Transcript Chapter 4
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