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Overview
• In this chapter, you will learn to– Identify and explain the basic functions of an
operating system– Identify the features and characteristics common to
all Windows PCs– Identify and differentiate the features an
characteristics of Windows 9x/Me– Identify and differentiate the features an
characteristics of Windows NT/2000/XP
Functions of an Operating System
• Communicate with hardware• Provide a user interface• Provide a structure for access to
applications• Enable users to manipulate programs
and data
Operating System Traits
• An OS works only with a particular type of processor
• An OS begins running as soon as the PC finishes its POST
• Application programs cannot run on a PC without an OS– The OS provides a set of application programming
interfaces (APIs)
• An OS must be able to use new software and hardware
Communicating with Hardware
• The system BIOS is programming code that tells the computer how to talk to basic hardware– The OS works with the BIOS to talk to these devices– When the BIOS does not know how to talk to a
piece of hardware, the OS talks directly to the device
• Most OS’s use device drivers provided by the manufacturer (Bring Your Own BIOS) to interpret the language necessary to talk to a new device
– When there’s a problem, the OS should provide error handling or at least error notification
Creating a User Interface
• A user interface needs to– Show what applications are available– Provide an easy way to access those applications– Provide a way to label and save the data generated
using the application– When a program starts, the user interface must
disappear and allow the application to take over the screen
• While the application is running, the OS must provide access to hardware as needed
• When the application is shut down, the OS must return the user to the user interface
Organizing Programs and Data
• The OS must be able to organize programs and data– What is data and how can we distinguish between
different types of data?– What are programs and what type of program is it?– How can I distinguish the various places to store
the data or programs?– How can I efficiently retrieve the data or program?
• Command Line– Character-based or
text-based– Disk Operating System
(DOS)– Single-tasking– DOS consists of
• IO.SYS• MSDOS.SYS• COMMAND.COM
– DOS configuration files• CONFIG.SYS• AUTOEXEC.BAT
• Graphical User Interface (GUI)– Not necessarily the OS– Win95, Win98, Win31
ran on top of DOS– Apple’s OS 9 and OS X
operate only as a GUI– WinNT, Win2K, WinXP
are GUI operating systems with a command line built in
Operating System Implementations
User Interface
• Login– Every version of Windows supports multiple users– Requiring a user login increases security
• Desktop– Primary interface to the computer
• Taskbar and Start Menu– Runs along the bottom of the desktop and
includes up to four sections• Start menu allows access the installed programs• System tray shows programs running in the background• Quick Launch enables you to launch often-used programs
with a single click
User Interface
• My Computer– Provides access to drives, folders, and files– Customizable: may display different views, show
hidden files, hide file extensions, and more
• Windows Explorer– Another utility for accessing drives, folders, and
files
• My Documents– My Pictures, My Music, My Videos
User Interface
• Recycle Bin– When you delete files they are sent to the Recycle
Bin, a special folder just in case you change your mind
• Network Neighborhood or My Network Places– Shows the current network connections available to
you
Tech Utilities: Control Panel
• Maintenance, upgrade, and configuration aspects of Windows– StartSettingsControl Panel– Contains programs, called applets– Any icon in the Control Panel is a file with a CPL
extension• If Control Panel won’t start, one of these is probably corrupt
– rename each one until you find the bad one
– Each applet displays text that helps to explain its functions
Tech Utilities: Device Manager
• Device Manager is a primary tool for dealing with devices and device drivers in Windows– A red “x” or a yellow exclamation
point is displayed, if Windows detects a problem
– Devices are organized in special groups called types
– Access thru the System applet in Control Panel
Tech Utilities: System Tools
• System Tools is a collection of tech utilities found on the Start menu– Start Programs Accessories System Tools
Tech Utilities: Command Line
• Command Line– Start Run command– Windows 2000/XP offer you a more powerful
command line: Start Run cmd
Tech Utilities: MMC
• Microsoft Management Console (MMC)– A shell program that holds individual utilities called
snap-ins– Start Run mmc– You start with a blank console and then add snap-
ins – then save the new customized console you created
• File Add/Remove Snap-ins Add
Tech Utilities: Adminstrative Tools
• Administrative Tools– A folder that holds many pre-defined MMC consoles
built by Microsoft– Go to Control Panel and click on Administrative
Tools– The three most used Administrative Tools are
• Computer Management• Event Viewer• Performance
Tech Utilities: Computer Management
• Computer Management– A pre-defined MMC that pulls together snap-ins
related to many computer management options
Tech Utilities: Performance
• Performance– System Monitor may show real time data– Performance Logs and Alerts
Services
• Services– Separate programs that handle a lot of functions for
Windows– Found in Administrative Tools– Double-click on any service to examine its
properties and settings– Services start automatically, manually, or may be
disabled
• System Folder– Folder where the OS files were installed– %systemroot%– %windir% for Win9x
System Folder
What is the Registry?
• Registry – A unified database where Windows stores all
hardware and software configuration information for the local computer
•Hardware, central processor, keyboard, mouse, etc.•Device drivers•Applications•Network protocols•NIC settings•User account information like group membership, rights and permissions
Registry Editors
• Regedit– Clearly better in key searching down to the value
of the keys– Used by Windows 9x/Me– Also installed in Windows NT/2000/XP
• Regedt32– Used by Windows NT/2000/XP Better for adding
keys and modifying their values– Searches only down to keys and subkeys – not
values
• When using the Registry Editors, be very careful!– Does not recognize syntax or semantic errors– May prevent your operating system from loading
Registry
• The Registry has six main groups , or root keys shown below
HKEY_DYN_DATA is used in Windows 9x – not 2000 or XP
HKEY_LOCAL_MACHINE
• Configuration data about local computer– Used by applications, device drivers and Windows– Determines which device drivers and services load
during startup– Same regardless of user
HKEY_USERS
• Stores all the personalization information for all users on the PC
• Subkeys are:– DEFAULT subkey
• System default profile used when Ctrl+Alt+Del logon screen is displayed
– Security identifier (SID) of user currently logged on the computer
HKEY_CURRENT_USER
• Data about user currently logged on interactively– Copy stored for each user account that has ever
logged on to the computer in systemroot\Profiles\user_name in Ntuser.dat
– Points to same data as under HKEY_USERS\SID_of_the_currently_logged_on_ user
– Takes precedence over duplicate settings in HKEY_LOCAL_MACHINE
HKEY_CLASSES_ROOT
• Information about file associations and data associated with COM objects (Component Object Model – OLE)– Points to CLASSES subkey under
HKEY_LOCAL_MACHINE\SOFTWARE
HKEY_CURRENT_CONFIG
• Data about active hardware profile– Extracted from SOFTWARE and SYSTEM keys of
HKEY_LOCAL_MACHINE
Virtual Memory
• All versions of Windows use virtual memory
• Windows swap files are used to implement virtual memory– Windows sets the initial size of the swap file
automatically according to the free space available on the C: drive
– The swap file in Windows 9x is called WIN386.SWP; it is known as PAGEFILE.SYS in Windows 2000
Virtual Memory
• When you need to run another program but your RAM is filled up, Windows will offload something that hasn’t been used recently from RAM to the hard drive into a swap file to make room
• If you need to access the data that was offloaded into RAM, Windows will retrieve it from the hard drive
Essential Windows
• You should already have basic user skills in Windows. As a review check out Essential Windows on line at www.totalsem.com
Windows
• Windows 3.1 was a graphical shell that ran on top of DOS
• Microsoft debuted Windows 95 as its first standalone GUI operating system
• Windows 9x and Me followed in later years– Many files and configuration utilities were held over
from earlier OSs
The Windows Boot Process
• Windows 9x is a combination of the DOS protected-mode interface (DPMI) and a protected-mode GUI– Windows 9x first starts the DOS aspect of Windows
and then the GUI– Booting Windows 9x without the GUI from the boot
menu is different than running a DOS window inside Windows 9x
FAT32
• Later versions of Windows 95 and all versions of Windows that followed support the FAT32 file format– Partitions up to 2 terabytes in size
Long Filenames
• Windows 9x/Me – Allows long file names up to 255 characters in
length• Removed the old 8.3 filename limitation of DOS
– Adopted the 16-bit unicode character set• Unicode supports 65,536 characters• ASCII used by DOS was 8-bits and supported only 256
characters
DPMI Core Files
• IO.SYS – Combined the previous IO.SYS and MSDOS.SYS into
IO.SYS
• MSDOS.SYS – Used as a startup options file – read-only, hidden
text file in root directory
• COMMAND.COM – Not needed if the system will always run in the GUI
mode
Boot Menu
Press F8 (or the left Ctrl key in Windows 98) when “Starting Windows..” appears to access the Boot Menu
Boot Menu
• Normal• Logged
– Creates a bootlog.txt file detailing the boot up process
• Safe mode– Only the OS, mouse, keyboard, and VGA video
drivers are loaded– Useful when Windows won’t boot due to a bad
driver
• Safe mode with network support• Step-by-step confirmation
Boot Menu
• Command prompt only– Does everything but start the GUI– Just type win to start Windows
• Safe mode command prompt only– Skips all startup files– Must reboot to start Windows
• Previous version of MS-DOS– Useful only if you installed Windows over a true
DOS system
MSDOS.SYS
• MSDOS.SYS– Hidden, read-only text file that replaces many of
the CONFIG.SYS and AUTOEXEC.BAT functions– Edit using any text editor (after unchecking its
attributes)– Organized like an INI file with groups and options
under each setting– There are many useful options in the [Options]
group – see pages 429-430 in the book for a listing
Configuration Files
• Windows 9x/Me will use CONFIG.SYS and AUTOEXEC.BAT to load legacy device drivers and terminate and stay resident (TSR) programs
Legacy GUI Files
• After the DPMI-level OS files, configuration files, and utilities load, WIN.COM runs and initiates the graphical portion of the OS– Incorporates legacy INI files to provide support to
older applications– INI files are text files that may be edited with any
text editor such as Notepad– INI files are broken in sections called groups– Two main INI files from Windows
3.1 that still exist in later versions of Windows are SYSTEM.INI and WIN.INI
SYSTEM.INI
• All resources were initialized in the SYSTEM.INI file in Windows 3.1– SYSTEM.INI still exists in Windows 2000/XP today to
provide backward compatibility– Windows 9x/Me require SYSTEM.INI
WIN.INI
• WIN.INI provided the personalizations of Windows 3.1– Rarely have a WIN.INI in Windows 9x/Me/2000/XP
• Dealing with SYSTEM.INI and WIN.INI is usually not necessary– Unless you get error messages indicating a device
driver can’t be found• Just find the culprit and put a semicolon in front of the line
to disable it
– There are two lines in WIN.INI that may cause problems
• LOAD= and RUN= that automatically loads programs when Windows starts
The Windows 9x GUI Architecture
Real-mode drivers are loaded by config.sys or autoexec.bat. Protected mode drivers are loaded with the GUI
Virtual Memory ManagerInstallable File System
Core functions handled by the Kernel, Graphical Device Interface, and User modules
User interface
• Windows 98 is basically Windows 95 with a lot of new toys to improve usability or to address bugs
• A startup disk is a special bootable floppy disk that contains utilities to help you fix a system that won’t boot Windows– Both 95 and 98 allow you to make a startup
disk• 95’s does not support a CD-ROM• 98’s supports almost all CD-ROMs
Major Difference Among Windows
Major Difference Among Windows
• FAT32 is supported in all Windows versions except the first version of Windows 95
• System Information Tool– Provides a launch point for almost every Windows
98/SE/Me utility
• Windows Update– Utility to keep
Windows up to date– Found on the
Start menu
• Disk Cleanup Utility• Active Desktop
– Load active web pages on your desktop
– Vastly improved version of Internet Explorer
Major Difference Among Windows
• Internet Connection Sharing– Included since Windows 98 SE– Enables multiple PCs to share an Internet
connection
• System Restore– Windows Me shares the core files and structure of
Windows 9x but has the look and feel of Windows 2000
– Enables you to create Restore Points that will take your system back to its previous state at a given point in time
Major Difference Among Windows
Windows NT
• Microsoft released Windows NT in 1996• High-performance 32-bit GUI OS• Windows 2000 and XP share the same
core structure, files, and features but differ in ease of use and hardware support
• Windows NT looks like Windows 95 but that’s where the similarities end
OS Organization
• Robust, scalable, cross-platform• Object-oriented approach designed to
support multiple platforms such as x86, DEC Alpha, MIPS, and PowerPC by using a Hardware Abstraction Layer
• Robustness comes from separating process and running them in various subsystems
• Supports symmetric multiprocessing (SMP) allowing support for up to 32 CPUs
NT File System (NTFS)
• NT File System (NTFS)– Robust and powerful– Long filenames containing up to 255 characters– Advanced FAT called the Master File Table (MFT)– Keeps a backup copy in the middle of the drive
which shows up as a small, immovable chunk of data when you defrag
– Backwards compatible with DOS and Windows 9x– Transaction logging determines incomplete file
transactions, and restores the file back to the original format automatically and invisibly
NTFS Security
• To gain access to a Windows NT/2000/XP system, you must have a valid user account and password– Every Windows NT/2000 PC has an administrator
account that has full access to everything– Create users using Users and Passwords in
Windows 2000 or User Accounts in Windows XP
Groups
• A group is a collection of user accounts that share the same access capabilities– Assign access to a group and then put users into
the group– Users will inherit the access assigned to the group– Windows provides several built-in groups
• Administrators– May perform all
administrative tasks on the computer
• Backup Operators– May use Windows
Backup
• Guests– May perform only
specific tasks that are granted
– Guest account is a member
• Power Users– May create and modify
local user accounts and share resources on the local computer
• Replicator– Supports file replication
in a domain• Users
– May perform only tasks specifically assigned
– Local user accounts that are created become members
• Everyone
Built-in Groups
NTFS Permissions
• NTFS permissions in NT/2000/XP– Details every user and group that has access to a
file or folder– Lists the specific level of access allowed– Available only on volumes formatted as NTFS– NTFS security is effective whether a user
• Gains access at the computer• Gains access over the network
NTFS Permissions
• Ownership– When you create a new file or folder you become
the owner– Owners have full control– Be default, everyone is given full control permission
• Take Ownership– Enables a user permission to take ownership of a
file or folder– Administrator account can take ownership without
being given permission
NTFS Permissions
• Change permission– Can give or take away permissions for other
accounts
• Folder permissions– Apply to folders
• File permissions– Apply to files
NTFS Folder Permissions
• Full Control– Enables you to do anything you want– To deny all access, deny Full Control
• Modify– Cannot delete files or subfolders but may modify
them
• Read & Execute– Enables you to see the contents of the folder and
subfolders
• List Folder Contents– Enables you to see the contents of the folder and
subfolders
NTFS Folder Permissions
• Read– Enables you to read any files in the folder
• Write– Enables you to write to files and create new files
and folders
• By default, permissions are inherited from parent folders– This may be prevented by removing the check
mark at the bottom
NTFS File Permissions
• Full Control– Enables you to do anything
• Modify– Enables you to do anything except take ownership
or change permissions
• Read & Execute– If the file is a program, you can run it
• Read– If the file is data, you can read it
• Write– Enables you to write to the file
• User’s effective permissions are the cumulative (or least restrictive) permissions resulting from a combination of user and group permissions
• Deny permission overrides all other permissions…Deny always becomes the effective permission
• File permissions override folder permissions
Combining Permissions
Booting Up vs. Going Graphical
• Windows 9x and Windows 2000 differ significantly in the level of integration between the graphical interface and the text-based functions
• Both operating systems have primary boot files that start the operating system
• The boot file must be on the boot partition and the GUI file can be installed in any other drive letter– Microsoft terminology for NT/2000
• System partition: partition you boot from• Boot partition: partition that holds NT or 2000 files
Booting Up vs. Going Graphical
• Windows NT and Windows 2000 do not have a pure command prompt environment
• Windows NT can log on to the command prompt only after the GUI is started
Preboot Sequence
1. The computer runs power-on self test (POST) routines to determine the amount of physical memory, hardware components, and so on
2. The computer BIOS locates the boot device and loads and runs the master boot record (MBR)
3. The MBR locates, loads into memory, and executes the boot sector
4. The computer loads and initializes the NTLDR file
The Boot Process
• NT Loader manages the booting process– Windows NT/2000/XP boot files that must be in the
root directory of the system partition are• NTLDR (NT Loader)• BOOT.INI• NTDETECT.COM• NTBOOTDD.SYS (only needed for SCSI controllers that don’t
have their own ROM BIOS)
• After the boot files start the PC, NTLDR passes control to the Windows NT kernel (NTOSKRNL.EXE)– The GUI begins to load
Boot Files: NTLDR
• NTLDR (NT Loader) manages the boot up process until control is handed over to NTOSKRL (NT kernel)– To find available operating systems, NTLDR reads
the boot.ini file– If multiple OSs are available a menu shows up
Boot Files: BOOT.INI
• BOOT.INI is a text file that lists the available OSs and where to find the boot partition
More Boot Files
• BOOTSEC.DOS is read by NTLDR if it finds a different OS to load
• NTDETECT.COM detects the hardware if you choose to boot to NT/2000/XP
• NTBOOTDD.SYS is used if NTLDR detects that the boot partition resides on a SCSI drive that lacks a ROM chip for BIOS support
Service Packs
• Windows NT uses service packs to fix operating system bugs and limitations in the architecture
Major Differences among Windows NT, 2000, and XP
• Windows 2000 combines an improved NT core with the ease-of-use and tech-friendly elements from Windows 9x– The robustness of NT with the Windows 98 user
interface
• Windows XP extended that merger into a fully new OS
• User organization is better to enhance file and folder security
• NTFS 5.0 added encryption, mount points, disk quotas, and dynamic disks to NT’s NTFS 4.0
• Easier administration through Microsoft Management Console and the Computer Management tool
• Windows XP improved upon 2000 by adding built in support for burning CDs, an improved Start menu, and the Windows Update utility
• Windows XP has the Files and Settings Transfer Wizard that allows you to transfer everything from an old drive to a new one (get the update before using)
Major Differences among Windows NT, 2000, and XP
• Windows XP comes with System Restore to take a snapshot of your system in order to restore it to its previous state
• Driver Rollback enables you to rollback individual device drivers in Windows XP
• Remote Assistance is possible with Remote Access– Gives you the ability to take control of any Windows
XP PC remotely
Major Differences among Windows NT, 2000, and XP