Jawaharlal Nehru Technological University Hyderabad 2007 M.C.A Computer Aplications OPERATING SYSTEMS -university exam paper

1.a) elaborate the main purposes of an operating system?
b) describe the essential differences ranging from the subsequent kinds of
operating systems:
i) Batch ii) Interactive
iii) Time sharing iv) Real time
c) What is the purpose of the command interpreter? Why is it usually
separate from the kernel?
2.a) describe the difference ranging from preemptive and non preemptive
scheduling. State why strict non preemptive scheduling is unlikely
to be used in a computer center.
b) 5 batch jobs A through E, arrive at a computer center at almost
the identical time. They have estimated running times of 10, 6, 2, four and
8 minutes. Their (externally determined) priorities are 3, 5, 2, one and
4, respectively, with five being the highest priority. For every of the
subsequent scheduling algorithms, determine the mean process turn
arount time. Ignore process switching overhead.
i) Round Robin ii) Priority scheduling
iii) 1st come, 1st served (run in order 10, 6, 2, 4, 8).
iv) Shortest job first.
For i) presume that the system is multi programmed and that every
job gets its fair share of the CPU. For ii) through iv) presume that
only 1 job at a time runs, until it finishes. All jobs are completely
CPU bound.
3.a) describe the critical part issue.
b) Write an algorithm for solving the critical-section issue for n
processes.
4.a) State and discuss the necessary conditions for a deadlock to occur.
b) discuss in detail how we can prevent the occurrence of a deadlock.
Contd….2
NR
Code No: NR-21/MCA -2-
5.a) discuss the difference ranging from logical and physical addresses.
b) Why are segmentation and paging combined into 1 scheme?
c) discuss briefly the use of inverted page table.
6.a) When do page faults occur? define the actions taken by the
operating system when a page fault occurs.
b) Consider the subsequent page reference string:
1,2,3,4,2,1,5,6,2,1,2,3,7,6,3,2,1,2,3,6 How many page faults
would occur for the subsequent replacement algorithms, assuming
three frames? Remember that all frames are initially empty, so your
first unique pages will all cost 1 fault every.
(i) LRU replacement (ii) optimal replacement
7.a) Distinguish ranging from the subsequent directory structures:
i) Acyclic – Graph Directories
ii) Tree structured directory structure.
b) discuss the various approaches used in implementing free-space
list.
8. Write notes on the following:
a) Capability based protection systems
b) Computer – security classifications.

Earning:   Approval pending.