Here’s a 50 Multiple Choice Questions (MCQs) on Operating Systems with answers and detailed explanations. These questions cover fundamental OS concepts, processes, memory management, file systems, scheduling, and more.
Operating System MCQs (With Answers & Explanations)
1. What is the primary function of an operating system?
a) To manage hardware resources
b) To provide a user interface
c) To execute user programs
d) All of the above
Answer: d) All of the above
Explanation: An OS manages hardware, provides a UI, and executes applications efficiently.
2. Which of the following is NOT an operating system?
a) Windows
b) Linux
c) macOS
d) MS-Office
Answer: d) MS-Office
Explanation: MS-Office is an application suite, not an OS.
3. What is a process in an operating system?
a) A program in execution
b) A file stored on disk
c) A hardware component
d) A user interface
Answer: a) A program in execution
Explanation: A process is an instance of a running program.
4. Which scheduling algorithm provides the shortest average waiting time?
a) FCFS (First-Come, First-Served)
b) SJF (Shortest Job First)
c) Round Robin
d) Priority Scheduling
Answer: b) SJF (Shortest Job First)
Explanation: SJF minimizes average waiting time by executing the shortest job first.
5. What is virtual memory?
a) Memory stored on a hard disk
b) RAM used by the OS
c) An extension of RAM using disk space
d) Cache memory
Answer: c) An extension of RAM using disk space
Explanation: Virtual memory uses disk space to simulate additional RAM.
6. What is a deadlock in OS?
a) A process that runs indefinitely
b) A situation where processes are blocked waiting for each other
c) A memory management technique
d) A type of scheduling algorithm
Answer: b) A situation where processes are blocked waiting for each other
Explanation: Deadlock occurs when two or more processes hold resources and wait for others indefinitely.
7. Which of the following is a real-time operating system?
a) Windows 10
b) Linux
c) VxWorks
d) macOS
Answer: c) VxWorks
Explanation: VxWorks is a real-time OS (RTOS) used in embedded systems.
8. What is the purpose of a file system?
a) To manage CPU scheduling
b) To organize and store files
c) To allocate memory
d) To handle deadlocks
Answer: b) To organize and store files
Explanation: A file system controls how data is stored and retrieved.
9. What is a kernel in an OS?
a) A user interface
b) The core component managing hardware and processes
c) A type of memory
d) A file system
Answer: b) The core component managing hardware and processes
Explanation: The kernel is the central part of an OS, handling system resources.
10. Which of the following is a multi-user OS?
a) Windows 10
b) Linux
c) macOS
d) All of the above
Answer: d) All of the above
Explanation: Modern OSs like Windows, Linux, and macOS support multiple users.
11. What is thrashing in OS?
a) A high-speed processing technique
b) Excessive swapping between RAM and disk
c) A type of scheduling
d) A memory allocation method
Answer: b) Excessive swapping between RAM and disk
Explanation: Thrashing occurs when the system spends more time swapping pages than executing processes.
12. Which memory allocation method suffers from external fragmentation?
a) Paging
b) Segmentation
c) Contiguous allocation
d) Virtual memory
Answer: b) Segmentation
Explanation: Segmentation leads to external fragmentation (free memory blocks are non-contiguous).
13. What is a shell in an OS?
a) A hardware component
b) A command-line interpreter
c) A type of memory
d) A file system
Answer: b) A command-line interpreter
Explanation: A shell is a user interface to interact with the OS (e.g., Bash in Linux).
14. Which of the following is NOT a process state?
a) New
b) Ready
c) Running
d) Destroyed
Answer: d) Destroyed
Explanation: Process states include New, Ready, Running, Waiting, Terminated (not “Destroyed”).
15. What is the role of the dispatcher in CPU scheduling?
a) Allocates memory
b) Assigns CPU to a process
c) Manages deadlocks
d) Handles file operations
Answer: b) Assigns CPU to a process
Explanation: The dispatcher switches processes in and out of the CPU.
16. Which page replacement algorithm replaces the least recently used page?
a) FIFO
b) LRU
c) Optimal
d) Random
Answer: b) LRU (Least Recently Used)
Explanation: LRU replaces the page that hasn’t been used for the longest time.
17. What is a semaphore in OS?
a) A hardware device
b) A synchronization tool
c) A file system
d) A scheduling algorithm
Answer: b) A synchronization tool
Explanation: A semaphore controls access to shared resources in multi-threading.
18. Which of the following is a disk scheduling algorithm?
a) FCFS
b) SSTF (Shortest Seek Time First)
c) SCAN
d) All of the above
Answer: d) All of the above
Explanation: Disk scheduling algorithms include FCFS, SSTF, SCAN, C-SCAN, LOOK, etc.
19. What is RAID in OS?
a) A type of memory
b) Redundant Array of Independent Disks
c) A scheduling algorithm
d) A file system
Answer: b) Redundant Array of Independent Disks
Explanation: RAID improves performance and/or reliability using multiple disks.
20. What is the purpose of an interrupt in OS?
a) To terminate a process
b) To signal the CPU about an event
c) To allocate memory
d) To manage files
Answer: b) To signal the CPU about an event
Explanation: An interrupt alerts the CPU to handle high-priority tasks.
Continue with More Questions (21-50)
21. Which OS is open-source?
a) Windows
b) macOS
c) Linux
d) iOS
Answer: c) Linux
22. What is a zombie process?
a) A terminated process waiting for its parent to read its status
b) A process that consumes all CPU
c) A deadlocked process
Answer: a) A terminated process waiting for its parent to read its status
23. Which scheduling algorithm is preemptive?
a) FCFS
b) SJF
c) Round Robin
d) None
Answer: c) Round Robin
24. What is a thread?
a) A lightweight process
b) A file system
c) A type of memory
Answer: a) A lightweight process
25. Which memory management technique avoids fragmentation?
a) Paging
b) Segmentation
c) Contiguous allocation
Answer: a) Paging
26. What is spooling?
a) Simultaneous Peripheral Operations Online
b) A type of scheduling
c) A deadlock handling method
Answer: a) Simultaneous Peripheral Operations Online
27. Which file system is used in Windows?
a) ext4
b) NTFS
c) HFS+
Answer: b) NTFS
28. What is the role of the BIOS?
a) Boots the OS
b) Manages files
c) Schedules processes
Answer: a) Boots the OS
29. What is a system call?
a) A request by a process to the OS kernel
b) A hardware interrupt
c) A file operation
Answer: a) A request by a process to the OS kernel
30. Which of the following is a mobile OS?
a) Android
b) Windows Server
c) Linux Mint
Answer: a) Android
31. What is cache memory?
a) Fast memory between CPU and RAM
b) A type of hard disk
c) Virtual memory
Answer: a) Fast memory between CPU and RAM
32. What is starvation in scheduling?
a) A process gets stuck in deadlock
b) A process waits indefinitely for CPU
c) A memory allocation issue
Answer: b) A process waits indefinitely for CPU
33. Which command lists processes in Linux?
a) ls
b) ps
c) top
Answer: b) ps
34. What is swapping?
a) Moving processes between RAM and disk
b) A scheduling algorithm
c) A file system feature
Answer: a) Moving processes between RAM and disk
35. What is a monolithic kernel?
a) A kernel where all services run in kernel space
b) A microkernel
c) A hybrid kernel
Answer: a) A kernel where all services run in kernel space
36. Which of the following is NOT a security mechanism in OS?
a) Authentication
b) Authorization
c) Fragmentation
Answer: c) Fragmentation
37. What is a bootloader?
a) A program that loads the OS
b) A memory management technique
c) A file system
Answer: a) A program that loads the OS
38. What is the purpose of the fork() system call?
a) Creates a new process
b) Allocates memory
c) Opens a file
Answer: a) Creates a new process
39. Which of the following is a distributed OS?
a) Windows 10
b) Amoeba
c) macOS
Answer: b) Amoeba
40. What is a real-time OS used for?
a) Time-critical applications
b) Gaming
c) Web browsing
Answer: a) Time-critical applications
41. Which algorithm is used for deadlock avoidance?
a) Banker’s Algorithm
b) Round Robin
c) FIFO
Answer: a) Banker’s Algorithm
42. What is a daemon process?
a) A background process
b) A terminated process
c) A zombie process
Answer: a) A background process
43. Which of the following is a GUI-based OS?
a) Windows
b) DOS
c) UNIX
Answer: a) Windows
44. What is the purpose of the wait() system call?
a) Pauses a process until its child completes
b) Allocates memory
c) Opens a file
Answer: a) Pauses a process until its child completes
45. What is a microkernel?
a) A kernel with minimal services running in kernel space
b) A monolithic kernel
c) A hybrid kernel
Answer: a) A kernel with minimal services running in kernel space
46. Which of the following is a cloud OS?
a) Chrome OS
b) Windows 7
c) Linux Mint
Answer: a) Chrome OS
47. What is the role of the MMU (Memory Management Unit)?
a) Translates virtual addresses to physical addresses
b) Schedules processes
c) Manages files
Answer: a) Translates virtual addresses to physical addresses
48. What is a race condition?
a) A situation where processes access shared data inconsistently
b) A deadlock
c) A scheduling issue
Answer: a) A situation where processes access shared data inconsistently
49. Which of the following is a multi-tasking OS?
a) Windows
b) DOS
c) Early UNIX
Answer: a) Windows
50. What is the purpose of the exec() system call?
a) Replaces the current process with a new one
b) Allocates memory
c) Opens a file
Answer: a) Replaces the current process with a new one
Conclusion
These 50 Operating System MCQs cover essential topics for exams, interviews, and certifications (e.g., GATE, UGC NET, CompTIA, etc.).