Types of Software and Interrupts (Copy)

1. Difference Between System Software and Application Software

• System Software
  • Definition: Software designed to operate, control, and manage the hardware components and provide a platform for running application software.
  • Purpose: Ensures the smooth functioning of a computer system.
  • Runs in the background, handling essential system tasks.
  • Examples:
    • Operating systems (Windows, macOS, Linux)
    • Utility programs (antivirus, disk defragmenter, backup tools)
    • Device drivers (printer driver, graphics card driver)
  • Characteristics:
    • Essential for system operation
    • Manages resources (CPU, memory, storage, I/O devices)
    • Communicates between hardware and software layers
• Application Software
  • Definition: Software designed to help the user perform specific tasks.
  • Purpose: Allows the user to interact with the system to carry out personal, business, or scientific activities.
  • Examples:
    • Word processors (Microsoft Word)
    • Web browsers (Google Chrome)
    • Spreadsheets (Microsoft Excel)
    • Graphics editors (Adobe Photoshop)
  • Characteristics:
    • Task-specific
    • Installed by the user based on needs
    • Runs on top of system software

Comparison Table:

2. Role and Basic Functions of an Operating System (OS)

• Role of OS:
  • Acts as an interface between the user and the hardware
  • Coordinates and manages hardware and software resources
  • Provides an environment where applications can run
• Basic Functions:
  1. Managing Files
     • Organises files into directories/folders
     • Handles file creation, reading, writing, deletion, and permissions
  2. Handling Interrupts
     • Detects and processes events that require immediate attention
     • Ensures efficient execution by responding to hardware/software signals
  3. Providing a User Interface
     • Command-line interface (CLI)
     • Graphical user interface (GUI)
  4. Managing Peripherals and Drivers
     • Controls input/output devices using device drivers
     • Translates OS commands into hardware-specific instructions
  5. Managing Memory
     • Allocates RAM to running applications
     • Handles virtual memory when RAM is insufficient
  6. Managing Multitasking
     • Schedules processes so multiple programs appear to run simultaneously
  7. Providing a Platform for Applications
     • Ensures applications can run without directly interacting with hardware
  8. Providing System Security
     • Protects data from unauthorised access using authentication and encryption
  9. Managing User Accounts
     • Creates and controls access rights for multiple users

3. Relationship Between Hardware, Firmware, and Operating System

• Hardware: Physical components (CPU, RAM, hard drive, keyboard, etc.)
• Firmware:
  • Software stored in ROM (e.g., BIOS/UEFI)
  • Manages basic hardware settings
  • Loads the operating system during startup (bootloader)
• Operating System:
  • Loaded into RAM from storage by the firmware
  • Provides the environment for running applications
• Applications:
  • Run on top of the operating system using OS services

Startup Sequence:

1. Power on → Firmware runs self-tests (POST)
2. Firmware loads the bootloader
3. Bootloader loads the operating system into RAM
4. OS initialises system and launches applications

4. Role and Operation of Interrupts

• Definition:
  • A signal that temporarily halts the CPU’s current activity to give attention to a specific event.
  • Ensures urgent tasks are handled immediately.
• Types of Interrupts:
  • Hardware Interrupts: Generated by external hardware devices
    • Example: Pressing a keyboard key, mouse movement, printer out of paper
  • Software Interrupts: Generated by programs or processes
    • Example: Division by zero error, illegal memory access
• How an Interrupt Works (Interrupt Handling Process):
  1. Event occurs → Interrupt signal sent to CPU
  2. CPU suspends current task (context saved)
  3. CPU identifies type of interrupt
  4. Interrupt Service Routine (ISR) executed to handle the event
  5. CPU restores saved task and continues execution
• Uses of Interrupts:
  • Ensure responsiveness to real-time events
  • Efficient CPU usage (no need for constant polling)
  • Enable multitasking

5. Examples of Interrupts

• Hardware Examples:
  • Key press detected by keyboard controller
  • Mouse click or movement
  • Network packet arrival
• Software Examples:
  • Application requesting operating system service
  • Error such as division by zero