Understanding Operating Systems
Seventh Edition
Chapter 14
Windows Operating Systems
Learning Objectives
After completing this chapter, you should be able to
describe:
• Design goals for Windows operating systems
designers
• The role of the Memory Manager and Virtual
Memory Manager in Windows
• Its use of the Device, Processor, and Network
Managers
• System security challenges for Windows
• Windows user interfaces
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Brief History
• Windows products before 1995 release: Windows
95 operating system
– Graphical user interfaces requiring the MS-DOS
operating system
– Disadvantages:
•
•
•
•
Multitasking not supported
Little built-in security
Lacked interprocess communication capability
Required customization to work with each system
hardware component
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(table 14.1)
Select Microsoft Windows operating systems. For details about these and
other versions, refer to www.microsoft.com.
© Cengage Learning 2014
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Brief History (cont’d.)
• Windows products since 1995
– Abandoned MS-DOS reliance
– More powerful networking products
• Windows product version number
–
–
–
–
Windows XP: version 5.1
Windows 7: version 6.2
Windows 8: version 6.2
Display by pressing Windows logo key and the R key
together
• Type winver
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Design Goals
• Windows networking operating systems
– Influenced by several operating system models
• Employed already-existing frameworks
• Introduced new features
– Object model: manage and allocate resources
– Symmetric multiprocessing (SMP): achieve maximum
multiprocessor performance
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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
Processor’s 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.)
• Additional features
– Modular structure
• New components added to executive process
– Objects
• Abstract data types manipulated by special services
• System resources managed uniformly
– Remote procedure call
• Application calls remote services
• Regardless of location on network
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Portability
• Operates on different platforms
– Different processors or configurations
– Minimum amount of recoding
• System guidelines to achieve goal
– Written in a standardized, high-level language
• Available in all machines
– Accommodate ported hardware
– Minimize direct code interaction with hardware
• Reduce incompatibility errors
– Isolate hardware-dependent code into modules
• Easily modifiable when ported
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Portability (cont'd.)
• Windows features
– Modular code
– Written in C (most of code)
• Graphic component and some networking portions
written in C++
• Code communicating directly with hardware written in
Assembly language
– Hardware abstraction layer (HAL)
• Dynamic-link library
• Provides isolation from vendors’ hardware
dependencies
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Reliability
• System robustness: error response predictability
• 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 including MS-DOS FAT,
CDFS, and NTFS
– Built-in verification
• Important hardware and software
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Performance
• Responds quickly to CPU-bound applications
• Windows features
– System calls, page faults, and other crucial
processes: respond in timely manner
– Incorporated local procedure call (LPC): guarantees
fast communication among protected subsystems
– Critical Windows networking software elements: built
into operating system privileged portion
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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 or POSIX)
• Without programs crashing into each other’s 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
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(figure 14.3)
Layout of Windows memory. This is a virtual memory system based on 32-bit
addresses in a linear address space. The 64-bit versions use a similar model
but on a much larger scale with 8TB for the user and 8TB for the kernel.
© Cengage Learning 2014
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User-Mode Features
• VM Manager (virtual machine manager)
– User-mode subsystems share memory efficiently
– Provides native services: allows process 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 part: 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: modified for each new hardware
platform
• Windows: small code and well-isolated
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Virtual Memory Implementation
(cont'd.)
• Paging (cont’d.)
– Processor chip translates program generated address
into a physical address
• Page with address not in memory: hardware generates
a page fault and calls the pager
– Processor uses translation look-aside buffer (TLB)
• Speeds memory access
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Virtual Memory Implementation
(cont'd.)
• Paging policies
– Dictate how and when paging is 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
• Process:
– Combination of executable program, private memory
area, and operating system allocated resources as
the program executes
– Requires at least one execution thread
• Thread
– Process entity: roughly equated to a task
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Processor Management (cont’d.)
• Windows
– Preemptive-multitasking, multithreaded operating
system
– Process contains one thread composed of:
• A unique identifier
• Volatile set of registers: contents indicate processor’s
state
• Two stacks used during thread’s execution
• Private storage area: used by subsystems and
dynamic-link libraries
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Processor Management (cont'd.)
• Threads
– Thread components called thread’s 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.)
(figure 14.4)
Unitasking in Windows. Here’s
how a process with a single
thread is scheduled for
execution on a system with a
single processor.
© Cengage Learning 2014
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Processor Management (cont'd.)
• Multithreading
– Systems with multiple processors
• Process has as many threads as CPUs available
• All threads belonging to one process: share global
variables, heap, and environment strings
• Windows operating systems
– Include some synchronization mechanisms
• Give exclusive access to global variables as
multithreaded processes execute
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(figure 14.5)
Multitasking using multithreading. Here’s how a process with four
threads can be scheduled for execution on a system with four
processors.
© Cengage Learning 2014
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Processor Management (cont'd.)
• Multithreading example: modifying a database
application
– Entering records: one thread writes the last record to
disk while another thread accepts new data
– Database searching: several threads search an array
simultaneously
• Client/server applications: CPU-intensive for server
– Client makes query requests; server’s processor
manages the query
– Windows handles requests allocating additional CPU
resources
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Device Management
• Windows I/O system provides:
– Multiple installable file systems (FAT, CDFS, and
NTFS)
– Services making device-driver development easy
• Workable on multiprocessor systems
– Drivers: added to or removed from system
dynamically
• System administrators
– Fast I/O processing
• Drivers written in high-level language
– Mapped file I/O capabilities
• Image activation, file caching, and 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:
– Creates an IRP representing each I/O operation
– Passes IRP to appropriate driver
– Disposes 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: device drivers and file
systems based on users’ needs
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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
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Device Management (cont'd.)
• I/O manager
– Determines driver called to process request
• Based on file object’s name
– Driver object
• Represents individual driver in system
• Created by I/O manager 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
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Device Management (cont'd.)
(table 14.2)
Example showing how a device object is created from an instruction to
read a file, illustrated in Figure 14.6.
© Cengage Learning 2014
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(figure14.6)
The driver object from Table 14.2 is connected to several device
objects. The last device object points back to the driver object.
© Cengage Learning 2014
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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
• System configuration changes
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(figure14.7)
Details of the layering of a
file system driver and a disk
driver. The steps shown
here take place when the
I/O Manager needs to
access a secondary storage
device to satisfy the
command shown in Step 1.
© Cengage Learning 2014
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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)
• Asynchronous I/O operations
– Nearly all low-level operations
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File Management
• Windows current versions
– Designed to be independent of file system on which
they operate
• Virtual file
– Primary file handling concept (current Windows
versions)
– Programs perform I/O on virtual files
• File handles manipulate them
– Executive file object representing all I/O sources and
destinations
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File Management (cont'd.)
• 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, or other
system-supported destinations
• File objects
–
–
–
–
Hierarchical names
Protected by object-based security
Support synchronization
Handled by object services
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File Management (cont'd.)
• Opening file
– Process supplies file’s name and type of access
required
• File objects bridge gap
– Between physical devices’ characteristics and
directory structures, file system structures, and data
formats
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File Management (cont'd.)
• File object
– Memory-based representation of shareable physical
resources
• Contains only data unique to an object handle
• File
– Contains data to be shared
• New file object created with new set of
handle-specific attributes
– Each time process opens a handle
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(figure14.8)
Illustrations of a file object,
its attributes, and the
services that operate on
them. The attributes are
explained in Table 14.3.
© Cengage Learning 2014
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File Management (cont'd.)
(table 14.3)
Description of the attributes shown in Figure 14.8.
© Cengage Learning 2014
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File Management (cont'd.)
• Mapped file I/O: important I/O system feature
– Achieved through cooperation between 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
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Network Management
• Networking
– Integral part of Windows operating system executive
– Provides services: user accounts and resource
security
– Implements 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
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Network Management (cont’d.)
• 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 later
Windows versions
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Network Management (cont'd.)
• Redirector
–
–
–
–
Coded in C programming language
Implemented as loadable file system driver
Not dependent on system’s hardware architecture
Function
• Direct I/O request from user or application to remote
server with appropriate file or resource
• Network can incorporate multiple redirectors
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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
• Passes I/O requests structured in SMB format to
remote computer
– SMB protocols and NetBIOS API
• Adopted in several networking products before
appearing in Windows
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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
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Directory Services
• Active Directory
– Database storing many information types
– General-purpose directory service for heterogeneous
network
– Built entirely around DNS and LDAP
– Groups machines into 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: locate objects on the network
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(figure 14.9)
Active Directory clients use standard DNS and LDAP protocols to locate
objects on the network.
© Cengage Learning 2014
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Security Management
• Windows network operating systems
– Provide object-based security model
– Security object
• Represents any resource in system (file, device,
process, program, or user)
– Allows administrators to give precise security access
• Monitor and record how objects used
• Windows biggest concern
– Aggressive patch management needed
• Combat many viruses and worms
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Security Concerns
• U.S. Department of Defense
– Identified and categorized seven levels of security
features
• Class C2 security level compliance
– Features in Windows
•
•
•
•
A secure logon facility
Discretionary access control
Auditing ability
Memory protection
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Security Concerns (cont'd.)
• Multilayered security system
– First security layer: password management
– 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 tracks
who uses files and how files used
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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: determines specific access
rights given to client
– Provides data integrity using various methods
• Windows operating systems feature Kerberos
security
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Security Terminology (cont'd.)
• Kerberos security
– Authentication (mutual), data integrity, and data
privacy
– Each domain has own Kerberos server
– Microsoft implemented standard Kerberos protocol
– Microsoft separates distributed security services
users from their providers
• Supports many options without unusable complexity
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Security Terminology (cont'd.)
(figure 14.10)
Requests from an application flow through these security stops on the
way to and from the network.
© Cengage Learning 2014
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User Interface
• Windows 8
– Offers same default screen
• All devices running the operating system
– Laptop or desktop users
• Can switch between tile-populated Start screen and
Desktop screen
• Windows Task Manager
– Open: press and hold Ctrl, Alt, and Delete keys
together
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(figure 14.13)
Using the Task Manager, users can view the system status, assign
priorities, and more.
© Cengage Learning 2014
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(figure 14.14)
The resource monitor offers running statistics for this session.
© Cengage Learning 2014
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User Interface (cont’d.)
• Command-line interface
– Available from most Windows desktops
– Use Help feature: learn a command’s syntax
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(table 14.4)
Selected commands that can be used in the Command Prompt
Window. For a complete listing, see your technical documentation or
www.microsoft.com.
© Cengage Learning 2014
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User Interface (cont'd.)
• Helpful Windows features
– Built-in input methods and fonts for many languages
• Accommodates users working in non-English
languages
– Enhanced accessibility options
• On-screen keyboard
– Other tools: magnifier, a narrator, speech recognition,
etc.
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Conclusion
• Windows operating systems
– Started as a microcomputer operating system
– Now includes complex multiplatform software
• Run computing systems of all sizes
• Windows 8
– Singular interface
• Both touch screens and traditional computers
• Windows recognized as:
– Powerful operating system
– Significant market force
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