Operating System MCQs - Threads, fork(), IPC and System Calls (Set 4)

Q1. Which of the following is NOT shared by threads of the same process?

a) Global variables

b) Open files

c) Stack

d) Code section

Q2. Why is switching between threads of the same process usually faster than switching between processes?

a) The address space does not have to be changed

b) Threads never use the CPU

c) The kernel is not involved at all

d) Threads have higher priority

Q3. What is the main drawback of the many-to-one threading model?

a) Threads cannot share memory

b) It needs special hardware

c) It uses too many kernel threads

d) A blocking system call by one thread blocks the entire process

Q4. What value does fork() return in the child process?

a) The parent's PID

b) 0

c) -1

d) The child's PID

Q5. How many times is "hello" printed by this C program?

#include <stdio.h>
#include <unistd.h>

int main() {
    fork();
    fork();
    fork();
    printf("hello\n");
    return 0;
}

a) 6

b) 8

c) 4

d) 3

Q6. What does a successful call to exec() do?

a) Terminates the parent process

b) Duplicates the file descriptors only

c) Creates a new child process

d) Replaces the current process image with a new program

Q7. A zombie process is one that:

a) Has finished, but its parent has not yet called wait() to read its exit status

b) Has lost its parent

c) Is using 100 percent of the CPU

d) Is waiting for I/O

Q8. What happens to an orphan process in Linux?

a) It is moved to swap space

b) It is killed immediately

c) It is adopted by init (PID 1) or systemd, which later reaps it

d) It becomes a zombie forever

Q9. An ordinary (unnamed) pipe is best described as:

a) A form of shared memory

b) A network socket

c) Bidirectional communication between any two processes

d) Unidirectional communication, usually between related processes such as parent and child

Q10. Which IPC mechanism is generally the fastest once it is set up?

a) Shared memory

b) Sockets

c) Pipes

d) Message queues

Q11. When a user program makes a system call, the CPU:

a) Disables all interrupts permanently

b) Stays in user mode

c) Switches from user mode to kernel mode through a trap

d) Restarts the process

Q12. In the classic dual-mode design described in textbooks, what is the mode bit's value in kernel mode?

a) 1

b) 0

c) 2

d) -1

Q13. Which Linux signal can be neither caught nor ignored by a process?

a) SIGKILL

b) SIGHUP

c) SIGTERM

d) SIGINT

Q14. What is a key advantage of kernel-level threads over user-level threads?

a) They need no system calls

b) They use no memory

c) They are always faster to create

d) The kernel can schedule them on different processors at the same time

Q15. How does a microkernel differ from a monolithic kernel?

a) It cannot support multitasking

b) It runs all services in kernel space

c) It keeps only essential services in the kernel and runs drivers and file systems as user-space processes

d) It has no kernel mode