Operating Systems Domains

OS Fundamentals part 1


1.1 Identify the operating system’s functions, structure, and major system files to navigate the operating system and how to get to needed technical information.

Major Operating System functions

Create folders In explorer click on the drive or folder you want to create the new folder in, next choose the file menu, click new, and then folder.

Checking OS Version

Windows 3.x or Windows NT 3.51

  • From program manager click help, and about to get version, or from DOS type winver.

Windows 95/98/ME/2000/CE

  • Control Panel /System / in the General tab. Or right click My Computer Icon, or from a DOS prompt type ver.

Windows NT 4.0

  • You need administrator or Power User rights , /Administrative Tools / Windows NT Diagnostics / Under the version tab. This will tell you the Version of NT also which service pack is installed.

Major Operating System components

Explorer.exe is the default shell of Windows, just as command.com is the shell of DOS. Explorer controls all direct interaction between the user and windows. It determines what you see on the screen and what you use to work with it. The desktop, my computer, start menu, and the windows explorer file manager etc. are all part of explorer.

My Computer When you double click the icon you can access drives, printers, and other systems folders from here. Also by right clicking a drive icon in my computer, you can access sharing (if file and print sharing is enabled) where you can set security for that drive.

If you right click the icon for my computer on the desktop, and select properties you can access version info, the device manager, hardware manager, and system performance settings.

Control Panel


  • Accessibility Options. You can adjust keyboard, sound, display, mouse, and other settings easier to use for people with disabilities.
  • Add New Hardware. Use this wizard to configure newly installed hardware through auto detection or by selecting the corresponding driver from a list. 
  • Add/Remove Programs. You can install/uninstall programs from here. Add components from the Windows setup disks, or create a new startup disk. 
  • Display. Change background and screen saver choices. Modify settings for on-screen fonts, colors, color palette, and so on.
  • Fonts. View installed fonts or install new fonts.
  • Passwords. Change Passwords, security options, enable/disable remote administration.
  • Keyboard. Change options for the style of keyboard you use and for the rate at which the characters you type are displayed.
  • Modems. Add a new modem. Also use this tool to configure or diagnose installed modems. 
  • Mouse. Change mouse or pointer options. 
  • Multimedia. Change options for audio playback and recording, MIDI output and schemes, and CD playback volume. Use the Advanced properties to install or configure multimedia hardware, drivers, and codecs. 
  • Printers. Add a new printer or configure existing printers. 
  • Sound. Create or modify sound events for windows.
  • Network Settings. Configures network hardware/software
  • Regional Setting. Change how numbers, dates, currency, and time are displayed
  • System. Information about hardware on your computer.

Contrasts between Windows 9X and Windows 2000

Windows 2000

  • Windows 2000 is actually Windows NT 5.0
  • designed to run in a secure network environment
  • Comes in a server version
  • Supports fat, fat32, and the NTFS file system, which improves security, and performance.
  • Compression which allows you to compress individual files or folders instead of whole volumes.
  • Encrypting File System allows users to encrypt individual files or folders.
  • AutoComplete for most dialog boxes that accept paths and file names.
  • My Network Places Folder replaces Network Neighborhood which makes locating network resources easier and faster.
  • More stable

System, Configuration, and User Interface files

IO.SYS Found in the root directory. DOS has two hidden system files. The first, IO.SYS, which must be the first entry in the root directory. MSDOS.SYS is the second entry.

Windows 9x uses a new, IO.SYS, which replaces the DOS system files IO.SYS and MSDOS.SYS. This real-mode operating system file contains the information needed to start the computer. Your computer no longer needs CONFIG.SYS and AUTOEXEC.BAT to start the Windows 9x operating system (these files are preserved for backward compatibility with certain applications and drivers).

Most of the common functions provided by the CONFIG.SYS are now provided by default in the windows version of IO.SYS. The following lists the common entries in CONFIG.SYS that are now incorporated into IO.SYS for Windows 9x.

  • dos=high
  • himem.sys
  • ifshlp.sys
  • setver.exe
  • files=
  • lastdrive=
  • buffers=
  • stacks=
  • shell=
  • fcbs=

The values in Io.sys cannot be edited, to override values in Windows 9x Io.sys, place the entry in Config.sys with the value you want. For example Io.sys does not load Emm386.exe. If any of your applications requires expanded memory or loads data into the high memory area, EMM386 must be loaded in Config.sys.

BOOT.INI Used in Win NT and 2000 (see below)

WIN.COM performs checks and loads the core components of Windows. (Kernel, User and GUI) If windows is not shut down properly, WIN.COM will run Scandisk. You can type WIN at the command prompt to start Windows.

MSDOS.SYS is a hidden system file,found in root directory. It contains settings that are processed during startup. Windows renames the DOS version to msdos.dos and replaces it with its own version (see above). It is divided into two sections.

Example MSDOS.SYS file

Defines the location of the Windows 9x Windows directory as specified during Setup.
Defines the location of the necessary startup files. The default is the directory specified during Setup.
Defines the location of the boot drive root directory.
Enables dual-boot capabilities. The default is 0. Setting this value to 1 enables the ability to start MS-DOS by pressing F4 or by pressing F8 to use the Windows Startup menu.
Enables automatic graphical startup into Windows 9x. The default is 1.
Enables ScanDisk to run automatically when your computer restarts. The default is 1. When this value is set to 1, ScanDisk will run automatically, setting this value to 0 disables this feature. 
Enables display of the animated logo. 

AUTOEXEC.BAT Stands for automatically executed batch file, the file that DOS automatically executes when a computer boots up. You can put commands in this file that you want to execute when your computer executes.

Win 9x does not need this file but includes it for compatibility with some older programs that use it.

CONFIG.SYS DOS configuration file which loads the device drivers, not necessary to run Windows but retained for backward compatibility.

Memory management

Conventional 1k-640k it is used by DOS for applications and TSR's.(Terminate and Stay Resident) programs.

Upper memory 640k-1024k loads DOS device drivers in Upper memory to free up conventional memory for DOS applications.

High memory 1024k - 1088k Reserved for use by single application.

Extended memory 1088k and above allows DOS applications to be able to access RAM outside of the first 640k.

Virtual memory refers to the fact that the operating system can actually allocate more memory than the computer physically contains. This memory is actually hard disk space in the form of a windows swap file.

HIMEM.SYS Extended memory manager. Coordinates the use of your computer's extended memory including the HMA so that no two applications or device drivers use the same memory at the same time.

EMM386.exe Provides access to the upper memory area and uses extended memory to simulate expanded memory.

Windows 9x

IO.SYS The win 95 file IO.SYS, replaces both of the DOS IO.SYS and MSDOS.SYS files. This file contains the information needed to start the computer. You no longer need CONFIG.SYS and AUTOEXEC.BAT to start Windows, but these files are kept for some drivers and programs that use still them.

The drivers loaded by default in win 9x IO.SYS include :


Most of the entries that used to be in your CONFIG.SYS are now included in the win 9x IO.SYS

IO.SYS does not load EMM386.EXE. If any application requires expanded memory , EMM386 must be loaded in CONFIG.SYS. To override default values in Windows 95 IO.SYS enter the value you want in your config.sys

WIN.INI This used to contain user and program settings. The registry replaces the basic functions of the ini files used in earlier versions of Windows, the System.ini, WIN.INI, and Winfile.ini. Windows 9x keeps these files for backward compatibility with 16 bit applications that can not access the windows registry.

User.dat Is one of three files that make up the windows registry. It is located in c:\windows directory , but if User Profiles are enabled then users may have there setting stored in c:\windows\profiles

USER.DAT contains the following settings:

  • Logon names
  • Desktop settings
  • Start menu settings

The other two files that make up the registry are:

System.dat Contains all the hardware configuration, Plug and Play settings, and application settings. It is located in c:\windows as a hidden file.

Policy.pol May override any settings contained in the other two registry files. And can contain additional data specific to a network .You do not need Policy.pol to run windows.

SYSEDIT System Configuration Editor , can be found in c:\windows\system. This program allows you to edit protocol.ini, System.ini, win.ini, config.sys, and your autoexec.bat files.

SYSTEM.INI In win 3.1 hardware setting were found here. Most configuration options for Windows 9x are now stored in the Registry and are no longer required in SYSTEM.INI. but this file is retained for backwards compatibility.

MSCONFIG (98) This is the System Configuration Utility located at c:\windows\system\msconfig.exe. This program lets you troubleshoot system configuration problems, by removing entries with check boxes, reducing the chance of typing errors which may happen if you use Notepad or the System Configuration Editor. It also allows you to create a backup of your system files before you change anything. It allows you to remove programs that are automatically started when windows starts.

COMMAND.COM DOS file that contains the DOS command processor, receives and executes operating system commands

REGEDIT.EXE Registry Editor is a tool for displaying and editing the registry database. It is located in c:\Windows directory . If you are running win 2000 you should use regedit32 instead.

SYSTEM.DAT Contains all the hardware configuration, Plug and Play settings, and application settings. It is located in c:\windows as a hidden file.

RUN COMMAND where you enter a command in the windows run box interpreted by windows not DOS

COMMAND LINE PROMPT where you enter a command in DOS which is interpreted and executed by command.com i.e.: c:\copy

Windows 2000

BOOT.INI Contains information that NTLDR reads on how to load win 2000 The BOOT.INI file has two sections, boot loader and operating systems.

BOOT.INI contains the information that you see on the bootstrap loader screen , and if you have more than one OS gives you the choice of which OS to start.

REGEDT32 (32-bit) win 2000 registry editor and is installed in the systemroot\system32 folder.

REGEDIT win 9X registry editor, installed in the systemroot folder. REGEDIT is included with 2000 primarily for its search capability. You can use it to make changes in the registry, but not all functions or data types can be viewed or edited properly. Microsoft recommends that you use REGEDIT.EXE only for its search capabilities and that you use Regedt32.exe when it is necessary to edit the registry.

REGEDIT does not provide the following functions or capabilities:

  • cannot set the security for registry keys.
  • cannot view or edit the value data types REG_EXPAND_SZ and REG_MULTI_SZ.

RUN CMD Click start button choose run type program you want to run or use the browse button.

Win 2000 also has a command called RUNAS , which allows a user to run specific tools and programs with different permissions than the user's current logon provides.

Syntax : RUNAS [/profile] [/env] [/netonly] /user:UserAccountName program


  • /profile Name of the user's profile.
  • /env Specifies that the current network environment be used instead of the user's local environment.
  • /netonly Indicates that the user information specified is for remote access only.
  • /user: UserAccountName Name of the user account under which to run the program. Format should be user@domain or domain\user.
  • program The program or command to run using the account specified in /user.

NTLDR is the bootstrap loader for win 2000 , and is responsible for the following operations

  • Enabling the user to select an operating system to start.
  • Loading the operating system files from the boot partition.
  • Controlling the operating system selection process and hardware detection prior to the Windows 2000 kernel initialization.

NTLDR and the following files must be in the active partition of your hard drive.

  • Ntdetect.com
  • Bootsect.dos (if you plan to boot more than one operating system on your computer)

NTDETECT.COM detects installed hardware during the win 2000 startup sequence. It passes this information to NTLDR and places a list in the registry. Ntdetect.com detects the following components:

  • Computer ID
  • Bus/adapter type
  • SCSI adapters
  • Video adapters
  • Keyboard
  • Communication ports
  • Parallel ports
  • Floppy disks
  • Mouse/pointing device
  • Floating-point coprocessor

NTBOOTDD.SYS Needed only if you are using a SCSI-controlled boot partition, and the SCSI adapter does not have a SCSI BIOS enabled.

Command Prompt Procedures (Command syntax)

DIR Displays a list of files and sub directories in a directory.
Syntax: DIR [drive:] [path] [filename] [/Switches]


  • /A all (including hidden and system) files and sub directories in the specified directory are displayed.
  • /S Displays files in the specified directory and all its sub directories
  • /W Wide list format. File and directory names are listed in 5 columns
  • /B Bare format. Files and directories are listed in a single column without header, summary, or any details.
  • /L Output is in lowercase.
  • /P Pauses with each screenfull of information. Press any key to see the next screen.
  • /V Verbose mode. This displays attributes, date last accessed, and disk space allocated for each file, in addition to the standard information.

ATTRIB Displays or changes file attributes.

attrib [+r|-r] [+a|-a] [+s|-s] [+h|-h] [[drive:][path] filename] [/s[/d]]

  • +r Sets the read-only file attribute.
  • -r Clears the read-only file attribute.
  • +a Sets the archive file attribute.
  • -a Clears the archive file attribute.
  • +s Sets the file as a system file.
  • -s Clears the system file attribute.
  • +h Sets the file as a hidden file.
  • -h Clears the hidden file attribute

VER Displays OS version , VER /r also displays revision and if DOS is in HMA.

MEM Displays information about allocated memory areas, free memory areas, and programs that are currently loaded into memory in DOS subsystem

mem /program or mem /p
/program Displays the status of programs that are currently loaded into memory

SCANDISK Is a utility that checks your hard disk for logical (lost clusters, cross-linked files, directory structure) and physical errors on the drive. Scandisk can then repair the damaged areas. All window versions except NT come with scandisk. If you are using win 3.1 you have to exit to DOS and use its version.

If you do not shut down the computer properly win 95 OSR2 and 98 will run the DOS version of scandisk automatically next time you start up your computer.

Win 9x provides two versions of Scandisk: a graphical windows-based version Scandskw.exe and an DOS-based version Scandisk.exe. No matter which version name you type while in windows, either from the run box or a DOS prompt the windows version will run, you must exit to DOS to run its version.

DEFRAG Starts Disk Defragmenter which rearranges files and un used space on your hard disk so that programs run faster.

Files are stored in clusters and over time, as programs read and write to a hard disk, these clusters can become fragmented, that is spread throughout the drive. Causing the hard disk to jump all over the drive to read and write data. What defrag does is realign these clusters in sequence, so programs will load faster.

In windows 98 Defragmenter also uses a process called Task Monitor which automatically monitors programs you use and records their disk access patterns, and number of times these programs are used. This information enables Defragmenter to favor more frequently used programs in optimizing the disk.

When running Defragmenter you should always close all programs, and disable any screen savers.

Windows 2000 automatically optimizes disk use. To optimize a disk manually, right-click it in My Computer, click Properties, and then, on the Tools tab, click Defragment Now.

EDIT Starts Dos-based ASCII text editor.

Syntax: EDIT [/B] [/H] [/R] [/S] [/nnn] [file]

  • /B Forces monochrome mode.
  • /H Displays the maximum number of lines possible for your hardware.
  • /R Loads file in read-only mode
  • /S Forces the use of short filenames.

XCOPY Copies files and directory trees. XCOPY is similar to the COPY command except that it has many more switches that allow considerable control over exactly what is copied when using wildcards.

Syntax: XCOPY source [destination] [/Switches]

  • /E Copies the complete sub directory structure of source and all files therein.
  • /S Copies the complete sub directory structure of source and all files therein but does not copy empty sub directories
  • /T Copies the sub directory structure of source but does not copy any files and does not copy empty sub directories To include empty sub directories, use with the /E switch.

COPY Is used to copy one or more files to another location.

Syntax: COPY source [destination]

SETVER Some MS-DOS-based applications require a specific version of MS-DOS to be running. This file responds to applications that query for the version number and sets the version number required. This command is usually put into config.sys, but is now incorporated into the windows IO.SYS file.

Example of line in config.sys. device=c:\windows\setver.exe

SCANREG Runs the Registry Checker program, which scans your registry. If Registry Checker notices a problem, it automatically replaces the registry with the backup copy.

Windows comes with a DOS version Scanreg.exe located in \windows\command and an windows version Scanregw.exe located in \windows

Command line options for Registry Checker

To restore the backup manually

  • Restart in DOS mode
  • Type scanreg /restore
  • Select latest backup

ScanReg and ScanRegW

  • /backup Backs up the registry with no prompts to the user.
  • /comment= Specifies that a comment is attached to the backup, which is displayed with /restore

ScanRegW only

  • /autoscan Scans the registry files every time it is run, but only backs up once per day.
  • /scanonly Scans the registry files and returns an error level. Does not back up.

ScanReg only

  • /restore Displays a list of backup files available, sorted by date and time of the backup
  • /fix Repairs the registry files

Error Codes

  • 2 The registry is bad
  • 0 No problems found
  • -2 Not enough memory; free some memory
  • -3 File not found; one or both of the registry files are missing
  • -4 Unable to create User.dat or System.dat
  • -5 Reading the registry failed
  • -6 Writing to the registry failed
  • -7 Sharing violation (protect mode only); another application has the registry open
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