Recents in Beach

System Structure View

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1. Simple  structure: 

 There are several commercial system that don’t have a well- defined 
structure such operating systems begins as small, simple & limited systems 
and then grow beyond their original scope. 
MS-DOS is an example of such system. 
It was not divided into modules carefully. 
Another example of limited structuring is the UNIX operating system. 


                                                    (MS DOS Structure) 
2. Layered approach: 
 In the layered approach, the OS is broken into a number of layers 
(levels) each built on top of lower layers.
 The bottom layer (layer o ) is the hardware & top most layer (layer N) is the user interface. 
The main advantage of the layered approach is modularity. 
• The layers are selected such that each users 
functions (or operations) & services of only 
lower layer. 
• This approach simplifies debugging & system verification, i.e. the first layer can be debugged without concerning the rest of the system. 
Once the first layer is debugged, its correct functioning is assumed while the 2nd layer is debugged & so on. 
• If an error is found during the debugging of a particular layer, the error must be on that layer because the layers below it are already debugged. 
Thus the design & implementation of the system are simplified when the system is broken down into layers. 
• Each layer is implemented using only operations provided by lower layers.
 A layer doesn’t need to know how these operations are implemented; it only needs to know what these operations do. 
• The layer approach was first used in the operating system. It was defined in six layers. 



The main disadvantage of the layered approach is: 

 • The main difficulty with this approach involves the careful definition of the layers, because a layer can use only those layers below it. 
For example, the device driver for the disk space used by virtual memory algorithm must be at a level lower than that of the memory management routines, because memory management requires the ability to use 
the disk space.  
• It is less efficient than a non layered system (Each layer adds overhead to the system call & the net result is a system call that take longer time than on a non layered system). 


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  1. What is an Operating System ?
  2. Discuss the structure off OS ?
  3. Explain type of OS?
  4. Explain Function of OS?
  5. Explain OS Services ?
  6. What do mean by system call ?List different type ofsystem call available ?

  1. what is process ? and Characteristics ?
  2. What is different process state? explain the same in details?
  3. write short note on user level and kernal level threads?
  4. explain what is thread and its type ?
  5. explain scheduler ? (short term,medium term,and long term)
  6. state and explain scheduling criteria ?
  7. Explain scheduling algorithm ? [ FCFS,SJF,PRIORITY,ROUND ROBINE.]    

  1. What is process synchronization ? explain critical section problem and race condition ?
  2. what is Race Condition ?
  3. what is critical section problem?
  4. explain classical problem of synchronization?
  5. explain bounded - buffer problem?
  6. explain reader - writer problem ?
  7. explain Dining Philosophers Problem ?
  8. explain semaphores ? its type ?

  1.  What is deadlock ?
  2. What are the 4 condition to produce deadlock ?
  3. explain methods of handling deadlock ?
  4. explain in detail deadlock prevention ?
  5. write short note on deadlock avoidance ?
  6. explain deadlock detection ? 
  7. explain Banker algorithm with example ? 

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