated by the computer and it is stored in the computer, then with the help of output devices, we can present them to the user. Von Neumann bottleneck – Whatever we do to enhance performance, we cannot get away from the fact that instructions can only be done one at a time and can only be carried out sequentially. Both of these factors hold back the competence of the CPU. This is commonly referred to as the „Von Neumann bottleneck‟. We can provide a Von Neumann processor with more cache, more RAM, or faster components but if original gains are to be made in CPU performance then an influential inspection needs to take place of CPU configuration. HARDWARE COMPONENTS OF COMPUTER SYSTEM Computer hardware is a collective term used to describe any of the physical components of an analog or digital computer. The term hardware distinguishes the tangible aspects of a computing device from software, which consists of written, machine-readable instructions or programs that tell physical components what to do and when to execute the instructions. Hardware and software are complementary. A computing device can function efficiently and produce useful output only when both hardware and software work together appropriately. Computer hardware can be categorized as being either internal or external components. Generally, internal hardware components are those necessary for the proper functioning of the computer, while external hardware components are attached to the computer to add or enhance functionality. INTERNAL COMPUTER HARDWARE COMPONENTS Internal components collectively process or store the instructions delivered by the program or operating system (OS). These include the following: Motherboard. This is a printed circuit board that holds the central processing unit (CPU) and other essential internal hardware and functions as the central hub that all other hardware components run through. CPU. The CPU is the brain of the computer that processes and executes digital instructions from various programs; its clock speed determines the computer's performance and efficiency in processing data. RAM. RAM -- or dynamic RAM -- is temporary memory storage that makes information immediately accessible to programs; RAM is volatile memory, so stored data is cleared when the computer powers off. Hard drive. Hard disk drives are physical storage devices that store both permanent and temporary data in different formats, including programs, OSes, device files, photos, etc. Solid-state drive (SSD). SSDs are solid-state storage devices based on NAND flash memory technology; SSDs are non-volatile, so they can safely store data even when the computer is powered down. Optical drive. Optical drives typically reside in an on-device drive bay; they enable the computer to read and interact with nonmagnetic external media, such as compact disc read- only memory or digital video discs. Heat sink. This is a passive piece of hardware that draws heat away from components to regulate/reduce their temperature to help ensure they continue to function properly. Typically, a heat sink is installed directly atop the CPU, which produces the most heat among internal components. Graphics processing unit. This chip-based device processes graphical data and often functions as an extension to the main CPU. Network interface card (NIC). A NIC is a circuit board or chip that enables the computer to connect to a network; also known as a network adapter or local area network adapter, it typically supports connection to an Ethernet network. Other computing components, such as USB ports, power supplies, transistors and chips, are also types of internal hardware. This computer hardware chart below illustrates what typical internal computer hardware components look like. EXTERNAL HARDWARE COMPONENTS External hardware components, also called peripheral components, are those items that are often externally connected to the computer to control either input or output functions. These hardware devices are designed to either provide instructions to the software (input) or render results from its execution (output). Common input hardware components include the following: Mouse. A mouse is a hand-held pointing device that moves a cursor around a computer screen and enables interaction with objects on the screen. It may be wired or wireless. Keyboard. A keyboard is an input device featuring a standard QWERTY keyset that enables users to input text, numbers or special characters. Microphone. A microphone is a device that translates sound waves into electrical signals and supports computer-based audio communications. Camera. A camera captures visual images and streams them to the computer or through a computer to a network device. Touchpad. A touchpad is an input device, external or built into a laptop, used to control the pointer on a display screen. It is typically an alternative to an external mouse. USB flash drive. A USB flash drive is an external, removable storage device that uses flash memory and interfaces with a computer through a USB port. Memory card. A memory card is a type of portable external storage media, such as a CompactFlash card, used to store media or data files. Other input hardware components include joysticks, styluses and scanners. Examples of output hardware components include the following: Monitor. A monitor is an output device similar to a TV screen that displays information, documents or images generated by the computing device. Printer. Printers render electronic data from a computer into printed material. Speaker. A speaker is an external audio output device that connects to a computer to generate a sound output. Headphones, earphones, earbuds. Similar to speakers, these devices provide audio output that's audible only to a single listener. UTILITY PROGRAM The utility program is a system software or application that executes a specific task, generally pertaining to optimal maintenance or operation of the system resources. Operating systems such as Windows, macOS, and Linux come with their own set of programs to maintain and execute different utility functions such as formatting, compressing, scanning, exploring, and more. In other words, Utility-program definition in simple terms is that it assists with the management of computer functions, resources, and files. You can ensure complete password protection and keep your systems virus-free using different utility programs. FUNCTIONS OF UTILITY PROGRAMS Various functions are executed by a utility program to make the system‟s operations smoother and more efficient. Overall, they can be broadly categorized into four parts: System Utilities Some of the system utility programs are memory manager, antivirus and firewall, registry checker and cleaner, package installer, and explorer. Also, with the help of such system in computers, users can execute functions that are crucial for the smooth running of an operating system. File Management Utilities File management utilities include tools such as data archivers, software backup tools, file compression tools, and managers. With the help of these, users can manage their data in the form of files and folders. These utilities help users sort out, store, and categorize files according to their requirements. Storage Device Management Utilities Storage device management utility programs provide solutions for enhancing disk capacity, such as disk clean-up, partition management, formatting, disk space allocation, defragmentation, etc. With the help of them, users can compartmentalize systems and external drives for efficient management of programs and files that are stored within. Miscellaneous Utilities Apart from these three utility program categories, various other programs help in managing business operations. Some of these programs include data generators, HTML checkers, and hex editors, to name a few. Advantages of Utility Program Let‟s check out the different advantages of utility program that can be beneficial for its users. Efficiently manage your data and files with proper storage Remove unnecessary files to ensure that you always have storage space for new applications and programs Enhance your system‟s security by protecting it from malicious virus threats and attacks Easily and quickly locate and access your files and folders in the system with the interface customization feature of the utility program Find your lost files and folders with file recovery software and recover any data loss Enhance your system‟s performance by creating space and efficiently managing system storage Disadvantages of the Utility Program After knowing the advantages of a Utility program, it becomes necessary to get familiar with some of its disadvantages too. Here are some drawbacks of utility programs. Let‟s check them out: System Instability: Certain utility programs sometimes alter a computer‟s system settings, leading to potential system instability or incompatibility issues with other software applications. False Positives: Antivirus programs often produce false positives. This leads to wrong flagging of legitimate software applications as security threats and causing unnecessary disruptions. Resource Consumption: Sometimes consume system resources like CPU and memory, impacting system performance and user experience. Compatibility Issues: Some utility programs are not compatible with specific operating systems or hardware configurations, resulting in compatibility concerns. Cost: While many applications are accessible for free or at low costs, specialized utility programs are expensive. This contributes to the overall cost of managing and maintaining a computer system. User Error: Improper use or configuration of utility program can lead to data loss, system instability, or other major consequences. COMMON TASKS PERFORMED BY UTILITY PROGRAMS As discussed earlier, utility applications help in executing some of the most basic yet important functions in the operating system. Some of these basic yet crucial programs are: Disk Defragmentation: Defragmentation is a process which helps reduce the amount of fragmentation in file systems. Utility programs function by organizing the disk content and storing the pieces of each file together. It also helps create large amount of free space using compaction to impede the return of fragmentation. This happens when any operating system is unable to allocate space for storage as single unit. Disk Clean-up: With the help of utility program on the computer, users can remove the unnecessary files that are taking up the space in their system. The program assists users in choosing the drives, folders, or files that need to be scanned and cleaned up. By removing unused files, the system will be able to increase the storage space and optimize the overall speed of the system. File Management: With the help of a file management program, users can perform various functions related to the files saved in the system, such as searching, renaming, opening, renaming deleting, and grouping. These functions can be executed with the help of file management programs such as Windows Explorer. In addition, Windows also help in keeping track of the root and the path of a file. Compression: One of the biggest concerns of any computer system is its storage space. With time, the limited storage space in the hard disk starts getting smaller. Therefore, with the help of compression programs such as WinZip and WinRAR, important yet unused files can be compressed, stored, and easily extracted when required. Disk Management: Disk Management is one of the most vital programs that an operating system like Windows provides. With the help of the system utility software and program, users can seamlessly manage various drives such as hard drives, optical drives, flash drives, etc. It helps users partition drives, allocate spaces, format drives, and much more. Antivirus and Firewall: Antivirus and firewall programs such as Windows Defender help users protect their computers from getting infected with viruses, adware, and malware. Firewalls prevent harmful programs and files from entering the system via the Internet or any external hardware. On the other hand, antivirus helps in removing malicious programs and files that have infected the system. TYPES OF UTILITY PROGRAMS Various types of utility programs are commonly used, including: Antivirus programs: These helps identify and remove viruses, malware, and other harmful software from a computer system. Disk cleaning tools: These types of utility programs help scan a computer‟s hard drive for redundant files and other data that can be safely deleted to create additional storage space. Backup and recovery applications: This type of utility program enables users to generate duplicates of their data and restore it in case of data loss or system malfunction. System optimization software: These helps boost a computer‟s performance by fine- tuning system settings, eliminating unnecessary files and programs, and administering system resources efficiently. Disk defragmentation utilities: These programs are designed to improve a computer‟s hard drive to enhance file access speed and overall system performance. File compression programs: File compression software helps compact files and folders to conserve storage space and facilitate easier transfer over the internet. Disk encryption applications: Disk encryption software encrypts data on a computer‟s hard drive to safeguard it from unauthorized access. Why Need Utility Program? There are different functions served by the Utility program. Some of them are system maintenance, efficiency, security, data recovery, and user experience. Let‟s read about them in detail below: System Maintenance: It encompasses a diverse set of tools and applications that help users manage and uphold their computer systems, enabling them to enhance system performance. This helps eliminate unnecessary files and programs and ensures the smooth operation of their system. Security: Integrates tools like antivirus and encryption software to enable users to shield their computer systems from security risks or threats like viruses, malware, and unauthorized access. Efficiency: Utility software helps optimize system performance, streamlining routine tasks such as disk cleanup, file compression, and data backup. This in turn reduces the time and effort required to perform routine tasks. Data Recovery: Backup and recovery tools of utility programs assist users in retrieving lost or deleted data in the event of system failure or data loss. User Experience: Utility software enables users to customize their system settings and preferences, enhancing their overall user experience. LANGUAGE TRANSLATOR A translator is a programming language processor that converts a computer program from one language to another. It takes a program written in source code and converts it into machine code. It discovers and identifies the error during translation. Purpose of Translator It translates a high-level language program into a machine language program that the central processing unit (CPU) can understand. It also detects errors in the program. DIFFERENT TYPES OF TRANSLATORS There are 3 different types of translators as follows: COMPILER: A compiler is a translator used to convert high-level programming language to low-level programming language. It converts the whole program in one session and reports errors detected after the conversion. The compiler takes time to do its work as it translates high- level code to lower-level code all at once and then saves it to memory. A compiler is processor-dependent and platform-dependent. But it has been addressed by a special compiler, a cross-compiler and a source-to-source compiler. Before choosing a compiler, the user has to identify first the Instruction Set Architecture (ISA), the operating system (OS), and the programming language that will be used to ensure that it will be compatible. ADVANTAGES OF THE COMPILER: The whole program is validated so there are no system errors. The executable file is enhanced by the compiler, so it runs faster. User do not have to run the program on the same machine it was created. DISADVANTAGES OF THE COMPILER: It is slow to execute as you have to finish the whole program. It is not easy to debug as errors are shown at the end of the execution. Hardware specific, it works on specific machine language and architecture. INTERPRETER: Just like a compiler, is a translator used to convert high-level programming language to low-level programming language. It converts the program one at a time and reports errors detected at once while doing the conversion. With this, it is easier to detect errors than in a compiler. An interpreter is faster than a compiler as it immediately executes the code upon reading the code. It is often used as a debugging tool for software development as it can execute a single line of code at a time. An interpreter is also more portable than a compiler as it is not processor- dependent, you can work between hardware architectures. ADVANTAGES OF THE INTERPRETER: You discover errors before you complete the program, so you learn from your mistakes. Program can be run before it is completed so you get partial results immediately. You can work on small parts of the program and link them later into a whole program. DISADVANTAGES OF THE INTERPRETER: There‟s a possibility of syntax errors on unverified scripts. Program is not enhanced and may encounter data errors. It may be slow because of the interpretation in every execution. ASSEMBLER: An assembler is a translator used to translate assembly language to machine language. It is like a compiler for the assembly language but interactive like an interpreter. Assembly language is difficult to understand as it is a low-level programming language. An assembler translates a low-level language, an assembly language to an even lower- level language, which is the machine code. The machine code can be directly understood by the CPU. ADVANTAGES OF THE ASSEMBLER: The symbolic programming is easier to understand thus time-saving for the programmer. It is easier to fix errors and alter program instructions. Efficiency in execution just like machine level language. DISADVANTAGES OF THE ASSEMBLER: It is machine dependent, cannot be used in other architecture. A small change in design can invalidate the whole program. It is difficult to maintain. EXAMPLES OF TRANSLATORS Translator Examples Microsoft Visual Studio Compiler GNU Compiler Collection (GCC) Common Business Oriented Language (COBOL) OCaml Interpreter List Processing (LISP) Python Fortran Assembly Program (FAP) Assembler Macro Assembly Program (MAP) Symbolic Optimal Assembly Program (SOAP) THE INTERNET AND THE WEB The internet is a global network of interconnected computers and servers that allows people to communicate, share information, and access resources from anywhere in the world. It was created in the 1960s by the US Department of Defense as a way to connect computers and share information between researchers and scientists. The World Wide Web, or simply the web, is a system of interconnected documents and resources, linked together by hyperlinks and URLs. It was created by Tim Berners-Lee in 1989 as a way for scientists to share information more easily. The web quickly grew to become the most popular way to access information on the internet. Together, the internet and the web have revolutionized the way we communicate, do business, and access information. They have made it possible for people all over the world to connect with each other instantly and have transformed many industries, from media and entertainment to education and healthcare. 1. The Internet: In simplest terms, the Internet is a global network comprised of smaller networks that are interconnected using standardized communication protocols. The Internet standards describe a framework known as the Internet protocol suite. This model divides methods into a layered system of protocols. These layers are as follows: 1. Application layer (highest) – concerned with the data(URL, type, etc.). This is where HTTP, HTTPS, etc., comes in. 2. Transport layer – responsible for end-to-end communication over a network. 3. Network layer – provides data route. The Internet provides a variety of information and communication facilities; contains forums, databases, email, hypertext, etc. It consists of private, public, academic, business, and government networks of local to global scope, linked by a broad array of electronic, wireless, and optical networking technologies. 2. The World Wide Web: The Web is a major means of access information on the Internet. It‟s a system of Internet servers that support specially formatted documents. The documents are formatted in a markup language called HTML, or “HyperText Markup Language”, which supports a number of features including links and multimedia. These documents are interlinked using hypertext links and are accessible via the Internet. To link hypertext to the Internet, we need: 1. The markup language, i.e., HTML. 2. The transfer protocol, e.g., HTTP. 3. Uniform Resource Locator (URL), the address of the resource. We access the Web using Web browsers. DIFFERENCE BETWEEN WEB AND INTERNET Internet Web The Internet is the network of networks and The Web is a way to access information the network allows to exchange of data through the Internet. between two or more computers. It is also known as the Network of The Web is a model for sharing Networks. information using the Internet. The Internet is a way of transporting The protocol used by the web is HTTP. information between devices. Accessible in a variety of ways. The Web is accessed by the Web Browser. Network protocols are used to transport Accesses documents and online sites data. through browsers. Global network of networks Collection of interconnected websites Connectivity Network of networks that Connectivity Allows users to access and allows devices to communicate and view web pages, multimedia content, and exchange data other resources over the Internet Protocols HTTP, HTTPS, FTP, SMTP, Protocols TCP/IP, FTP, SMTP, POP3, etc. etc. Infrastructure Consists of web servers, Infrastructure Consists of routers, switches, web browsers, and other software and servers, and other networking hardware hardware Used for communication, sharing of Used for publishing and accessing web resources, and accessing information from pages, multimedia content, and other around the world resources on the Internet No single creator Creator Tim Berners-Lee Provides a platform for publishing and Provides the underlying infrastructure for accessing information and resources on the Web, email, and other online services the Internet URI: URI stands for ‘Uniform Resource Identifier’. A URI can be a name, locator, or both for an online resource whereas a URL is just the locator. URLs are a subset of URIs. A URL is a human-readable text that was designed to replace the numbers (IP addresses) that computers use to communicate with servers. A URL consists of a protocol, domain name, and path (which includes the specific subfolder structure where a page is located) like-protocol: //WebSiteName.topLevelDomain/path 1. Protocol – HTTP or HTTPS. 2. WebSiteName – geeksforgeeks, google etc. 3. topLevelDomain-.com,.edu,.in etc. 4. path- specific folders and/or subfolders that are on a given website.. USES OF INTERNET AND THE WEB : 1. Communication: The internet and web have made communication faster and easier than ever before. We can now send emails, chat online, make video calls, and use social media platforms to connect with people all over the world. 2. Information sharing: The web has made it possible to access vast amounts of information on any topic from anywhere in the world. We can read news articles, watch videos, listen to podcasts, and access online libraries and databases. 3. Online shopping: The internet and web have revolutionized the way we shop. We can now browse and purchase products online, from clothes and groceries to electronics and furniture. 4. Entertainment: The internet and web provide a wealth of entertainment options, from streaming movies and TV shows to playing online games and listening to music. 5. Education: The web has made it possible to access educational resources from anywhere in the world. We can take online courses, access e-books and digital libraries, and connect with educators and other learners through online communities. 6. Business: The internet and web have transformed the way businesses operate. Companies can now use e-commerce platforms to sell products and services, collaborate with remote workers, and access global markets. 7. Research: The internet and web have made it easier for researchers to access and share information. We can now access scientific journals and databases, collaborate with other researchers online, and conduct surveys and experiments through online platforms. ISSUES IN INTERNET AND THE WEB 1. Privacy and security: The internet and web are vulnerable to various security threats, such as hacking, identity theft, and phishing attacks. These threats can compromise our personal information, such as login credentials, financial information, and personal data. 2. Cyberbullying: The anonymity of the internet and web can lead to cyberbullying, where individuals are harassed or threatened online. Cyberbullying can have severe consequences, including depression, anxiety, and suicide. 3. Online addiction: The internet and web can be addictive, and individuals can spend hours browsing social media or playing online games, leading to neglect of other important aspects of their lives. 4. Disinformation: The internet and web are filled with inaccurate or false information, which can lead to misinformation, propaganda, and conspiracy theories. 5. Digital divide: Access to the internet and web is not universal, and many individuals, particularly those in low-income areas or rural communities, lack access to reliable and high- speed internet. 6. Online censorship: Some governments or organizations may censor or restrict access to certain websites or information, limiting freedom of speech and expression. 7. Environmental impact: The internet and web consume a significant amount of energy, contributing to carbon emissions and climate change. NETWORK DEVICES Network Devices: Network devices, also known as networking hardware, are physical devices that allow hardware on a computer network to communicate and interact with one another. For example Repeater, Hub, Bridge, Switch, Routers, Gateway, Brouter, and NIC, etc. Network Devices. 1. Repeater – A repeater operates at the physical layer. Its job is to amplifies (i.e., regenerates) the signal over the same network before the signal becomes too weak or corrupted to extend the length to which the signal can be transmitted over the same network. When the signal becomes weak, they copy it bit by bit and regenerate it at its star topology connectors connecting following the original strength. It is a 2-port device. 2. Hub – A hub is a basically multi-port repeater. A hub connects multiple wires coming from different branches, for example, the connector in star topology which connects different stations. Hubs cannot filter data, so data packets are sent to all connected devices. In other words, the collision domain of all hosts connected through Hub remains one. Also, they do not have the intelligence to find out the best path for data packets which leads to inefficiencies and wastage. Types of Hub Active Hub:- These are the hubs that have their power supply and can clean, boost, and relay the signal along with the network. It serves both as a repeater as well as a wiring center. These are used to extend the maximum distance between nodes. Passive Hub:- These are the hubs that collect wiring from nodes and power supply from the active hub. These hubs relay signals onto the network without cleaning and boosting them and can‟t be used to extend the distance between nodes. Intelligent Hub:- It works like an active hub and includes remote management capabilities. They also provide flexible data rates to network devices. It also enables an administrator to monitor the traffic passing through the hub and to configure each port in the hub. 3. Bridge – A bridge operates at the data link layer. A bridge is a repeater, with add on the functionality of filtering content by reading the MAC addresses of the source and destination. It is also used for interconnecting two LANs working on the same protocol. It has a single input and single output port, thus making it a 2 port device. Types of Bridges Transparent Bridges:- These are the bridge in which the stations are completely unaware of the bridge‟s existence i.e. whether or not a bridge is added or deleted from the network, reconfiguration of the stations is unnecessary. These bridges make use of two processes i.e. bridge forwarding and bridge learning. Source Routing Bridges:- In these bridges, routing operation is performed by the source station and the frame specifies which route to follow. The host can discover the frame by sending a special frame called the discovery frame, which spreads through the entire network using all possible paths to the destination. 4. Switch – A switch is a multiport bridge with a buffer and a design that can boost its efficiency(a large number of ports imply less traffic) and performance. A switch is a data link layer device. The switch can perform error checking before forwarding data, which makes it very efficient as it does not forward packets that have errors and forward good packets selectively to the correct port only. In other words, the switch divides the collision domain of hosts, but the broadcast domain remains the same. Types of Switch Unmanaged switches: These switches have a simple plug-and-play design and do not offer advanced configuration options. They are suitable for small networks or for use as an expansion to a larger network. Managed switches: These switches offer advanced configuration options such as VLANs, QoS, and link aggregation. They are suitable for larger, more complex networks and allow for centralized management. Smart switches: These switches have features similar to managed switches but are typically easier to set up and manage. They are suitable for small- to medium-sized networks. Layer 2 switches: These switches operate at the Data Link layer of the OSI model and are responsible for forwarding data between devices on the same network segment. Layer 3 switches: These switches operate at the Network layer of the OSI model and can route data between different network segments. They are more advanced than Layer 2 switches and are often used in larger, more complex networks. PoE switches: These switches have Power over Ethernet capabilities, which allows them to supply power to network devices over the same cable that carries data. Gigabit switches: These switches support Gigabit Ethernet speeds, which are faster than traditional Ethernet speeds. Rack-mounted switches: These switches are designed to be mounted in a server rack and are suitable for use in data centers or other large networks. Desktop switches: These switches are designed for use on a desktop or in a small office environment and are typically smaller in size than rack-mounted switches. Modular switches: These switches have modular design, which allows for easy expansion or customization. They are suitable for large networks and data centers. 5. Routers – A router is a device like a switch that routes data packets based on their IP addresses. The router is mainly a Network Layer device. Routers normally connect LANs and WANs and have a dynamically updating routing table based on which they make decisions on routing the data packets. The router divides the broadcast domains of hosts connected through it. 6. Gateway – A gateway, as the name suggests, is a passage to connect two networks that may work upon different networking models. They work as messenger agents that take data from one system, interpret it, and transfer it to another system. Gateways are also called protocol converters and can operate at any network layer. Gateways are generally more complex than switches or routers. 7. Brouter – It is also known as the bridging router is a device that combines features of both bridge and router. It can work either at the data link layer or a network layer. Working as a router, it is capable of routing packets across networks and working as the bridge, it is capable of filtering local area network traffic. 8. NIC – NIC or network interface card is a network adapter that is used to connect the computer to the network. It is installed in the computer to establish a LAN. It has a unique id that is written on the chip, and it has a connector to connect the cable to it. The cable acts as an interface between the computer and the router or modem. NIC card is a layer 2 device which means that it works on both the physical and data link layers of the network model. BASICS OF COMPUTER NETWORKING Computer networking is a cornerstone of modern technology, enabling the interconnected systems that power the Internet, business communications, and everyday digital interactions. Understanding the fundamentals of computer networking is essential for anyone involved in technology, from enthusiasts to professionals. This article will explore the basics of computer networking, including network types, components, protocols, and essential services like the Domain Name System (DNS). Computer Networking What is a Computer Network? A computer network is a collection of interconnected devices that share resources and information. These devices can include computers, servers, printers, and other hardware. Networks allow for the efficient exchange of data, enabling various applications such as email, file sharing, and internet browsing. BASIC TERMINOLOGIES OF COMPUTER NETWORKS Network: A network is a collection of computers and devices that are connected together to enable communication and data exchange. Nodes: Nodes are devices that are connected to a network. These can include computers, Servers, Printers, Routers, Switches, and other devices. Protocol: A protocol is a set of rules and standards that govern how data is transmitted over a network. Examples of protocols include TCP/IP, HTTP, and FTP. Topology: Network topology refers to the physical and logical arrangement of nodes on a network. The common network topologies include bus, star, ring, mesh, and tree. Service Provider Networks: These types of Networks give permission to take Network Capacity and Functionality on lease from the Provider. Service Provider Networks include Wireless Communications, Data Carriers, etc. IP Address: An IP address is a unique numerical identifier that is assigned to every device on a network. IP addresses are used to identify devices and enable communication between them. DNS: The Domain Name System (DNS) is a protocol that is used to translate human- readable domain names (such as www.google.com) into IP addresses that computers can understand. Firewall: A firewall is a security device that is used to monitor and control incoming and outgoing network traffic. Firewalls are used to protect networks from unauthorized access and other security threats. TYPES OF ENTERPRISE COMPUTER NETWORKS LAN: A Local Area Network (LAN) is a network that covers a small area, such as an office or a home. LANs are typically used to connect computers and other devices within a building or a campus. WAN: A Wide Area Network (WAN) is a network that covers a large geographic area, such as a city, country, or even the entire world. WANs are used to connect LANs together and are typically used for long-distance communication. Cloud Networks: Cloud Networks can be visualized with a Wide Area Network (WAN) as they can be hosted on public or private cloud service providers and cloud networks are available if there is a demand. Cloud Networks consist of Virtual Routers, Firewalls, etc. These are just a few basic concepts of computer networking. Networking is a vast and complex field, and there are many more concepts and technologies involved in building and maintaining networks. Now we are going to discuss some more concepts on Computer Networking. Open system: A system that is connected to the network and is ready for communication. Closed system: A system that is not connected to the network and can‟t be communicated with. TYPES OF COMPUTER NETWORK ARCHITECTURE Computer Network falls under these broad Categories: Client-Server Architecture: Client-Server Architecture is a type of Computer Network Architecture in which Nodes can be Servers or Clients. Here, the server node can manage the Client Node Behaviour. Peer-to-Peer Architecture: In P2P (Peer-to-Peer) Architecture, there is not any concept of a Central Server. Each device is free for working as either client or server. NETWORK PROTOCOLS A protocol is a set of rules or algorithms which define the way how two entities can communicate across the network and there exists a different protocol defined at each layer of the OSI model. A few such protocols are TCP, IP, UDP, ARP, DHCP, FTP, and so on. Protocol Function Transmission Control TCP: Ensures data is delivered reliably and in order. Protocol/Internet Protocol IP: Routes data packets to their destination based on IP (TCP/IP) addresses. Hypertext Transfer Protocol Function: The protocols used for transmitting web pages. (HTTP) and HTTPS HTTP: Unsecured communication.. HTTPS: Secured communication using SSL/TLS encryption Simple Mail Transfer Protocol Function: Protocol for sending email. (SMTP) Components: Works with other protocols like POP3 and IMAP for email retrieval. File Transfer Protocol (FTP) Function: Protocol for transferring files between computers. Components: Includes commands for uploading, downloading, and managing files on a remote server Dynamic Host Configuration Function: Automatically assigns IP addresses to devices on a Protocol (DHCP) network. Components: Reduces manual configuration and IP address conflicts. Domain Name System (DNS) Function: Translates human-friendly domain names into IP addresses. Components: Ensures seamless navigation on the internet. Unique Identifiers of Network Hostname: Each device in the network is associated with a unique device name known as Hostname. Type “hostname” in the command prompt(Administrator Mode) and press „Enter‟, this displays the hostname of your machine. IP Address (Internet Protocol address): Also known as the Logical Address, the IP Address is the network address of the system across the network. To identify each device in the world- wide-web, the Internet Assigned Numbers Authority (IANA) assigns an IPV4 (Version 4) address as a unique identifier to each device on the Internet. The length of an IPv4 address is 32 bits, hence, we have 232 IP addresses available. The length of an IPv6 address is 128 bits. In Windows Type “ipconfig” in the command prompt and press „Enter‟, this gives us the IP address of the device. For Linux, Type “ifconfig” in the terminal and press „Enter‟ this gives us the IP address of the device. MAC Address (Media Access Control address): Also known as physical address, the MAC Address is the unique identifier of each host and is associated with its NIC (Network Interface Card). A MAC address is assigned to the NIC at the time of manufacturing. The length of the MAC address is: 12-nibble/ 6 bytes/ 48 bits Type “ipconfig/all” in the command prompt and press „Enter‟, this gives us the MAC address. Port: A port can be referred to as a logical channel through which data can be sent/received to an application. Any host may have multiple applications running, and each of these applications is identified using the port number on which they are running. A port number is a 16-bit integer, hence, we have 216 ports available which are categorized as shown below: Port Types Range Well known Ports 0 – 1023 Registered Ports 1024 – 49151 Ephemeral Ports 49152 – 65535 Number of ports: 65,536 Range: 0 – 65535 Type “netstat -a” in the command prompt and press „Enter‟, this lists all the ports being used. List of Ports Socket: The unique combination of IP address and Port number together is termed a Socket. Other Related Concepts DNS Server: DNS stands for Domain Name System. DNS is basically a server that translates web addresses or URLs (ex: www.google.com) into their corresponding IP addresses. We don‟t have to remember all the IP addresses of each and every website. The command „nslookup‟ gives you the IP address of the domain you are looking for. This also provides information on our DNS Server. \ Domain IP Address ARP: ARP stands for Address Resolution Protocol. It is used to convert an IP address to its corresponding physical address(i.e., MAC Address). ARP is used by the Data Link Layer to identify the MAC address of the Receiver‟s machine. RARP: RARP stands for Reverse Address Resolution Protocol. As the name suggests, it provides the IP address of the device given a physical address as input. But RARP has become obsolete since the time DHCP has come into the picture. The Domain Name System (DNS) is a critical component of computer networking. It converts easily recognizable domain names, such as www.example.com, into numerical IP addresses that computers use to identify each other on the network. How DNS Works? User Input: When a user enters a domain name in a browser, the system needs to find its IP address. DNS Query: The user‟s device sends a DNS query to the DNS resolver. Resolver Request: The DNS resolver checks its cache for the IP address. If not found, it forwards the request to the root DNS server. Root DNS Server: The root DNS server provides the address of the TLD (Top-Level Domain) server for the specific domain extension (e.g.,.com). TLD DNS Server: The TLD server directs the resolver to the authoritative DNS server for the actual domain. Authoritative DNS Server: The authoritative DNS server knows the IP address for the domain and provides it to the resolver. Response to User: The resolver stores the IP address in its cache and sends it to the user‟s device. Access Website: With the IP address, the user‟s device can access the desired website. DNS works efficiently, translating user-friendly domain names into IP addresses, allowing seamless navigation on the internet. NETWORK SECURITY Ensuring the security of a network is crucial to protect data and resources from unauthorized access and attacks. Key aspects of network security include: Firewalls: Devices or software that monitor and control incoming and outgoing network traffic based on security rules. Encryption: The process of encoding data to prevent unauthorized access. Commonly used in VPNs, HTTPS, and secure email. Intrusion Detection Systems (IDS): Tools that monitor network traffic for suspicious activity and potential threats. Access Control: Mechanisms that restrict access to network resources based on user identity and role. Regular Updates and Patching: Keeping software and hardware up to date to protect against vulnerabilities. NETWORK TOPOLOGY Network topology refers to the arrangement of different elements like nodes, links, or devices in a computer network. It defines how these components are connected and interact with each other. Understanding various types of network topologies helps in designing efficient and robust networks. Common types include bus, star, ring, mesh, and tree topologies, each with its own advantages and disadvantages. In this article, we are going to discuss different types of network topology their advantages and disadvantages in detail. TYPES OF NETWORK TOPOLOGY The arrangement of a network that comprises nodes and connecting lines via sender and receiver is referred to as Network Topology. The various network topologies are: Point to Point Topology Mesh Topology Star Topology Bus Topology Ring Topology Tree Topology Hybrid Topology Point to Point Topology Point-to-point topology is a type of topology that works on the functionality of the sender and receiver. It is the simplest communication between two nodes, in which one is the sender and the other one is the receiver. Point-to-Point provides high bandwidth. Point to Point Topology Mesh Topology In a mesh topology, every device is connected to another device via a particular channel. In Mesh Topology, the protocols used are AHCP (Ad Hoc Configuration Protocols), DHCP (Dynamic Host Configuration Protocol), etc. Mesh Topology Figure 1 : Every device is connected to another via dedicated channels. These channels are known as links. Suppose, the N number of devices are connected with each other in a mesh topology, the total number of ports that are required by each device is N-1. In Figure 1, there are 5 devices connected to each other, hence the total number of ports required by each device is 4. The total number of ports required = N * (N-1). Suppose, N number of devices are connected with each other in a mesh topology, then the total number of dedicated links required to connect them is N C 2 i.e. N(N-1)/2. In Figure 1, there are 5 devices connected to each other, hence the total number of links required is 5*4/2 = 10. Advantages of Mesh Topology Communication is very fast between the nodes. Mesh Topology is robust. The fault is diagnosed easily. Data is reliable because data is transferred among the devices through dedicated channels or links. Provides security and privacy. Disadvantages of Mesh Topology Installation and configuration are difficult. The cost of cables is high as bulk wiring is required, hence suitable for less number of devices. The cost of maintenance is high. A common example of mesh topology is the internet backbone, where various internet service providers are connected to each other via dedicated channels. This topology is also used in military communication systems and aircraft navigation systems. For more, refer to the Advantages and Disadvantages of Mesh Topology. Star Topology In Star Topology, all the devices are connected to a single hub through a cable. This hub is the central node and all other nodes are connected to the central node. The hub can be passive in nature i.e., not an intelligent hub such as broadcasting devices, at the same time the hub can be intelligent known as an active hub. Active hubs have repeaters in them. Coaxial cables or RJ-45 cables are used to connect the computers. In Star Topology, many popular Ethernet LAN protocols are used as CD(Collision Detection), CSMA (Carrier Sense Multiple Access), etc. Star Topology Figure 2 : A star topology having four systems connected to a single point of connection i.e. hub. Advantages of Star Topology If N devices are connected to each other in a star topology, then the number of cables required to connect them is N. So, it is easy to set up. Each device requires only 1 port i.e. to connect to the hub, therefore the total number of ports required is N. It is Robust. If one link fails only that link will affect and not other than that. Easy to fault identification and fault isolation. Star topology is cost-effective as it uses inexpensive coaxial cable. Disadvantages of Star Topology If the concentrator (hub) on which the whole topology relies fails, the whole system will crash down. The cost of installation is high. Performance is based on the single concentrator i.e. hub. A common example of star topology is a local area network (LAN) in an office where all computers are connected to a central hub. This topology is also used in wireless networks where all devices are connected to a wireless access point. For more, refer to the Advantages and Disadvantages of Star Topology. Bus Topology Bus Topology is a network type in which every computer and network device is connected to a single cable. It is bi-directional. It is a multi-point connection and a non-robust topology because if the backbone fails the topology crashes. In Bus Topology, various MAC (Media Access Control) protocols are followed by LAN ethernet connections like TDMA , Pure Aloha , CDMA, Slotted Aloha , etc. Bus Topology Figure 3 : A bus topology with shared backbone cable. The nodes are connected to the channel via drop lines. Advantages of Bus Topology If N devices are connected to each other in a bus topology, then the number of cables required to connect them is 1, known as backbone cable, and N drop lines are required. Coaxial or twisted pair cables are mainly used in bus-based networks that support up to 10 Mbps. The cost of the cable is less compared to other topologies, but it is used to build small networks. Bus topology is familiar technology as installation and troubleshooting techniques are well known. CSMA is the most common method for this type of topology. Disadvantages of Bus Topology A bus topology is quite simpler, but still, it requires a lot of cabling. If the common cable fails, then the whole system will crash down. If the network traffic is heavy, it increases collisions in the network. To avoid this, various protocols are used in the MAC layer known as Pure Aloha, Slotted Aloha, CSMA/CD, etc. Adding new devices to the network would slow down networks. Security is very low. A common example of bus topology is the Ethernet LAN, where all devices are connected to a single coaxial cable or twisted pair cable. This topology is also used in cable television networks. For more, refer to the Advantages and Disadvantages of Bus Topology. Ring Topology In a Ring Topology, it forms a ring connecting devices with exactly two neighboring devices. A number of repeaters are used for Ring topology with a large number of nodes, because if someone wants to send some data to the last node in the ring topology with 100 nodes, then the data will have to pass through 99 nodes to reach the 100th node. Hence to prevent data loss repeaters are used in the network. The data flows in one direction, i.e. it is unidirectional, but it can be made bidirectional by having 2 connections between each Network Node, it is called Dual Ring Topology. In-Ring Topology, the Token Ring Passing protocol is used by the workstations to transmit the data. Ring Topology Figure 4 : A ring topology comprises 4 stations connected with each forming a ring. The most common access method of ring topology is token passing. Token passing: It is a network access method in which a token is passed from one node to another node. Token: It is a frame that circulates around the network. Operations of Ring Topology 1. One station is known as a monitor station which takes all the responsibility for performing the operations. 2. To transmit the data, the station has to hold the token. After the transmission is done, the token is to be released for other stations to use. 3. When no station is transmitting the data, then the token will circulate in the ring. 4. There are two types of token release techniques: Early token release releases the token just after transmitting the data and Delayed token release releases the token after the acknowledgment is received from the receiver. Advantages of Ring Topology The data transmission is high-speed. The possibility of collision is minimum in this type of topology. Cheap to install and expand. It is less costly than a star topology. Disadvantages of Ring Topology The failure of a single node in the network can cause the entire network to fail. Troubleshooting is difficult in this topology. The addition of stations in between or the removal of stations can disturb the whole topology. Less secure. For more, refer to the Advantages and Disadvantages of Ring Topology. Tree Topology This topology is the variation of the Star topology. This topology has a hierarchical flow of data. In Tree Topology, protocols like DHCP and SAC (Standard Automatic Configuration ) are used. Tree Topology Figure 5 : In this, the various secondary hubs are connected to the central hub which contains the repeater. This data flow from top to bottom i.e. from the central hub to the secondary and then to the devices or from bottom to top i.e. devices to the secondary hub and then to the central hub. It is a multi-point connection and a non-robust topology because if the backbone fails the topology crashes. Advantages of Tree Topology It allows more devices to be attached to a single central hub thus it decreases the distance that is traveled by the signal to come to the devices. It allows the network to get isolated and also prioritize from different computers. We can add new devices to the existing network. Error detection and error correction are very easy in a tree topology. Disadvantages of Tree Topology If the central hub gets fails the entire system fails. The cost is high because of the cabling. If new devices are added, it becomes difficult to reconfigure. A common example of a tree topology is the hierarchy in a large organization. At the top of the tree is the CEO, who is connected to the different departments or divisions (child nodes) of the company. Each department has its own hierarchy, with managers overseeing different teams (grandchild nodes). The team members (leaf nodes) are at the bottom of the hierarchy, connected to their respective managers and departments. For more, refer to the Advantages and Disadvantages of Tree Topology. Hybrid Topology This topological technology is the combination of all the various types of topologies we have studied above. Hybrid Topology is used when the nodes are free to take any form. It means these can be individuals such as Ring or Star topology or can be a combination of various types of topologies seen above. Each individual topology uses the protocol that has been discussed earlier. Hybrid Topology The above figure shows the structure of the Hybrid topology. As seen it contains a combination of all different types of networks. Advantages of Hybrid Topology This topology is very flexible. The size of the network can be easily expanded by adding new devices. Disadvantages of Hybrid Topology It is challenging to design the architecture of the Hybrid Network. Hubs used in this topology are very expensive. The infrastructure cost is very high as a hybrid network requires a lot of cabling and network devices. A common example of a hybrid topology is a university campus network. The network may have a backbone of a star topology, with each building connected to the backbone through a switch or router. Within each building, there may be a bus or ring topology connecting the different rooms and offices. The wireless access points also create a mesh topology for wireless devices. This hybrid topology allows for efficient communication between different buildings while providing flexibility and redundancy within each building. For more, refer to the Advantages and Disadvantages of Hybrid Topology. Conclusion In conclusion, network topologies play a crucial role in determining the efficiency and reliability of a computer network. Each topology, whether it‟s bus, star, ring, mesh, or tree, offers unique benefits and potential drawbacks. By understanding these different arrangements, network designers can choose the most appropriate topology to meet the specific needs of their systems, ensuring optimal performance and connectivity. TYPES OF AREA NETWORKS – LAN, MAN AND WAN The Network allows computers to connect and communicate with different computers via any medium. LAN, MAN, and WAN are the three major types of networks designed to operate over the area they cover. There are some similarities and dissimilarities between them. One of the major differences is the geographical area they cover, i.e. LAN covers the smallest area, MAN covers an area larger than LAN and WAN comprises the largest of all. There are other types of Computer Networks also, like : PAN (Personal Area Network) SAN (Storage Area Network) EPN (Enterprise Private Network) VPN (Virtual Private Network) Personal Area Network (PAN)- PAN is a personal area network having an interconnection of personal technology devices to communicate over a short distance. It covers only less than 10 meters or 33 feet of area. PAN has fewer users as compared to other networks such as LAN, WAN, etc. PAN typically uses some form of wireless technology. PAN involves the transmission of data between information devices such as smartphones, personal computers, tablet computers, etc. Advantages: Allows for easy communication between personal devices in close proximity. Can be set up easily and quickly. Uses wireless technology, which eliminates the need for wires and cables. PANs are designed to be energy efficient, which means that devices can communicate with each other without draining their batteries quickly. PANs are typically secured using encryption and authentication protocols, which helps to prevent unauthorized access to data and resources. Disadvantages: Limited coverage area. May not be suitable for large-scale data transfer or communication.PANs typically have limited bandwidth, which means that they may not be able to handle large amounts of data or high-speed communication. May experience interference from other wireless devices. Local Area Network (LAN) – LAN or Local Area Network connects network devices in such a way that personal computers and workstations can share data, tools, and programs. The group of computers and devices are connected together by a switch, or stack of switches, using a private addressing scheme as defined by the TCP/IP protocol. Private addresses are unique in relation to other computers on the local network. Routers are found at the boundary of a LAN, connecting them to the larger WAN. Data transmits at a very fast rate as the number of computers linked is limited. By definition, the connections must be high-speed and relatively inexpensive hardware (Such as hubs, network adapters, and Ethernet cables). LANs cover a smaller geographical area (Size is limited to a few kilometres) and are privately owned. One can use it for an office building, home, hospital, school, etc. LAN is easy to design and maintain. A Communication medium used for LAN has twisted-pair cables and coaxial cables. It covers a short distance, and so the error and noise are minimized. Early LANs had data rates in the 4 to 16 Mbps range. Today, speeds are normally 100 or 1000 Mbps. Propagation delay is very short in a LAN. The smallest LAN may only use two computers, while larger LANs can accommodate thousands of computers. LAN has a range up to 2km. A LAN typically relies mostly on wired connections for increased speed and security, but wireless connections can also be part of a LAN. The fault tolerance of a LAN is more and there is less congestion in this network. For example A bunch of students playing Counter-Strike in the same room (without internet). Advantages: Provides fast data transfer rates and high-speed communication. Easy to set up and manage. Can be used to share peripheral devices such as printers and scanners. Provides increased security and fault tolerance compared to WANs. Disadvantages: Limited geographical coverage. Limited scalability and may require significant infrastructure upgrades to accommodate growth. May experience congestion and network performance issues with increased usage. Metropolitan Area Network (MAN) – MAN or Metropolitan area Network covers a larger area than that covered by a LAN and a smaller area as compared to WAN. MAN has a range of 5-50km. It connects two or more computers that are apart but reside in the same or different cities. It covers a large geographical area and may serve as an ISP (Internet Service Provider). MAN is designed for customers who need high-speed connectivity. Speeds of MAN range in terms of Mbps. It‟s hard to design and maintain a Metropolitan Area Network. The fault tolerance of a MAN is less and also there is more congestion in the network. It is costly and may or may not be owned by a single organization. The data transfer rate and the propagation delay of MAN are moderate. Devices used for transmission of data through MAN are Modem and Wire/Cable. Examples of a MAN are part of the telephone company network that can provide a high-speed DSL line to the customer or the cable TV network in a city. Advantages: Provides high-speed connectivity over a larger geographical area than LAN. Can be used as an ISP for multiple customers. Offers higher data transfer rates than WAN in some cases. Disadvantages: Can be expensive to set up and maintain. May experience congestion and network performance issues with increased usage. May have limited fault tolerance and security compared to LANs. Wide Area Network (WAN) – WAN or Wide Area Network is a computer network that extends over a large geographical area, although it might be confined within the bounds of a state or country. WAN has a range of above 50 km. A WAN could be a connection of LAN connecting to other LANs via telephone lines and radio waves and may be limited to an enterprise (a corporation or an organization) or accessible to the public. The technology is high-speed and relatively expensive. There are two types of WAN: Switched WAN and Point-to-Point WAN. WAN is difficult to design and maintain. Similar to a MAN, the fault tolerance of a WAN is less and there is more congestion in the network. A Communication medium used for WAN is PSTN(Public Switched Telephone Network) or Satellite Link. Due to long-distance transmission, the noise and error tend to be more in WAN. WAN‟s data rate is slow about a 10th LAN‟s speed since it involves increased distance and increased number of servers and terminals etc. The speed of WAN ranges from a few kilobits per second (Kbps) to megabits per second (Mbps). Propagation delay is one of the biggest problems faced here. Devices used for the transmission of data through WAN are Optic wires, Microwaves, and Satellites. An example of a Switched WAN is the asynchronous transfer mode (ATM) network and Point-to-Point WAN is a dial-up line that connects a home computer to the Internet. Advantages: Covers large geographical areas and can connect remote locations. Provides connectivity to the internet. Offers remote access to resources and applications. Can be used to support multiple users and applications simultaneously. Disadvantages: Can be expensive to set up and maintain. Offers slower data transfer rates than LAN or MAN. May experience higher latency and longer propagation delays due to longer distances and multiple network hops. May have lower fault tolerance and security compared to LANs. TRANSMISSION MODES IN COMPUTER NETWORKS (SIMPLEX, HALF-DUPLEX AND FULL-DUPLEX) Transmission modes also known as communication modes, are methods of transferring data between devices on buses and networks designed to facilitate communication. They are classified into three types: Simplex Mode, Half-Duplex Mode, and Full-Duplex Mode. In this article, we will discuss Transmission Modes. What is Transmission Modes? Transmission mode means transferring data between two devices. It is also known as a communication mode. Buses and networks are designed to allow communication to occur between individual devices that are interconnected. There are three types of transmission modes: Simplex Mode In Simplex mode, the communication is unidirectional, as on a one-way street. Only one of the two devices on a link can transmit, the other can only receive. The simplex mode can use the entire capacity of the channel to send data in one direction. Example: Keyboard and traditional monitors. The keyboard can only introduce input, the monitor can only give the output. Advantages of Simplex Mode Simplex mode is the easiest and most reliable mode of communication. It is the most cost-effective mode, as it only requires one communication channel. There is no need for coordination between the transmitting and receiving devices, which simplifies the communication process. Simplex mode is particularly useful in situations where feedback or response is not required, such as broadcasting or surveillance. Disadvantages of Simplex Mode Only one-way communication is possible. There is no way to verify if the transmitted data has been received correctly. Simplex mode is not suitable for applications that require bidirectional communication. Half-Duplex Mode In half-duplex mode, each station can both transmit and receive, but not at the same time. When one device is sending, the other can only receive, and vice versa. The half-duplex mode is used in cases where there is no need for communication in both directions at the same time. The entire capacity of the channel can be utilized for each direction. Example: Walkie-talkie in which message is sent one at a time and messages are sent in both directions. Channel capacity=Bandwidth * Propagation Delay Advantages of Half Duplex Mode Half-duplex mode allows for bidirectional communication, which is useful in situations where devices need to send and receive data. It is a more efficient mode of communication than simplex mode, as the channel can be used for both transmission and reception. Half-duplex mode is less expensive than full-duplex mode, as it only requires one communication channel. Disadvantages of Half Duplex Mode Half-duplex mode is less reliable than Full-Duplex mode, as both devices cannot transmit at the same time. There is a delay between transmission and reception, which can cause problems in some applications. There is a need for coordination between the transmitting and receiving devices, which can complicate the communication process. Full-Duplex Mode In full-duplex mode, both stations can transmit and receive simultaneously. In full_duplex mode, signals going in one direction share the capacity of the link with signals going in another direction, this sharing can occur in two ways: Either the link must contain two physically separate transmission paths, one for sending and the other for receiving. Or the capacity is divided between signals traveling in both directions. Full-duplex mode is used when communication in both directions is required all the time. The capacity of the channel, however, must be divided between the two directions. Example: Telephone Network in which there is communication between two persons by a telephone line, through which both can talk and listen at the same time. Channel Capacity=2* Bandwidth*propagation Delay Advantages of Full-Duplex Mode Full-duplex mode allows for simultaneous bidirectional communication, which is ideal for real-time applications such as video conferencing or online gaming. It is the most efficient mode of communication, as both devices can transmit and receive data simultaneously. Full-duplex mode provides a high level of reliability and accuracy, as there is no need for error correction mechanisms. Disadvantages of Full-Duplex Mode Full-duplex mode is the most expensive mode, as it requires two communication channels. It is more complex than simplex and half-duplex modes, as it requires two physically separate transmission paths or a division of channel capacity. Full-duplex mode may not be suitable for all applications, as it requires a high level of bandwidth and may not be necessary for some types of communication. DIFFERENCE BETWEEN SIMPLEX, HALF DUPLEX, AND FULL DUPLEX TRANSMISSION MODES Parameters Simplex Half Duplex Full Duplex Half Duplex mode is a two- Full Duplex mode is a two- The direction Simplex mode is a uni- way directional way directional of directional communication but one at a communication communication communication. time. simultaneously. In simplex mode, In Half Duplex mode, In Full Duplex mode, Sender Sender and Sender can send the Sender can send the data can send the data and also can Receiver data but that sender and also can receive the receive the data can‟t receive the data. data but one at a time. simultaneously. Usage of one channel Usage of one channel for Usage of two channels for the Channel usage for the transmission of the transmission of data. transmission of data. data. The simplex mode The Half Duplex mode Full Duplex provides better provides less Performance provides less performance performance than simplex and performance than half than full duplex. half duplex mode. duplex and full duplex. The Half-Duplex involves Simplex utilizes the The Full-Duplex doubles the Bandwidth lesser utilization of single maximum of a single utilization of transmission Utilization bandwidth at the time of bandwidth. bandwidth. transmission. It is suitable for those It is suitable for those It is suitable for those transmissions when transmissions when there is transmissions when there is Suitable for there is requirement of requirement of sending data requirement of sending and full bandwidth for in both directions, but not at receiving data simultaneously delivering data. the same time. in both directions. Example of simplex Example of half duplex Example of full duplex mode Examples mode are: Keyboard mode is: Walkie-Talkies. is: Telephone. and monitor. TYPES OF TRANSMISSION MEDIA A transmission medium is a physical path between the transmitter and the receiver i.e. it is the channel through which data is sent from one place to another. Transmission media refer to the physical pathways through which data is transmitted from one device to another within a network. These pathways can be wired or wireless. The choice of medium depends on factors like distance, speed, and interference. Types of Transmission Media 1. Guided Media Guided Media is also referred to as Wired or Bounded transmission media. Signals being transmitted are directed and confined in a narrow pathway by using physical links. Features: High Speed Secure Used for comparatively shorter distances There are 3 major types of Guided Media: Twisted Pair Cable It consists of 2 separately insulated conductor wires wound about each other. Generally, several such pairs are bundled together in a protective sheath. They are the most widely used Transmission Media. Twisted Pair is of two types: Unshielded Twisted Pair (UTP): UTP consists of two insulated copper wires twisted around one another. This type of cable has the ability to block interference and does not depend on a physical shield for this purpose. It is used for telephonic applications. Unshielded Twisted Pair Advantages of Unshielded Twisted Pair Least expensive Easy to install High-speed capacity Disadvantages of Unshielded Twisted Pair Susceptible to external interference Lower capacity and performance in comparison to STP Short distance transmission due to attenuation Shielded Twisted Pair Shielded Twisted Pair (STP): This type of cable consists of a special jacket (a copper braid covering or a foil shield) to block external interference. It is used in fast-data-rate Ethernet and in voice and data channels of telephone lines. Advantages of Shielded Twisted Pair Better performance at a higher data rate in comparison to UTP Eliminates crosstalk Comparatively faster Disadvantages of Shielded Twisted Pair Comparatively difficult to install and manufacture More expensive Bulky Coaxial Cable It has an outer plastic covering containing an insulation layer made of PVC or Teflon and 2 parallel conductors each having a separate insulated protection cover. The coaxial cable transmits information in two modes: Baseband mode(dedicated cable bandwidth) and Broadband mode(cable bandwidth is split into separate ranges). Cable TVs and analog television networks widely use Coaxial cables. Advantages of Coaxial Cable Coaxial cables support high bandwidth. It is easy to install coaxial cables. Coaxial cables have better cut-through resistance so they are more reliable and durable. Less affected by noise or cross-talk or electromagnetic inference. Coaxial cables support multiple channels Disadvantages of Coaxial Cable Coaxial cables are expensive. The coaxial cable must be grounded in order to prevent any crosstalk. As a Coaxial cable has multiple layers it is very bulky. There is a chance of breaking the coaxial cable and attaching a “t-joint” by hackers, this compromises the security of the data. Optical Fiber Cable Optical Fibre Cable uses the concept of refraction of light through a core made up of glass or plastic. The core is surrounded by a less dense glass or plastic covering called the cladding. It is used for the transmission of large volumes of data. The cable can be unidirectional or bidirectional. The WDM (Wavelength Division Multiplexer) supports two modes, namely unidirectional and bidirectional mode. Advantages of Optical Fibre Cable Increased capacity and bandwidth Lightweight Less signal attenuation Immunity to electromagnetic interference Resistance to corrosive materials Disadvantages of Optical Fibre Cable Difficult to install and maintain High cost Fragile Applications of Optical Fibre Cable Medical Purpose: Used in several types of medical instruments. Defence Purpose: Used in transmission of data in aerospace. For Communication: This is largely used in formation of internet cables. Industrial Purpose: Used for lighting purposes and safety measures in designing the interior and exterior of automobiles. Stripline Stripline is a transverse electromagnetic (TEM) transmission line medium invented by Robert M. Barrett of the Air Force Cambridge Research Centre in the 1950s. Stripline is the earliest form of the planar transmission line. It uses a conducting material to transmit high-frequency waves it is also called a waveguide. This conducting material is sandwiched between two layers of the ground plane which are usually shorted to provide EMI immunity. Microstripline In this, the conducting material is separated from the ground plane by a layer of dielectric. 2. Unguided Media It is also referred to as Wireless or Unbounded transmission media. No physical medium is required for the transmission of electromagnetic signals. Features of Unguided Media The signal is broadcasted through air Less Secure Used for larger distances There are 3 types of Signals transmitted through unguided media: Radio Waves Radio waves are easy to generate and can penetrate through buildings. The sending and receiving antennas need not be aligned. Frequency Range:3KHz – 1GHz. AM and FM radios and cordless phones use Radio waves for transmission. Further Categorized as Terrestrial and Satellite. Microwaves It is a line of sight transmission i.e. the sending and receiving antennas need to be properly aligned with each other. The distance covered by the signal is directly proportional to the height of the antenna. Frequency Range:1GHz – 300GHz. Micro waves are majorly used for mobile phone communication and television distribution. Microwave Transmission Infrared Infrared waves are used for very short distance communication. They cannot penetrate through obstacles. This prevents interference between systems. Frequency Range:300GHz – 400THz. It is used in TV remotes, wireless mouse, keyboard, printer, etc. DIFFERENCE BETWEEN RADIO WAVES VS MICRO WAVES VS INFRARED WAVES Basis Radiowave Microwave Infrared wave These are omni- These are unidirectional in These are unidirectional in Direction directional in nature. nature. nature. At low frequency, they can penetrate At low frequency, they through solid objects can penetrate through They cannot penetrate Penetration and walls but high solid objects and walls. at through any solid object and frequency they high frequency, they walls. bounce off the cannot penetrate. obstacle. Frequency Frequency range: 3 Frequency range: 1 GHz Frequency range: 300 GHz range KHz to 1GHz. to 300 GHz. to 400 GHz. These offers poor These offers medium Security These offers high security. security. security. Attenuation Attenuation is high. Attenuation is variable. Attenuation is low. Some frequencies in Some frequencies in the There is no need of Government the radio-waves microwaves require government license to use License require government government license to use these waves. license to use these. these. Setup and usage Cost Setup and usage Cost is Usage Cost Usage Cost is very less. is moderate. high. These are used in long These are used in long These are not used in long Communication distance distance communication. distance communication. communication. Factors Considered for Designing the Transmission Media Bandwidth: Assuming all other conditions remain constant, the greater a medium‟s bandwidth, the faster a signal‟s data transmission rate. Transmission Impairment : Transmission Impairment occurs when the received signal differs from the transmitted signal. Signal quality will be impacted as a result of transmission impairment. Interference: Interference is defined as the process of disturbing a signal as it travels over a communication medium with the addition of an undesired signal. Causes of Transmission Impairment Transmission Impairment Attenuation – It means loss of energy. The strength of signal decreases with increasing distance which causes loss of energy in overcoming resistance of medium. This is also known as attenuated signal. Amplifiers are used to amplify the attenuated signal which gives the original signal back and compensate for this loss. Distortion – It means changes in the form or shape of the signal. This is generally seen in composite signals made up with different frequencies. Each frequency component has its own propagation speed travelling through a medium. And thats why it delay in arriving at the final destination Every component arrive at different time which leads to distortion. Therefore, they have different phases at receiver end from what they had at senders end. Noise – The random or unwanted signal that mixes up with the original signal is called noise. There are several types of noise such as induced noise, crosstalk noise, thermal noise and impulse noise which may corrupt the signal.