The document describes the functions and types of operating systems. It discusses personal computer OSes like MS-DOS, Windows, Mac OS, and Linux. It also covers network operating systems and large computer OSes. The key functions of an OS include managing system resources and providing a user interface. It describes OS concepts like multiprocessing, multiprogramming, timesharing, and virtual memory. Utility programs are also discussed which perform secondary tasks to support the OS.

1. OPERATING SYSTEMS
Software in the Background
Chapter 2

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

3. 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

4. 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

5. Systems Software
• Definition:
– All programs related to coordinating
computer operations
• Components
– Operating System
– Utility programs
– Program language translators

6. 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

7. 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

8. Platform
• Definition:
Computer hardware and operating
system software that dictate what other
software can run
• Wintel
Intel-based PC running Microsoft
Windows

9. 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

10. Types of OS
Command line
Single user PC
Network Operating System (NOS)

11. MS-DOS
• Command-line interface
• Prompt – system is waiting for you to do
something
• Key a command
• Not user-friendly

12. Microsoft Windows
• Graphical user
interface
• Eases access to
the OS
• Most new
computers come
with Windows
already installed

13. GUI
• On-screen pictures
– Icons
– Menus
• Pull down
• Pop up
– Click to activate a
command or function
• Fast
• Easy
• Intuitive

14. Early Days of Windows
Operating environment for MS-DOS
Shell – layer added between users
and DOS

15. 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

16. 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)

17. Windows 98 Additions
• Internet / intranet browsing
• Support for DVD and additional
multimedia components
• Support for large hard drives
• TV viewer and broadcast ability
• Wizards

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

19. Windows
Helps reduce the cost of owning and
maintaining a PC

20. 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

21. 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

22. 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

23. 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

24. 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

25. 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

26. 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

27. Windows CE
Consumer Electronics
Subset of Windows
• Less memory
• Smaller screens
• Little or no file storage
• Provides Internet connectivity

28. Accessibility Options
• Seeing
• Hearing
• Touching

29. Mac OS
• First
commercially
successful GUI
(1984)
• Served as a
model to other
GUI systems

30. 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

31. 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

32. LINUX
• Advantages over Windows
– Extremely stable
– Internet support
– Reinstallation is simpler
• Disadvantage
– Scarcity of applications

33. 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

34. 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

35. 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

36. 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

37. Allocating the CPU
• One CPU
– Multiprogramming
• Event-driven
• Timesharing
• More than one CPU
– Multiprocessing – multiple CPUs can run
several programs simultaneously

38. 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

39. 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

40. 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

41. 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

42. 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

43. 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

44. Memory Management
• The process of providing separate
memory space to programs
• Memory Protection keeps one
program from interfering with another

45. Memory Management
Methods
Partitions or regions
Foreground and background
Virtual storage (virtual memory)

46. Partitions or Regions
• Divide memory into sections
• The partition must accommodate the
largest possible program
• Problem
– May cause wasted memory space

47. 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

48. 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

49. 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

50. 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

51. 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

52. 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

53. 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.

54. 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

55. Additional Printing Problem
• Printers are slow compared to the
CPU speed
• Solution
– The CPU writing to the disk
– The program completes quicker

56. Utility Programs
• Come with System Software
• Handle special needs
• Perform secondary chores
• Do not need to be memory resident

57. 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