Sample paper for Operating System

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Maximum Marks=100

Time Taken=3 hours

operating system

operating system

Attempt any five questions selecting atleast one question from each unit. All questions carry 20 marks each.

Unit 1:

Q.1 Describe the system’s programmer’s view of an operating system and name the most common schemes for defining the logical structure of directory.

Ans : System Programmer’s view – The systems programs are file management, status info, file modification, communication.

The most common schemes are single level directory, two – level directory, 3 – structured directories and graph directories.

Q.2 Discuss the concept of fragmentation in detail.

Ans : Fragmentation – When fixed partitioning scheme with equal partitions is used then due to the difference in size of the process and the partition, there occurs a hole or wasted space within the partition.

 

fragmentation

fragmentation

Unit 2

Q.3 (a) Explain the characteristics and function of an operating system.

Ans : An operating can be said to be a resource allocator, controls and coordinates the use of hardware, controls various user input-output programs.

(b) Briefly state and explain the functions of an operating system.

Ans : Processor management and scheduling, device management, file and data management, memory management are the functions of operating system.

Q.4 (a) What are critical regions? Explain semaphores with example.

Ans : Critical regions shift the responsibility for enforcing mutual exclusion from the programmer to the compiler.

Semaphores are negative integers on which operations are defined.

(b) Name the conditions whose occurence can be prevented by deadlock prevention?

Ans : Mutual exclusion, hold and wait, no preemption and circular wait.

 

Unit 3

Q.5 What is Belady’s anamoly? In which algorithm does it occur?

Ans : When the assumption turned out to be false in context that for some page replacement algorithms, the page fault rate may increase as the number of allocated frames increases. This  is known as belady’s anamoly.

Q.6 Discuss the following terms : 

(a) Banker’s Algorithm

Ans : This algorithm is used in banking system to ensure that it never allocates its available cash such that it can no longer satisfy the needs of all customers.

(b) Swapping in memory management

Ans : When a high priority process wants to be in ready state and there is no free partition to hold its process image then a process with lower priority is swapped from main memory to secondary memory.

 

Unit 4

Q.7 (a) Explain the file system of Unix.

Ans : The structure of Unix file system is hierarchical. The root of file system is always represented by slash.

(b) Write and explain ten external commands of DOS.

Ans : The various commands of DOS are append, attrib, backup, diskcomp, mick, format, join, mode, mem, tree, restore, recover, sys, xcopy.

Q.8 Discuss Interprocess communication of Unix.

Ans : Unix provides a rich environment for allowing processes to communicate with each other. Communication may be just a matter of letting another process know that some event has occurred, or it may involve transferring data from one process to another.

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