Test Papers / Previous Question Papers of IGNOU CS13 Operating Systems December 2005

MCA (III Yr)
Term-End Examination

December, 2005

CS13 (S) : Operating Systems

Time: 3 hours
Maximum Marks: 75

1. (a) What type of operating systems would you prefer to work with for the following types of applications ? (4)
(i) Pay-slip generation
(ii) Process control of a chemical plant
Justify your answers.

(b) With the help of an example reference string diffetentiate between the Least Recently Used and Optimal Page Replacement policies. (6)

(c) Write, and explain, the Dekker's solution to the mutual exclusion Problem. (8)

(d) With the help of a diagram, explain the address translation scheme in segmented paging. (8)

(e) Explain why cross bar connected multiprocessors are generally regarded as having limited scalability. (4)

2. (a) There are five jobs in a queue, waiting to be processed. Their respective total process times are 6, 1, 2, 1 and 5.
(i) For the following scheduling policies, draw a Gantt chart showing when each of the five jobs will be executed :
(1) SJF (Shortest job first)
(2) Round Robin (quantum=1)
(ii) Assuming that jobs arrived at the same time, but were queued in the given order, determine the average turnaround time and average waiting time for each job under each of the policies above. (8)

(b) Write, and explain, the algorithm for election of a successor in a distributed system. Also discuss the correctness and performance of the algorithm. (7)

3. (a) Explain the common performance measures and optimization criteria that schedulers may use in attempting to maximize system performance. (7)

(b) Bell and LaPadula have devised a model of protection that combines the access matrix model with the classification hierarchy. Explain this model. (8)

4. (a) Explain the following dynamic memory allocation algorithms with an example for each : (6)
(i) First fit
(ii) Best fit
(iii) worst fit

(b) Explain the processor's scheduling in a multiprocessor O/S. (4)

(c) Explain the system programmer's view of the file system. (5)

5. (a) Explain the two basic strategies of non-contiguous allocation of disk space. (8)

(b) Write an algorithm to solve the producer/consumer problem with a bounded buffer using monitors. (7)