Operating Systems — DU B. Sc. (Hons) Electronics Previous Year Question Papers

(a) Differentiate between concurrent programming, multiprogramming and multitasking. (b) List three major responsibilities of the operating system kernel for memory management. (c) Name different process scheduling algorithms. How is scheduling different from synchronization? (d) Differentiate between internal and external fragmentation. Explain in brief the use of virtual memory. (e) Briefly explain disk scheduling. Name any two disk scheduling algorithms. (f) What is Indexed Sequential File structure? Explain with a suitable diagram. 2. (a) Explain the four layered architecture of a computer system. Is it possible for the user to interact directly with the hardware without involving the kernel and application layers? How? What are the roles of the Operating system kernel? Explain briefly the syntax and use of the OS kernel system calls - fopen( ) and fclose( ). (b) Discuss the Process state transition diagram. In how many states a process can exist in the memory. Explain in detail the transitions between these states with the help of flow diagram. 3. (a) For the processes listed in the following table, draw a GANTT chart illustrating their execution using the following: (ii) Non-preemptive Priority scheduling Process Arrival Time Burst Time Priority In this scenario, a larger priority number means a higher priority. Calculate the turnaround time for each process (rounded to the nearest hundredth) and the average throughput. (b) What is a critical section problem? Explain how semaphores can be used to solve it. Write the algorithm for a semaphore applied to the Dining Philosopher’s problem. 4 (a) Define deadlock among the processes. Discuss four necessary conditions for a deadlock to occur. Comment on Safe / Unsafe process execution zones. (b) Differentiate between deadlock prevention and deadlock avoidance. For the following Resource Allocation Table (RAT), develop the Resource Allocation Graph and verify if there is any deadlock in the system? Process Current Allocation Outstanding Requests Resources Available 5 (a) Explain paging with segmentation. Explain this hybrid concept with the help of a block diagram. How can you implement this concept in a modern operating system? (b) What is virtual memory? Discuss the working of demand paging with the help of virtual memory. (c) Illustrate how Least Recently Used (LRU) and FIFO page replacement policies work with a reference string example. 6. (a) What are the different directory structures used in operating systems? Explain any two. (b) Describe the following in detail: (i) File allocation methods (ii) Free-space management techniques in file systems 7. (a) Compare the working of the following disk scheduling algorithms: (iii) SCAN (b) What are three major methods of allocating disk space for effective file management? Explain the advantages and disadvantages of contiguous, linked and indexed file space allocation schemes.