Top 250+ Most Asked Operating System Interview Questions

Comprehensive collection of OS interview questions covering fundamentals, kernel architecture, hardware interfaces, and process concepts. Each answer is technical and interview-ready.

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1.What is an Operating System?

2.What are the main functions of an Operating System?

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

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