Download Chapter 4 - Killarney Secondary School

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 – 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 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


To load DOS into upper memory


Device=C: \Windows\Emm386.exe NOEMS
DOS=UMB
To allow DOS to use high memory

DOS=HIGH, UMB
Memory Management

To allow DOS programs access to
expanded memory


To allow device drivers to load into high
memory


Device=C: \Windows\Emm386.exe RAM
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