20 Most Repeated Operating System MCQs from NTS, CSS, PMS, KPPSC, PPSC, ETEA, SPSC, BPSC, and FPSC Past Papers

Here is 20 most repeated Operating System MCQs from Pakistani past papers, complete with correct answers and explanations. These Operating Systems MCQs is a highly tested subject across all these testing agencies.

1. What is the core of an Operating System that manages memory, CPU, and other hardware?

A) Shell
B) GUI
C) Kernel
D) System Call

Correct Answer: C) Kernel
Explanation: The kernel is the central component (or the heart) of an operating system. It remains in the main memory and manages all hardware and system resources, acting as a bridge between software applications and the physical hardware.

2. Which of the following is a synchronization tool used to solve the critical section problem?

A) Deadlock
B) Semaphore
C) Thread
D) Paging

Correct Answer: B) Semaphore
Explanation: A semaphore is an integer variable used to manage concurrent processes. It helps control access to a common resource by multiple processes and avoids race conditions in the critical section.

3. The Banker’s Algorithm is used for which of the following purposes?

A) Deadlock Prevention
B) Deadlock Recovery
C) Deadlock Avoidance
D) Deadlock Detection

Correct Answer: C) Deadlock Avoidance
Explanation: The Banker's Algorithm ensures that a system never enters an unsafe state. It simulates the allocation of predetermined maximum possible amounts of all resources, making an "avoidance" decision before actually allocating them.

4. A situation where a process spends more time paging than executing is called:

A) Thrashing
B) Swapping
C) Spooling
D) Context Switching

Correct Answer: A) Thrashing
Explanation: Thrashing occurs when a computer's virtual memory subsystem is in a constant state of paging, rapidly exchanging data in memory for data on disk, to the exclusion of most application-level processing.

5. Which scheduling algorithm allocates the CPU first to the process that arrives first?

A) Shortest Job First (SJF)
B) Round Robin (RR)
C) First-Come, First-Served (FCFS)
D) Priority Scheduling

Correct Answer: C) First-Come, First-Served (FCFS)
Explanation: FCFS is the simplest CPU scheduling algorithm. Processes are dispatched according to their arrival time on the ready queue.

6. The Round Robin (RR) scheduling algorithm is primarily designed for:

A) Batch Systems
B) Time-Sharing Systems
C) Real-Time Systems
D) Distributed Systems

Correct Answer: B) Time-Sharing Systems
Explanation: Round Robin assigns a fixed time quantum (or time slice) to each process in equal portions and in a circular order, ensuring fairness and responsiveness, which is essential for time-sharing environments.

7. What is Virtual Memory?

A) A technique to allow a program to execute even if it is larger than the main memory
B) An extremely large main memory
C) An extremely large secondary memory
D) A type of network memory

Correct Answer: A) A technique to allow a program to execute even if it is larger than the main memory
Explanation: Virtual memory gives the illusion of a large main memory by swapping pages of data back and forth between the RAM and the hard disk, allowing large applications to run smoothly.

8. The process of saving the state of an old process and loading the saved state of a new process is known as:

A) Multiprogramming
B) Context Switching
C) Thrashing
D) Spooling

Correct Answer: B) Context Switching
Explanation: Context switching enables multiple processes to share a single CPU. The OS saves the Process Control Block (PCB) of the currently running process and loads the PCB of the next process to be executed.

9. What does "PCB" stand for in the context of Operating Systems?

A) Program Control Block
B) Process Control Block
C) Printed Circuit Board
D) Process Communication Block

Correct Answer: B) Process Control Block
Explanation: A PCB is a data structure in the operating system kernel containing the information needed to manage a particular process (like process state, program counter, CPU registers, etc.).

10. Which memory allocation strategy allocates the smallest hole that is large enough to accommodate the process?

A) First Fit
B) Best Fit
C) Worst Fit
D) Next Fit

Correct Answer: B) Best Fit
Explanation: Best fit searches the entire list of free memory blocks and allocates the smallest block that is large enough. This strategy minimizes wasted memory space (internal fragmentation).

11. What is a "Thread" in OS terminology?

A) A heavy-weight process
B) A memory management block
C) A lightweight process
D) An interrupt handler

Correct Answer: C) A lightweight process
Explanation: A thread is the smallest sequence of programmed instructions that can be managed independently by a scheduler. Multiple threads can exist within the same process and share its resources.

12. The time taken by the disk arm to locate the specific cylinder or track on a hard disk is called:

A) Rotational Latency
B) Transfer Time
C) Seek Time
D) Turnaround Time

Correct Answer: C) Seek Time
Explanation: Seek time is the physical time it takes for the read/write head of the disk drive to move to the correct track on the platter.

13. What is the primary objective of Multiprogramming?

A) To maximize CPU utilization
B) To minimize memory usage
C) To increase disk space
D) To execute one job at a time

Correct Answer: A) To maximize CPU utilization
Explanation: Multiprogramming keeps multiple programs in main memory at the same time so the CPU always has something to execute, thereby maximizing CPU utilization and preventing it from sitting idle.

14. The term "Spooling" stands for:

A) System Peripheral Operations On-Line
B) Simultaneous Peripheral Operations On-Line
C) Secondary Peripheral Operations On-Line
D) Storage Peripheral Operations On-Line

Correct Answer: B) Simultaneous Peripheral Operations On-Line
Explanation: Spooling is a process in which data is temporarily held to be used and executed by a device, program, or the system (e.g., sending multiple documents to a printer queue).

15. A situation where two or more processes are waiting indefinitely for an event that can be caused by only one of the waiting processes is known as:

A) Starvation
B) Deadlock
C) Race Condition
D) Mutual Exclusion

Correct Answer: B) Deadlock
Explanation: In a deadlock, each process holds a resource and waits to acquire a resource held by another process in the set, creating a cycle where no process can proceed.

16. Which of the following is not a valid state of a process?

A) Ready
B) Running
C) Blocked
D) Stored

Correct Answer: D) Stored
Explanation: The standard process states in an OS lifecycle are New, Ready, Running, Blocked (or Waiting), and Terminated. "Stored" is not an official process state.

17. Dividing logical memory into blocks of the same size is called:

A) Segmentation
B) Paging
C) Swapping
D) Fragmentation

Correct Answer: B) Paging
Explanation: Paging is a memory management scheme that eliminates the need for contiguous allocation of physical memory. Logical memory is divided into equal-sized blocks called "pages," and physical memory is divided into equal-sized blocks called "frames."

18. Inter-Process Communication (IPC) is required for:

A) Executing a single process efficiently
B) Processes executing concurrently to share data and synchronize actions
C) Stopping the CPU execution
D) Booting the operating system

Correct Answer: B) Processes executing concurrently to share data and synchronize actions
Explanation: IPC mechanisms (like shared memory or message passing) allow processes to communicate with each other and synchronize their actions when they are cooperating to perform a specific task.

19. What is "Bootstrapping" in an Operating System?

A) Installing the OS
B) Compiling an application
C) The process of starting or restarting a computer
D) Managing memory

Correct Answer: C) The process of starting or restarting a computer
Explanation: Bootstrapping (or booting) is the initial set of operations that a computer system performs when electrical power to the CPU is switched on. It loads the operating system into the main memory.

20. A program in execution is called a:

A) File
B) Process
C) Thread
D) Task

Correct Answer: B) Process
Explanation: While a program is a passive entity (like a file on a disk), a process is an active entity. It is a program that has been loaded into memory and is currently being executed by the CPU.