All Operating Systems questions

Single correct

• AShortest Remaining Time First (SRTF) Scheduling
• BFirst Come First Serve (FCFS) Scheduling
• CRound Robin Scheduling
• DPriority Scheduling

Wait(A);
Print(*);
X = X+1;
If (X == 2)
   {
      Print($);
      Signal(B);
   }
Signal(A);
Wait(B);
Print(#);
Signal(B);

One or more correct

• A**$*###
• B**$#*##
• C**$##*#
• D***$###

Numerical answer

Numerical answer

Numerical answer

Single correct

• A22
• B15
• C37
• D19

One or more correct

• ALeast Recently Used page replacement policy
• BLeast Frequently Used page replacement policy
• CMost Frequently Used page replacement policy
• DOptimal page replacement policy

One or more correct

• AAborting $P_1$ makes the system deadlock free.
• BAborting $P_3$ makes the system deadlock free.
• CAborting $P_2$ makes the system deadlock free.
• DAborting $P_1$ and $P_4$ makes the system deadlock free.

Numerical answer

One or more correct

• AAllocate a new page table for a newly created process
• BTranslate a virtual address to a physical address using the page table
• CRaise a trap when a virtual address is not found in the page table
• DRaise a trap when a process tries to write to a page marked with read-only permission in the page table

One or more correct

• AP makes a blocking system call to read a block of data from the disk
• BP tries to access a page that is in the swap space, triggering a page fault
• CAn interrupt is raised by the disk to deliver data requested by some other process
• DA timer interrupt is raised by the hardware

Single correct

• ASRTF = 6, NP-SJF = 7
• BSRTF = 6, NP-SJF = 7.5
• CSRTF = 7, NP-SJF = 7.5
• DSRTF = 7, NP-SJF = 8.5

// code of T1          // code of T2
wait(s1);               wait(s1);
x = x+1;                x = x+1;
print(x);               print(x);
wait(s2);               signal(s2);
signal(s1);             signal(s1);

One or more correct

• AT1 runs first and prints 1, T2 runs next and prints 2
• BT2 runs first and prints 1, T1 runs next and prints 2
• CT1 runs first and prints 1, T2 does not print anything (deadlock)
• DT2 runs first and prints 1, T1 does not print anything (deadlock)

Numerical answer

Numerical answer

One or more correct

• ATurnaround time includes waiting time.
• BThe goal is to only maximize CPU utilization and minimize throughput.
• CRound-robin policy can be used even when the CPU time required by each of the processes is not known apriori.
• DImplementing preemptive scheduling needs hardware support.

Answer key coming soon

int x = 0;  // global
Lock L1;    // global
main() {
  create a thread to execute foo();  // Thread T1
  create a thread to execute foo();  // Thread T2
  wait for the two threads to finish execution;
  print (x);}

foo() {
  int y = 0;
  Acquire L1;
  x = x + 1;
  y = y + 1;
  Release L1;
  print (y);}

One or more correct

• ABoth P1 and P2 will print the value of x as 2.
• BAt least one of P1 and P2 will print the value of x as 4.
• CAt least one of the threads will print the value of y as 2.
• DBoth T1 and T2, in both the processes, will print the value of y as 1.

Answer key coming soon

function OwnResource(Resource R)
    Acquire lock L // a global lock
    if R is available then
        Acquire R
        Release lock L
    else
        if R is owned by another process P then
            Terminate P, after releasing all resources owned by P
            Acquire R
            Restart P
            Release lock L
        end if
    end if
end function

One or more correct

• AThe scheme ensures that deadlocks will not occur.
• BThe scheme may lead to live-lock.
• CThe scheme may lead to starvation.
• DThe scheme violates the mutual exclusion property.

Answer key coming soon

<-------------- 39-bit virtual address -------------->
 ----------------------------------------------------
| Level 1  | Level 2  | Level 3  |    Page    |
| offset   | offset   | offset   |   offset   |
|__________|__________|__________|____________|
  9 bits     9 bits     9 bits      12 bits

Numerical answer

Answer key coming soon

Single correct

• AI and II only
• BIII only
• CIV only
• DIII and IV only

Answer key coming soon