Operating System

What Is an Operating System? : 

An operating system is software that does the following :
Provides a file system structure.
Provides a means of communicating with computer system hardware.
Prevents running programs from interfering with one another.

                            Operating System

Kernel : 

The kernel is the core of the operating system.
Interface à  File Sysytem à KERNEL ß Computer Management ß Security.

Operating System Communication : 

Application software Operating system software BIOS Computer hardware User

Operating System Characteristics : 

Ability to multitask.
A user interface.
A file structure.

Multitasking : 

The process of supporting two or more programs running at the same time.
It is supported by some operating systems.

Cooperative Multitasking :

With cooperative multitasking, one program dominates control of the operating system.
A program will allow another program to run while it remains idle.

Preemptive Multitasking : 

Allows two or more programs to share control of the operating system.
Also called time slicing.

Threading : 

 Running multiple threads at the same time via multiple CPUs.

User Interface : 

Text line command.
Graphical user interface (GUI).

Text Line Command : 

A text line command is typed in at a command line.

Graphical User Interface (GUI) : 

Insert Figure 2-5 Folder Icon In a graphical user interface (GUI), a file system is easily displayed.

File Structure : 

Subdirectory.. Directory.. Root directory.. Pathname.. File.

File Allocation Table (FAT) : 

A file allocation table is used in an operating system to keep track of file locations on a disk.
Examples of file allocation tables are FAT12, FAT16, FAT32, VFAT, HPFS, and NTFS.

Common OS Terminology : 

 Configuration file.
Application software.
Drivers.
Software patches.

Configuration File : 

A file that contains information about the system hardware and file.
Examples of configuration file information are the amount of system memory and type of video adapter used in the computer.

Typical Configuration Files : 

DOS – Config sys..
Windows 3.x – win.ini, system.ini, (app specific ini files).
Windows 95 & later – Registry.

Application Software : 

Also called end-user software.
Designed for a specific purpose, such as creating a database, spreadsheet, or document.
Relies on the OS to communicate with the computer.

Drivers : 

Drivers are software that enable proper communication between the PC and peripherals.
MS-DOS system driver files have a .sys extension.
Windows drivers have a .drv extension.
Windows stores many drivers in cabinet files.

Software Patches : 

Designed for the OS and application programs.
Used to fix bugs.

                                                           Review : 

·     

  Describe three functions of an operating system.
A : Provides a file system structure.
Provides a means of communicating with computer system hardware. Prevents running programs from interfering with one another.

·       The _____ is the core of an operating system.
A : kernel

·       The _____ provides communication between application software and the BIOS.
A : operating system

·       A(n) _____ is used in an OS to keep track of file locations on a disk.
A : file allocation table (FAT)

·       A software program that enables proper communication between the PC and peripherals is called a(n) _____.
A : driver

                       Disk Operating System

Disk Operating System (DOS) : 

Set standards for Windows operating systems to follow.
The command line is used to enter commands and to open programs.
No multitasking or multiprocessor support.

DOS Core Files :

FILE : io.sys.. msdos.sys.. command.com.
DESCRIPTION : contains generic drivers.. kernel.. Interprets commands (command 

interpreter).

DOS Commands : 

Internal commands are commands contained within the command.com file. External commands are located in the DOS directory. 

Internal Commands :

External Commands : 

Chkdsk – Checks condition of disk & displays report.
edit – Text editor program.
format – prepares a disk for storing data.
print – prints a text file in printer.

DOS System Boot Disk : 

A DOS system boot disk contains the necessary files needed to boot the computer.
Booting refers to starting the computer and loading the OS.
To create a DOS boot disk, the format a: /s command is used.

Naming DOS Files : 

 Eight point three (8.3) naming convention.
Filename of Eight-character or less, a period (dot), and a three-character extension.
Examples : config.sys, autoexec.bat, myfile.txt

 
Common File Extensions :

 

Unacceptable Filename Characters : 

| + = > < ? : [ ]

A period can only be used between the filename and extension.

Warm and Cold Boot : 

Warm boot initiated by [Ctrl] [Alt] [Del].
Cold boot initiated by turning the computer on with the switch.

Config.sys : 

Used to load device drivers and to configure, disable, or enable OS features, such as number of files that can be opened.
Used in new operating systems to support legacy software applications.

Config.sys Commands : 

 Autoexec.bat Commands : 

Autoexec.bat : 

A text file used to load and run programs at startup.
Required for legacy programs.

                                                           Review : 

·      

 What are the names of the three core DOS files?
A : io.sys, msdos.sys, command.com

·       Which of the following commands is used to create a DOS boot disk?

chkdsk a: /s
chkdsk a: /DOS
format a: /s
format a: /DOS

A : 3

·       Which file is used to load device drivers and to configure, disable, or enable OS features, such as the number of files that can be opened ?

autoexec.bat
config.bat
autoexec.sys
config.sys

A : 4

What are some limitations of DOS?
8.3 character-naming convention.
Command line only.
No multitasking or multiprocessor support.

            Microsoft Windows Operating Systems

The Microsoft Windows Family : 

Windows 3.x :
Built on DOS.
Offered a GUI.
Stores configuration information in system.ini and win.ini.

Windows 95 : Introduced the registry, Plug and Play, and the shortcut menu.
32-bit OS. Enhanced CD player.
Windows 98 Introduced support for DVD, MMX, AGP, and FAT32.
Integrated the Web browser.

Windows NT : Workstation and server version.
32-bit OS with preemptive multitasking.
Enhanced security.
Limited user access.

Windows Me : Introduced Advanced Network Wizard and System Restore tool. Introduced support and drivers for video cameras.
New technologies added to the Windows 95 kernel.

Windows 2000 : Uses a modified NT kernel.
Dynamic file system (NTFS5.0).

Improved security.

Windows XP : Uses a modified NT kernel.
Home Edition & Windows XP Professional.

Windows Vista : Not based on the NT kernel.
Enhanced user interface.
Enhanced security.

File Names—Windows 95 and Later : 

Long file names introduced.
Allowed for 255 characters.
Characters not allowed consist of the following: | * > < ? : / \ ″

Windows 95, 98, Me Boot Sequence : 

Bootstrap program runs the Power-on self-test (POST).
MBR
io.sys
msdos.sys
config.sys
command.com
autoexec.bat
win.com

Windows NT, 2000, XP Boot Sequence : 

Power-on self-test (POST)
MBR
NTLDR
boot.ini
ntdetect.com
ntoskrnl.exe
hall.dll
winlogon.exe

Windows Vista Boot Sequence : 

Power-on self-test (POST)
MBR
bootmgr
winload.exe
ntoskrnl.exe
hal.dll
smss.exe
winlogon.exe

Boot Sequence Comparison :

Dual- and Multi-Boot Systems : 

Dual-Boot System = 2 only
Multiple-Boot System = @ & more

Virtual Machines : 

Windows Server 2008 Windows Vista Linux

 
Windows Startup Disk : 

Used for recovering from a failed or corrupt operating system.

Registry :

The registry is found in Windows 95, 98, NT, 2000, and XP.
It is a database that stores configuration information.
Accessed by entering regedit in the Run dialog box or Search box off the Start menu in Windows XP and Vista.

Registry Editor : 

HKEY_CLASSES_ROOT Object linking and embedding (OLE) information and how files are associated.
HKEY_LOCAL_MACHINE Information specific to the local computer. HKEY_CURRENT_USER Information about the current workstation user. HKEY_USERS Information for each user of this workstation. HKEY_CURRENT_CONFIG Display and printer settings.

Registry Files : 

The system.dat file contains information about the computer’s settings.
The user.dat file contains information about individuals who use the computer. Can be backed up, copied to disk, and modified.

                                                       Review : 

·       Which Windows operating systems use a modified NT kernel?
(Select all that apply.)

Windows 95
Windows XP
Windows Me
Windows 2000

A : B, D

·       Which Windows operating systems introduced Plug and Play and the registry?

Windows 95
Windows XP
Windows Me
Windows 98

A : A

·       Which Windows operating systems introduced the dynamic file system?

Windows 95
Windows XP
Windows Me
Windows 2000

A : D

·       Place the following Windows Vista boot sequence steps in their proper order.

smss.exe hal.dll ntoskrnl.exe bootmgr winlogon.exe MBR POST winload.exe

A : G, F, D, H, C, B, A, E

Non-WindowsOperating Systems

Linux : 

Derivative of UNIX.
Many varieties such as Red Hat, SUSE, Caldera, and Debian.
Can be installed on a single PC or used as a file server.
Programmable code to make the OS is called source code.
Source code can be readily downloaded, viewed, and manipulated.

OS/2 : 

Developed by Microsoft for IBM computers.
Had impressive features for its time, such as the ability to use long file names. Compatible with DOS and Windows programs. OS/2 programs cannot run on DOS or Windows.

OS/9 :

 Developed jointly by Microware Systems and Motorola.
Supports multitasking.
It is the operating system behind many industrial technologies as well as WebTV boxes.

OS X : 

The replacement OS for Apple computers.
Based on the Linux OS.
Will run on an Intel processor.

                                                    Review : 

·       Which of the following operating systems is based on Linux?
UNIX
OS/2
SUSE
OS 9

A : C

·       Which of the following operating systems is the operating system behind many industrial technologies as well as WebTV boxes?
UNIX
OS/2
Linux
OS 9

A : D

·       Which of the following operating systems was developed by Microsoft and is compatible with DOS and Windows programs?

UNIX
OS/2
Linux
OS 9

A : B

·       Which of the following operating systems is used on Apple computers that have an Intel processor?

OS X
OS/2
Linux
OS 9

A : A

                                   Glossary

Application Software : 

Software designed for a specific purpose such as creating databases or spreadsheets, word processing, producing graphics, or just for entertainment.

Bootstrap Program : 

A short program that loads some basic files into memory and then turns the startup operation over to the operating system.

Bugs : 

Errors in programming.

Cabinet Files : 

Compressed files that contain the operating system software.
Called cab files for short.

Cold Boot : 

Turning on the computer at the power switch.

Configuration File : 

A file that contains information about the system hardware and software.

Cooperative Multitasking : 

One program dominating the operating system but allowing another program to run while the primary program is idle.

Directory : 

A file used to group other files together in a hierarchical file structure.
A directory is analogous to a file folder in a conventional paper filing system.
Directories are referred to as folders in many operating systems.

Disk Operating System (DOS) : 

An operating system typically requiring the user to issue text line commands to perform operations.

DOS System Boot Disk : 

A floppy disk that contains the files necessary to run a computer with DOS.

Drivers : 

Software that enables proper communication between the PC and peripheral devices.

Dual-Boot System : 

A computer with two operating systems installed.

Extension : 

The second part of a filename.
An extension is typically three characters long and indicates the function of the file.

External Commands : 

Individual executable files that extend DOS’s functionality beyond the limits of its internal commands.

File : 

A collection of data that forms a single unit.

File Allocation Table (FAT) : 

A table used by the operating system to record and recall the locations of files on the disk.

Graphical User Interface (GUI) : 

 An operating system interface that allows the user to perform functions by selecting on-screen icons rather than by issuing text line commands.

Internal Commands : 

A set of programs that are wholly contained within the command processor program (command.com).

Kernel : 

The core of the operating system.

Multiple-Boot System : 

A computer with more than two operating systems installed.

Multitasking : 

The ability of an operating system to support two or more programs running at the same time.

Operating System (OS) : 

Software that provides the user with a file system structure and allows the user to communicate with the computer system’s hardware.

Pathname : 

A string of characters used to identify a file’s location in the directory structure.

Plug and Play (PnP) : 

A BIOS function that enables the automatic detection and configuration of new hardware components.
Also, the automatic assignment of system resources such as DMA channels, interrupts, memory, and port assignments.

Preemptive Multitasking : 

Multiple programs sharing control of the operating system.

Registry : 

A database that stores configuration information.

Root Directory : 

The directory at the top of the file structure hierarchy.
A root directory is analogous to a file cabinet drawer in a conventional, paper filing system.
A root directory is also referred to as the root.

Source Code : 

The programming code used to make the operating system.

Subdirectory : 

A file that subdivides the contents of a directory.
A subdirectory is analogous to a folder within a folder in a conventional, paper filing system.

Text Line Command : 

Commands issued by entering text at a command prompt.

Virtual Machine : 

 A computer on which more than one operating system can be executed at the same time.

Warm Boot : 

Using the reset button or key combination to restart a computer that is already running.