Gene Perkins, Lassen High School Networking Academy

Chapter 4

Operating Systems

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 InterfaceKernelFile 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

Windows3.x9.x (includes ME)2000 (includes NT)XP

LinuxUNIXMac OS X (based on UNIX)

DOS

Is a CLI (Command Line Interface)Made up of 3 boot files:

IO.SYSMSDOS.SYSCommand.com

Contains file system utilitiesHas 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 directoryAll other directories branch off of the root

directoryMust know the path to find files in DOSPaths are typed in either relatively or

absoluteC:\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 – The archive contains a backup copy of files.

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

DOS Commands

DIR – Displays the content of a folderCD – Change the working directoryMD – Make a new folder (directory)RD – Removes a folderDEL – Deletes a fileREN – Renames a filesCOPY – 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 memoryTYPE – Shows the contents of a fileFDISK – Sets partitions on a hard driveTIME – Sets system timeDATE – Sets system dateCHKDSK – 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 fileCopyDir

Some commands are separate filesXcopyFormat

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 – keyDir /w – Wide formatDir /a – displays all filesDir /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.sysMsdos.sysCommand.com

Other files are also needed to work with the hard driveFdisk.exeFormat.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 parametersConfigures system to run added hardware

devices Installs TSR programsRedirects 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 promptEdit 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 memoryDevice=C: \Windows\Emm386.exe NOEMS

To load DOS into upper memoryDOS=UMB

To allow DOS to use high memoryDOS=HIGH, UMB

Memory Management

To allow DOS programs access to expanded memoryDevice=C: \Windows\Emm386.exe RAM

To allow device drivers to load into high memoryDEVICEHIGH=C: \DOS\MOUSE.SYS

This allows Windows 3.x and 9x to workDEVICE=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 DOSSystem crash will bring down the whole

system Protected mode used with Windows

Allows a program to crash without affecting the system

Perform Practice Test