Chapter 4

Operating Systems Gene Perkins, Lassen High School Networking Academy

Need for Operating Systems

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

Parts of an Operating System

 3 major parts:  User Interface  Kernel  File Management

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

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

Common Types of OS’s

 Windows  3.x

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

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

Command Line Screen

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.

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

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

of files. – The archive contains a backup copy

System File

– The DOS operating system must have these files for a successful boot up.

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

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

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

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

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)

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

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 Start>Settings>Control Panel>Add Progams and select the

create boot disk

tab

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

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

Autoexec.bat

 Batch file that can perform any DOS command  Common autoexec.bat commands:   Prompt $P$G – Displays working directory Set temp=c:\temp – Sets an area to hold data temporarily   Path=C:\;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

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

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

Memory Management

 In the config.sys file to disable expanded memory 

Device=C: \Windows\Emm386.exe NOEMS

 To load DOS into upper memory 

DOS=UMB

 To allow DOS to use high memory 

DOS=HIGH, UMB

Memory Management

 To allow DOS programs access to expanded memory 

Device=C: \Windows\Emm386.exe RAM

 To allow device drivers to load into high memory 

DEVICEHIGH=C: \DOS\MOUSE.SYS

 This allows Windows 3.x and 9x to work 

DEVICE=C: \DOS\HIMEM.SYS

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)

RAM Drive

 In some cases, RAM can be setup to act as a hard drive  Configured in config.sys using this command: 

DEVICE=C:\DOS\ RAMDRIVE.SYS 4096

 When data is stored in this manner, it can be lost when powered off

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  GPF’s can also cause the program to lock

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

Perform Practice Test