Operating System Test 1

Question 1
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The main function of the dispatcher (the portion of the process scheduler) is:

A
swapping a process to the disk

B
assigning ready process to the CPU

C
suspending some of the processes when the CPU load is high

D
bring processes from the disk to the main memory

Question 2
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Consider the following set of processes {A, B, C, D}, with the arrival time and the CPU burst time given in milliseconds.
Process Id
Arrival time
Burst time
A
4
3
B
9
1
C
0
4
D
8
5

What is the average waiting time in millisecond for these processes with the shortest job first algorithm?

A
0.75

B
1

C
1.25

D
1.5

Question 3
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Suppose there is a paging system with a translation lookaside buffer. Assuming that the entire page table and all the pages are in the physical memory, what is the effective memory access time in ms if it takes 5 msec to search the TLB and 70 msec to access physical memory? The TLB hit ratio is 0.8.

A
89-89

B
894-891

C
897-896

D
899-892

Question 4
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Consider a computer system having R resources of the same type and these resources are shared by 6 processes that have maximum demands of 7, 5, 3, 8, 4, 6 respectively. Then for what minimum values of R, the system will not be in deadlock?

A
26

B
27

C
28

D
29

Question 5
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Which of the following addressing modes permits relocation without any change whatsoever in the code?

A
Indirect addressing

B
Indexed addressing

C
PC relative addressing

D
None of the above

Question 6
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Which of the following is TRUE about user-level threads and kernel-level threads?
S₁: Typically if a user-level thread is performing blocking system call then the entire process will be blocked
S₂: Kernel level threads are designed as dependent threads
S₃: Every thread has its own register and stack

A
S₁ and S₂ only

B
S₂ and S₃ only

C
S₁ and S₃ only

D
All are true

Question 7
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Consider a hypothetical system with byte-addressable memory, 64-bit logical addresses, 8 Megabyte page size and page table entries of 16 bytes each. What is the size of the page table in the system in terabytes?

A
32-32

B
324-321

C
327-326

D
329-322

Question 8
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Suppose that jobs arrive according to the following schedule :

Process Arrival time Run time

A 0 12

B 3 7

C 6 2

D 8 5

E 9 2

F 12 12

Now give the sequence of the processes as they gets share of CPU if the scheduler used is Shortest Remaining Time First.

A
A,B,C,B,E,D,B,A,F

B
A,B,C,B,E,B,D,B,A,F

C
A,B,C,B,E,B,D,A,F

D
A,B,C,B,B,B,E,D,A,F

Question 9
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The maximum number of processes that can be in Ready state for a computer system with n CPUs is:

A
n

B
n²

C
2ⁿ

D
Independent of n

Question 10
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The process executes the code where x is an integer and x is initialized to 10
while(--x){
fork();
if(x == 2)
break;
}
The total number of child processes created is

A
255-255

B
2554-2551

C
2557-2556

D
2559-2552

Question 11
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A certain processor supports only the immediate and the direct addressing modes. Which of the following programminglanguage features cannot be implemented on this processor?

A
Pointers

B
Arrays

C
Records

D
Recursive procedures with local variable

Question 12
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A system has 12 identical resources and Y processes competing for them. Each process can request at most 3 resources. Which one of the following values of Y could lead to a deadlock?

A
5

B
6

C
7

D
Both 6 and 7

Question 13
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At time 0, an OS with round-robin scheduling (time quantum = 5 units) has 5 processes P_1,P₂, P₃, P₄, P₅ with burst times 15, 10, 20, 5, 15 respectively. What is the average turn-around time?

A
40 units

B
46 units

C
56 units

D
65 units

Question 14
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Which is the most appropriate match for the items in the first column with the items in the second column

A
(X, III) (Y, I) (Z, II)

B
(X, II) (Y, III) (Z, I)

C
(X, III) (Y, II) (Z, I)

D
(X, I) (Y, III) (Z, II)

Question 15
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Which of the following is/are not true about the deadlock scheme?
I. In deadlock avoidance, number the resource uniquely and never requests a lower-numbered resource
II. In deadlock avoidance, the request for the resources is always granted if the resulting state is safe.
III. In deadlock prevention, never request a resource after releasing any resource.

A
Only II

B
Only II and III

C
Only I and III

D
Only I, II and III

Question 16
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Consider a counting semaphore S. The operation P(S) performs the operation S = S – 1 and operation V(S) performs the operation V = V + 1. During program execution, 13P and 5V operation is performed in the some order. Find the number of processes in a blocked state with initial counting semaphore value 1.

A
7-7

B
74-71

C
77-76

D
79-72

Question 17
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In the absolute addressing mode

A
the operand is inside the instruction

B
the address of the operand in inside the instruction

C
the register containing the address of the operand is specified inside the instruction

D
the location of the operand is implicit

Question 18
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Which of the following addressing modes are suitable for program relocation at run time?

I. Absolute addressing

II. Based addressing

III. Relative addressing

IV. Indirect addressing

A
I and IV

B
I and II

C
II and III

D
I, II and IV

Question 19
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A computer uses 48 bits Virtual Address Space, 256 GB of physical memory with page size of 4 KB. The page table size is 4 bytes and if each entry fits in a single page the number of levels of paging required is _____.

A
4-4

B
44-41

C
47-46

D
49-42

Question 20

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Consider two processes P1 and P2 executing their respective codes initial values of global variables P1_inside and P2_inside are “false”.

while(true)

{

while(P1_inside);

P1 inside=true;

C.S. // critical section

P1 inside =false;

}

while(true)

{

while(P2_inside);

P2 inside=true;

C.S. // critical section

P2 inside=false;

}

Consider the below statements:

Mutual exclusion is satisfied
Mutual Exclusion is not satisfied
It is possible for deadlock

Which of the above are true?

Only 1

Only 2

Only 1 and 3

Only 2 and 3

Question 21
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Which of the following statements about relative addressing mode is FALSE?

A. It enables reduced instruction size

B. It allows indexing of array element with same instruction

C. It enables easy relocation of data

D. It enables faster address calculation than absolute addressing

A
A

B
B

C
C

D
D

Question 22

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	Allocation	Max	Available
	A B C D	A B C D	A B C D
P0	0 0 1 2	0 0 1 2	1 5 2 0
P1	1 0 0 0	1 7 5 0
P2	1 3 5 4	2 3 5 6
P3	0 6 3 2	0 6 5 2
P4	0 0 1 4	0 6 5 6

Which of the following is true for the above-given resource allocation table?

The system is in safe state

The system is in unsafe state

The system is in deadlock

Insufficient Information

Question 23
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Consider a file system that uses inodes to represent files. Disk blocks are 12 KB in size, and a pointer to a disk block requires 8 bytes. This file system has 10 direct disk blocks, as well as single and double indirect disk blocks. What is the maximum size in GB (up to two decimals) of a file that can be stored in this file system?

A
27.01-27.02

B
27.014-27.021

C
27.017-27.026

D
27.019-27.022

Question 24
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Consider a n-way set associative cache memory with 8 sets and 16 cache blocks (0-15) and a main memory with 512 blocks (0 - 511). What memory blocks will be present in the cache after the sequence 17, 4, 13, 105, 28, 29, 200, 408, 127, 205, 411, 251 if LRU is used as a cache replacement block?

A
17, 4, 13, 105, 28, 29, 200, 408, 127, 205, 411

B
17, 13, 105, 28, 29, 200, 408, 127, 205, 411, 251

C
17, 4, 105, 28, 29, 200, 408, 127, 205, 411, 251

D
4, 13, 105, 28, 29, 200, 408, 127, 205, 411, 251

Question 25
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Three CPU-bound tasks, with execution times of 15, 12 and 5 time units respectively arrive at times 0, t and 8, respectively. If the operating system implements a shortest remaining time first scheduling algorithm, what should be the value of t to have 4 context switches?
Ignore the context switches at time 0 and at the end.

A
0 < t < 3

B
t = 0

C
t < = 3

D
3 < t < 8

Submit Test

Process	Arrival time	Run time
A	0	12
B	3	7
C	6	2
D	8	5
E	9	2
F	12	12

Process Id	Arrival time	Burst time
A	4	3
B	9	1
C	0	4
D	8	5

Operating Syste...

Question 1

swapping a process to the disk

assigning ready process to the CPU

suspending some of the processes when the CPU load is high

bring processes from the disk to the main memory

Question 2

0.75

1

1.25

1.5

Question 3

89-89

894-891

897-896

899-892

Question 4

26

27

28

29

Question 5

Indirect addressing

Indexed addressing

PC relative addressing

None of the above

Question 6

S1 and S2 only

S2 and S3 only

S1 and S3 only

All are true

Question 7

32-32

324-321

327-326

329-322

Question 8

A,B,C,B,E,D,B,A,F

A,B,C,B,E,B,D,B,A,F

A,B,C,B,E,B,D,A,F

A,B,C,B,B,B,E,D,A,F

Question 9

n

n2

2n

Independent of n

Question 10

255-255

2554-2551

2557-2556

2559-2552

Question 11

Pointers

Arrays

Records

Recursive procedures with local variable

Question 12

5

6

7

Both 6 and 7

Question 13

40 units

46 units

56 units

65 units

Question 14

(X, III) (Y, I) (Z, II)

(X, II) (Y, III) (Z, I)

(X, III) (Y, II) (Z, I)

(X, I) (Y, III) (Z, II)

Question 15

Only II

Only II and III

Only I and III

Only I, II and III

Question 16

7-7

74-71

77-76

S₁ and S₂ only

S₂ and S₃ only

S₁ and S₃ only

n²

2ⁿ