πŸ“˜ CHAPTER 1 β€” COMPUTER SYSTEMS & DATA COMMUNICATION Final Exam Notes 1. Computer A computer is a programmable electronic device that performs arithmetic and logical operations automatically according to instructions provided by the user. 2. History / Early Computing Devices Abacus One of the earliest calculating devices, using beads for counting and basic arithmetic. Napier's Bones Invented by John Napier. Numbered rods used mainly for multiplication and division. Pascaline Invented by Blaise Pascal in 1642. A mechanical calculator using gears for automatic calculations. Step Reckoner / Leibniz Wheel Developed by Gottfried Wilhelm Leibniz in 1673. Improved upon the Pascaline using wheels and gears. Difference Engine Designed by Charles Babbage for performing mathematical calculations. Analytical Engine Also designed by Charles Babbage. Included concepts similar to modern computers such as: Input using punched cards Memory Processing Output Charles Babbage = Father of Computer Hollerith Tabulating Machine Developed by Herman Hollerith. Used punched cards to process statistical data. Differential Analyzer Developed by Vannevar Bush for solving mathematical problems. Harvard Mark I Developed by Howard Aiken in 1944. A large electromechanical computer using switches, punched cards, and an electric typewriter for output. 3. Generations of Computers Generation Period Main Technology 1st 1942–1956 Vacuum tubes 2nd 1956–1963 Transistors 3rd 1963–1971 Integrated Circuits 4th 1971–Present Microprocessors 5th Late 20th century–Present Artificial Intelligence 1st Generation Vacuum tubes Very large and expensive Produced much heat Consumed high electricity Unreliable Machine language Punch cards Memory: Huge + Hot + Expensive + Unreliable 2nd Generation Transistors replaced vacuum tubes Smaller and faster More reliable Less expensive Less power consumption Assembly language and high-level languages 3rd Generation Used Integrated Circuits (ICs) Smaller and faster More reliable Lower cost Less power consumption Keyboard and monitor became common 4th Generation Uses microprocessors Very small and fast Reliable and cost-effective Still widely used 5th Generation Based heavily on Artificial Intelligence Natural language processing Voice recognition Robotics Expert systems Goal of performing human-like tasks Memory: 4th = Microprocessor 5th = AI 4. Computer System A system is a collection of interconnected components working together to achieve a specific purpose. Natural System A system that exists naturally. Examples: Ecosystem, solar system, biological system. Artificial System A system created by humans to achieve a specific purpose. Examples: Transportation system, communication system, computer system. Main Components of a Computer System Input devices System unit Output devices 5. Input Devices Input device: Hardware used to enter data and instructions into a computer. Keyboard Used to enter text, numbers, symbols, and commands. Types of keys: Alphabetic Numeric Function Control Navigation Mouse Used to select, open, and interact with objects on screen. Left button β†’ select/open Right button β†’ options/context menu Wheel β†’ scrolling Microphone Converts sound into electrical signals and then digital data for processing. Scanner Captures images/documents and converts them into digital form. Barcode Reader Reads information stored in barcodes. Digital Camera Captures and stores images in digital form. Touch Screen Pressure-sensitive display that allows users to interact directly by touching the screen. 6. System Unit & Motherboard System Unit Main part of a computer containing the motherboard, power supply, storage devices, and other electronic components. Motherboard The main circuit board connecting major components of a computer. It contains: CPU Main memory Expansion slots ICs Connectors Buses Bus An electronic pathway used to transfer information between computer components. 7. CPU CPU (Central Processing Unit) is the main processing unit responsible for executing program instructions. It consists mainly of: Control Unit (CU) Controls and coordinates the activities of the computer. Arithmetic Logic Unit (ALU) Performs: Arithmetic operations Logical operations Registers Small, high-speed storage locations inside the CPU. 8. CPU Registers MAR β€” Memory Address Register Stores the address of the memory location being accessed. MDR β€” Memory Data Register Stores data/instructions being transferred to or from memory. AC β€” Accumulator Stores intermediate arithmetic and logical results. PC β€” Program Counter Stores the address of the next instruction to be executed. CIR β€” Current Instruction Register Stores the current instruction being processed. 9. Von Neumann Architecture Developed by John von Neumann in 1945. Its important feature is the stored-program concept, where instructions and data are stored in the same memory. Main components: Control Unit ALU Memory Registers Input/Output 10. Storage Devices Storage devices store programs and data. Hard Disk Drive (HDD) Magnetic storage device with large storage capacity. CD Optical storage medium using a laser. Diameter: 120 mm Capacity: approximately 700 MB DVD Optical storage medium with greater capacity than a CD. DVD = Digital Versatile Disc Memory Card Small portable storage device. USB Flash Drive Portable storage device connected through a USB port. 11. Output Devices Output devices present processed information to the user. Hard Copy Physical/printed form of information. Soft Copy Electronic form displayed on a screen. Monitor Displays soft-copy output. CRT Bulky and heavy High power consumption Produces more heat Mostly obsolete LED Thin and lightweight Less power consumption Less heat Better display quality Printer Impact Printer Physically strikes the paper. Example: Dot matrix printer. Non-Impact Printer Does not physically strike the paper. Examples: Laser printer, Inkjet printer. Plotter Used to produce large, precise drawings such as: Blueprints Engineering diagrams Building designs Speaker Converts electrical signals into sound. 12. Ports, Expansion Slots & Cards Port Interface used to connect external devices to a computer. Expansion Slot Socket on the motherboard used to install additional cards. Expansion Card Circuit board that adds extra functionality to a computer. 13. Memory Computer memory consists of physical devices used to store programs and data temporarily or permanently. Primary/Main Memory Includes: RAM ROM Cache Registers Secondary Memory Used for long-term storage. Examples: HDD SSD USB drive 14. Memory Terminology Bit Smallest unit of data; either 0 or 1. Byte 8 bits. Memory Word Amount of data processed by a computer as a single unit. Word Size Number of bits in a computer word, such as 16, 32, or 64 bits. Memory Units KB β†’ MB β†’ GB β†’ TB β†’ PB β†’ EB β†’ ZB β†’ YB 15. Types of Memory by Technology Chip Memory Uses semiconductor integrated circuits. Examples: RAM, ROM, cache, registers, flash memory. Magnetic Memory Stores data using magnetized areas. Examples: HDD, magnetic tape. Optical Memory Uses laser/light to read or write data. Examples: CD, DVD, Blu-ray. Memory: Chip = Electronics Magnetic = Magnetism Optical = Laser 16. RAM, ROM & Cache RAM Random Access Memory Read/write High-speed Temporary working memory Volatile ROM Read Only Memory Non-volatile Retains information without power Stores firmware/boot-related instructions Types: PROM EPROM EEPROM Cache Small, extremely fast memory associated with the CPU. Stores frequently/recently used data and instructions to improve performance. Levels: L1 L2 L3 Volatile Memory Loses data when power is turned off. Example: RAM Non-Volatile Memory Retains data without power. Examples: ROM, HDD, SSD 17. Instruction Cycle The CPU follows three basic stages: Fetch β†’ Decode β†’ Execute Fetch: Retrieve instruction from memory. Decode: Determine what the instruction means. Execute: Perform the required operation. 18. Pipelining Pipelining allows multiple instructions to be processed at different stages simultaneously, improving CPU efficiency. Interrupt A signal that temporarily causes the CPU to stop its current activity and handle an important event/request. Parallelism Processing multiple tasks or parts of tasks simultaneously. 19. Buses Address Bus Carries memory addresses. Data Bus Carries data. Control Bus Carries control signals. Memory: Address = WHERE Data = WHAT Control = HOW 20. I/O Controller & Bus Architecture I/O Controller Controls communication and data flow between the CPU and input/output devices. Bus Architecture The communication pathways used to transfer data between CPU, memory, storage, and other components. 21. Software Software is a collection of programs, data, and instructions that tells a computer how to perform specific tasks. Two major types: System Software Application Software 22. System Software System software manages hardware and provides a platform for other programs. Operating System Manages hardware resources and provides services to programs. Examples: Windows, macOS, Linux, Android. OS Functions User interface Process scheduling Memory management File management I/O management Device management Security and authentication 23. Device Drivers Software that allows the operating system to communicate with and control hardware. Examples: Printer driver, graphics driver, DVD drive driver. 24. System Utilities Tools used to maintain and manage a computer. Examples: Disk cleanup Backup Antivirus Disk defragmentation System monitoring 25. Compiler, Assembler, Linker & Loader Compiler Translates high-level source code into machine/executable code. Assembler Translates assembly language into machine code. Linker Combines object files and libraries into a complete executable program. Loader Loads the executable program into RAM for execution. Flow: Source Code β†’ Compiler/Assembler β†’ Object Code β†’ Linker β†’ Executable β†’ Loader β†’ RAM 26. Firmware Software stored in or closely associated with hardware that provides low-level control of the device. Examples: BIOS/UEFI firmware, washing-machine firmware. 27. Application Software Software designed to perform specific tasks for users. Productivity Software Used to create and organize information. Examples: Microsoft Office, Google Workspace, LibreOffice. Business Software Designed for business operations and management. Examples: QuickBooks, Salesforce, Trello. Entertainment Software Used for leisure and enjoyment. Examples: Minecraft, Spotify, Netflix, YouTube. Educational Software Supports learning and skill development. Examples: Duolingo, Kahoot, LMS. 28. Programming Languages A programming language is a structured method of communicating instructions to a computer using predefined commands, syntax, and rules. Two categories: Low-level languages High-level languages 29. Low-Level Languages Machine-oriented languages closely related to computer hardware. Machine Language Directly understood by computer Written in binary Difficult for humans to read/write Assembly Language Uses symbolic codes called mnemonics Easier than machine language Must be converted into machine code using an assembler Allows hardware-specific programming Assembly β†’ Assembler β†’ Machine Code 30. High-Level Languages Designed to be easier for humans to read and write. Examples: C, Java, Pascal, Visual Basic. Procedural / Structured Programming Programs are divided into smaller modules, each performing a specific task. Three basic structures: Sequence β†’ instructions execute in order Selection β†’ choose based on a condition (if, else, switch) Repetition β†’ repeat instructions using loops Object-Oriented Programming Programming approach based on objects containing data and related behavior. Examples: Student, Car, BankAccount. 31. Data Communication Data communication is the exchange of data between two or more devices through a wired or wireless medium. Components Sender β€” sends the message. Message β€” data being transmitted. Medium β€” pathway used for transmission. Receiver β€” receives the message. Protocol β€” rules governing communication. 32. Communication Modes Simplex One-way communication. Example: Server β†’ Client Half-Duplex Two-way communication, but not simultaneously. Example: Walkie-talkie Full-Duplex Two-way communication simultaneously. Example: Telephone call 33. Asynchronous & Synchronous Transmission Asynchronous Data transmitted one character/byte at a time. Uses start and stop bits. Generally slower due to additional control bits. Synchronous Data transmitted in synchronized blocks/streams. Does not require start/stop bits for every character. Generally faster. Requires synchronization between sender and receiver. 34. Communication Devices Hub Connects devices in a LAN and sends incoming data to all connected devices/ports. Hub = Everyone Switch Connects devices in a LAN and forwards data to the intended device/port. Switch = Specific device Data Packet A small unit of data transmitted across a network. Data can be divided into packets and reassembled at the destination. Router Connects different networks and selects an appropriate path for forwarding data packets. Router = Connects networks + chooses path Gateway Connects networks using different communication protocols. Gateway = Different protocols 35. Network Architecture Server Computer that provides/shares resources and services. Client Computer that accesses/uses resources from a server. Client-Server Network One or more dedicated servers provide services to client computers. Advantages: Centralized control Centralized security Easier administration Peer-to-Peer Network Each computer can act as a client and server. Each computer is a peer. Suitable for small networks. Large P2P networks are difficult to manage. 36. Types of Networks LAN β€” Local Area Network A network covering a small geographical area, such as a building or group of nearby buildings. Characteristics: Small physical area High-speed communication Wired or wireless Usually fewer computers Commonly used for sharing printers, files, applications, etc. Memory: LAN = Small Area WAN β€” Wide Area Network A network covering a large geographical area, such as cities, countries, or continents. Characteristics: Large physical area Can connect multiple LANs May use leased lines, satellites, or public networks Generally slower than LAN More complex, so communication errors can occur Memory: WAN = Wide Area MAN β€” Metropolitan Area Network A network larger than a LAN but smaller than a WAN. Can cover a large campus or city. Connects multiple LANs. Usually provides high-speed communication. Often uses fiber-optic connections. Typically covers several to tens of kilometers. Memory: MAN = City-sized VPN β€” Virtual Private Network A network that provides secure remote access to an organization's network using public infrastructure such as the Internet. Characteristics: Uses public networks Secure remote access Allows access to organizational resources Can support file sharing/video conferencing Cheaper than dedicated leased lines for remote access Memory: VPN = Private connection over public Internet 37. Wireless Networks Wireless networks transmit data without physical wired connections. Wi-Fi Wireless networking technology used to connect devices to LANs and the Internet. Common in: Homes Offices Airports Public places Bluetooth Short-range wireless technology used between nearby devices. Uses: Audio streaming File sharing Connecting peripherals Cellular Network Provides wireless communication over large areas divided into cells, each served by a cell tower/base station. Used for: Calls Messaging Mobile Internet Satellite Communication Uses satellites orbiting Earth to provide communication over very large areas. Uses: Satellite Internet Satellite radio GPS/navigation 38. Advantages & Disadvantages of Wireless Networks Advantages Easy installation Cost-effective Easy expansion No expensive cabling Remote access within coverage area Disadvantages Interference from other devices/networks Security risks Limited range May require signal boosters Can be slower in crowded areas Wireless devices consume battery power 39. Network Topology ⭐ Network topology is the arrangement of network nodes/devices and the connections between them. 1. Bus Topology All devices are connected to a single main cable (backbone). Advantages: Simple Requires less cable Relatively inexpensive Disadvantages: Failure of main cable can affect the whole network Performance decreases as devices increase Troubleshooting can be difficult Memory: 🚌 One main road. 2. Star Topology All devices connect to a central device, usually a switch or hub. Advantages: Easy to install/manage Failure of one device usually doesn't affect others Easy to identify problems Disadvantage: Failure of central device can affect the whole network Requires more cable Memory: ⭐ Everything connects to the center. 3. Ring Topology Each device connects to two neighboring devices, forming a ring. Advantages: Data travels in an organized manner Equal access for devices Disadvantages: Failure of one connection/device can disrupt the network Adding/removing devices can be difficult Memory: πŸ’ Circle. 4. Mesh Topology Devices are connected to multiple or all other devices. Advantages: Highly reliable Multiple paths for data Failure of one connection does not necessarily stop communication Disadvantages: Expensive Requires lots of cables/connections Complex to install Memory: πŸ•ΈοΈ Web. 5. Tree Topology Devices are arranged in a hierarchical structure, combining characteristics of star and bus topologies. Advantages: Easy to expand Suitable for large networks Easier management of groups Disadvantages: More complex Failure of higher-level connections can affect sections of the network Memory: 🌳 Branches. 6. Hybrid Topology A combination of two or more different topologies. Example: Star + Bus. Advantage: Flexible and scalable. Disadvantage: More complex and expensive. 40. Circuit Switching vs Packet Switching ⭐ Circuit Switching A dedicated communication path is established between sender and receiver before communication begins. The path remains reserved for the duration of the communication. Example: Traditional telephone networks. Advantages Dedicated path Predictable connection Continuous transmission Disadvantages Wastes resources when no data is being transmitted Connection setup required Less efficient for bursty data Memory: Circuit = One dedicated road for the whole conversation. Packet Switching Data is divided into small packets before transmission. Each packet may travel through different routes and is reassembled at the destination. Example: Internet. Advantages Efficient use of network resources No dedicated path required Multiple users can share network links Suitable for Internet/data communication Disadvantages Packets may arrive at different times Packets may take different routes Network congestion can cause delays Memory: Packet = Data broken into pieces and sent through the network. Main Difference Circuit Switching Packet Switching Dedicated path No dedicated path Path reserved Resources shared Continuous connection Data divided into packets Traditional telephone networks Internet Less efficient for bursty data Efficient for data networks 41. Data Communication Standards Data communication standards are rules/protocols that define how data is transmitted, received, and processed between computers and networks. The International Organization for Standardization (ISO) developed the OSI reference model. 42. OSI Model ⭐⭐⭐ OSI = Open Systems Interconnection It has 7 layers. From top to bottom: Application β†’ Presentation β†’ Session β†’ Transport β†’ Network β†’ Data Link β†’ Physical 1. Application Layer Provides network services directly to applications/users. Examples: Web, email, file-transfer services. 2. Presentation Layer Handles the format and representation of data. Functions include: Translation Encryption/decryption Compression Memory: "How should the data look?" 3. Session Layer Establishes, manages, and terminates communication sessions between devices. Memory: "Start/manage/end the conversation." 4. Transport Layer Provides end-to-end data delivery. Functions include: Segmentation Flow control Error control Reliable delivery Memory: "Make sure data gets there properly." 5. Network Layer Determines paths and handles logical addressing/routing of packets. Memory: "Which route?" 6. Data Link Layer Provides reliable transfer between directly connected devices and handles frames/MAC addressing. Memory: "Device-to-device." 7. Physical Layer Transmits raw bits (0s and 1s) through the physical medium. Deals with: Cables Signals Connectors Physical transmission Memory: "Actual wires/signals." 🧠 OSI Layer Memory Trick A P S T N D P All People Seem To Need Data Protection Top β†’ Bottom: Application Presentation Session Transport Network Data Link Physical 43. Data Communication Protocols TCP/IP Transmission Control Protocol / Internet Protocol The fundamental protocol suite used for Internet communication. TCP provides reliable, connection-oriented delivery. IP handles addressing and routing. HTTP Hypertext Transfer Protocol Used for transferring web pages and related resources over the Web. FTP File Transfer Protocol Used for transferring files between computers over a network. SMTP Simple Mail Transfer Protocol Used for sending email messages. 🧠 CHAPTER 1 β€” LAST-MINUTE MEMORY MAP If you're revising this the night before, remember the chapter like this: Computer β†’ History β†’ Generations β†’ System β†’ Input β†’ CPU/Motherboard β†’ Storage β†’ Output β†’ Architecture β†’ Memory β†’ Buses Software β†’ System Software β†’ OS β†’ Drivers β†’ Utilities β†’ Compiler/Assembler β†’ Linker/Loader β†’ Firmware β†’ Application Software Programming β†’ Low-level β†’ Machine β†’ Assembly β†’ High-level β†’ Procedural/Structured β†’ OOP Data Communication β†’ Components β†’ Simplex/Half/Full Duplex β†’ Synchronous/Asynchronous β†’ Hub/Switch/Router/Gateway β†’ Client-Server/P2P β†’ LAN/WAN/MAN/VPN β†’ Wireless β†’ Topologies β†’ Circuit/Packet Switching β†’ OSI β†’ Protocols πŸ”₯ THE ABSOLUTE MUST-KNOW LIST If you're short on revision time, these are the things I'd make sure you can explain without looking: Computer generations + technologies CPU, CU, ALU, registers MAR/MDR/AC/PC/CIR Von Neumann architecture RAM vs ROM vs Cache Primary vs secondary memory Volatile vs non-volatile System vs application software Compiler vs assembler vs linker vs loader Low-level vs high-level languages Data communication components Simplex vs half-duplex vs full-duplex Hub vs switch vs router vs gateway Client-server vs P2P LAN vs MAN vs WAN vs VPN Wireless networks Network topologies Circuit vs packet switching 7 OSI layers TCP/IP, HTTP, FTP, SMTP