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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

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OPERATING SYSTEMS Software in the Background

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  • 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
  • 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
Operating SystemHidden 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
Systems Software
  • Definition:
    • All programs related to coordinating computer operations
  • Components
    • Operating System
    • Utility programs
    • Program language translators
functions of os
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
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
  • Definition:

Computer hardware and operating system software that dictate what other software can run

  • Wintel

Intel-based PC running Microsoft Windows

os is hidden
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
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
Microsoft Windows
  • Graphical user interface
  • Eases access to the OS
  • Most new computers come with Windows already installed
  • On-screen pictures
    • Icons
    • Menus
      • Pull down
      • Pop up
    • Click to activate a command or function
  • Fast
  • Easy
  • Intuitive
early days of windows
Early Days of Windows

Operating environment for MS-DOS

Shell – layer added between users and DOS

windows today
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
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
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
Improved Windows Features
  • Backup
  • Interfaces with other software
  • Networking features
  • Security
  • Dr. Watson

Helps reduce the cost of owning and maintaining a PC

windows me millennium edition
Windows MEMillennium 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 edition21
Windows MEMillennium 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
Windows NTNew 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
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 200024
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
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
Windows CEConsumer 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 electronics27
Windows CEConsumer Electronics

Subset of Windows

  • Less memory
  • Smaller screens
  • Little or no file storage
  • Provides Internet connectivity
accessibility options
Accessibility Options
  • Seeing
  • Hearing
  • Touching
mac os
Mac OS
  • First commercially successful GUI (1984)
  • Served as a model to other GUI systems
  • 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
  • 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
  • Advantages over Windows
    • Extremely stable
    • Internet support
    • Reinstallation is simpler
  • Disadvantage
    • Scarcity of applications
network operating system nos
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
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
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 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
Allocating the CPU
  • One CPU
    • Multiprogramming
      • Event-driven
      • Timesharing
  • More than one CPU
    • Multiprocessing – multiple CPUs can run several programs simultaneously
  • 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
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
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 example41
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
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
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
Memory Management
  • The process of providing separate memory space to programs
  • Memory Protection keeps one program from interfering with another
memory management methods
Memory ManagementMethods

Partitions or regions

Foreground and background

Virtual storage (virtual memory)

partitions or regions
Partitions or Regions
  • Divide memory into sections
  • The partition must accommodate the largest possible program
  • Problem
    • May cause wasted memory space
foreground and background
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
Virtual StorageVirtual 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
virtual storage virtual memory49
Virtual StorageVirtual Memory

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 memory50
Virtual StorageVirtual 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
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
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
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 resources54
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
Additional Printing Problem
  • Printers are slow compared to the CPU speed
  • Solution
    • The CPU writing to the disk
    • The program completes quicker
utility programs
Utility Programs
  • Come with System Software
  • Handle special needs
  • Perform secondary chores
  • Do not need to be memory resident
functions of utility programs
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