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Operating System Mcq [SET - 18] | gate questions on operating system with answers pdf

 

gate questions on operating system with answers pdf



1. When the page fault rate is low

    the turnaround time increases
    the effective access time increases
    the effective access time decreases

ANSWER= (C)  the effective access time decreases

 

2. An edge from process Pi to Pj in a wait for graph indicates that                          

    pi is waiting for pj to release a resource that pi needs
    pj is waiting for pi to release a resource that pj needs
    pi is waiting for pj to leave the system

ANSWER= (A) pi is waiting for pj to release a resource that pi needs

 

3. Swapping be done when a process has pending I/O, or has to execute I/O operations only into operating system buffers.

    must
    can
     must never

ANSWER= (C) must never

 

4. The usefulness of signals as a general inter process communication mechanism is limited because                          

    they do not work between processes
    they are user generated
    they cannot carry information directly

ANSWER= (C) they cannot carry information directly

 

5. Which of the following condition(s) is/are required for a deadlock to be possible?

    mutual exclusion
    a process may hold allocated resources while awaiting
     no resource can be forcibly removed from a process

ANSWER= (D) All of the mentioned

 

6. The model in which one kernel thread is mapped to many user-level threads is called

    many to one model
    one to many model
    many to many model

ANSWER= (A) many to one model

 

7. Which of the following page replacement algorithms suffers from Belady’s Anomaly?

    optimal replacement
    lru
    fifo

ANSWER= (C) fifo

 

8. In question 2, if the number of page frames is increased to 4, then the number of page transfers                          

    decreases
    increases
    remains the same

ANSWER= (B) increases

 

9. A memory page containing a heavily used variable that was initialized very early and is in constant use is removed, then the page replacement algorithm used is                          

    lru
    lfu
    fifo

ANSWER= (C) fifo

 

10. Users   that their processes are running on a paged system.

    are aware
    are unaware
    may unaware

ANSWER= (B) are unaware

 

11. The wait-for graph is a deadlock detection algorithm that is applicable when

     all resources have a single instance
    all resources have multiple instances
    all resources have a single 7 multiple instances

ANSWER= (A)  all resources have a single instance

 

12. The content of the matrix Need is

    allocation – available
     max – available
    max – allocation

ANSWER= (C) max – allocation

 

13. The data structures available in the Banker’s algorithm are                          

    available
    need
    allocation

ANSWER= (D) all of the mentioned

 

14. In the Many to One model, if a thread makes a blocking system call                        

     the entire process will be blocked
    a part of the process will stay blocked, with the rest running
    the entire process will run

ANSWER= (A) the entire process will be blocked

 

15.If the offset is legal 

    it is used as a physical memory address itself
    it is subtracted from the segment base to produce the physical memory address
     it is added to the segment base to produce the physical memory address

ANSWER= (A) it is used as a physical memory address itself

 

16. Which of the following system calls does not return control to the calling point, on termination?

    fork
    exec
    ioctl

ANSWER= (B) exec

 

17. File type can be represented by                          

    file name
    file extension
    file identifier

ANSWER= (C)  file extension

 

18. In virtual memory, which is not a page replacement algorithm ?

    FIFO
    BFS
     LRU
ANSWER= (B) BFS

 

19. The larger the block size, the the internal fragmentation.

     greater
    lesser
    same

ANSWER= (A) greater

 

20. Which of the following is FALSE?

     context switch time is longer for kernel level threads than for user level threads
    user level threads do not need any hardware support
    related kernel level threads can be scheduled on different processors in a multiprocessor system

ANSWER= (A) blocking one kernel level thread blocks all other related threads


 

21. Thrashing the CPU utilization.

    increases
    keep constant
    decreases

ANSWER= (C) decreases

 

22. The child process completes execution, but the parent keeps executing, then the child process is known as

     Orphan
    Zombie
     Body

ANSWER= (B) Zombie

 

23. A Process Control Block(PCB) does not contain which of the following?

    Code
    Stack
    Bootstrap Program

ANSWER= (C) Bootstrap Program

 

24. If one thread opens a file with read privileges then                        

    other threads in the another process can also read from that file
    other threads in the same process can also read from that file
    any other thread can not read from that file

ANSWER= (B) other threads in the same process can also read from that file

 

25. A thread is also called                        

    light weight process(lwp)
    heavy weight process(hwp)
     process

ANSWER= (A) light weight process(lwp)

 

26. The model in which one user-level thread is mapped to many kernel level threads is called                        

    many to one model
    one to many model
    many to many model

ANSWER= (B) one to many model

 

27. The time taken to move the disk arm to the desired cylinder is called the                          

    positioning time
    random access time
    seek time

ANSWER= (A) seek time

 

28. Operating System maintains the page table for

    each process
     each thread
    each instruction

ANSWER= (A)  each process

 

29. What is the idea behind thread pools?

     a number of threads are created at process startup and placed in a pool where they sit and wait for work
    when a process begins, a pool of threads is chosen from the many existing and each thread is allotted equal amount of work
    all threads in a pool distribute the task equally among themselves

ANSWER= (A)  a number of threads are created at process startup and placed in a pool where they sit and wait for work

 

30. The time taken for the desired sector to rotate to the disk head is called

    positioning time
     random access time
    seek time

ANSWER= (D) rotational latency



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