Operating System (OS)

• Software


  Programs that run on a computer
• Categories of software


  • Application software
  • System software
• Application software


  Software for user benefit, e.g. word processors, browsers, games
• System software


  Software that performs tasks related to hardware and provides services for other software, e.g. operating systems, game engines, drivers, utility software
• Operating system (OS)


  The most important system software, managing hardware and linking hardware to application software
• Examples of operating systems

  • Android
  • Windows
  • Linux
  • iOS
• Purposes of an operating system

  • Manages hardware
  • Allows other software to interact with hardware
  • Manages applications installed
  • Provides user interface
  • Provides security layer between hardware and software
• Types of user interface

  • Command-line interface (CLI)
  • Graphical user interface (GUI)
• Command-line interface (CLI)


  Shell that responds to text commands
• Graphical user interface (GUI)


  Uses icons, menus and other visual indicators
• Process


  A program being executed by the processor
• Process management in single-tasking OS

  • Executes one process at a time
  • Suspends/interrupts necessary
• Process management in multitasking OS

  • Allocates CPU time to each process
  • Prioritises important processes
• Memory management


  • Allocates and manages RAM space for programs
  • Uses virtual memory to extend RAM capacity
• Boot loader


  Small program that loads the OS into RAM on startup
• Peripheral device


  Supplementary hardware device like keyboard, printer, camera
• Device driver


  Program that converts signals between peripheral device and OS
• User management


  Maintains user accounts, passwords, permissions
• File management


  Maintains file structure, permissions, and records