Which feature does NTFS provide that the older FAT32 file system lacks?
Correct answer D. Journaling for recovery plus file permissions through access control lists
Topic / 93 questions
Operating Systems MCQs
Operating Systems MCQs cover how an OS manages processes, memory, files and devices, a core subject in computer science degrees, GATE and UGC NET, lecturer exams and IT recruitment tests. Questions include numerical problems on CPU scheduling, the Banker's algorithm, paging, page replacement and disk scheduling, and every answer comes with a teaching explanation. Numerical answers were recomputed by script.
With 3 initially empty frames, how many page faults does LRU page replacement cause for the reference string 1, 3, 0, 3, 5, 6, 3, 1, 0, 5, 6, 3?
Correct answer D. 10
With 3 initially empty frames, how many page faults does the optimal (OPT) algorithm cause for the reference string 1, 3, 0, 3, 5, 6, 3, 1, 0, 5, 6, 3?
Correct answer C. 7
Advertisement
For the reference string 1, 2, 3, 4, 1, 2, 5, 1, 2, 3, 4, 5, FIFO causes 9 page faults with 3 frames but 10 with 4 frames. What is this called?
Correct answer D. Belady's anomaly
What is thrashing?
Correct answer C. A process spends more time paging pages in and out than executing, because it lacks enough frames
Why does the page-replacement code check the modify (dirty) bit of a victim page?
Correct answer B. A page that has not been modified need not be written back to disk before its frame is reused
After fork() on Linux, how are the parent’s memory pages normally handled?
Correct answer A. They are shared copy-on-write, so a page is copied only when either process writes to it
Which file allocation method suffers most from external fragmentation and difficulty growing files?
Correct answer B. Contiguous allocation
Which allocation method gives each file an index block containing pointers to all its data blocks?
Correct answer D. Indexed allocation
Advertisement
The File Allocation Table (FAT) used by MS-DOS and FAT32 is a variation of which allocation method?
Correct answer D. Linked allocation
Which of these is NOT stored in a UNIX/Linux inode?
Correct answer D. The file's name
How does a hard link differ from a symbolic link in Linux?
Correct answer C. A hard link is another directory entry for the same inode, while a symbolic link is a separate file containing a path
A disk has cylinders 0 to 199. The head is at cylinder 70 and the request queue is 120, 35, 180, 10, 95, 150, 60. What is the total head movement under FCFS disk scheduling?
Correct answer D. 680 cylinders
An inode has 12 direct block pointers and the block size is 4 KB. What is the largest file that can be addressed using the direct pointers alone?
Correct answer C. 48 KB
On most modern Linux distributions, which program runs as process ID 1 and starts the rest of user space?
Correct answer C. systemd
Advertisement
Why is double buffering used in I/O?
Correct answer D. So a device can fill one buffer while the process empties the other, overlapping I/O with processing
Several users send documents to one printer, and the OS stores each job on disk and feeds them to the printer one at a time. What is this technique called?
Correct answer C. Spooling
What is the main benefit of direct memory access (DMA)?
Correct answer A. A device controller moves whole blocks of data to or from memory without the CPU handling each byte
What is the main drawback of SSTF disk scheduling?
Correct answer A. Requests far from the current head position can starve
A disk has cylinders 0 to 199. The head is at cylinder 70 and the request queue is 120, 35, 180, 10, 95, 150, 60. The head moves towards higher cylinders under C-SCAN. Counting the return sweep from 199 to 0 as head movement, what is the total?
Correct answer D. 388 cylinders
About Operating Systems MCQs
The first part covers OS types (batch, time-sharing, real-time, distributed), kernel and user mode, privileged instructions, system calls, interrupts, traps and kernel structures such as monolithic kernels and microkernels.
Process management questions deal with the process control block, process states, context switching, zombie processes, fork() and exec(), threads and multithreading models, followed by CPU scheduling: FCFS, SJF, SRTF, priority, round robin and multilevel feedback queues, with waiting and turnaround time calculations.
Synchronisation and deadlock questions cover race conditions, the critical-section requirements, Peterson's solution, spinlocks, semaphores, mutexes and monitors, the classic producer-consumer, readers-writers and dining philosophers problems, the four Coffman conditions, resource-allocation graphs and the Banker's algorithm.
The last part covers memory management (fragmentation, allocation strategies, paging, TLBs, segmentation, demand paging, FIFO, LRU and optimal replacement, Belady's anomaly and thrashing), file systems (allocation methods, FAT, inodes, links) and I/O (disk scheduling, DMA, spooling and buffering).
Key facts to remember
- A deadlock needs four conditions at once: mutual exclusion, hold and wait, no preemption and circular wait.
- fork() returns 0 in the child, the child's process ID in the parent and -1 on failure.
- Round robin with a very large time quantum behaves like FCFS.
- FIFO page replacement can suffer from Belady's anomaly; LRU and the optimal algorithm cannot.
- With n processes each needing up to k units of a resource, n(k-1)+1 units guarantee freedom from deadlock.
Exams that include Operating Systems MCQs
Pakistan
- PPSC and FPSC Computer Science Lecturer
- NTS and PTS IT tests
- FPSC programmer and system administrator posts
- University exams
India
- GATE CS
- UGC NET Computer Science
- ISRO and BARC scientist tests
- Campus placements
Bangladesh
- BCS (technical cadre)
- Bank IT officer tests
- Government assistant programmer posts
How to prepare for Operating Systems MCQs
- Draw a Gantt chart for every scheduling problem before working out waiting and turnaround times.
- For page replacement questions, track the frames in a table, one column per reference, and count the faults.
- Learn the Banker's algorithm steps: Need = Max - Allocation, then repeatedly find a process whose Need fits in Available.
- For disk scheduling, write the order of service first, then add the distances between consecutive cylinders.
Frequently asked questions
What is the difference between a process and a thread?
A process is a program in execution with its own address space and resources. A thread is a unit of execution inside a process; threads of the same process share its code, data and open files but each has its own stack and registers, so creating and switching threads is cheaper.
Which OS topics are most important for GATE and job tests?
CPU scheduling calculations, process synchronisation with semaphores, deadlocks and the Banker's algorithm, paging and TLB effective access time, page replacement algorithms and disk scheduling are asked most often.
Last reviewed October 2026