Top 50 Most Important Questions in Operating Systems for GATE 2026 Aspirants

This article will show the Top 50 Most Important Questions in Operating Systems for GATE 2026 Aspirants. Practising all of these Operating System GATE questions is a very popular way to grasp every subject from the topic, Operating System. Additionally, candidates can study more about the ideas discussed in this topic, including CPU scheduling, deadlocks, memory management, and process notions. In this page, we’ve tried to put together a list of GATE questions about operating systems. Download Free GATE CSE Study Material

Top 50 Most Important Questions in Operating Systems for GATE 2026 Aspirants

In the GATE CSE test, the Operating System (OS) subject is vital because it carries significant weightage (9–11 marks) and accounts for approximately 10–12% of the total across several years. This is also displayed in the table below:

Year	Approx. Marks from OS	Number of Questions	Difficulty Level
GATE 2024	10–11 marks	4–5	Moderate
GATE 2023	9 marks	4	Moderate–Hard
GATE 2022	11–12 marks	5	Moderate
GATE 2021	10.5 marks	3–4	Easy–Moderate

Top 50 Most Important Questions in Operating Systems for GATE 2026 Aspirants

In order to achieve the best outcomes, candidates are advised to practise the below listed questions on operating system for GATE 2026. Operating systems are a key component of the GATE CSE question paper, and answering these questions will enable candidates to better prepare for the GATE exams. In the meanwhile, applicants can practise and solve the GATE Questions for Operating System in this table below.

Question	Options
1. Consider a system with a single-CPU and the following processes arriving at time 0: P1(10), P2(5), P3(2). If scheduled using non-preemptive SJF, what is the average turnaround time?	6.33 7.10 8.67 9.00
2. In a paging system, logical address space is 32 KB and page size is 1 KB. What is the number of bits in the page offset?	8 9 10 11
3. A page table entry contains a valid bit and frame number. Physical memory is 512 MB and frame size is 4 KB. How many bits represent the frame number?	16 17 18 19
4. Which scheduling algorithm can lead to starvation of longer processes?	FCFS Round Robin SJF Multilevel Queue
5. In the context of deadlock, which is NOT one of Coffman’s conditions?	Mutual exclusion Hold and wait Preemption Circular wait
6. A process references pages such that the working set exceeds physical frames, causing frequent page faults. This is called:	Thrashing Swapping Segmentation Demand paging
7. Which page replacement algorithm is stack-based and immune to Belady’s anomaly?	FIFO LRU Clock Random
8. Using contiguous allocation with first-fit, external fragmentation can be reduced by:	Using smaller blocks Compaction Increasing process sizes Using large fixed partitions
9. A binary semaphore initialized to 1 ensures what when P and Q both call wait() simultaneously?	Both enter Only one enters None enter Deadlock
10. System uses 16-bit logical address & 256-byte pages. Number of page table entries?	64 128 256 65536
11. Which kernel design keeps most services in user space?	Monolithic kernel Microkernel Layered kernel Modular kernel
12. In UNIX, when a process forks(), the child gets:	Copy of parent memory but shares file descriptors Separate fd table Different UID Same PID
13. Semaphore S initialized to 0. If P executes wait(S) before signal(S), what happens?	wait returns immediately Blocks until signal Undefined behavior Semaphore overflows
14. Which deadlock handling strategy allows maximum concurrency but is expensive?	Deadlock prevention Deadlock avoidance Detection and recovery Resource ordering
15. FIFO with 3 frames. Pages: 1,2,3,4,1,2,5,1,2,3,4,5. Number of page faults?	8 9 10 12
16. Effective access time in a TLB-based system: EAT = (hit_ratio)(TLB + memory) + (1-hit)(TLB + 2*memory). If TLB=10ns, memory=100ns, hit=0.9, compute EAT.	110 ns 120 ns 210 ns 220 ns
17. Which file allocation method suffers most from external fragmentation?	Contiguous Linked Indexed None
18. Two-level paging, 32-bit logical addresses, 4 KB pages, 4-byte PTEs. First-level and second-level pages are 4 KB. How many entries in first-level table?	1024 4096 256 512
19. Demand paging: fault rate p, memory access time M, page fault service S. EAT = (1–p)M + pS. If M=100ns, S=8ms, p=0.001, EAT = ?	100.8 ns 900 ns 81 ms 801 ms
20. Which algorithm used by OSes approximates LRU with low overhead?	True LRU Clock (Second Chance) FIFO Optimal
21. In inode-based Unix file systems, which inode field points to file data blocks?	File name Direct and indirect block pointers Directory entries File descriptor
22. Many processes share a single writer in a multiple-reader–writer lock. Many readers arrive continuously, starving the writer. This is an example of:	Priority inversion Starvation Deadlock Livelock
23. Which of the following is true about copy-on-write (COW)?	Parent and child share pages until one writes Pages are copied at fork immediately COW increases memory usage immediately COW requires kernel to disallow writes
24. A mutex lock provides which of the following guarantees?	Mutual exclusion only Mutual exclusion and deadlock freedom Mutual exclusion and progress Mutual exclusion and bounded waiting
25. The Banker’s algorithm is used for:	Memory allocation Deadlock avoidance Scheduling File management
26. Which of the following is a disadvantage of multilevel feedback queue scheduling?	It cannot approximate SJF Complex tuning and parameters Starvation impossible No preemption
27. System with 4 frames and page reference string: 1,2,3,1,4,5,2,1,2,3,4,5. Using LRU, page faults = ?	8 9 10 11
28. In segmentation, a logical address consists of:	Segment number and offset Page number and offset Base and limit only Frame and offset
29. In virtual memory, internal fragmentation is caused by:	Fixed-size pages Variable-sized segments File headers Swapping
30. Which IPC mechanism is most efficient for processes on the same machine that need high-throughput communication?	Pipes Message passing via kernel Shared memory Remote procedure call
31. When using demand paging, the working set model aims to:	Minimize disk usage Reduce process’s active pages in memory Maintain locality by keeping the set of pages a process actively uses Improve throughput by swapping out entire processes
32. Which of these is true about a ‘race condition’?	Deterministic behavior Occurs when processes access shared data without synchronization Prevented by increasing CPU speed Same as deadlock
33. In a CPU-bound vs I/O-bound classification, which scheduler favoring short CPU bursts improves interactive response?	Long quantum in RR Short quantum in RR FCFS Non-preemptive SJF
34. The ‘nice’ value in UNIX primarily affects:	Memory allocation Process priority for CPU scheduling File I/O priority Disk scheduling
35. Disk scheduling algorithm that reduces seek time by sweeping head back and forth is:	FCFS SSTF SCAN (elevator) C-SCAN
36. A critical section solution must satisfy:	Mutual exclusion Progress Bounded waiting All of the above
37. In context switching, which of the following is saved/restored?	Program counter, registers, and memory contents Program counter Only registers Nothing
38. A system with virtual memory and demand paging: page size = 4 KB, process references 100,000 memory accesses/s, fault rate = 0.001. If service time per fault = 10 ms, approximate overhead?	1 second 10 seconds 100 seconds 0.1 seconds
39. Which of these is true for atomic operations used in synchronization?	They can be interrupted They execute as a single indivisible step They require user-level locks only They are slow and rarely used
40. In a two-phase lock protocol (2PL) used in databases for concurrency, which property is ensured?	Deadlock freedom Serializability No blocking No read locks
41. If a file system uses journaling, the primary benefit is:	Faster writes always Improved reliability after crashes Unlimited file sizes No need for backups
42. Consider address translation using a TLB of 64 entries. If page size is 4KB, logical address is 32-bit. If TLB hit rate increases, CPU utilization:	Increases Increases Unchanged Drops to zero
43. An OS uses demand segmentation with paging. Which benefit is achieved?	Eliminates fragmentation entirely Combines logical view of segments with fixed-size page management Removes need for page tables Disallows protection
44. In the Readers-Writers problem, which variant gives priority to writers, preventing writer starvation but may starve readers?	First readers-writers problem (readers preference) Second readers-writers problem (writers preference) Both are same Neither
45. The purpose of ‘address space layout randomization (ASLR)’ is to:	Speed up address translation Improve memory utilization Increase security by randomizing base addresses Decrease fragmentation
46. For page replacement, Belady’s optimal algorithm requires:	Future knowledge of references Only past information No information LRU stack
47. In classic Producer-Consumer problem using semaphores, if buffer size is $N$, initial semaphore values are:	empty=0, full=0, mutex=1 empty=N, full=0, mutex=1 empty=0, full=N, mutex=0 empty=1, full=N, mutex=1
48. A context switch is expensive because:	It requires disk I/O It may flush CPU cache and TLB, causing performance loss It creates new processes It frees memory
49. In swap-based memory management, ‘paging’ differs from ‘swapping’ in that:	Paging moves whole process Swapping moves pages Paging moves fixed-size pages; swapping moves entire process They are identical
50. Which of the following best describes ‘livelock’?	Processes blocked waiting for resources Processes constantly changing state but making no progress Permanent halt Memory leak

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