Operating Systems Interview Questions

1. Difference Between Process and Thread

2. What is a Deadlock?

3. Difference Between Paging and Segmentation

4. What is a Semaphore?

5. What is a Context Switch?

6. What is Virtual Memory?

7. Difference Between Mutex and Semaphore

8. What is CPU Scheduling?

9. What is Thrashing in Operating Systems?

10. What is a Page Fault?

11. Preemptive vs Non-Preemptive Scheduling

12. What is a Race Condition?

13. What is the Critical Section Problem?

14. What is a System Call?

15. What is Demand Paging?

16. What is a Zombie Process?

17. What is Inter-Process Communication (IPC)?

18. What is the Producer-Consumer Problem?

19. What is an Interrupt?

20. What Is Fragmentation?

21. What Is a File System?

22. Kernel Mode vs User Mode

23. What Is Round Robin Scheduling?

24. What Is a Monitor in OS?

25. What is First-Come-First-Served (FCFS) Scheduling?

26. What is Shortest-Job-First (SJF) Scheduling?

27. What is Shortest-Remaining-Time-First (SRTF) Scheduling?

28. What is Priority Scheduling?

29. What is Multilevel Queue Scheduling?

30. What is Multilevel Feedback Queue Scheduling?

31. What is Lottery Scheduling?

32. What is the Completely Fair Scheduler (CFS)?

33. What is Earliest Deadline First (EDF) Scheduling?

34. Round Robin vs Priority Scheduling: What is the Difference?

35. What Is the Banker’s Algorithm?

36. What Is Deadlock Prevention?

37. What Is Deadlock Avoidance?

38. What Is Deadlock Detection?

39. What Is a Resource-Allocation Graph?

40. How Does Deadlock Recovery Work?

41. What Are the Necessary Conditions for Deadlock?

42. Deadlock vs Starvation: What Is the Difference?

43. What Is the Circular Wait Condition in Deadlock?

44. What Is the Hold and Wait Condition in Deadlock?

45. What is the LRU Page Replacement Algorithm?

46. What is the FIFO Page Replacement Algorithm?

47. What is the Optimal (OPT/Belady’s) Page Replacement Algorithm?

48. What is the Clock (Second-Chance) Page Replacement Algorithm?

49. What is the LFU Page Replacement Algorithm?

50. What is Belady’s Anomaly?

51. What is a Translation Lookaside Buffer (TLB)?

52. What is the Structure of a Page Table?

53. What is a Multilevel Page Table?

54. What is an Inverted Page Table?

55. What are Memory-Mapped Files?

56. What is Copy-on-Write (COW)?

57. What is Swapping in Operating Systems?

58. What is the Working Set Model?

59. What is Segmentation with Paging?

60. What is the Buddy System for Memory Allocation?

61. What is the Slab Allocator?

62. Internal vs External Fragmentation

63. What is Memory Compaction?

64. What is Contiguous Memory Allocation?

65. Peterson’s Solution for Mutual Exclusion

66. What is the Test-and-Set Instruction?

67. What is a Spinlock?

68. The Readers-Writers Problem Explained

69. The Dining Philosophers Problem Explained

70. What is the Sleeping Barber Problem?

71. What is a Condition Variable?

72. What is Priority Inversion?

73. What is a Livelock?

74. What is Barrier Synchronization?

75. What is the Compare-and-Swap (CAS) Instruction?

76. How is a Mutex Lock Actually Implemented?

77. What is Busy Waiting and Why is it Costly?

78. What Are Atomic Operations in an Operating System?

79. Overview of Synchronization Primitives: Mutex, Semaphore, Condition Variable, Spinlock

80. What Does the fork() System Call Do?

81. What Does the exec() Family of System Calls Do?

82. What Does the wait() System Call Do?

83. What is an Orphan Process?

84. What is a Daemon Process?

85. What is a Thread Pool and Why Use One?

86. User-Level Threads vs Kernel-Level Threads

87. Explain the Three Multithreading Models (1:1, N:1, M:N)

88. How Does Thread Scheduling Work?

89. What is a Process Control Block (PCB)?

90. What are the Different Process States in an OS?

91. What Causes Context Switch Overhead and How Is It Reduced?

92. How Does Process Creation and the Process Hierarchy Work?

93. How Does Process Termination Work in an OS?

94. CPU-Bound vs I/O-Bound Processes: What Is the Difference?

95. What are Pipes in Operating Systems?

96. What is a Named Pipe (FIFO)?

97. What is Message Passing in Operating Systems?

98. What is Shared Memory IPC?

99. What are Sockets as an IPC Mechanism?

100. What Are Signals in an Operating System?

101. Compare Different IPC Mechanisms (Pipes, Shared Memory, Message Queues)

102. What is a Remote Procedure Call (RPC)?

103. What is Mailbox-Based (Message-Passing) Communication?

104. Why Does IPC Require Synchronization?

105. What is an Inode and What Does It Store?

106. What is the FAT File System and How Does It Work?

107. What is NTFS and How Does It Improve on FAT?

108. What is ext4 and What Improvements Does It Bring?

109. What is Journaling in a File System and Why Does It Matter?

110. What are File Allocation Methods in an OS?

111. What are Directory Structure Types in an OS?

112. What is FCFS Disk Scheduling?

113. What is SSTF Disk Scheduling?

114. What is SCAN Disk Scheduling?

115. What is the C-SCAN Disk Scheduling Algorithm?

116. What is the LOOK Disk Scheduling Algorithm?

117. What are RAID Levels and How Do They Differ?

118. What is Disk Partitioning and Why is it Used?

119. What is File System Mounting?

120. What is Direct Memory Access (DMA)?

121. Polling vs Interrupt-Driven I/O: What Is the Difference?

122. What is Spooling in Operating Systems?

123. What is a Device Driver and Why Does an OS Need One?

124. What is I/O Buffering and Why Is It Needed?

125. What Are the Stages of the Boot Process?

126. BIOS vs UEFI: What Is the Difference?

127. What Is a Bootloader and What Does It Do?

128. What Are the Types of Hypervisors?

129. Containers vs VMs: How Do They Differ at the OS Level?

130. What is a Real-Time Operating System (RTOS)?

131. Microkernel vs Monolithic Kernel: Key Differences

132. What Are the Types of System Calls?

133. What is Cache Coherence in Multiprocessor Systems?

134. What is a Hybrid Kernel Architecture?

135. What is an Exokernel Architecture?

136. What is the Layered Approach to OS Structure?

137. What is a Virtual Machine Monitor (Hypervisor)?

138. What is Paravirtualization?

139. What is Full Virtualization?

140. What is Turnaround Time in CPU Scheduling?

141. Waiting Time vs Response Time in Scheduling

142. What is Throughput in Operating Systems?

143. What is the Convoy Effect in CPU Scheduling?

144. What is Starvation in CPU Scheduling?

145. What is Gang Scheduling?

146. Cooperative vs Preemptive Multitasking

147. What is Rate Monotonic Scheduling?

148. What is Aging in CPU Scheduling?

149. What is Dispatcher Latency?

150. What is the Memory Hierarchy in a Computer System?

151. What are Cache Memory Mapping Techniques?

152. What is Associative Memory (Content-Addressable Memory)?

153. What is the Dirty Bit in Paging?

154. What is the Reference Bit in Paging?

155. What is Pure Demand Paging?

156. What is Prepaging?

157. What are the Tradeoffs of Page Size?

158. What are Memory Protection Mechanisms?

159. What is Address Binding?

160. Logical vs Physical Address in Operating Systems

161. Dynamic Linking vs Static Linking

162. What is the Overlay Technique in Memory Management?

163. What is Relocation in Memory Management?

164. Memory Allocation Strategies: First Fit, Best Fit, Worst Fit

165. First Fit vs Best Fit vs Worst Fit Memory Allocation

166. What Causes External Fragmentation and How Is It Solved?

167. How Do Threads and Processes Differ in Memory Sharing?

168. How Are Kernel Threads Implemented and Scheduled?

169. What Are Green Threads and How Do They Differ From Kernel Threads?

170. What is a Light-Weight Process (LWP)?

171. What Hardware Support Exists for Process Synchronization?

172. How is a Mutex Implemented Internally?

173. How is a Semaphore Implemented Internally?

174. Binary Semaphore vs Counting Semaphore

175. What Are the Basic Security Mechanisms in an Operating System?

176. What Are Access Control Lists (ACLs) in an Operating System?

177. What Is Capability-Based Security in an Operating System?

178. What Are Protection Rings in an Operating System?

179. What Is the System Call Interface in an Operating System?

180. Trap vs Interrupt: What Is the Difference?

181. How Does Interrupt Handling Work in an OS?

182. What is an Interrupt Vector Table?

183. What is a Software Interrupt?

184. What Are Nested Interrupts and How Are They Handled?

185. What are DMA Controller Modes?

186. Memory-Mapped I/O vs Port-Mapped I/O

187. What are I/O Scheduling Strategies?

188. What are the Basics of Disk Structure?

189. SSD Scheduling Considerations vs Hard Disks

190. What is File System Consistency Checking (fsck)?

191. What is a Log-Structured File System?

192. What is a Distributed File System?

193. What is NFS (Network File System)?

194. What is the Virtual File System (VFS) Layer?

195. What are Linux Namespaces and OS-Level Virtualization?

196. What are Control Groups (cgroups) and How Do They Limit Resources?

197. What are OS Sandboxing Techniques and How Do They Work?

198. What is a chroot Jail and What Are Its Limitations?

199. What is Linux Capability Dropping and Why Does It Matter?

200. What is Load Balancing in a Multiprocessor OS?

201. Symmetric vs Asymmetric Multiprocessing (SMP vs AMP)

202. What is NUMA Architecture?

203. What is Processor Affinity?

204. What Are the Key Challenges in Multicore Scheduling?

205. How Does Clock Synchronization Work in a Distributed OS?

206. How Does Distributed Mutual Exclusion Work?

207. How Is Deadlock Detected in a Distributed System?

208. What Is Consensus in Distributed Systems?

209. What Is a Distributed Operating System?

210. What is Energy-Aware Scheduling in an OS?

211. What is DVFS (Dynamic Voltage and Frequency Scaling)?

212. How Does an OS Support GPU Computing?

213. What is a Unikernel and How Does it Differ from a Traditional OS?

214. What Makes Embedded OS Design Different from a General-Purpose OS?

215. What is a File Descriptor Table?

216. What is the Open File Table?

217. What is the Buffer Cache in an Operating System?

218. Page Cache vs Buffer Cache: What Is the Difference?

219. What Does the mmap() System Call Do?

220. What Are the Process Scheduling Queues in an OS?

221. Long-Term vs Short-Term Scheduler: What Is the Difference?

222. What Is the Medium-Term Scheduler and How Does Swapping Work?

223. What Metrics Are Used to Evaluate a CPU Scheduling Algorithm?

224. Context Switch vs Mode Switch: What Is the Difference?