9th Class Computers Operating System

Operating System

Category : 9th Class


Operating System



An Operating System is a master control program. Basically it is system software that manages the operation of a computer. Without an operating system computer cannot work. The computer is useless unless it is provided with essential software that makes it ready to use. As we have seen that an operating system is software, which makes the computer ready to use by a process called booting. Basically booting is a process which loads operating system from disk to RAM.


About twenty years ago Steve Jobs and Wozniak, the founders of Apple, came up with the very strange idea of selling information processing machines for use at the home. The business took off, and its founders made a lot of money and received the credit they deserved for being daring visionaries. But around the same time, Bill Gates and Paul Alien came up with an idea even stranger and more fantastically: selling computer operating systems. This was much wider than the idea of Jobs and Wozniak. A computer at least had some sort of physical reality to it. It came in a box, you could open it up and plug it in and watch lights blink. An operating system had no tangible incarnation at all. It arrived on a disk, of course, but the disk was, in effect, nothing more than the box that the OS came in. The product itself was a very long string of ones and zeroes .that, when properly installed and coddled, gave you the ability to manipulate other very long strings of ones and zeroes. Yet, now the company that Gates and Alien founded is selling operating systems like Hindustan Lever Limited sells detergents. New releases of operating systems were launched as if they were Bollywood blockbusters, with celebrity endorsements, talk show appearances and world tours. The market for them is vast enough that people worry about whether it has been monopolized by one company. Even the least technically minded people in our society now have at least a hazy idea of what operating systems do; what is more, they have strong opinions about their relative merits. To be more elaborative on the topic, every general-purpose computer requires some type of operating system that tells the computer how to operate and how to utilize other software and hardware that are installed on to the computer. All software programs developed today require some type of Operating System to operate properly. MSDOS, Unix and Windows are all examples of operating systems. Because the history of computer operating systems parallels that of computer hardware, it can be generally divided into five distinct time periods, called generations, that are characterized by hardware component technology, software development and mode of delivery of computer services.


Structure of OS

The internal structure of operating system is divided into layers. The outermost layer is called user interface and innermost layer is hardware.


The following are the main layers in OS:


v  Kernel

v  Shell

v  User Interface




Kernel is a central controlling part of OS that implements the most primitive of the system's functions. This part cannot be replaced or modified by user. Basically kernel performs basic function for memory management, device management, low-level security and process management.



Shell is a part of software that serves as a user interface it forms the outer layer of an operating system covering the other modules of the operating system. The shell can be a command-line interface or GUI (Graphical User Interface). An operating system can support many shells. UNIX supports three command-line shells known as Bourne shell, C shell and Korn shell.


User Interface

User interface plays an important role to use an OS. Basically there are two types of interface command line interface and GUI. The command line interface is a textual user interface in which the user gives instruction to the computer by typing command. For example, in DOS you need to type whole command to perform some operations. GUI provides user friendly environment to use a computer. In command line interface you need to write a command to perform any operation but in GUI you just need to-click. Microsoft Windows OS is the best example of GUI. Due to Windows a simple user who does not know about computer science theory can use computer easily.


Commonly Asked Question?



  1. Apple is an organization which developed Mac operating system. Who is the founder of Apple?

(a) Bill Gate                                                       (b) Steve Jobs

(c) Paul Alien                                                     (d) All of these

(e) None of these

Answer (b)


  1. The internal structure of OS is divided into three parts including kernel, shell and interface. Which one of the following parts of OS cannot be replaced or modified by user?

(a) Kernel                                                           (b) Shell

(c) Interface                                                        (d) All of these

(e) None of these

Answer (a)


  1. Which of the following statements is true?

Statement A: UNIX operating system supports three command-line shells.

Statement B: C shell is a type of command line shell.

Statement C: The Korn shell is the unix shell that was developed by David Korn.

(a) Statement A is correct

(b) Statement B is correct

(c) Statement C is correct

(d) All statement are correct

(e) None of these

Answer (d)


Multitasking OS

Operating systems that allows multiple software processes to be run at the same time is called multitasking OS, such as Microsoft Windows 10 and Linux. It means multitasking operating systems allow a user to do more than one thing at the same time. For example, when working on Windows operating system, you can listen to music and work on MS Word simultaneously. This is one of the best examples of multitasking OS.


OS as Resource Manager

Operating system works as a resource manager. It involves the following.


v  Process management

v  Multiprogramming

v  Memory Management

v  Spooling.


Process Management

In computer science process is a program execution. During program execution, a process needs various resources such as CPU time, memory space, files and I/O devices. At a particular instance of time, a computer system normally consists of a collection of processes. The process management module of an operating system involves creation and deletion of processes, scheduling of various system resources to the different processes requesting them and providing mechanism for synchronization and communication among processes.


Job Scheduling is a kind of software application which provides a GUI and a single point of control for monitoring of background executions.



The concept of multiprogramming brings new revolution in computer's world. Basically multiprogramming is a technique to execute number of programs simultaneously by one processor. In multiprogramming more than one job reside in main memory at a time. The operating system picks the job one by one and executes simultaneously in the main memory. For example, you can work MS Word, MS Excel and Power point simultaneously. Various operating systems, such as Windows 7, Mac and Linux support multiprogramming.


Memory Management

Memory management is one of the most important parts of the operating system. In early days, execution of computer programs was based on existing memory. The concept of virtual memory overcomes this limitation. Basically virtual memory is a technique which enables to run a big program on available memory. For example, you can run 600 MB program on 32 MB RAM. The memory management module of an operating system takes care of the allocation and deal location of memory space to the various programs in need of this resource.



Simultaneous Peripheral Operations On Line (Spooling) is a process of transferring data. Program is used to buffer data for the printer and remote batch terminals. This process sends the output to the disk and printer does not interact with CPU during printing. Spooling utilities are used mainly in computer systems with multi - user/ networking - environment. In networking/ multi - user environments, the input and output devices are generally slow. Due to this the processing of computer is also slowed down. To control such kind of slowed down, the spooling programs are used.


Time Sharing Operating Systems

In time sharing system multiple jobs are executed by switching the CPU between them and the CPU time is shared by different processes. In this environment various users are sharing the central processor, the memory and other resources of the computer system in a manner facilitated, controlled and monitored by the operating system. UNIX is the best example of time sharing operating system.


Common Asked Question?



  1. Multitasking OS allows performing more than one task simultaneously. Which one of the following OS does not support multitasking?

(a) Linux                                                                       (b) Windows 7

(c) DOS                                                                         (d) All of these

(e) None of these

Answer (c)


  1. OS is a master control programs which performs various functions. Which of the following are the functionality of an OS?

(a) Process Management                                      (b) Spooling

(c) Memory Management                                     (d) All of these

(e) None of these

Answer (d)


  1. Which one of the following is the correct full form of Spooling?

(a) Simultaneous Peripheral Operations Of Line

(b) Simultaneous Peripheral Operations On Line

(c) Simultaneous Practical Operations On Line

(d) Simultaneous Peripheral On Line Operations

(e) None of these

Answer (b)

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