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computer_basics:operating_system_fundamentals

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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
Feb. 19, 2012

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

Function 1: Starting the computer

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

Function 1: Starting the computer


Booting: six steps in starting the computer

Function 1: Starting the computer

  • Booting Step 1: Load BIOS (Basic Input/Output System) instructions into memory
  • Allows computer to
    • Accept keyboard input
    • Show information on the monitor
  • BIOS is usually stored on a ROM chip.

Function 1: Starting the computer

  • Booting Step 2: Conduct the power-on self-test (POST)
    • Confirms that both the computer and its peripheral devices are working properly.

Function 1: Starting the computer

  • Booting Step 3: Load the operating system
    • BIOS loads the kernel, the central part of the OS, into memory.
    • The kernel is usually stored on the hard drive.
    • The OS then loads remainder of what's needed.

Function 1: Starting the computer

  • Booting Step 4: Check the system configuration
    • The OS checks the system configuration for device drivers
      • driver: utility program that enables communication between the OS and a peripheral device.
    • The OS installs and loads the needed drivers.

Function 1: Starting the computer

  • Booting Step 5: Load system utilities
    • Antivirus software
    • Speaker volume control
    • Etc.

Function 1: Starting the computer

  • Booting Step 6: Authenticate users
    • If necessary, facilitate authentication/login, a user name and password

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.

Function 3: Managing memory

  • The OS gives each program a portion of RAM memory and keeps them from interfering with each other.
  • OS processes often involve using a buffer
    • An area that holds data temporarily to make programs run faster
    • RAM memory functions as the buffer.

Function 3: Managing memory

  • RAM is organized into pages: units of large fixed size containing program instructions and data.
  • Virtual memory uses a portion of the hard disk to extend RAM.
    • When RAM is full, copies of pages are temporarily stored in a swap file, a special hard disk file.
    • Transferring files between RAM and the hard disk is called paging.

Virtual memory

Function 3: Managing memory

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

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.

Function 5: Providing the 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

Function 5: Providing 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.1361314502.txt.gz · Last modified: 2013/02/19 22:55 by mithat

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