Operating System Test 2

Question 1
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The process executes the code where i is an integer:
for(i = 0; i <=15; i++)
{
if(i == 5)
continue;
fork();
if(i == 10)
break;
}
The total number of new processes created is _____.

A
2047

B
511

C
11

D
1023

Question 2
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Consider a system has hit ratio as h%. Average access time to service a page fault is s milliseconds and average effective memory access time is e in milliseconds. What is the memory access time in microseconds (m is considered with service time)?

A
100 × (10 × (s - e) + s × h)

B
1000 × e - 1000 × s + 100 × s × h

C
10 × (100 × (e - s) + s × h)

D
100 × (10 × (e - s) + s × h)

Question 3
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Which of the following is/are true of the auto-increment addressing mode?

I. It is useful in creating self-relocating code

II. If it is included in an Instruction Set Architecture, then an additional ALU is required for effective address calculation

III. The amount of increment depends on the size of the data item accessed

A
I only

B
II only

C
III only

D
II and III only

Question 4
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Consider a hypothetical processor with an instruction of type, which during execution reads a 32-bit word from memory and stores it in a 32-bit register. The effective address of the memory location is obtained by the addition of a constant 20 and the contents of register.

Which of the following best reflects the addressing mode implemented by this instruction for the operand in memory?

A
Immediate addressing

B
Register addressing

C
Register Indirect Scaled Addressing

D
Base Indexed Addressing

Question 5
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Which of the following statements are true?
(a) External Fragmentation exists when there is enough total memory space to satisfy a
request but the available space is contiguous.
(b) Memory Fragmentation can be internal as well as external.
(c) One solution to external Fragmentation is compaction.

A
(a) and (b) only

B
(a) and (c) only

C
(b) and (c) only

D
(a), (b) and (c)

Question 6
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Which of the following statement is not true about round – robin scheduling?

A
To implement RR scheduling, we keep the ready queue as a FIFO queue of processes.

B
If there are n processes in the ready queue and time quantum is q , then each process gets nq of the CPU time in chunks of atmost q time units.

C
Each process must wait for no longer than (n-1)/q time units until its next time quantum.

D
If the time quantum is too large, then Round robin scheduling behaves like FCFS.

Question 7
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Which of the following statement is correct about cascading termination of a child process?

A
The child has exceeded its usage of some of the resources that it has been allocated.

B
When the parent has terminated and operating system does not allow a child to exist.

C
When the task assigned to the child is no longer required.

D
When the child process finishes its execution

Question 8
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Given the Burst Time (BT) of 4 processes P1, P2, P3, and P4 as BT(t1, t2, t3, t4) – (4, 8, 6, 7), smoothening factor(α) – 0.5, and T1 = 10, what will be the burst time of process P5 for shortest Job first scheduling, using the technique of exponential averaging?

A
5.785 unit time

B
6.25 unit time

C
5.5 unit time

D
6.875 unit time

Question 9
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The probability that a process spends its time in performing I/O operations is 50%. In a multi programmed operating system environment, if there are 4 processes in memory at once, then the probability that all processes are waiting for I/O and the system utilization are respectively

A
¼, 5⁴

B
(0.5)⁴, 1 – (0.5)⁴

C
5, 5⁴

D
1/5⁴, 1 – (0.5)⁴

Question 10
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Consider the C struct defined below:

The base address of student is available in register R1. The field student.grade can be accessed efficiently using

A
Post-increment addressing mode, (R1)+

B
Pre-decrement addressing mode, -(R1)

C
Register direct addressing mode, R1

D
Index addressing mode, X(R1), where X is an offset represented in 2's complement 16-bit representation.

Question 11
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Mutual exclusion problem occurs

A
Between two disjoint processes that do not interact

B
Among processes that share resources

C
Among processes that do not use the same resource

D
Between two processes that uses different resources of different machine

Question 12
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Consider a system having 20 resources of same type. These resources are shared by 4 process which have peak demands of 4, 5, x, y respectively. What is the maximum value of x + y to ensure that there will be no deadlock in the system?

A
16

B
20

C
14

D
12

Question 13

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Consider the following scenario: A, B, C, D are processes and X, Y are resources used by the processes.

Process	has-X	has-Y	max-needs-X	max-needs-Y
A	35	10	65	40
B	55	80	105	220
C	35	20	110	50
D	0	70	50	90

If Resources available: [X: 40 Y: 40] then what will be a safe sequence so that the processes complete execution without deadlock?

ABDC

ACDB

ADCB

ACBD

Question 14
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Consider a shared variable with initial value 10, this shared variable is used by four concurrent processes A, B, C and D. Process A reads the shared variable and decrements it by two and process B reads the shared variable and increment it by three before writing it to the memory. Process C reads the shared variable and decrement it by three while process D reads the shared variable and increment it by two before writing it to the memory. All the process before reading the value performs the wait operation on a counting semaphore variable S and after writing it to the memory, a signal operation is performed before the processes get terminated. Find the minimum possible value of the shared variable in the memory if S is 2?

A
5-5

B
54-51

C
57-56

D
59-52

Question 15
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For the daisy chain scheme of connecting I/O devices, which of the following statements is true?

A
It gives non-uniform priority to various devices

B
It gives uniform priority to all devices

C
It is only useful for connecting slow devices to a processor device

D
It requires a separate interrupt pin on the processor for each device

Question 16
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Consider six memory partitions of size 250KB, 470KB, 600 KB, 500 KB, 300KB, and 410 KB where KB refers to kilobyte. These partitions need to be allotted to four processes of sizes 350 KB, 200 KB , 468 KB and 480 KB in that order. Which partitions are not allotted to any process when we use best fit and worst fit algorithm?

A
Best fit: 600KB, 300KBWorst fit: 250KB, 300KB, 410KB

B
Best fit: 250KB, 300KBWorst fit: 450 KB, 300KB, 250KB

C
Best fit: 450KB, 300 KBWorst fit:300KB, 410 KB

D
Best fit: 600KB, 500 KBWorst fit: 250 KB, 300 KB, 410KB

Question 17
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A demand - paging uses a TLB (Translation Look - aside Buffer) and single level page table stored in main memory. The memory access time is 5 μs and the page fault service time is 25 ms. If 70% of access is in TLB with no page fault and of the remaining, 20% is not present in main memory. The effective memory access time in ms is _________. (Write answer up to two decimal places)

A
1.49-1.51

B
1.494-1.511

C
1.497-1.516

D
1.499-1.512

Question 18
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Which of the following is/are TRUE about user-level threads and kernel-level threads?

A
Typically if a user-level thread is performing blocking system call then the entire process will be blocked

B
Kernel level threads are designed as dependent threads

C
Every thread has its own register and stack

D
Communication between multiple threads is easier than between two process.

Question 19
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A system uses FIFO policy for page replacement. It has 4 page frames with no pages loaded to begin with. The system first accesses 50 distinct pages in some order and then accesses the same 50 pages in reverse order. How many page faults will occur?

A
96

B
100

C
97

D
92

Question 20
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Consider the three processes P1, P2 and P3 shown below with their arrival time and burst time.
Which of the following statement is correct for this process table.
Processes
Arrival time
Burst time
P1
0
5
P2
1
7
P3
2
4

NOTE:
Time Quantum 2 units for Round robin

A
Average turn around time for SRTF = 9

B
Average turn around time for FCFS = 11

C
Average turn around time for Round robin = 12.6

D
Average turn around time for SJF = 10

Question 21
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Consider a Unix node which maintains 16 direct blocks pointer, 2 single indirect, 4 double indirect and 8 triple indirect block pointers. Disk block size if 8 KB and disk address is 32 bits. The maximum possible size of file is ____ TB (up to 1 decimal places).

A
512.0-512.2

B
512.04-512.21

C
512.07-512.26

D
512.09-512.22

Question 22
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The address sequence generated by tracing a particular program executing in a pure demand paging system with 100 records per page, with 1 free main memory frame is recorded as follows. What is the number of Page Faults?
0100, 0200, 0430, 0499, 0510, 0530, 0560, 0120, 0220, 0240, 0260, 0320, 0370

A
15

B
6

C
7

D
4

Question 23
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A system has n resources R₀,...., R ₁₂, and k processes P₀,...P_k-1.The implementation of the resource request logic of each process P_iis as follows:
if (i%2 == 0)
{
if (i < n) request R_i
if (i+2 < n) request R_i+2
}
else
{
if(i < n) request R_{n - i}
if (i+2 < n) request R_n-i-2
}
Maximum number of the process so deadlock is possible ______

A
8-8

B
84-81

C
87-86

D
89-82

Question 24
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The correct matching for the following pairs is:

(A) DMA I/O (1) High speed RAM

(B) Cache (2) Disk

(C) Interrupt I/O (3) Printer

(D) Condition Code Register (4) ALU

A
A-4 B-3 C-1 D-2

B
A-2 B-1 C-3 D-4

C
A-4 B-3 C-2 D-1

D
A-2 B-3 C-4 D-1

Question 25
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Which of the following control signals has separate destinations?

A
Data Paths

B
ALU & System Bus

C
Data Paths, ALU & System Bus

D
None of the above

Submit Test

Processes	Arrival time	Burst time
P1	0	5
P2	1	7
P3	2	4

Operating Syste...

Question 1

2047

511

11

1023

Question 2

100 × (10 × (s - e) + s × h)

1000 × e - 1000 × s + 100 × s × h

10 × (100 × (e - s) + s × h)

100 × (10 × (e - s) + s × h)

Question 3

I only

II only

III only

II and III only

Question 4

Immediate addressing

Register addressing

Register Indirect Scaled Addressing

Base Indexed Addressing

Question 5

(a) and (b) only

(a) and (c) only

(b) and (c) only

(a), (b) and (c)

Question 6

To implement RR scheduling, we keep the ready queue as a FIFO queue of processes.

If there are n processes in the ready queue and time quantum is q , then each process gets nq of the CPU time in chunks of atmost q time units.

Each process must wait for no longer than (n-1)/q time units until its next time quantum.

If the time quantum is too large, then Round robin scheduling behaves like FCFS.

Question 7

The child has exceeded its usage of some of the resources that it has been allocated.

When the parent has terminated and operating system does not allow a child to exist.

When the task assigned to the child is no longer required.

When the child process finishes its execution

Question 8

5.785 unit time

6.25 unit time

5.5 unit time

6.875 unit time

Question 9

¼, 54

(0.5)4, 1 – (0.5)4

5, 54

1/54, 1 – (0.5)4

Question 10

Post-increment addressing mode, (R1)+

Pre-decrement addressing mode, -(R1)

Register direct addressing mode, R1

Index addressing mode, X(R1), where X is an offset represented in 2's complement 16-bit representation.

Question 11

Between two disjoint processes that do not interact

Among processes that share resources

Among processes that do not use the same resource

Between two processes that uses different resources of different machine

Question 12

16

20

14

12

Question 13

ABDC

ACDB

ADCB

ACBD

Question 14

5-5

54-51

57-56

59-52

Question 15

It gives non-uniform priority to various devices

It gives uniform priority to all devices

It is only useful for connecting slow devices to a processor device

It requires a separate interrupt pin on the processor for each device

Question 16

Best fit: 600KB, 300KBWorst fit: 250KB, 300KB, 410KB

Best fit: 250KB, 300KBWorst fit: 450 KB, 300KB, 250KB

Best fit: 450KB, 300 KBWorst fit:300KB, 410 KB

¼, 5⁴

(0.5)⁴, 1 – (0.5)⁴

5, 5⁴

1/5⁴, 1 – (0.5)⁴