Understanding Operating Systems Sixth Edition

1
Understanding Operating Systems Sixth Edition

• Chapter 15Windows Operating Systems

2
Learning Objectives

• After completing this chapter, you should be
  able to describe
• The design goals for Windows operating systems
• The role of MS-DOS in early Windows releases
• The role of the Memory Manager and Virtual Memory
  Manager
• The use of the Device, Processor, and Network
  Managers
• System security challenges
• The Windows user interface

3
Windows Development

• First Windows product communication method
• Graphical user interface (GUI)
• Primary user communication method
• Needed underlying operating system to translate
  users requests into system commands
• Windows 1.0 (1985)
• First Windows application
• Ran on PC-compatible microcomputers
• Not a true operating system
• Ran on top of MS-DOS
• Interface between MS-DOS and user

4
Early Windows Products

• Advancements in Windows
• Increasingly sophisticated GUI design
• Increasingly powerful desktop computers
• Windows 3.1
• Standardized look and feel
• Similar to Apples Macintosh computer
• Entry level product
• Single-user installations or small-business
  environments

5
Early Windows Products (cont'd.)

• Windows for Workgroups
• Accommodate network users needs (small business)
• Programs and features for small LANs
• Share directories, disks, printers
• Personal intercommunication e-mail, chat programs

6
Operating Systems for Home and Professional Users

• Disadvantages running Windows on MS-DOS
• Little built-in security
• No multitasking
• No interprocess communication capability
• Difficulty moving MS-DOS to other platforms
• MS-DOS worked closely with hardware
• Microsoft response
• Developed and released succession of Windows
• Not mere GUIs had home and office user appeal
• Development of powerful networking products
• Windows NT (New Technology)

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Operating Systems for Home and Professional Users
(cont'd.)
8
Operating Systems for Networks

• Windows NT Development (1993)
• No reliance on MS-DOS support
• Primary market requirements
• Portability
• Multiprocessing capabilities
• Distributed computing support
• Government procurement compliance requirements
• Government security certification

9
Operating Systems for Networks (cont'd.)
10
Operating Systems for Networks (cont'd.)

• Windows NT versions
• Windows NT Workstation
• Individuals
• Desktop operating system
• Windows NT Server
• Small to medium-sized offices
• Web servers and off-site locations
• Windows NT Server Enterprise Edition
• Larger and more complex networks

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Operating Systems for Networks (cont'd.)

• Windows NT name changed (1999)
• Windows 2000 four packages
• Windows 2000 Professional
• Windows 2000 Server
• Windows 2000 Advanced Server
• Windows 2000 Datacenter Server
• Windows Server 2003
• Same four packages plus Web edition
• Windows Server 2008 Release 2 (2009)

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Design Goals

• Fulfilling marketing requirements
• Incorporate security features
• Facilitate decision making (coding process)
• Windows networking operating systems
• Influenced by several operating system models
• Use already-existing frameworks
• Introduced new features
• Object model
• Manage and allocate resources
• Symmetric multiprocessing (SMP)
• Maximum multiprocessor performance

13
Design Goals (cont'd.)

• Needs
• Accommodate user needs
• Optimize resources
• Response
• Five design goals
• Extensibility
• Portability
• Reliability
• Compatibility
• Performance

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Extensibility

• Easily enhancing operating system
• Ensuring code integrity separate functions
• Privileged executive process
• Kernel mode
• Processors mode of operation
• All machine instructions allowed
• System memory accessible
• Nonprivileged processes protected subsystems
• User mode
• Certain instructions not allowed
• System memory not accessible

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Extensibility (cont'd.)

• Four more features
• Modular structure
• New components added to executive process
• Objects
• Abstract data types manipulated by special
  services
• System resources managed uniformly
• Drivers
• New file systems, devices, and networks added to
  system at any time
• Remote procedure call
• Application calls remote services
• Regardless of location on network

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Portability

• Operate on different machines
• Different processors or configurations
• Minimum amount of recoding
• System guidelines to achieve goal
• Written in a standardized, high-level language
• Available in all machines
• Accommodated ported hardware
• Minimized direct code interaction with hardware
• Reduced incompatibility errors
• Hardware-dependent code isolated into modules
• Easily modifiable when ported

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Portability (cont'd.)

• Windows NT and successors features
• Modular code
• Written in C (most of code)
• Hardware abstraction layer (HAL)
• Dynamic-link library
• Provides isolation from vendors hardware
  dependencies

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Reliability

• Robustness of system
• Ability to protect itself and users
• Accidental or deliberate user programs damage
• Features strengthening system
• Structured exception handling
• Modular design
• NTFS file system (NT file system)
• Can recover from all error types
• Advanced security architecture
• Virtual memory strategy

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Compatibility

• Execute programs written for other operating
  systems (or earlier system versions)
• Use protected subsystems
• Provide application execution different from
  primary programming interface
• Provides source-level POSIX application
  compatibility
• Recent Windows versions
• Support existing file systems
• FAT, CDFS, NTFS
• Built-in verification
• Important hardware and software

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Performance

• Achieve good performance levels
• Windows features
• Testing and optimization system calls, page
  faults, crucial processes
• Incorporate local procedure call (LPC) guarantee
  fast communication among protected subsystems
• Maximize speed of frequently used system services
• Critical Windows networking software elements
  built into operating system privileged portion

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IQ TEST 1

• 1. Which of the following Microsoft Windows
  networking operating systems includes a Web
  edition?
• A. Window NT 4.0
• B. Windows 2000
• C. Windows Server 2003
• D. All of the above
• Answer C
•  
• 2. Which of the following is a design goal of the
  Windows operating systems? (Choose all that
  apply.)
• A. Extensibility
• B. Profitability
• C. Compatibility
• D. Performance
• Answer A, C, and D
• 3. Which of the following file systems is
  supported by recent versions of Windows operating
  systems? (Choose all that apply.)
• A. POSIX
• B. CDFS
• C. NTSC
• D. NTFS

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Memory Management

• Every operating system
• Has own physical memory view
• Makes application programs access memory in
  specified ways
• Full physical memory
• Virtual Memory Manager pages some memory contents
  to disk
• Challenge for all Windows operating systems
• Run application programs (Windows, POSIX)
• Without programs crashing into each others memory

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Memory Management (cont'd.)

• Memory layout (recent Windows versions)
• Operating system high virtual memory
• User code and data low virtual memory
• User process
• Cannot read or write system memory directly
• Memory paged to disk
• User-accessible memory
• System memory segment labeled paged pool
• Memory never paged to disk
• System memory segment labeled nonpaged pool

24
Memory Management (cont'd.)
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User-Mode Features

• VM Manager (virtual machine manager)
• User-mode subsystems share memory efficiently
• Provides process services to manage virtual
  memory
• Allocate memory in two stages
• Read and/or write protection for virtual memory
• Lock virtual pages in physical memory
• Retrieve information about virtual pages
• Protect virtual pages
• Rewrite virtual pages to disk

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Virtual Memory Implementation

• VM manager reliance
• Address space management
• Paging techniques
• Address space management
• Upper half of virtual address space
• Accessible only to kernel-mode processes
• Code in lower part (kernel code and data)
• Never paged out of memory

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Virtual Memory Implementation (cont'd.)

• Paging (VM manager is pager)
• Transfers pages
• Between memory page frames and disk storage
• Complex combination
• Software policies when to bring a page into
  memory and where to put it
• Hardware mechanisms exact manner VM Manager
  translates virtual addresses into physical
  addresses
• Pager not portable
• Windows small code and well isolated

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Virtual Memory Implementation (cont'd.)

• Paging policies
• Dictate how and when paging done
• Composition
• Fetch policy determines when pager copies a page
  from disk to memory
• Placement policy determines where virtual page
  is loaded in memory
• Replacement policy determines which virtual page
  is removed from memory to make room for a new
  page

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Processor Management

• Windows
• Preemptive-multitasking, multithreaded operating
  system
• Windows NT process
• Requires at least one thread
• Default
• Process contains one thread

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Processor Management (cont'd.)

• Thread composition
• A unique identifier
• Contents of volatile set of registers indicating
  processors state
• Two stacks used during threads execution
• Private storage area used by subsystems and
  dynamic-link libraries

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Processor Management (cont'd.)

• Threads
• Thread components called threads context
• Actual data forming context varies from one
  processor to another
• Kernel
• Schedules threads for execution on a processor
• Thread actually executes code
• Overhead incurred by thread is minimal
• Unitasking
• Process with single thread

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Processor Management (cont'd.)
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Processor Management (cont'd.)

• Multithreading using multitasking
• Systems with multiple processors
• Process has as many threads as CPUs available
• All threads belonging to one process share
  global variables, heap, environment strings
• Versions of Windows since NT
• Include some synchronization mechanisms
• Avoid problems with multiple threads

34
Processor Management (cont'd.)
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Device Management

• Windows NT I/O system and networking descendents
  provide
• Multiple installable file systems (FAT, CDFS,
  NTFS)
• Services making device-driver development easy
• Workable on multiprocessor systems
• Adding drivers to the system (system
  administrators)
• Remove them dynamically
• Fast I/O processing
• Drivers written in high-level language
• Mapped file I/O capabilities
• Image activation, file caching, application use

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Device Management (cont'd.)

• I/O system
• Packet driven
• I/O request represented by I/O request packet
  (IRP)
• IRP
• Data structure controlling how I/O operation
  processed at each step
• I/O manager IRP creation
• Creates an IRP representing each I/O operation
• Passes IRP to appropriate driver
• Disposes of packet when operation complete

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Device Management (cont'd.)

• Driver IRP receipt
• Performs specified operation
• Passes it back to I/O manager or
• Passes it through I/O manager to another driver
  for further processing

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Device Management (cont'd.)

• I/O manager tasks
• Supplies code, common to different drivers
• Manages buffers for I/O requests
• Provides time-out support for drivers
• Records installable file systems loaded into
  operating system
• Provides flexible I/O facilities
• Subsystems (POSIX) implement their respective I/O
  application programming interfaces
• Allows dynamic loading of device drivers and file
  systems
• Based on users needs

39
Device Management (cont'd.)

• Windows I/O services
• Device-independent model
• Multilayered device driver concept
• Device driver made up of standard set of routines
• Initialization routine, dispatch routine, start
  I/O routine, completion routine, unload routine,
  error logging routine

40
Device Management (cont'd.)

• I/O manager
• Determine driver called to process request
• Using file objects name
• Driver object
• Represents individual driver in system
• I/O manager creates
• Created when driver loaded into system
• May have multiple device objects connected to it
• Device object
• Physical, logical, or virtual device on the
  system
• Describes device characteristics

41
Device Management (cont'd.)
42
Device Management (cont'd.)
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Device Management (cont'd.)

• Device objects list
• Represents physical, logical, virtual devices
• Controlled by the driver
• Advantages of using different objects
• Portability
• Frees I/O manager from knowing details about
  drivers
• Follows pointer to locate driver
• Easy loading of new drivers
• Easy assigning drivers to control additional or
  different devices
• If system configuration changes

44
Device Management (cont'd.)
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Device Management (cont'd.)

• I/O manager knows nothing about file system
• Overhead
• I/O manager passes information requests back and
  forth
• Uses single-layer device driver approach
• Simple devices (serial and parallel printer
  ports)
• Uses multilayered approach
• More complicated devices (hard drives)
• I/O operations asynchronous
• Almost all low-level operations

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File Management

• Windows current versions
• Designed to be independent of file system on
  which they operate
• Support multiple file systems for hard disks
  including
• MS-DOSs FAT file system
• 32-bit FAT file system
• NTFS

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File Management (cont'd.)

• Virtual file
• Primary file handling concept (current windows)
• Programs perform I/O on virtual files
• File handles manipulate them
• Executive file object representing all sources
  and destinations of I/O
• Processes call native file object services to
  read from or write to file
• I/O manager directs virtual file requests
• Real files, file directories, physical devices

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File Management (cont'd.)

• File objects
• Hierarchical names
• Protected by object-based security
• Support synchronization
• Handled by object services
• Opening file
• Process supplies files name and type of access
  required

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File Management (cont'd.)

• File objects bridge gap
• Between physical devices characteristics and
  directory structures, file system structures,
  data formats
• Provides memory-based representation of shareable
  physical resources
• Created with new set of handle-specific
  attributes
• Each time process opens a handle

50
File Management (cont'd.)
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File Management (cont'd.)
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File Management (cont'd.)

• Mapped file I/O
• Important feature of I/O system
• Achieved by cooperation with I/O system and VM
  Manager
• Memory-mapped files exploit VM capabilities
• Cache manager uses mapped I/O
• Manages its memory-based cache
• File management system supports long filenames
• Include spaces and special characters
• Automatically shortens filenames when required

53
Network Management

• Networking
• Integral to Windows NT-based operating systems
• Provides services
• User accounts, resource security
• Communication between computers
• Named pipes
• Provide high-level interface for passing data
  between two processes (regardless of locations)
• Mailslots
• Provide one-to-many and many-to-one communication
  mechanisms

54
Network Management (contd.)

• Microsoft Networks (MS-NET)
• Released in 1984
• Model for NT Network Manager
• Three components
• Redirector
• Server message block (SMB) protocol
• Network server
• MS-NET components
• Extensively refurbished and incorporated into
  Windows NT and later versions

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Network Management (cont'd.)

• Redirector
• Coded in C programming language
• Implemented as loadable file system driver
• Not dependent on systems hardware architecture
• Function
• Direct I/O request from user or application to
  remote server that has appropriate file or
  resource
• Network can incorporate multiple redirectors

56
Network Management (cont'd.)

• SMB Protocol
• High-level specification
• Formatting messages sent across network
• OSI model correlation
• Application layer (layer 7)
• Presentation layer (layer 6)
• API called NETBIOS interface
• Used to pass I/O requests structured in SMB
  format to remote computer
• SMB protocols and NETBIOS API
• Adopted in several networking products before
  appearing in Windows

57
Network Management (cont'd.)

• Windows Server operating systems
• Written in C
• Complete compatibility with existing MS-NET and
  LAN manager SMB protocols
• Implemented as loadable file system drivers
• No dependency on hardware architecture
• Where operating system running

58
Directory Services

• Active Directory
• Database storing all information types
• General-purpose directory service for
  heterogeneous network
• Built entirely around DNS and LDAP
• Groups machines into administrative units called
  domains
• Each domain gets a DNS domain name (e.g.,
  pitt.edu)
• Each domain must have at least one domain
  controller
• Domain can have more than one domain controller
• Active Directory clients use standard DNS and
  LDAP protocols to locate objects on the network

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Directory Services (cont'd.)
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Security Management

• Windows network operating systems
• Provide object-based security model
• Security object
• Represent any resource in system (file, device,
  process, program, or user)
• Allows administrators to give precise security
  access
• To specific objects in system allowing them to
  monitor and record how objects used
• Windows biggest concern
• Aggressive patch management needed
• Combat many viruses and worms

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Security Basics

• U.S. Department of Defense
• Identified and categorized operating system
  features
• Seven levels of security
• Compliance with Class C2 level security
• Features in Windows
• A secure logon facility
• Discretionary access control
• Auditing ability
• Memory protection

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Security Basics (cont'd.)

• Multilayered security system
• Strives to prevent access by unauthorized users
• Password management first security layer
• NTFS second security layer
• File access security
• Distinguishes between owners and groups
• Users decide operation types person is allowed to
  perform on a file
• Gives user auditing capabilities
• Automatically keeps track of who uses files and
  how

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Security Terminology

• Built-in security
• Necessary element for managers of Web servers and
  networks
• Requires authentication mechanism allowing client
  to prove identity to server
• Client supplies authorization information
• Server uses information to determine specific
  access rights given to client
• Provides data integrity using various methods
• Windows uses Kerberos security

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Security Terminology (cont'd.)

• Kerberos Security
• Authentication, data integrity, data privacy,
  mutual authentication
• Each domain has own Kerberos server
• Microsoft implemented standard Kerberos protocol
• Microsoft separated users of distributed security
  services from their providers
• Allows support for many options without unusable
  complexity

65
Security Terminology (cont'd.)
66
User Interface

• Start an application
• Double-click application icon
• Select it from Start menu
• Quit application
• Select Exit from File menu
• Click x in top-right corner of window

67
User Interface (cont'd.)

• Start Menu
• Divides functions into logical groups
• Users access common functions
• All Programs
• Documents, Pictures, Music, and Computer
• Control Panel
• Help and Support
• Search

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User Interface (cont'd.)
69
User Interface (cont'd.)

• Windows Task Manager
• Open
• Pressing and holding the CTRL, ALT, delete keys
• User view running applications and processes
• Set priorities of each
• User views information
• Performance, networking, users logged into system
• Windows Explorer (standard utility program)
• Contains director, file display tools,
  file-finding tool
• Series of pull-down menus
• File, Edit, View, Tools, Help, etc.

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User Interface (cont'd.)
71
User Interface (cont'd.)
72
User Interface (cont'd.)

• Networked systems
• Identify and access network resources
• Folders, printers, connections to other nodes
• Command interface
• Resembles MS-DOS
• Available from most Windows desktops
• Keyboard shortcuts (CTRLC for copy)
• Built-in input methods and fonts for languages
• Windows offers an on-screen keyboard
• Resource monitor

73
User Interface (cont'd.)
74
User Interface (cont'd.)
75
User Interface (cont'd.)
76
User Interface (cont'd.)
77
User Interface (cont'd.)
78
IQ TEST 2
1. The VM Manager uses a(n) ____________________
replacement policy. A. LRU B. MRU C. FCFS D.
FIFO Answer D   2. A(n) ____________________ is
a data structure that controls how the I/O
operation is processed at each step. Answer I/O
request packet (IRP)   3. The segment of system
memory labeled ____________________ is never
paged to disk because its used to store critical
NT objects. Answer nonpaged pool
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Summary

• Current Windows operating systems
• Ease-of-use with technical power
• Operate network across several platforms
• Significant security controls
• Allowed inroads to organizations requiring
  consistent protection
• Authentication models support new user interfaces
• Implementation of different security
  architectures
• Require aggressive patch management
• Target of viruses and worms