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Operating System Fundamentals

Adapted from:
LaBerta, Catherine. “System Software.” In Computers Are Your Future. 11th ed. Boston: Prentice Hall., 2010

Mithat Konar
Dec. 4, 2019

The Operating System

  • The operating system (OS) is a set of programs that coordinates:
    • Hardware functions
    • Interaction between application software and computer hardware

The Operating System

  • Five basic OS functions:
    • Starting the computer
    • Managing applications
    • Managing memory
    • Handling input and output device messages
    • Providing a user interface for communication

OS function 1: Starting the computer

  • OS's first job is to load itself into RAM
    • Called booting.

OS function 1: Starting the computer

Booting: six steps

Booting step 1: BIOS and EFI

  • Many computers use a BIOS (Basic Input/Output System) to begin the booting process.
  • The first thing that is loaded into memory and starts running when you turn on.
  • Manages some core hardware settings.
  • Handles the very first stages of the booting process.
  • Usually stored in flash memory or CMOS memory chip.

Booting step 1: BIOS and EFI

  • Most newer desktops and laptops use EFI (Extensible Firmware Interface) instead of a BIOS.
    • UEFI (Unified Extensible Firmware Interface) is one example.
  • Like a mini OS.
  • Does everything BIOS does.
  • Lets user run small utility applications that run on the Extensible Firmware Interface.
  • Considered more secure than traditional BIOS.

Booting step 2: Test the hardware

  • Many BIOS/EFIs initiate a power-on self-test (POST) or similar test.
  • Confirms that both the computer and its peripheral devices are working properly.

Booting step 3: Load the operating system

  • BIOS or EFI loads an OS's kernel into memory.
    • kernel: the central part of the OS.
    • Usually stored on main storage device.
  • The OS then loads remainder of what's needed.

Booting step 4: Check the system configuration

  • The OS checks the system configuration for device drivers.
    • device driver: utility program that enables communication between the OS and a peripheral device.
  • The OS installs and loads the needed drivers.

Booting step 5: Load system utilities

  • Antivirus software
  • Speaker volume control
  • Etc.

Booting step 6: Authenticate user

  • Final part of booting is to facilitate user authentication or login.
  • Typically a user name and password or fingerprint scan or special code.

OS function 2: Managing applications

  • Multitasking operating systems permit more than one application to run at the same time.
    • The foreground application is the active one.
    • The background applications appear inactive.

OS function 3: Managing memory

  • The OS
    • gives each program a portion of RAM memory.
    • keeps them from interfering with each other.

OS function 3: Managing memory

  • RAM is organized into pages: units of large fixed size.
  • Virtual memory uses a portion of the hard disk to extend RAM.
    • When RAM is full, the contents of the most inactive page or pages are temporarily moved to a swap file, a special hard disk file.
    • When the page is again needed, it is transferred back into RAM.
    • Transferring files between RAM and the hard disk is called paging.

Virtual memory

OS function 3: Managing memory

  • Adding more RAM is often a good way to improve computer performance because:
    • Paging slows the computer.
    • Accessing data from the hard disk is slower than accessing it from RAM.

OS function 4: Handling input and output

  • Applications access input and output devices via the OS.
  • Device drivers enable communication between the OS and input and output (and other) devices.

OS function 5: Provide a user interface

  • The user interface allows the user to:
    • Start application programs
    • Manage storage devices
    • Safely shut down the computer
    • Perform other interactions

User interfaces

a) graphical, b) menu-driven, and c) command-line user interfaces

OS function 5: Provide a user interface

  • Types of user interfaces:
    • graphical user interface (GUI) uses icons and other visual metaphors.
    • menu-driven interface:
      • Provides text-based menus.
      • Displays available user options.
    • command-line interface:
      • Requires the user to type commands to instruct the OS to perform the desired actions.
computer_basics/operating_system_fundamentals.txt · Last modified: 2019/12/06 05:11 by mithat