Ch. 10: Windows 2000

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Ch. 10 Windows 2000 Linux

• History
• Design Goals
• Memory Management
• Processor Management
• Device Management
• File Management
• User Interface

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Windows 2000
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History

• Windows products began as interfaces created by
  Microsoft Corporation for desktop computer users.
• Began as front-end for MS-DOS.
• Windows 2000 is descendant of Windows-NT.
• Eventually grew into complex network operating
  system.

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Design Goals for Windows 2000

• Influenced by several OS models used
  already-existing frameworks with new features
• Uses client/server model to provide variety of OS
  environments (Windows, MS-DOS, OS/2, POSIX).
• Uses object model to manage OS resources
  consistently allocate them to users.
• Uses symmetric multiprocessing (SMP) to achieve
  maximum performance from multiprocessor
  computers.
• To accommodate various user needs optimize
  resources, 5 design goals identified
  extensibility, portability, reliability,
  compatibility, performance.

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Design Goal 1 Extensibility
Design Goal 2 Portability
Design Goal 3 Reliability
Design Goal 4 Compatibility
Design Goal 5 Performance
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Memory Management

• Every OS uses own view of physical memory makes
  its application programs access memory in
  specified ways.
• Challenge for Windows 2000 to run application
  programs written for Windows, MS-DOS, POSIX, or
  OS/2 without crashing into each other in memory.
• Each environment subsystems provides view of
  memory that matches what applications expect.
• In Windows 2000, OS resides in high VM users
  code data reside in low VM.
• All user-accessible memory paged to disk segment
  of system memory labeled paged pool.
• Non-paged pool never paged to disk since stores
  critical NT objects.

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Processor Management

• Goal of NTs executive process manager --
  provide a set of native process services that
  environment subsystems can use to emulate their
  unique process structures.
• Differences between native NT processes those
  in other OS
• NT processes implemented as objects accessed
  using object services.
• NT process have multiple threads executing within
  address space.
• Process objects thread objects have built-in
  synchronization capabilities.
• NT process manager doesnt maintain parent/child
  or other relationships among the processes it
  creates.

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Device Management

• I/O system
• Accommodate needs of existing devices.
• Consider future storage and input technologies.
• Provide uniform high-level interface for
  executive-level I/O operations.
• Protect application programs from differences
  among physical devices.
• Shields rest of OS from details of device
  manipulation minimizes isolates
  hardware-dependent code.

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File Management

• Windows 2000 be independent of file system on
  which it operates.
• Supports multiple file systems including MS-DOSs
  FAT file system, OS/2s high performance file
  system (HPFS).
• NT file system (NTFS) extends capabilities of FAT
  HPFS file systems by adding
• File system recovery for quick restoration of
  disk-based data.
• Ability to handle large storage media (e.g,
  approx. 17 billion GB).
• Security features, including execute-only files.
• Unicode filenames.
• Support for the POSIX OS.
• Features for future extensibility (e.g.,
  transaction-based operations for fault-tolerant
  applications, user-controlled version numbers,
  multiple data streams per file, flexible options
  for file naming/ attributes, support for
  popular file servers.)

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File Management 2

• Supports CD-ROM file system, eliminating need for
  MSCDX patch to file system required by all CD-ROM
  drives used with MS-DOS.
• NTFS advanced server emulates Macintosh file
  system handles network services as though they
  were file systems.
• Windows 2000 provides access to files on LAN
  manager network through a file system called
  redirector.
• Accepts requests for remote files directs them
  to a LAN manager server on another machine.
• Windows 2000 is capable of running all of these
  file systems simultaneously.

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USER INTERFACE
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Start Menu Functions

• Programs launches applications directly.
• Documents launches applications through a
  recently-used data file.
• Settings directly accesses key system settings.
• Search initiates a searching routine.
• Help goes directly to help file.
• Run can be used to run application from command
  line screen or browse function.
• Shut Down logs out, temporarily exits, shuts
  down, or restarts OS.

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Windows Explorer

•  A standard utility program contains directory
  file display tools file finding tool.

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Pull-Down Menus In Windows Explorer

• File contains menu items for creating new folders
  and creating shortcuts to applications.
• Edit contains menu items for undoing, cutting,
  pasting, and selecting files and directories.
• View shows options used to customize the way the
  page looks.
• Favorites shows a list of favorite web sites,
  customizable by the user.
• Tools contains helpful tools including a file or
  folder search capability and a network mapping
  function.
• Help accesses the hypertext help system.

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Windows 2000 Interface

• Program items can also be data files.
• Can use commands within file menu to move, copy,
  delete icons from Program Managers desktop.
• Provides many keyboard shortcuts to help users
  navigate, if the mouse becomes impaired.
• Accommodates users working in non-English
  languages.

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Linux
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Linux

• Developed in Finland, by Linus Torvalds in 1991. 
• Linux was based on UNIX, multi-platform OS.
• Brought speed, efficiency flexibility of UNIX
  to a PC environment.
• Open-source program -- source code is freely
  available to anyone for improvement.
• Under constant development by uncounted people
  around world.
• Linux is not UNIX, its clone.
• Linuxs ncurses (new curses) -- screen handling
  library that improved on curses libraries
  featured in UNIX Release V.
• First used by programmers at universities and
  research environments, but becoming widely
  adopted in commercial industrial markets.

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Linux Design Goals
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Linux Memory Management

• Allocates memory space to each process.
• Address space divided process code, process
  data, code shared library data used by process,
  stack used by process.
• When process begins execution its segments have
  fixed size but sometimes process handles
  variables with unknown number size.
• System calls change size of process data segment
  (expanding it to accommodate extra data values or
  reducing it when certain values positioned at end
  of data segment no longer needed).

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Linux Memory Management - 2

• Memory protection based on type of info stored in
  each region belonging to process address space.
• If process modifies access authorization assigned
  to a memory region, kernel changes protection
  info assigned to corresponding memory pages.
• When process requests pages, Linux loads them
  into memory.
• When kernel needs the memory space, pages are
  released using a least recently used (LRU)
  algorithm.

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Linux Memory Management - 3

• Linux maintains dynamically managed area in
  memory (page cache) where new pages inserted or
  old pages deleted.
• If necessary, Linux deactivates swap devices
  without rebooting.
• To track free/busy pages, uses system of page
  tables.
• With certain chip architectures, memory access
  uses segments.
• Uses VM mechanism provided by processor on which
  it is executing, converting virtual addresses
  into physical addresses.

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Linux Processor Management

• Linux scheduler scans list of processes in READY
  state uses predefined criteria to choose which
  process to execute.
• 3 different scheduling policies 1 for "normal"
  processes, and 2 for "real time" processes.
• Each process has associated process type, fixed
  priority variable priority.
• Used by scheduler to determine which scheduling
  policy used on processes in READY queue.

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Linux Device Drivers

• Building on UNIX architecture, each device has
  special section in kernel (device driver).
• Includes all instructions necessary to
  communicate with device.
• When new device is developed, it can be used with
  Linux by writing its own device driver.
• Instructions for talking to devices are loaded as
  needed (seldom used devices) or can be kept in
  memory all the time when OS system boots.
• Although device files may be kept anywhere on
  file system, kept in /dev directory.

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Linux File Management

• All Linux files organized in directories
  connected to each other in treelike structure.
• Linux specifies 5 types of files used by system
  to determine what file is to be used for.

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Linux User Interface

• Linux can be used in command-based mode.
• Also has built-in GUI support for X-Windows
  developed at MIT as part of Athena project.
• Windows Application Binary Interface (Wabi)
• Linux tape archive utility is significant
  improvement over UNIX tar utility.
• Features built-in error recovery.
• Accommodates both command line interface and
  menu-driven GUI.