Welcome to the Operating System MCQs Page

Dive deep into the fascinating world of Operating System with our comprehensive set of Multiple-Choice Questions (MCQs). This page is dedicated to exploring the fundamental concepts and intricacies of Operating System, a crucial aspect of GATE CSE Exam. In this section, you will encounter a diverse range of MCQs that cover various aspects of Operating System, from the basic principles to advanced topics. Each question is thoughtfully crafted to challenge your knowledge and deepen your understanding of this critical subcategory within GATE CSE Exam.

Check out the MCQs below to embark on an enriching journey through Operating System. Test your knowledge, expand your horizons, and solidify your grasp on this vital area of GATE CSE Exam.

Note: Each MCQ comes with multiple answer choices. Select the most appropriate option and test your understanding of Operating System. You can click on an option to test your knowledge before viewing the solution for a MCQ. Happy learning!

Operating System MCQs | Page 12 of 16

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Q111.

Assume every process requires 3 seconds of service time in a system with single processor. If new processes are arriving at the rate of 10 processes per minute, then estimate the fraction of time CPU is busy in system?

20%

30%

50%

60%

Discuss

Answer: (c).50%

Q112.

Consider the following code fragment:

if (fork() == 0)
{ a = a + 5; printf("%d,%d\n", a, &a); }
else { a = a –5; printf("%d, %d\n", a, &a); }

Let u, v be the values printed by the parent process, and x, y be the values printed by the child process. Which one of the following is TRUE?

u = x + 10 and v = y

u = x + 10 and v != y

u + 10 = x and v = y

u + 10 = x and v != y

Discuss

Answer: (c).u + 10 = x and v = y

Q113.

The atomic fetch-and-set x, y instruction unconditionally sets the memory location x to 1 and fetches the old value of x in y without allowing any intervening access to the memory location x. consider the following implementation of P and V functions on a binary semaphore .

void P (binary_semaphore *s) {
unsigned y;
unsigned *x = &(s->value);
do {
fetch-and-set x, y;
} while (y);
}

void V (binary_semaphore *s) {
S->value = 0;
}

Which one of the following is true?

The implementation may not work if context switching is disabled in P

Instead of using fetch-and-set, a pair of normal load/store can be used

The implementation of V is wrong

The code does not implement a binary semaphore

Discuss

Answer: (a).The implementation may not work if context switching is disabled in P

Q114.

Three concurrent processes X, Y, and Z execute three different code segments that access and update certain shared variables. Process X executes the P operation (i.e., wait) on semaphores a, b and c; process Y executes the P operation on semaphores b, c and d; process Z executes the P operation on semaphores c, d, and a before entering the respective code segments. After completing the execution of its code segment, each process invokes the V operation (i.e., signal) on its three semaphores. All semaphores are binary semaphores initialized to one. Which one of the following represents a deadlockfree order of invoking the P operations by the processes?

X: P(a)P(b)P(c) Y:P(b)P(c)P(d) Z:P(c)P(d)P(a)

X: P(b)P(a)P(c) Y:P(b)P(c)P(d) Z:P(a)P(c)P(d)

X: P(b)P(a)P(c) Y:P(c)P(b)P(d) Z:P(a)P(c)P(d)

X: P(a)P(b)P(c) Y:P(c)P(b)P(d) Z:P(c)P(d)P(a)

Discuss

Answer: (b).X: P(b)P(a)P(c) Y:P(b)P(c)P(d) Z:P(a)P(c)P(d)

Q115.

A shared variable x, initialized to zero, is operated on by four concurrent processes W, X, Y, Z as follows. Each of the processes W and X reads x from memory, increments by one, stores it to memory, and then terminates. Each of the processes Y and Z reads x from memory, decrements by two, stores it to memory, and then terminates. Each process before reading x invokes the P operation (i.e., wait) on a counting semaphore S and invokes the V operation (i.e., signal) on the semaphore S after storing x to memory. Semaphore S is initialized to two. What is the maximum possible value of x after all processes complete execution?

-2

-1

Discuss

Answer: (d).2

Q116.

A process executes the code
fork();
fork();
fork();
The total number of child processes created is

Discuss

Answer: (c).7

Q117.

Fetch_And_Add(X,i) is an atomic Read-Modify-Write instruction that reads the value of memory location X, increments it by the value i, and returns the old value of X. It is used in the pseudocode shown below to implement a busy-wait lock. L is an unsigned integer shared variable initialized to 0. The value of 0 corresponds to lock being available, while any non-zero value corresponds to the lock being not available.

AcquireLock(L){
while (Fetch_And_Add(L,1))
L = 1;
}
ReleaseLock(L){
L = 0;
}

This implementation

fails as L can overflow

fails as L can take on a non-zero value when the lock is actually available

works correctly but may starve some processes

works correctly without starvation

Discuss

Answer: (b).fails as L can take on a non-zero value when the lock is actually available

Q118.

The time taken to switch between user and kernel modes of execution be t1 while the time taken to switch between two processes be t2. Which of the following is TRUE?

t1 > t2

t1 = t2

t1 < t2

nothing can be said about the relation between t1 and t2

Discuss

Answer: (c).t1 < t2

Q119.

A thread is usually defined as a "light weight process" because an operating system (OS) maintains smaller data structures for a thread than for a process. In relation to this, which of the following is TRUE?

On per-thread basis, the OS maintains only CPU register state

The OS does not maintain a separate stack for each thread

On per-thread basis, the OS does not maintain virtual memory state

On per-thread basis, the OS maintains only scheduling and accounting information

Discuss

Answer: (c).On per-thread basis, the OS does not maintain virtual memory state

Q120.

Consider the methods used by processes P1 and P2 for accessing their critical sections whenever needed, as given below. The initial values of shared boolean variables S1 and S2 are randomly assigned.

Method Used by P1
while (S1 == S2) ;
Critica1 Section
S1 = S2;

Method Used by P2
while (S1 != S2) ;
Critica1 Section
S2 = not (S1);

Which one of the following statements describes the properties achieved?

Mutual exclusion but not progress

Progress but not mutual exclusion

Neither mutual exclusion nor progress

Both mutual exclusion and progress

Discuss

Answer: (a).Mutual exclusion but not progress

Page 12 of 16

Welcome to the Operating System MCQs Page

Operating System MCQs | Page 12 of 16

Explore more Topics under GATE CSE Exam

Networking

Data Structures and Algorithms

Computer Architecture

DBMS

Compiler Design

Theory of Computation(TOC)

Engineering Mathematics

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