Operating System_class 11

An operating system is the collecting of program that acts as an interface between the user and the computer and hardware of the computer providing an operational environment to the users and application programs. Example of operating system are MS-DOS, Windows 95/98/2000/ME/XP/Vista/7/8/8.1/10, Windows Server 200/2003/2008/2012/2016/2019, Linux, Unix, OS/2, Mac OS etc.

According to the definition, OS has two objective

Operating System as a resource manager: A computer can be thought of as a pool of resources like CPU, memory, secondary storage devices, printer etc. organized in a proper way to carry out computational function. One needs a manager for an orderly and controlled allocation of the resources among the various user programs computing for them. When the computer has multiple users, there is the needed for managing and protecting the memory.

Operating system as an extended machine: The application programs require certain common services from hardware resources such as those communicating with I/O devices. The common functions of controlling and allocating resources are then brought together into one piece of software, the operating system. Thus an operating system acts as an extended machine.

Role of Operating System: - some of the roles of OS are as follows

·        It act as an interface between user and computer

·         Master control program

·        It performs basic operations that are accept input from users through input devices and send output to the output devices.

·         Allocating the resources

·         Tracking the use of resources

·         File and disk management

·         Detects and notifies the errors.

Function of an operating System: - The major function of an operating system are:-

       I.          Input/output Management: This function keeps track of I/O devices i.e. which job is in use and by which job that device is using. It allocates job and de-allocates the devices after the completion of the job. Input and output management operating system is responsible for

·       It activates general device driver software. Device driver software is used or utilization of input /output device.

·       To run driver software for specific hardware when required.

    II.          Command Interpreter: - This function of operating system takes care of interpreting user commands and directs the system resource to handle the request. In MS-DOS, command.com is a command interpreter.

   III.          Memory Management: Memory management function of an operating system takes care of allocation and de-allocation of memory space to the program need of these resources.

Memory management operating system is responsible for

·       Keep track which memory segment is using by whom allocate and deallocate various memory spaces as needed.

·       Manages for blank memory space available

·       Decides the location for storage of new program.

  IV.          Security Management: -This function protects the resources and information of computer system against destruction and unauthorized access. Some OS provides various methods sucha s password, backup, scandisk etc. for security.

Security Management of operating system is responsible for

·        Protection and security of files and folders

·        Preventing theft, corruption and loss of data.

·        Hiding the system files and folders from unwanted modification.

    V.          File Management: This function take cares of file related activities such as organization, storage, retrieval, naming, sharing and protection of files.

File management is responsible for

·        Create and deletion of files

·        Access to files for reading and writing

·        Protect files against system failure.

·        Saving of files among various users.

·        Mapping files into disk storage.

·        Support for manipulation of file and folders.

  VI.          Deadlock prevention: - Deadlock is the situation which can arise when a resource is shared by two or more process. In such situation the operating system carefully handles and allows the resource properly to avoid the problems.

Here, P1 request for the resource printer that is being utilized by P2 and P2 request for the resource DVD-ROM that is being utilized by P1. Thus both the processes end up waiting each other to free up required resource. Thus situation is called deadlock.

Method through which deadlock can be avoided

o   Ignore deadlock

o   Detect and recovery from deadlock

o   Avoid deadlock

·       Interrupt handling: - An interrupt is an event that allows the normal processing of a computer. It allows the current program to be suspended while higher priority program is executed.  There are two types of interrupt

Hardware or external interrupt: -They are initiated through the computers interrupt pins by external devices.

Software or internal interrupt: - internal interrupt arise from illegal or erroneous ise of an instruction or data. Internal interrupt is called traps. Interrupts due to internal error conditions are registered overflow, attempt to divided by zero, stack overflow etc.

VII.          Virtual Memory management: This function operates by in which the free space of secondary memory such as hard disk is used as primary or main memory when we are running large program than capacity of main memory especially in multiprogramming system.

IX. Process management: This function takes care of creation and detection of processes, scheduling of system resources to different processes required them and providing mechanism for communicating between the processes.

Process management is responsible for

·       Creation and deletion of processes

·       Providing a mechanism for communication among them

·       Scheduling of various system resources to the different process request them.

   

Types of Operating System: OS can be classified on the basis of following factors:

Based on Processing Method:

      I.  Batch Operating System: In this type of operating system, job is not processed until all the data are fully input. The jobs are stores in a disk in a batch queue and run one or more at one time under the control of operating system. This is the oldest type of operating system. Batch OS are used for weather forecasting, statistical analysis etc. Example MS-DOS, IBM DOS, Apple DOS.

   II.  Multitasking Operating System: It provides the ability to run more than one programs at once. For example, a user could be running a word processing package, printing a document, copying files to the DVD and backing up the selected file to disk. Each of these tasks the user is doing to be running at the same time. Example UNIX, LINUX, Windows 95/98/200/XP/Vista/2007/8/8.1, Windows NT, Windows 10.

III.  Multi-processing Operating System: A multiprocessing system is one in which more than one process operates in a coordinate way. They share the main memory and I/O devices. These processors can execute different programs independently and simultaneously, Example UNIX, MVS.(multiple Virtual System/Storage).

IV. Time sharing operating System:  Here, several users work on the computer through the terminal, which are connected to a single CPU and operates as a time-shared basis. The CPU allows the fixed period to each user and server them in time. Example UNIX and Windows NT.

   V. Real -Time Operating System: It is the online system that responds to input immediately. These types of operating system are used to handle machine tools, controlling and monitoring of a nuclear power station, missile-launching system.

Example: RMX (real time multitasking executive), CCP (Communication control program), BLMX (Broad level multi-tasking executive)

There are two types of real time system

Hard real time system: - The operating system in which the action absolutely must occur at certain moment and occasional delays is not acceptable

Soft real time system: - The real time system in which occasional delay is acceptable.

Application

·        Rocket launching system

·        Monitoring and controlling nuclear power station

·        Robotics

·        Traffic light control

·        Weapon control system

·        Airlines reservation or railways

Example

·        Basic real time monitor

·        BSO/RTOS

·        RT Linux

VI) Multithreading: - This type of OS has the ability to execute different parts of a program called threads simultaneously. Threads are the light weight process which are independent part of a process or program. In Multithreading system, more than one thread is executed parallel on a single CPU.

Based on Mode of user: - The number of user that can use the computer resources at a time is called user mode. There are two types of operating system

1.      Single User Operating System: A single operating system allows one user to work at a time. These operating system are used mainly used for computer having only one terminal. Example MS-DOS, PC-DOS.

2.      Multi-User operating System: A multi-user Operating system lets more than one user access to the computer system at a time through network remotely using a terminal or other computer. Example UNIX, LINUX, NETWARE 0S/400.

Based On User Interface: - Based in user interface there are two types of operating system which are as follows

1.          CUI (Character user Interface)/ TUI (Text user Interface)/ CLI (Command Line interface): It is also called Command Line Interface.  This type of operating system provides the user facility of giving command either from keyboard or from a script. Example MS-DOS, PC DOS etc.

Feature:

·        CUI operating system commands are issued by text only.

·        In CUI system, the user has to memorized the command and syntax.

·        Single user operating system

·        It is faster than GUI

·        It does not support multimedia and animation

·        Input and output to the user in the form of text line

·        Hierarchical file directory structure

·        It requires less amount of memory

·        It is generally 8 or 16 bit operating system

2.          GUI (Graphical User Interface): It allows the user to interact with the system using windows icons, menus and a pointer to control the operating system. GUI is easier for the beginner to use.

Features:

·       User do not have to understand command and syntax.

·       It is easy to operate and user friendly

·       In GUI operating system commands line are through graphical component like menu, toolbar, folder etc.

·       GUI operating system supports multiple programs to execute simultaneously.

·       GUI are generally 32 or 64 bit operating system.

·       It supports multitasking, multiprogramming and multithreading

·       It needs large amount of memory.

·       It supports multimedia and animation.

Difference between CUI and GUI Operating System

CUI Operating System	GUI Operating System
1.      It stand for Command User interface or Character user interface	1.      It stands for Graphical user inerface
2.     It is difficult to use and understand because user has to remember each command	2.     It is easy to use and understand because commands /programmers are graphically presented
3.     It does not support additional peripheral devices and multimedia.	3.     It supports extra devices and multimedia system.
4.     It does not support networking and internet.	4.     It supports network and internet fully.
5.      They are single user, single tasking operating system	5.      They are multi-user, multitasking operating system
6.      These operating system are much faster than GUI operating system	6.      These operating system are much slower than CUI operating system.
7.      These operating system can be run with low configures computers	7.      These operating system need high configured computer to run.
8.      The appearance may not be as good as that of GUI	8.      The appearance of GUI is very attractive
9.      It is generally 8 or 16 bits operating system	9.      It is generally 32 or 64 or 128 bits operating system
10.   Example MSDOS, PC DOS	10.    Example windows, UNIX, Linux

MS-DOS (Microsoft Disk Operating System): MS-DOS is a command based, single user and single-tasking operating system software developed by Microsoft INC, USA, in 1981. It is a popular operating system for microcomputer. It is design for IBM PC and IBM compatible computer. MS-DOS performs the operation of input output management, memory management, disk checking and formatting, control the flow of data from one part of the computer to other part such as disk to memory and vice-versa. It is responsible for controlling peripheral device such as monitor, keyboard, printer, modems.

Features of MS - DOS

       i.          It is a single user and single-tasking operating system software.

     ii.          It supports both hard disk and floppy disk.

   iii.          It supports various languages (machine independent)

   iv.          It is a CUI based operating system.

      v.          Hierarchical file directory structure.

    vi.          It uses two types of command: internal and external command.

  vii.          MS-DOS has three essential files for booting the computer: they are IO.SYS (handle input/output process), MSDOS.SYS (manage workspace for application), COMMAND.COM (command interpreter receiver and execute commands)

viii.          It is 16-bit operating system developed for personal computers.

System Files of MSDOS

IO.SYS: It is a hidden file in the root directory of the primary drive. This file provides the basic I/O capabilities for the system, allowing communicating with different peripherals.

MSDOS.SYS: It is also hidden file in the root directory. When an application needs to access a device or peripheral, this file translates the request into actions that IO.SYS can perform.

COMMAND.COM: This is the command Interpreter. It can accept commands from the user, launch programs and pass this information to MSDOS.SYS

Other DOS related file are 

CONFIG.SYS: This file also contains certain command that set the setting for the computer and DOS. This file contains two types of commands. The first is configuration command, which determine the capabilities that are to be made available for use. Second commands are the device drivers that are used to help control the peripheral devices and memory as well.

AUTOEXEC.BAT: The files contain a set of commands that are to be executed once after other when the PC is booted, it is also called STARTUP file. When we start out computer and the DOS begins to run, it looks for this file in the root directory of the disk from which we have to boot the system.

Booting: Booting is the process of loading the system files to the memory from bootable disk. There are three system files of MS-DOS. They are IO.SYS, MS-DOS.SYS and COMMAND.COM. Booting is the process of starting or restarting the computer so that it can perform in two ways:

   i) Cold booting: when a computer is turned on, the computer reads its RAM space and search for the DOS system file from the disk drives. As soon as it finds the system file, it loads into the computer memory. This type of starting the computer is called cold booting.

      ii)    Warm booting: When the computer is at on state and again you want to reboot the computer by pressing (ALT+CTRL+DEL) keys simultaneously at the same time, the computer stays power on during the process and searches for DOS system files and loads them into the RAM.

 File: A file is a collection of related data stored to disk. A file may be in different types such as document file, program file database file etc. A disk can contain many files and each file can be recognized by file name. File name has two parts; file name and extension. File name is a complete name given to the file and extension identifies the type of file. Example: santosh.txt

Naming the file

1.      File name can be up to eight characters.

2.      The extension can be up to three characters.

3.      The ".: dot separates the file name and extension

4.      The characters set for the file name can contain letters(A-Z), numbers (0-9), and other special symbols (_ ^ $ # % & -{} () @).

5.      File name should not contain any blank space.

6.      File name accepts any uppercase or lowercase characters.

Extension:- Extension helps to identifies the file. MS-DOS uses the following extension

.EXE(executable) or .COM(command) is used for files that contain programs. Example EDIT.EXE, COMMAND.COM etc.

.SYS(system) is used for files that contain information about the hardware. Example CONFIG.SYS, ANSI.SYS etc.

.BAT(batch) is used for files that contain lists of commands that MS-DOS carries ot as a sext Example AUTOEXEC.BAT

Directory: A directory is a place holder of files. A directory contains the files with detail information such as name, size, address, date of creation, last date of modification etc.  There are two types of directories

1.      Root directory: Root directory is the main directory of a disk which contains many other directories and files. Disk have at least one directory which creates itself when a disk is formatted is called root directory, Root directory is indicted by back slash (\).

2. Sub directory: A sub directory is a directory inside another directory. A sub directory is also called child directory. Sub directory can contain other directory and files inside it.   A subdirectory containing sub directories is called parent directory.

Disk Drive: Disk drive is a computer peripheral device which is used to read the data from a disk and copies into the memory and vice versa. Different disk drives are hard disk, Floppy Disk, CD-ROM

Default drive: The disk drive that selects automatically by the computer for input and output operation is called default drive.

Prompt: The character set or symbols provided by the computer to indicate that the computer is ready to use is called prompt. Example C :\>

Wild character (Global Character):  They are the special character or symbols that are used in MS-DOS to represent one of many character in a filename, extension, character, drive, directories etc. The wild char characters are:

*	ALL	>	Direction	|	Pipe	:	Drive
?	One character	/	Option being added	^	Control Sign

Example:- .* Indicates any extension

*.* Indicates any fine name and extension

Path: Path is the route through subdirectories on a disk to a particular file. It will search the path in the order that you type it in. We have to maintain sequence of directory name followed by file name separated from each other by back-slash (\).

Example: path=C:\DOS\Future

Windows Operating System:   Microsoft Windows is the popular and widely used graphical user interface(GUI) based operating system developed by Microsoft Corporation USA. Microsoft introduced the first GUI base set of software which is properly known as Windows. Windows OS is very common operating system for personal computer including desktop and laptop. Windows operating system provides WIMP (Windows, Icons, Mouse and Pointer) environment, GUI, desktop, control panel, multitasking. Example: Windows 95, Windows NT, Windows 98, Windows 2000, Windows ME, Windows XP, Windows Server 2003, Windows Vista, Windows Server 2008, Windows 7, Windows 8, Windows Server 2012, Windows 8.1, Windows 10, Windows Server 2016, Windows Server 2019.

Features/ Advantages of using windows

·        It is GUI based software and user friendly

·        Users don’t have to remember syntax and commands.

·        It needs large amount of memory space

·        It consists of different components such as text box, icon, desktop, pointing devices etc.

·        It allows the user to work on a number of applications simultaneously.

·        In Windows, other peripheral like mouse, light pen, joystick can be used.

·        It provides utility software to improve the functionality of a computer such as scandisk, bckup utility, disk clearner, disk defragmenter etc.

·        It runs other windows based programs like MSWord, Excel, Powerpoint, Access etc.

·        Failures to any application do not harm the computer system.

·        It has features of communicating with other computers.

·        It has fast processing capability.

Open Source operating system: Open source operating system is an operating software whose source code is freely available to the user for edit as per the user requirements. We do not have to buy license to use this software. It enables them to use, modify/enhance the operating system and redistribute the modified (or unmodified) form of the operating system. Example: Linux, Free BSD, Open BSD, Net BSD, Dragonfly BSD, Free DOS, SOS, ReactOS, House, MINIX, Plan 9, Biscuit etc.

Features of open source software

This software's are freely available and no license is required to use them

Source code of this software is freely available and it can be downloaded from the internet.

It has freedom at work. Everyone is free to modify the codes or develop new operating system using these codes.

·Everyone can re-distribute the software to any others.

There is no restriction of law to use them.

The process of eliminating bugs and improving the system happens at a much quicker rate than the traditional development of commercial software

Anyone can study how the software works.

Disadvantages

Since open source software is free to use, there is typically no technical support included with this software.

Some open source operating system software licenses are copy license, which states that anyone redistributing the software does no under the same license and also includes the sane source code.

Some popular operating System:

UNIX: UNIX is a popular operating system used in large variety of scientific engineering and other application. It was developed at AT&T lab by Dennis Ritchie and Ken Thompson for for PDP-11 computers in 1970. It is a stable, multiuser, multitasking system for servers, desktop and laptops.

Special features

1.      Multi-user operating system: More than one user can use the same machine via terminal computer.

2.      Multitasking operating system: More than on program can be run at a time on a single computer.

3.      Portability operating system: UNIX has less amount of machine dependent code. So it can run on different hardware having fewer amounts of resources.

4.      Reliable and efficient operating system: It is reliable operating system and handles thousands of users.

LINUX: LINUX is an open source operating system based on UNIX.. It is a multitasking, multi-processing operation system designed to use on personal computers. It was developed by Linus Torvalds; hence the name is LINUX.

Advantages of Linux

Low cost: There is no need to spend time and huge amount money to obtain licenses.

Stability: Linux has high stability compared with with other operating systems. There is no need to reboot the linux system to maintain performed levels.

Networking: Linux provides a strong support for network functionality, client and server system. It can perform tasks like network backup faster than other operating systems.

Flexibility: Linux can be used for high performance server application, desktop application and embedded systems.

Wider choice: There is a large number of Linux distribution (Red hat Linux, Centos, Fedora, openSUSE, Mandrake Linux, Miracle Linux, Oracle Linux) which gives you a wider choice.

Fast and easy installation: Linux distributions come with user-friendly installation.

Better use of hard disk: Linux uses its resources well enough even when the hard disk is almost full.

Multitasking: It is a multitasking operating system. It can handle may application at a same time.

Security: File ownership and permission make LINUX more secure.

Common DOS commands: Commands are the sets of instruction given to the computer to do specific task. DOS commands are classified into two groups:

1.      Internal Command: Internal commands are the part of COMMAND.COM file. Internal commands are loaded to the memory during the time of booting. Some of the internal command are CD, CLS, Copy, copy con, date, del, dir, md, rd,  ren, time, type, ver, vol

2.      External Command: The commands which are stored on the system disk as program file are called external command. These commands are only loaded to the memory when they used.

Example: attrib, CHKDSK, DISKCOPY,DISKCOMP,FORMAT,EDIT,LABEL,SCANDISK,SYS,TREE,XCOPY

Internal command

dir: Dir displays the list of files, directories and sub-directories

Syntax: dir

/P – It displays all files and directories with detail information page wise.

/W- It display in wide specified attributes

/A-It displays the files with specified attributes

D directories

H Hidden files

A Files ready for archiving

S system files

R read only files

/S It displays including sub directories

/O It displays by sorting the files into ascending or descending order

N sort by name

S Sort by size

E Sort by extension

D sort by date

G sort by group

"-" prefix the sort reverses the action or displays in descending order.

 Example:

C:\>dir

cls: This command clears the screen

Syntax: cls

Example

time: It display current system time and allows setting new time

Syntax: time [time]

Example

date: It display current system date and allows setting new date

Syntax: date [date]

Example

copy con: This command is used to create a new file

Syntax: copy con <file name>

Example: copy con santosh.txt

ren: This command allows renames a files.

Syntax: ren <old filename> <new filename>

Example: ren santosh.txt poudel.txt

type: This command displays the content of file.

Syntax: type

Example:

md(mkdir): MD creates a new directory.

Syntax: md

Example:

cd: This command is used to change the directory and display current directory.

Syntax: cd

Example

rd(rmdir):- This command is used to remove a directory.

Syntax: rd

Example

ver: This command displays the MS-DOS version currently in use.

Syntax: ver

Example:C:\>vol

vol:- This command is used to display the disk volume label

Syntax:vol

Example: c:/> vol

path: this command specifies the directory in which DOS look for program such as (.com,.exe) files etc.

Syntax: path

Example:

prompt: this command changes the MS-DOS command prompt.

Syntax: prompt

Example

External commands

attrib: This command is used to set or remove the file attributes.

syntax:  attrib

+ :- sets an attributes

- :- removes an attributes

R:- Read only files attributes

S: system file attributes

/S: indicates sub directories

A: Archive file attributes

H: Hidden file attribute

Example:

C:\>attrib

chkdsk: This command checks the drive and displays a status report

Syntax: chkdsk

/f   fixes error on the disk

/V displays the full path and name of every file on the disk

Example:

diskcomp: This command is used to compare between two diskettes.

Syntax diskcomp [Drive1:] [Drive2:]

Example

C:\> diskcomp A: B:

Compares two floppy disks in drive A and drive B: Remember that both disk drives and the disk are the same capacity.

diskcopy: This command allows making duplicate copy of the floppy disk. It also must have same capacity two disks.

Syntax: diskcopy [drive1:] [drive2:]

Example

edit:- this command is used to edit MS-DOS text files. Edit provides a full screen editor

Syntax: edit

Example:c:\>edit config.sys

sys:-This command is used to transfer system files of DOS from one disk to another. This command allows her user to make a bootable disk. This copy has two hiiden files (IO.SYS & MSDOS.SYS) and COMMAND.COM file into another disk.

Syntax: sys[drive1:] [path:] [drive2:]

Example:

Restore: Restores files that were backed up by using the backup command.

Syntax: restore <drive 1:> <drive 2:>

/s restores all subdirectories

/p prompts you for permission to restore files that are read only.

Example

Undeltree: This command is used to restore files previously deleted with a DEL command.

Syntax: undeltree

Example:

xcopy: This command is used to copy the files, directories and subdirectories together.

Syntax: xcopy

/S copies directories and sub directories except empty ones.

/V verifies each new file when written into the disk.

Example:

Scandisk: This command is used to scan the disk. SCANDISK checks the status of disk drive fixes errors if any and gives the detail reports of the disk drive.

Syntax: scandisk

Example: C:\>scandisk C:

tree:- This command displays the directory structure of a driver or path.

Syntax: tree

Example: c:\>tree

label: This command is used to display and set the volume level of a disk.

Syntax: label

Example:

Format: - This command is used to format a disk.

Syntax: format [drive:]

Example:

move:- This command is used to change the location of files also used the change the name of directory.

Syntax: move [source filename] [Target location]

Move[old dir. name] [New dir. name]

Example:

More: This command is used to display full screen text.

Syntax: more

Example:

Backup: this command backs up the files specified for future storage. For execution of this command the computer needs to read a program file.

Example:

C:\>

 

 

 

 
 

 

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