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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 Interface Kernel File Management. Functions of an Operating System.

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Chapter 4

Chapter 4

Operating Systems

Gene Perkins, Lassen High School Networking Academy

Need for 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
Parts of an Operating System

  • 3 major parts:

    • User Interface

    • Kernel

    • File Management

Functions of an operating system
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
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
Common Types of OS’s

  • Windows

    • 3.x

    • 9.x (includes ME)

    • 2000 (includes NT)

    • XP

  • Linux

  • UNIX

  • Mac OS X (based on UNIX)


  • Is a CLI (Command Line Interface)

  • Made up of 3 boot files:

    • IO.SYS



  • Contains file system utilities

  • Has file management commands

Dos properties
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
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
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
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 commands1
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 commands2
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
Internal & External Commands

  • Some commands are within the file

    • Copy

    • Dir

  • Some commands are separate files

    • Xcopy

    • Format

  • External commands need to be copied onto a floppy when performing diagnostics procedures


  • 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
Creating a Boot Disk

  • Three files are absolutely needed to make a boot disk:

    • Io.sys

    • Msdos.sys


  • Other files are also needed to work with the hard drive

    • Fdisk.exe


Creating a boot disk1
Creating a Boot Disk

  • Insert floppy into the drive

  • Type in the following commands:

    • format A: /s

    • Copy C:\ A:\

  • 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
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

  • 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
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
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
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


Memory management1
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


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


Virtual memory
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
RAM Drive

  • In some cases, RAM can be setup to act as a hard drive

  • Configured in config.sys using this command:


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

General protection faults
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 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