9th Class Computers Science Understanding Basic Concepts of Operating System Structure of OS

     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: 

• Kernel
• Shell
• User Interface  

  Kernel

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

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 lie 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.  

 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)

Explanation

Correct Option:

(B) Steve Jobs and Wozniak are the founder of Apple

Incorrect Options:

Rest of the options is incorrect.    

 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)  

Explanation

Correct Option:

(A) Kernel cannot be replaced or modified by user.

Incorrect Options:

Rest of the options is incorrect.    

 Which of the following statements is true?

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

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

(A) Statement A is correct

(B) Statement B is correct

(C) Both statement A and B are correct

(D) Neither statement A nor statement B is correct

(E) None of these

Answer: (C)

Explanation

Correct Option:

(C) Both statements are correct.

Incorrect Options:

Rest of the options is incorrect.