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OS OS Presentation Transcript

  • OPERATING SYSTEMS Software in the Background Chapter 2
  • Objectives
    • Describe the functions of an Operating System
    • Explain the basics of a personal computer operating system
    • Describe the advantages of a graphical operating system
    • Differentiate among different versions of Microsoft Windows
    • Explain the need for network operating systems
    • Describe the methods of resource allocation on large computers
    • Be able to describe the differences among multiprocessing, multiprogramming, and timesharing
    • Explain the principles of memory management
    • List several functions typically performed by utility programs
  • Contents
    • Operating System: Hidden Software
    • Systems Software
    • Functions of OS
    • Types of OS
      • MS-DOS
      • Microsoft Windows
      • Mac OS
      • UNIX
      • LINUX
      • Network Operating System NOS
    • Resource Allocation
    • Utility Programs
  • Operating System Hidden Software
    • Definition – provides access to all resources
    • Kernel
      • Manages the operating system
      • Memory resident
      • Loads set of programs that lies between applications software and the hardware
      • Fundamental software that controls non-resident portions of the OS as needed
    • Booting – Loads the kernel into memory
  • Systems Software
    • Definition:
      • All programs related to coordinating computer operations
    • Components
      • Operating System
      • Utility programs
      • Program language translators
  • Functions of OS
    • Manage the computer’s resources
      • CPU
      • Memory
      • Disk drives
      • Printers
    • Establish a user interface
    • Execute and provide services for applications software
    • Carries out all input and output operation
  • User Interface
    • Facilitates communication between the user and the operating system
    • Two forms
      • Command line
        • Text-based
        • Key commands
        • Examples: MS-DOS, Unix
      • Graphical user interface (GUI)
        • Visual images
        • Menus
        • Examples: Windows, Mac OS, Linux
  • Platform
    • Definition:
      • Computer hardware and operating system software that dictate what other software can run
    • Wintel
      • Intel-based PC running Microsoft Windows
  • OS is Hidden
    • User interested in application software to make the PC useful
    • Application software is platform specific
    • User must be aware of the type of OS
    • User should be aware of the functions of OS
  • Types of OS
    • Command line
    • Single user PC
    • Network Operating System (NOS)
  • MS-DOS
    • Command-line interface
    • Prompt – system is waiting for you to do something
    • Key a command
    • Not user-friendly
  • Microsoft Windows
    • Graphical user interface
    • Eases access to the OS
    • Most new computers come with Windows already installed
  • GUI
    • On-screen pictures
      • Icons
      • Menus
        • Pull down
        • Pop up
      • Click to activate a command or function
    • Fast
    • Easy
    • Intuitive
  • Early Days of Windows
      • Operating environment for MS-DOS
      • Shell – layer added between users and DOS
  • Windows Today
    • Home/consumer market
      • Windows 95
      • Windows 98
      • Windows Millennium Edition (ME)
    • Corporate market
      • Windows NT
      • Windows 2000
    • Windows XP
    • Pocket computers and Internet appliances
      • Windows CE
  • Windows 95 and 98
    • Self-contained OS
    • DOS commands still available
    • Start programs by
      • Start button
      • Double clicking the icon
    • Task bar permits movement between open programs
    • Long file names up to 255 characters
    • Plug and play
    • Object linking and embedding (OLE)
  • Windows 98 Additions
    • Internet / intranet browsing
    • Support for DVD and additional multimedia components
    • Support for large hard drives
    • TV viewer and broadcast ability
    • Wizards
  • Improved Windows Features
    • Backup
    • Interfaces with other software
    • Networking features
    • Security
    • Dr. Watson
  • Windows
    • Helps reduce the cost of owning and maintaining a PC
  • Windows ME Millennium Edition
    • Multimedia support -- Windows Media Player 7
    • Jukebox
      • Record music CDs as digital files
    • Windows Movie Maker
      • Basic video editing
    • Windows Image Acquisition
      • Scanner and digital camera
  • Windows ME Millennium Edition
    • Reliability Features
      • System File Protection
      • AutoUpdate
      • System Restore
    • Help Center
    • Home Network Support
      • Wizard for connecting multiple computers and peripherals
      • Multiple users can share a single Internet connection
  • Windows NT New Technology
    • Engineered for stability
    • Strong security
    • Versions
      • NT Workstation
      • NT Server
    • Drawbacks
      • Lacks support for older Windows and MS-DOS software and hardware
      • Complex to learn and use
      • Requires more memory and processing power
  • Windows 2000
    • Stability features
    • Security features
    • Uses simple approach to hardware setup from Windows 98
    • Versions
      • Windows 2000 Professional for individual users
      • Windows 2000 for network servers
    • Was intended for both the corporate and home use, replacing Win NT and Win 98
  • Windows 2000
    • Complex
    • Heavy demand for computer resources
    • Improvements over windows NT
      • Maintains user preferences
      • Self-healing applications software
      • Supports Windows 98 file structure
      • Uses plug and play
      • Provides improved support for laptops
  • Windows XP
    • Extends Windows ME and provides a more stable environment
    • Two categories
      • Network server
        • 3 versions based upon network complexity
      • Desktop computer
        • 2 versions
          • Professional Client
          • Personal Client
  • Windows CE Consumer Electronics
    • Where used
    • Embedded systems
      • Industrial controllers
      • Robots
      • Office equipment
      • Cameras
      • Telephones
      • Home entertainment devices
      • Automobile navigation systems
    • Pocket PC
    • Internet appliance market
  • Windows CE Consumer Electronics
    • Subset of Windows
    • Less memory
    • Smaller screens
    • Little or no file storage
    • Provides Internet connectivity
  • Accessibility Options
    • Seeing
    • Hearing
    • Touching
  • Mac OS
    • First commercially successful GUI (1984)
    • Served as a model to other GUI systems
  • UNIX
    • Supports
      • Multi-user
      • Time-sharing
    • Character-based system
    • Command-line interface
    • Runs on various processors and many types of computers
    • Primary OS used on Internet servers
  • LINUX
    • UNIX-like OS
    • Open-source software
      • Download it free
      • Make changes
      • Distribute copies
      • Restriction – any changes must be freely available to the public
    • PC Setup
      • PC comes with Windows installed
      • Install LINUX in a dual-boot configuration
  • LINUX
    • Advantages over Windows
      • Extremely stable
      • Internet support
      • Reinstallation is simpler
    • Disadvantage
      • Scarcity of applications
  • Network Operating System NOS
    • Designed to permit computers on a network to share resources
    • Examples
      • Windows 2000 Server
      • Novell Net Ware
    • Provides
      • Data security
      • Troubleshooting
      • Administrative control
  • NOS Functions
    • Split between client and server computers
    • Server
      • File management
    • Client
      • Requests to the server
      • Messaging
      • Has own local OS
    • Makes the resources appear as if they are local to the client’s computer
  • Large Computers
    • Used by many people at once
    • OS works “behind the scenes” so users can share
    • OS must control
      • Who gets access to resources
      • What keeps the programs from different users from getting mixed up with one another
  • Resource Allocation
    • Resource – hardware or software that is needed to complete a task
    • Resource Allocation – assigning computer resources to certain programs
    • Resource De-allocation – releasing resources when a task is complete
  • Allocating the CPU
    • One CPU
      • Multiprogramming
        • Event-driven
        • Timesharing
    • More than one CPU
      • Multiprocessing – multiple CPUs can run several programs simultaneously
  • Multiprogramming
    • One CPU
    • Concurrent execution of two or more processes
      • Several processes open at once
      • Only one process can receive the attention of the CPU at any given moment
      • Effective because CPU speeds are many times faster than input/output speeds
  • Event-driven Multiprogramming
    • One program receives the attention of the CPU
    • Its processing will be interrupted based upon events in the program
    • When processing needs to be temporarily suspended, an interrupt is generated
    • This is a signal to the operating system to evaluate the cause of the interrupt and determine who should now have CPU time
  • Event-driven Multiprogramming Example
    • Two programs are running – Payroll and Inventory Management
    • Payroll needs to read an employee record
    • Payroll generates an interrupt
    • Normal processing is temporarily suspended
    • The CPU looks at the interrupt and initiates the read operation
    • While waiting for the read to complete, the CPU begins processing the Inventory Management program
  • Event-driven Multiprogramming Example
    • When the read operation is complete, another interrupt is generated
    • Normal processing is temporarily suspended
    • The CPU looks at the interrupt and determines its cause
    • The CPU will either continue processing the Inventory Management program or return to the Payroll program depending upon their priority
  • Time-sharing Multiprogramming
    • One program receives the attention of the CPU
    • A small fraction of CPU time is allocated to the program
    • The time slice ends
    • The CPU begins processing a different program
    • Response time can vary based upon the number of users on the system
  • Sharing Memory
    • Program must be in memory to be executed
    • Problems
      • Programs compete for space
      • May have a very large program
      • Memory space for each program must not overlap
  • Memory Management
    • The process of providing separate memory space to programs
    • Memory Protection keeps one program from interfering with another
  • Memory Management Methods
    • Partitions or regions
    • Foreground and background
    • Virtual storage (virtual memory)
  • Partitions or Regions
    • Divide memory into sections
    • The partition must accommodate the largest possible program
    • Problem
      • May cause wasted memory space
  • Foreground and Background
    • Programs are placed in either Foreground or Background
    • Programs in Foreground have priority for CPU time
    • While performing read / write operations for the Foreground program, the CPU gives time to a program in Background
    • Programs are placed in a holding queue while waiting to run
  • Virtual Storage Virtual Memory
    • Uses concept of Paging
    • Divide the program into equal-size pieces (pages)
    • Store each piece in equal-size memory spaces (page frames)
    • Typical size is 2KB or 4KB
    • Create an index to each page and store in a Page Table
    • Paging Process
    • A portion of the program is placed in memory
    • The remainder is on disk
    • Sections on disk will be brought into memory as needed (one page at a time)
    Virtual Storage Virtual Memory
  • Virtual Storage Virtual Memory
    • Problem -- Thrashing
      • Too large a portion of CPU time is spent locating the correct page and bringing it into memory
    • Solution
      • Run fewer programs concurrently
      • Add memory
  • Memory Protection
    • Keeps one program from straying into another
    • Confines each program to certain defined limits in memory
    • Why needed
      • Possible for one program to destroy or modify another by transferring to the wrong memory location
      • May cause destruction of data
    • Action if assigned memory space is violated
      • Termination of executing program
  • Sharing Storage
    • Several users need to access the same disk pack
      • One wants to write
      • Another wants to read
    • OS keeps track of the I/O requests
    • OS processes I/O requests in order received
  • Sharing Printing Resources
    • Print resources are shared between active programs
    • Printouts are generated in pieces as the CPU gives each concurrent program some time
    • Problem
      • The current program may generate a few print lines
      • The CPU moves to the next program
      • The second program may generate a few print lines, etc.
  • Sharing Printing Resources
    • Result
      • Printout is worthless as it contains a few lines from several programs
    • Solution – Spooling
      • Each program thinks it is writing to the printer
      • The program actually writes to the hard disk
      • When the program is complete, the file on the hard disk is sent to the printer
  • Additional Printing Problem
    • Printers are slow compared to the CPU speed
    • Solution
      • The CPU writing to the disk
      • The program completes quicker
  • Utility Programs
    • Come with System Software
    • Handle special needs
    • Perform secondary chores
    • Do not need to be memory resident
  • Functions of Utility programs
    • File manager – provide access to lists of stored files
    • Backup and Restore – make duplicate copies of important files and return the copy to the hard drive if needed
    • File compression – reduces the amount of disk space required by a file
    • Disk defragmenter – reorganize files so they are stored contiguously on disk providing for faster access
    • Device drivers – convert operating system instructions into commands that are known to a specific device
  •