Operating Systems

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Chapter 4

• Operating Systems

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Need for Operating Systems

• It serves as a interface between you and the
  computer hardware
• Necessary to manage applications

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Parts of an Operating System

• 3 major parts
• User Interface
• Kernel
• File Management

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Functions of an Operating System

• The OS provides a way for the user to control
  applications
• Works with the BIOS and device drivers to fetch
  and store data
• Contains utilities to optimize the hardware

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Operating System Types

• Multitasking more than one application running
  at the same time
• Multiuser more than one user sharing
  applications or hardware at the same time
• Multiprocessing more than one processor working
  at the same time
• Multithreading a program that is broken down
  into smaller parts and run at the same time

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Common Types of OSs

• Windows
• 3.x
• 9.x (includes ME)
• 2000 (includes NT)
• XP
• Linux
• UNIX
• Mac OS X (based on UNIX)

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DOS

• Is a CLI (Command Line Interface)
• Made up of 3 boot files
• IO.SYS
• MSDOS.SYS
• Command.com
• Contains file system utilities
• Has file management commands

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Command Line Screen
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DOS Properties

• DOS is not user-friendly. The best way to learn
  about DOS is to use it.
• DOS can only run one program at a time.
• DOS can only run small programs and has memory
  limitations (640 Kb max).
• DOS is an essential tool for IT professionals and
  is used extensively for troubleshooting.

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File Structure

• All files start at the root directory
• All other directories branch off of the root
  directory
• Must know the path to find files in DOS
• Paths are typed in either relatively or absolute
• C\myfiles\mypicts\nba.gif
• \mypicts\nba.gif

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Types of DOS Files

• Hidden File The user will not see hidden files
  when using a normal file search
• Read Only The user can open and read this type
  of file but cannot modify the file in any way.
• Archive The archive contains a backup copy of
  files.
• System File The DOS operating system must have
  these files for a successful boot up.

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DOS Commands

• DIR Displays the content of a folder
• CD Change the working directory
• MD Make a new folder (directory)
• RD Removes a folder
• DEL Deletes a file
• REN Renames a files
• COPY Copies a file from one place to another

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DOS Commands

• SET Sets a path for programs to work from or to
• MEM Displays the system memory
• TYPE Shows the contents of a file
• FDISK Sets partitions on a hard drive
• TIME Sets system time
• DATE Sets system date
• CHKDSK Checks a drive for errors

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DOS Commands

• DISKCOPY Copies a floppy disk to another
• EDIT Opens a file for editing
• FORMAT Prepares the disk to receive data
• PRINT Prints contents of screen or file
• ATTRIB Changes attributes of a file (hidden,
  read-only, archive)
• - Wildcard that represents everything

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Internal External Commands

• Some commands are within the command.com file
• Copy
• Dir
• Some commands are separate files
• Xcopy
• Format
• External commands need to be copied onto a floppy
  when performing diagnostics procedures

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Switches

• Most DOS commands can be modified by using a
  switch behind them
• Attrib can be modified to hide or unhide files
  using the or key
• Dir /w Wide format
• Dir /a displays all files
• Dir /h displays hidden files
• Each command has special switches it can use (See
  4.2.3)

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Creating a Boot Disk

• Three files are absolutely needed to make a boot
  disk
• Io.sys
• Msdos.sys
• Command.com
• Other files are also needed to work with the hard
  drive
• Fdisk.exe
• Format.com

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Creating a Boot Disk

• Insert floppy into the drive
• Type in the following commands
• format A /s
• Copy C\format.com A\format.com
• These commands will transfer the system files and
  other external files needed
• The other way is to select from the
  StartgtSettingsgtControl PanelgtAdd Progams and
  select the create boot disk tab

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Boot Sequence

• BIOS searches for the MBR
• The bootstrap loader moves the MBR into RAM
• The MBR locates and loads the boot files into
  memory
• Io.sys loads msdos.sys
• Msdos.sys runs config.sys
• msdos.sys runs command.com
• Command.com runs autoexec.bat

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Config.sys

• Used to modify system parameters
• Configures system to run added hardware devices
• Installs TSR programs
• Redirects program paths
• Pressing the F5 or left SHIFT key bypasses
  config.sys and autoexec.bat
• Pressing F8 enters the option screen which allows
  you to modify bootup

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Autoexec.bat

• Batch file that can perform any DOS command
• Common autoexec.bat commands
• Prompt PG Displays working directory
• Set tempc\temp Sets an area to hold data
  temporarily
• PathC\C\DOS Sets search path(s) when
  looking for data
• Smartdrive.exe 2048 1024 Sets 1Mb of memory
  cache for DOS and 2Mb for Windows

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Editing System Configuration Files

• Type in edit and file name at dos prompt
• Edit autoexec.bat
• Type in sysedit in the command prompt box
• Edit files in Notepad

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DOS Memory

• First 640 Kb reserved for running programs
• 640 to 1024 Kb used to run older DOS programs and
  BIOS applications
• 1024 to 1088 used for DOS command files
• 1088 Kb to 4Gb used for Windows applications

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Memory Management

• In the config.sys file to disable expanded memory
• DeviceC \Windows\Emm386.exe NOEMS
• To load DOS into upper memory
• DOSUMB
• To allow DOS to use high memory
• DOSHIGH, UMB

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Memory Management

• To allow DOS programs access to expanded memory
• DeviceC \Windows\Emm386.exe RAM
• To allow device drivers to load into high memory
• DEVICEHIGHC \DOS\MOUSE.SYS
• This allows Windows 3.x and 9x to work
• DEVICEC \DOS\HIMEM.SYS

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Virtual Memory

• When a section of the hard drive is set aside to
  be used as the system RAM
• The slowest memory available
• Usually set to automatically adjust as needed
• If there is inadequate virtual memory, your
  system will freeze
• Stored in WIN386.SWP (Win9x) or PAGEFILE.SYS
  (Win2000)

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RAM Drive

• In some cases, RAM can be setup to act as a hard
  drive
• Configured in config.sys using this command
• DEVICEC\DOS\ RAMDRIVE.SYS 4096
• When data is stored in this manner, it can be
  lost when powered off

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General Protection Faults

• When windows crashes (blue screens), there is a
  problem with 2 programs trying to share the same
  spot in memory
• Can also be caused by bad drivers or trying to
  directly gain access to windows programs
• GPFs can also cause the program to lock

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Real vs Protected Mode

• Real mode is used with DOS
• System crash will bring down the whole system
• Protected mode used with Windows
• Allows a program to crash without affecting the
  system

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Perform Practice Test