Core Subjects
OS Questions Comprehensive collection of OS interview questions covering fundamentals, kernel architecture, hardware interfaces, and process concepts. Each answer is technical and interview-ready.
1. What is an Operating System? Beginner 2. What are the main functions of an Operating System? Beginner 3. What services are provided by an Operating System? Beginner 4. What is the difference between 32-bit and 64-bit Operating Systems? Intermediate 5. What is a Kernel? Explain its role. Intermediate 6. What is the difference between Kernel and OS? Intermediate 7. What is a Shell? Beginner 8. What are System Calls? Give examples. Intermediate 9. What is an API (Application Programming Interface)? Beginner 10. What is the difference between System Call and API? Intermediate 11. What is the difference between RAM and ROM? Beginner 12. What is the difference between SRAM and DRAM? Intermediate 13. What is the difference between PROM, EPROM, and EEPROM? Intermediate 14. What is the role of BIOS? Beginner 15. What is the difference between BIOS and UEFI? Intermediate 16. What is the difference between MBR and GPT? Intermediate 17. What happens when you turn on your computer? Explain the booting process. Advanced 18. What is the difference between Compiler, Interpreter, Assembler, and Loader? Intermediate 19. What is JVM (Java Virtual Machine)? Beginner 20. What is Virtualization? Beginner 21. What is Containerization? Intermediate 22. What is the difference between Virtualization and Containerization? Advanced 23. What is the difference between Monolithic Kernel and Microkernel? Advanced 24. Why does Windows use a Monolithic Kernel architecture? Advanced 25. What are the advantages and disadvantages of Microkernel architecture? Advanced 26. What is a Batch Operating System? Beginner 27. What is a Time-Sharing Operating System? Intermediate 28. What is a Distributed Operating System? Intermediate 29. What is a Network Operating System? Beginner 30. What is a Real-Time Operating System (RTOS)? Intermediate 31. What is the difference between Hard Real-Time and Soft Real-Time OS? Advanced 32. What is a Multi-user Operating System? Beginner 33. What is an Embedded Operating System? Intermediate 34. What is a Mobile Operating System? Beginner 35. Which type of OS is best suited for servers? Intermediate 36. What is a Process? Beginner 37. What is the difference between Process and Program? Intermediate 38. What are the different states of a Process? Intermediate 39. Draw and explain the Process State Diagram. Intermediate 40. What is a Process Control Block (PCB)? Intermediate 41. What information does a PCB contain? Advanced 42. How does a process look like in memory? Intermediate 43. What are the different sections of process memory layout? Advanced 44. What is the difference between Stack and Heap memory? Intermediate 45. What is a Zombie Process? Advanced 46. What is an Orphan Process? Advanced 47. What is the maximum number of Zombie processes a system can handle? Advanced 48. What is Context Switching? Intermediate 49. Why is Context Switching expensive? Advanced 50. What is Process Scheduling? Beginner 51. What are the different types of Schedulers? Intermediate 52. What is Long-Term Scheduler (Job Scheduler)? Intermediate 53. What is Short-Term Scheduler (CPU Scheduler)? Intermediate 54. What is Medium-Term Scheduler? Advanced 55. What is the difference between CPU-bound and I/O-bound processes? Intermediate 56. What is a Job Queue, Ready Queue, and Device Queue? Beginner 57. What is Inter-Process Communication (IPC)? Intermediate 58. What are the methods of IPC? Intermediate 59. What is the difference between Shared Memory and Message Passing? Advanced 60. What is a Pipe? Explain its types. Advanced 61. What is a Thread? Beginner 62. What is the difference between Process and Thread? Intermediate 63. What are the benefits of Multithreading? Intermediate 64. Give real-world examples of Multithreaded applications. Beginner 65. What is a User-Level Thread? Intermediate 66. What is a Kernel-Level Thread? Intermediate 67. What are the different Multithreading models? Advanced 68. Explain Many-to-One Threading Model. Advanced 69. Explain One-to-One Threading Model. Advanced 70. Explain Many-to-Many Threading Model. Advanced 71. Which is the best Threading Model and why? Advanced 72. What is the optimal number of threads per core? Advanced 73. How do multiple cores affect Multithreading performance? Intermediate 74. Why are static variables dangerous in Multithreading? Advanced 75. What is Thread Pool? Intermediate 76. What is Multiprogramming? Beginner 77. What is Multiprocessing? Beginner 78. What is Multitasking? Beginner 79. What is Multithreading? Beginner 80. What is the difference between Multiprogramming and Multitasking? Intermediate 81. What is the difference between Multitasking and Multithreading? Intermediate 82. What is the difference between Multiprocessing and Multithreading? Advanced 83. What is the difference between Concurrency and Parallelism? Advanced 84. What is Hyper-Threading? Intermediate 85. What is the degree of Multiprogramming? Intermediate 86. Why is CPU Scheduling needed? Beginner 87. What is a CPU Burst Cycle? Intermediate 88. What is CPU Scheduler? Beginner 89. What is Preemptive Scheduling? Intermediate 90. What is Non-Preemptive Scheduling? Intermediate 91. What is the difference between Preemptive and Non-Preemptive Scheduling? Advanced 92. Why is Preemptive Kernel better than Non-Preemptive Kernel? Advanced 93. What is Dispatcher? Intermediate 94. What is Dispatch Latency? Intermediate 95. What are the different Scheduling Criteria? Intermediate 96. What is CPU Utilization? Beginner 97. What is Throughput? Beginner 98. What is Turnaround Time (TAT)? Intermediate 99. What is Waiting Time? Intermediate 100. What is Response Time? Intermediate 101. Explain FCFS (First Come First Serve) Scheduling Algorithm. Beginner 102. Explain SJF (Shortest Job First) Scheduling Algorithm. Intermediate 103. Explain SRTF (Shortest Remaining Time First) Scheduling Algorithm. Advanced 104. Explain Priority-Based Scheduling Algorithm. Intermediate 105. Explain Round Robin Scheduling Algorithm. Intermediate 106. Explain Multilevel Queue Scheduling (MLQS). Advanced 107. Explain Multilevel Feedback Queue Scheduling (MLFQS). Advanced 108. Which Scheduling Algorithm is used in real-world Operating Systems? Advanced 109. What is Starvation in Scheduling? Intermediate 110. What is Aging? How does it prevent Starvation? Intermediate 111. Why is Process Synchronization needed? Beginner 112. What is Race Condition? Intermediate 113. What is Data Inconsistency? Intermediate 114. What is Critical Section? Intermediate 115. What is the Critical Section Problem? Advanced 116. What are the requirements for solving Critical Section Problem? Advanced 117. What is Mutual Exclusion? Beginner 118. Explain Peterson's Solution for Critical Section Problem. Advanced 119. What is a Semaphore? Intermediate 120. What is Binary Semaphore? Intermediate 121. What is Counting Semaphore? Advanced 122. What is the difference between Binary Semaphore and Mutex? Advanced 123. What is Busy Waiting? Intermediate 124. What is Spin Lock? Advanced 125. Give examples of Busy Waiting and Spin Lock. Advanced 126. How do you implement Semaphore in real-world programming? Intermediate 127. What is the Producer-Consumer Problem (Bounded Buffer Problem)? Advanced 128. What is the Reader-Writer Problem? Advanced 129. What is the Dining Philosopher Problem? Advanced 130. How is the Dining Philosopher Problem solved? Advanced 131. What is Deadlock? Beginner 132. What is Starvation? Intermediate 133. What is the difference between Deadlock and Starvation? Intermediate 134. Can a system be in Starvation without Deadlock? Advanced 135. Can a system be in Deadlock without Starvation? Advanced 136. What are the necessary conditions for Deadlock? Intermediate 137. Explain Mutual Exclusion condition. Intermediate 138. Explain Hold and Wait condition. Intermediate 139. Explain No Preemption condition. Intermediate 140. Explain Circular Wait condition. Intermediate 141. What are the effects of Deadlock on system performance? Beginner 142. What are the methods for handling Deadlock? Intermediate 143. What is Deadlock Prevention? Intermediate 144. How can you prevent Mutual Exclusion? Advanced 145. How can you prevent Hold and Wait? Advanced 146. How can you prevent No Preemption? Advanced 147. How can you prevent Circular Wait? Advanced 148. What is Deadlock Avoidance? Intermediate 149. What is Banker's Algorithm? Advanced 150. Explain Safe State and Unsafe State in Banker's Algorithm. Advanced 151. What is Deadlock Detection? Intermediate 152. What is Deadlock Recovery? Intermediate 153. What is Resource Preemption in Deadlock Recovery? Advanced 154. What is the Ostrich Algorithm? Beginner 155. When should we ignore Deadlock? Intermediate 156. What are the goals of Memory Management? Beginner 157. Why is Memory Management needed? Beginner 158. What is Logical Address Space? Intermediate 159. What is Physical Address Space? Intermediate 160. What is the difference between Logical and Physical Address? Intermediate 161. What is MMU (Memory Management Unit)? Advanced 162. How does mapping from Logical to Physical Address work? Advanced 163. What are Base and Limit Registers? Intermediate 164. How does OS protect Memory Space? Intermediate 165. What is Swapping? Intermediate 166. When is Swapping used? Beginner 167. What is the role of Dispatcher in Swapping? Advanced 168. Why is Context Switch time very high in Swapping? Advanced 169. What is Memory Allocation? Beginner 170. What is Contiguous Memory Allocation? Intermediate 171. What is Fixed Partitioning? Intermediate 172. What is Variable Partitioning? Advanced 173. What is the Dynamic Storage Allocation Problem? Advanced 174. Explain First Fit algorithm. Intermediate 175. Explain Best Fit algorithm. Intermediate 176. Explain Worst Fit algorithm. Intermediate 177. Which is the best Memory Allocation algorithm? Advanced 178. What is Internal Fragmentation? Intermediate 179. What is External Fragmentation? Intermediate 180. What is the difference between Internal and External Fragmentation? Intermediate 181. What is Compaction? Advanced 182. What is the difference between Compaction and Defragmentation? Intermediate 183. What is Non-Contiguous Memory Allocation? Intermediate 184. What is Paging? Intermediate 185. What is a Page and Frame? Beginner 186. What is a Page Table? Intermediate 187. What is Page Number and Page Offset? Advanced 188. What is PTLR (Page Table Limit Register)? Advanced 189. Why does Paging increase Context Switch time? Advanced 190. What is TLB (Translation Lookaside Buffer)? Advanced 191. What is Segmentation? Intermediate 192. What is a Segment Table? Intermediate 193. What is the difference between Paging and Segmentation? Advanced 194. Which is better: Paging or Segmentation? Intermediate 195. What is Segmentation with Paging? Advanced 196. What is a TLB Miss? Intermediate 197. What is the difference between TLB Miss and Page Fault? Advanced 198. What is the difference between Cache Miss and TLB Miss? Advanced 199. Can we use both Paging and Segmentation together? Intermediate 200. What are the advantages of Segmentation over Paging? Intermediate 201. What is Virtual Memory? Beginner 202. Why is Virtual Memory needed? Intermediate 203. Where is Virtual Memory physically located? Beginner 204. How is Virtual Memory implemented? Advanced 205. What is Demand Paging? Intermediate 206. What is the strategy of Demand Paging? Advanced 207. What is a Lazy Swapper? Intermediate 208. What is a Pager? Intermediate 209. What is a Page Fault? Intermediate 210. What happens when a Page Fault occurs? Advanced 211. What is Pure Demand Paging? Advanced 212. What is Swap Space? Beginner 213. What are the advantages of Virtual Memory? Beginner 214. How does Virtual Memory increase CPU Utilization? Intermediate 215. How does Virtual Memory increase Degree of Multiprogramming? Intermediate 216. Can Virtual Memory decrease performance? Intermediate 217. What is Page Replacement? Intermediate 218. Why is Page Replacement needed? Beginner 219. Explain FIFO Page Replacement Algorithm. Beginner 220. What is Belady's Anomaly? Advanced 221. Explain Optimal Page Replacement Algorithm. Intermediate 222. Explain LRU (Least Recently Used) Page Replacement Algorithm. Intermediate 223. What is Frame Allocation? Intermediate 224. What is Thrashing? Advanced 225. What causes Thrashing? Advanced 226. How does Thrashing affect CPU Utilization? Intermediate 227. What are the solutions to Thrashing? Advanced 228. What is Working Set Model? Advanced 229. What is Page Fault Frequency? Advanced 230. Can we replace Physical Memory (RAM) with Virtual Memory? Beginner 231. Is the performance of Virtual Memory and Physical Memory the same? Intermediate 232. What is Memory Mapping? Intermediate 233. What is Shared Memory in Virtual Memory? Advanced 234. What is Copy-on-Write? Advanced 235. What is Memory-Mapped Files? Intermediate 236. What is the difference between Demand Paging and Demand Segmentation? Advanced 237. What is Prepaging? Advanced 238. What is Page Buffering? Advanced 239. What is the difference between Global and Local Page Replacement? Advanced 240. What is Allocation of Frames? Intermediate 241. What is Secondary Storage? Beginner 242. What is the difference between Primary and Secondary Storage? Beginner 243. What is Disk Scheduling? Intermediate 244. Why is Disk Scheduling needed? Intermediate 245. Explain FCFS Disk Scheduling Algorithm. Beginner 246. Explain SSTF (Shortest Seek Time First) Disk Scheduling Algorithm. Intermediate 247. Explain SCAN Disk Scheduling Algorithm. Intermediate 248. Explain C-SCAN Disk Scheduling Algorithm. Advanced 249. Explain LOOK and C-LOOK Disk Scheduling Algorithms. Advanced 250. Which is the best Disk Scheduling Algorithm? Advanced 251. What is a File System? Beginner 252. What is a File? Beginner 253. What are File Attributes? Intermediate 254. What are File Operations? Intermediate 255. What is a Directory? Beginner 256. What is the difference between File and Directory? Beginner 257. What are different Directory Structures? Intermediate 258. What is File Allocation? Intermediate 259. Explain Contiguous, Linked, and Indexed File Allocation. Advanced 260. What is Free Space Management? Advanced 261. What is the difference between Security and Protection? Intermediate 262. What is Authentication? Beginner 263. What is Authorization? Intermediate 264. What is Access Control? Intermediate 265. What are Access Control Lists (ACL)? Intermediate 266. What is Encryption? Intermediate 267. What is a Virus? Beginner 268. What is a Trojan Horse? Beginner 269. What is a Worm? Intermediate 270. What is the difference between Virus and Worm? Intermediate