Introduction to Computing and Information Systems: Lecture 1

Basic Concepts

1. Computing

Definition:
Computing refers to any activity that requires the use of computers to complete a task. This encompasses data processing, problem-solving, and programming.

Example:
When you use a word processor to write an essay or run a software application, you're engaging in computing activities.

Illustration:
Imagine a computer solving complex math problems or running a simulation of weather patterns — this is computing in action.

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2. Information System (IS)

Definition:
An Information System is a structured arrangement of components (hardware, software, data, procedures, and people) designed to collect, process, store, and distribute information to support decision-making and coordination within an organization.

Example:
A payroll system that calculates employee salaries and generates pay slips based on working hours and tax data is an example of an Information System.

Illustration:
Picture an online shopping platform that processes your order, updates inventory, and sends confirmation — this is an Information System at work.

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3. Software

Definition:
Software refers to the set of instructions or programs that tell a computer how to perform specific tasks.

Example:
Microsoft Word, a web browser, and an operating system like Windows are all examples of software.

Illustration:
Think of software as the brain behind all the functions you use on a computer — without it, the hardware wouldn’t know what to do.

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4. Hardware

Definition:
Hardware includes the physical components of a computer system, such as the monitor, keyboard, mouse, and internal components like the processor and motherboard.

Example:
The laptop you use to browse the web or the phone in your pocket are all examples of hardware.

Illustration:
Imagine hardware as the body of a computer, while software is the mind that controls it.

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5. Differences Between Hardware and Software

• Hardware: Physical components that you can touch, such as the computer itself, the keyboard, and internal parts like the CPU.

• Software: Non-physical components, including applications and programs that instruct the hardware on how to operate.

Example:
The screen you're reading this on is hardware, while the web browser displaying it is software.

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6. Data vs. Information

• Data: Raw, unprocessed facts. For example, a list of sales figures.

• Information: Data that has been processed, organized, and interpreted to provide meaning. For example, a sales report showing trends and insights based on the figures.

Illustration:
Imagine a spreadsheet full of numbers (data). Once analyzed to show sales trends (information), it helps businesses make decisions.

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7. Operating System (OS)

Definition:
The operating system is system software that manages hardware resources and provides services for running applications.

Example:
Windows, macOS, and Linux are all operating systems.

Illustration:
The operating system is like the conductor of an orchestra, coordinating all the different instruments (hardware) to play together (run applications smoothly).

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8. Kernel

Definition:
The Kernel is the core part of an operating system, managing system resources and communication between hardware and software.

Example:
Linux Kernel is a widely used kernel that powers various distributions of Linux.

Illustration:
The Kernel acts like the engine in a car, making sure all parts are running in harmony and without conflict.

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9. Differences Between Operating System and Kernel

• Operating System: The full suite of system software that manages hardware and provides an environment for applications.

• Kernel: The core of the operating system, handling critical tasks like resource management and communication between hardware and software.

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Booting Process

The steps involved when a computer is powered on:

1. Power Button Pressed:
   The power supply sends electricity to the motherboard, initiating the boot process.

2. Power-On Self-Test (POST):
   The system runs diagnostic tests on the hardware components like RAM, input/output devices, and the hard drive. If errors occur, the system may produce error beeps.

3. Loading the OS:
   The BIOS (Basic Input/Output System) or UEFI (Unified Extensible Firmware Interface) locates and loads the operating system using configuration data stored in the CMOS.

4. System Configuration Loaded:
   The OS loads system configuration data, preparing the system for use.

5. System Utility Load:
   Utilities and services required by the OS are initialized.

6. User Authentication and Authorization:
   The user is prompted to enter credentials, granting access to the system based on the correct authorization.

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10. Boot Loader

Definition:
The boot loader is software that loads the operating system when the computer starts. It allows the user to select which OS to boot (in systems with multiple OS).

Example:
In systems with Windows and Linux installed, the boot loader allows the user to choose which OS to load.

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11. Random Access Memory (RAM)

Definition:
RAM is volatile memory used by the system to store working data and machine code temporarily.

Example:
When you open a web browser, its data is loaded into RAM for quick access.

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12. CMOS

Definition:
CMOS is a battery-powered chip on the motherboard that stores system configuration settings such as date and time.

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13. Central Processing Unit (CPU)

Definition:
The CPU, or processor, is the brain of the computer that executes instructions from programs and controls tasks like arithmetic, logic, and input/output operations.

Illustration:
Think of the CPU as the decision-maker that ensures your computer processes instructions quickly and efficiently.

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14. Network

Definition:
A network is a collection of computers connected to share resources and data.

Example:
The internet is the largest example of a computer network.

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15. OSI Model (Open Systems Interconnection Model)

The OSI model is a conceptual framework that describes how data is transmitted over a network, broken down into seven distinct layers. Each layer has specific responsibilities, and they work together to enable communication between devices on a network. The layers operate sequentially, meaning that each layer serves the one above it and is served by the one below it.

The Seven Layers of the OSI Model:

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1. Physical Layer (Layer 1)

Definition:
The Physical Layer is responsible for the physical connection between devices. It defines the hardware elements such as cables, switches, and network interface cards (NICs), and manages how data is transmitted over these physical media.

Responsibilities:

• Data transmission in the form of electrical signals, light, or radio waves.

• Definition of hardware specifications like voltage levels, timing, data rates, and the physical topology (e.g., bus, ring, or star configurations).

• Conversion of bits into signals and vice versa.

Example:
Ethernet cables, fiber optics, and Wi-Fi antennas work at the physical layer.

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2. Data Link Layer (Layer 2)

Definition:
The Data Link Layer is responsible for node-to-node data transfer and error detection and correction. It ensures data is transferred correctly over the physical layer by dividing data into frames and adding error detection bits.

Responsibilities:

• Organizing data into frames for transmission.

• Error detection and correction using methods like Cyclic Redundancy Check (CRC).

• Managing access to the physical medium (Media Access Control or MAC).

• Flow control to avoid overwhelming receiving devices with too much data at once.

Sub-Layers:

• Logical Link Control (LLC): Handles flow control and error detection.

• Media Access Control (MAC): Manages access to the physical transmission medium.

Example:
Ethernet operates at the Data Link Layer by organizing bits into frames and adding error detection.

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3. Network Layer (Layer 3)

Definition:
The Network Layer is responsible for determining the best path for data to travel from source to destination across multiple networks. It handles logical addressing (e.g., IP addresses) and routing through routers.

Responsibilities:

• Logical addressing using IP addresses.

• Routing data packets between networks using routing protocols (e.g., OSPF, BGP).

• Fragmentation and reassembly of data packets when they need to pass through networks with different maximum transmission units (MTUs).

Example:
The Internet Protocol (IP) is used at this layer, assigning unique IP addresses to each device and determining the best route for data to take.

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4. Transport Layer (Layer 4)

Definition:
The Transport Layer is responsible for reliable data transfer between systems. It controls data flow, error recovery, and ensures that data is delivered in sequence and without errors.

Responsibilities:

• Segmentation of large data blocks into smaller packets.

• Reliable data transmission using protocols like Transmission Control Protocol (TCP).

• Error detection and recovery.

• Flow control to prevent sending more data than the receiving device can handle.

• Port addressing to ensure the data reaches the correct application on the destination device.

Protocols:

• TCP (Transmission Control Protocol): Ensures reliable, connection-oriented data transmission.

• UDP (User Datagram Protocol): Provides connectionless, fast data transmission without guaranteed delivery.

Example:
When you load a web page, TCP ensures that all the packets of data are delivered correctly and in order.

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5. Session Layer (Layer 5)

Definition:
The Session Layer is responsible for establishing, maintaining, and terminating communication sessions between devices. It ensures that ongoing communication is organized and synchronized.

Responsibilities:

• Session establishment, maintenance, and termination.

• Managing data exchanges between devices, ensuring they occur in an orderly manner.

• Synchronizing data flow, allowing for recovery if the session is interrupted.

• Dialogue control, determining whether communication will be full-duplex or half-duplex.

Example:
When you log into an online service, the session layer is responsible for establishing and maintaining your login session.

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6. Presentation Layer (Layer 6)

Definition:
The Presentation Layer ensures that data sent by the application layer of one system is readable by the application layer of another system. It is responsible for data translation, encryption, and compression.

Responsibilities:

• Data translation between different formats (e.g., converting data between different character encoding schemes like ASCII and Unicode).

• Data encryption to protect information during transmission (e.g., SSL/TLS encryption).

• Data compression to reduce the size of files transmitted over the network.

Example:
The conversion of a web page from its original format into HTML for display in your browser happens at the presentation layer. Additionally, encryption protocols like SSL/TLS that secure web traffic operate at this layer.

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7. Application Layer (Layer 7)

Definition:
The Application Layer is the closest layer to the end user. It provides the interface for user applications to interact with the network. This layer includes services such as email, file transfer, and web browsing.

Responsibilities:

• Interaction with user applications, such as web browsers or email clients.

• Providing protocols for specific tasks, such as HTTP for web browsing, FTP for file transfer, and SMTP for email.

• Supporting network services that end users interact with directly.

Example:
When you use your web browser (e.g., Chrome or Firefox), the HTTP protocol is used at the application layer to request and load web pages.

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How the OSI Model Works:

When data is transmitted from one device to another, the OSI model breaks it down as follows:

1. Sender:

   • The Application Layer prepares the data for sending.

   • The Presentation Layer translates and encrypts the data.

   • The Session Layer establishes and maintains a communication session.

   • The Transport Layer segments data and adds port numbers for the correct application.

   • The Network Layer assigns logical addresses and routes the data.

   • The Data Link Layer organizes data into frames, adds physical addresses (MAC addresses), and checks for errors.

   • The Physical Layer converts frames into electrical signals (or radio waves, light signals) and transmits them over the physical medium.

2. Receiver:

   • The Physical Layer receives signals and converts them back into bits.

   • The Data Link Layer reassembles the bits into frames, checks for errors, and extracts data.

   • The Network Layer determines the destination device using the IP address and forwards data accordingly.

   • The Transport Layer reassembles the segments and ensures they are in the correct order.

   • The Session Layer maintains synchronization of data exchanges.

   • The Presentation Layer decrypts and translates the data.

   • The Application Layer provides the data to the user’s application.

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Example in Action:

• When you browse a website, your browser (working in the application layer) sends an HTTP request.

• The request is passed through all the layers, each performing its function, until it reaches the network card (physical layer) and is transmitted over the network.

• On the receiving server, the OSI layers reverse the process, delivering the website's content to your browser.