OS Process Management

Question 101

On a system using non-preemptive scheduling, processes with expected run times of 5, 18, 9 and 12 are in the ready queue. In what order should they be run to minimize wait time?

• 5, 12, 9, 18
• 5, 9, 12, 18
• 12, 18, 9, 5
• 9, 12, 18, 5

Question 102

Feedback queues

• are very simple to implement
• dispatch tasks according to execution characteristics
• are used to favour real time tasks
• require manual intervention to implement properly

Question 103

Which of the following conditions does not hold good for a solution to a critical section problem ?

• No assumptions may be made about speeds or the number of CPUs.
• No two processes may be simultaneously inside their critical sections.
• Processes running outside its critical section may block other processes.
• Processes do not wait forever to enter its critical section.

Question 104

For switching from a CPU user mode to the supervisor mode following type of interrupt is most appropriate

• Internal interrupts
• External interrupts
• Software interrupts
• None of the above

Question 105

In a dot matrix printer the time to print a character is 6 m.sec., time to space in between characters is 2 m.sec., and the number of characters in a line are 200. The printing speed of the dot matrix printer in characters per second and the time to print a character line are given by which of the following options?

• 125 chars/second and 0.8 seconds
• 250 chars/second and 0.6 seconds
• 166 chars/second and 0.8 seconds
• 250 chars/second and 0.4 seconds
• 125 chars/second and 1.6 seconds

Question 106

Monitor is an Interprocess Communication (IPC) technique which can be described as

• It is higher level synchronization primitive and is a collection of procedures, variables, and data structures grouped together in a special package.
• It is a non-negative integer which apart from initialization can be acted upon by wait and signal operations.
• It uses two primitives, send and receive which are system calls rather than language constructs.
• It consists of the IPC primitives implemented as system calls to block the process when they are not allowed to enter critical region to save CPU time.

Question 107

The following C program

main()
{
    fork() ; fork() ; printf ("yes");
}

If we execute this core segment, how many times the string yes will be printed ?

• Only once
• 2 times
• 4 times
• 8 times

Question 108

Here are the two concurrent process P₁, P₂ with respective codes: P₁ code:

while (true) // infinite condition
{
A :____;
printf("%d", 1);
printf("%d", 1);
B:____;
}

P₂ code:

while (true) // infinite condition
{
C:____;
printf("%d", 0);
printf("%d", 0);
D:____;
}

What should be the binary semaphore operation on A,B,C,D respectively and what must be the intial values of semaphore M,N inorder to get the output 110011001100....? Where P is down and V is up operation respectively.

• A = P(N), B = V(M), C = P(M), D = V(N); M = 0, N = 1;
• A = P(N), B = V(M), C = P(M), D = P(N); M = N = 1;
• A = P(N), B = V(N), C = P(M), D = V(M); M = 1, N = 0;
• A = P(N), B = V(N), C = P(M), D = V(M); M = N = 1;

Question 109

At a particular time of computation, the value of a counting semaphore is 10. Then 12 P operations and “x” V operations were performed on this semaphore. If the final value of semaphore is 7, x will be:

• 8
• 9
• 10
• 11

Question 110

Consider the following statements about process state transitions for a system using preemptive scheduling.

• I. A running process can move to ready state.
• II. A ready process can move to running state.
• III. A blocked process can move to running state.
• IV. A blocked process can move to ready state.

Which of the above statements are TRUE ?

• I, II, and III only
• II and III only
• I, II, and IV only
• I, II, III and IV only