ENCT 254Bachelor in Computer Engineering · Semester 43 Papers Available
Operating System
Past examination question papers and complete curriculum syllabus for Operating System (ENCT 254), Bachelor in Computer Engineering Semester 4 under Institute of Engineering (IOE), Tribhuvan University.
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Most Frequently Asked Questions
Top recurring IOE board exam questions for Operating System with verified mark schemes, formula notation, and recurrence frequency.
Showing 30 of 30 top repeated questions
Introduction
3 Questions
#1Asked in 7 Exam Sessions[8 Marks]Introduction
How does an operating system act as an extended machine and a resource manager? Explain with examples. What are the architectural trade-offs between Monolithic, Layered, and Microkernel operating system structures?
Appeared in:2082 Bhadra2081 Bhadra2080 Baishakh2079 Bhadra2078 Bhadra2076 Ashwin2074 Ashwin
#2Repeated 6 Times[6 Marks]Introduction
Explain dual-mode operation (User Mode vs Kernel/Privileged Mode) and hardware protection using mode bits. Trace the step-by-step mechanism of a system call from user-space invocation to kernel-space service execution.
Appeared in:2081 Bhadra2079 Bhadra2078 Bhadra2076 Chaitra2074 Ashwin2070 Ashad
#3Repeated 2 Times[6 Marks]Introduction
Explain dual-mode operation (User mode vs Kernel mode) in modern operating systems. How does a system call switch modes using hardware interrupts?
Appeared in:2082 Kartik2081 Chaitra
Process Management
6 Questions
#1Asked in 8 Exam Sessions[10 Marks]Process Management
Explain the significance of the Process Control Block (PCB). For the given set of processes with arrival time, burst time, and priority, draw Gantt charts and calculate average Turnaround Time (TAT), average Waiting Time (WT), CPU utilization, and throughput according to FCFS, Shortest Remaining Time First (SRTF), and Round Robin (RR) scheduling algorithms.
Appeared in:2082 Bhadra2081 Bhadra2080 Baishakh2079 Bhadra2078 Bhadra2076 Chaitra2074 Ashwin2072 Kartik
#2Asked in 7 Exam Sessions[6 Marks]Process Management
Why are threads called lightweight processes (LWP)? Compare User-Level Threads (ULT) and Kernel-Level Threads (KLT) with respect to context switching overhead, kernel scheduling, and system call blocking.
Appeared in:2081 Bhadra2080 Baishakh2079 Bhadra2078 Bhadra2076 Ashwin2074 Ashwin2072 Kartik
#3Repeated 6 Times[6 Marks]Process Management
Explain process lifecycle states (New, Ready, Running, Waiting, Terminated) and draw the complete state transition diagram. Explain context switching and what data structures are saved and restored during a context switch.
Appeared in:2082 Bhadra2081 Bhadra2080 Baishakh2078 Bhadra2076 Chaitra2073 Shrawan
#4Repeated 2 Times[6 Marks]Process Management
Differentiate between user-level threads and kernel-level threads. Explain multithreading models: Many-to-One, One-to-One, and Many-to-Many.
Appeared in:2082 Kartik2080 Chaitra
#5Repeated 2 Times[6 Marks]Process Management
Explain the process life cycle state transition diagram. What happens during a context switch and what are its overheads?
Appeared in:2081 Chaitra2079 Chaitra
#6Repeated 2 Times[8 Marks]Process Management
Consider five processes P1, P2, P3, P4, P5 with arrival times (0, 1, 2, 3, 4) and burst times (10, 1, 2, 1, 5). Draw Gantt charts and calculate average turnaround time and average waiting time for: (i) FCFS, (ii) SJF (preemptive), and (iii) Round Robin (quantum = 2).
Appeared in:2082 Kartik2081 Chaitra
Process Communication and Synchronization
9 Questions
#1Asked in 8 Exam Sessions[10 Marks]Process Communication and Synchronization
What are the four necessary conditions for deadlock? Consider a system with 5 processes (P0-P4) and 3 resource types (A, B, C) with given Allocation, Max, and Available matrices. (a) Compute the Need matrix, (b) Check if the system is in a safe state and show the safe execution sequence using Banker's Algorithm, and (c) Determine if an immediate resource request from P1 can be granted.
Appeared in:2082 Bhadra2081 Bhadra2080 Baishakh2079 Bhadra2078 Bhadra2076 Chaitra2075 Ashwin2073 Chaitra
#2Asked in 8 Exam Sessions[8 Marks]Process Communication and Synchronization
What is a race condition and critical section problem? Explain binary and counting semaphores along with wait() and signal() operations. Provide pseudocode to solve the Producer-Consumer problem using bounded-buffer semaphores (mutex, empty, full).
Appeared in:2082 Bhadra2081 Bhadra2080 Baishakh2079 Bhadra2078 Bhadra2076 Ashwin2074 Ashwin2072 Kartik
#3Repeated 6 Times[6 Marks]Process Communication and Synchronization
Explain deadlock handling strategies: Deadlock Prevention, Deadlock Avoidance, and Deadlock Detection and Recovery. How does eliminating mutual exclusion, hold-and-wait, no preemption, or circular wait prevent deadlocks?
Appeared in:2082 Bhadra2080 Baishakh2079 Bhadra2076 Chaitra2074 Ashwin2071 Chaitra
#4Repeated 5 Times[6 Marks]Process Communication and Synchronization
What is the Critical Section Problem? State the three requirements (Mutual Exclusion, Progress, Bounded Waiting) that any valid solution must satisfy. Explain Peterson's algorithm for two processes.
Appeared in:2082 Bhadra2081 Bhadra2078 Bhadra2076 Baisakh2073 Shrawan
#5Repeated 2 Times[8 Marks]Process Communication and Synchronization
Explain Peterson's algorithm for two-process mutual exclusion. Prove that it satisfies Mutual Exclusion, Progress, and Bounded Waiting requirements.
Appeared in:2082 Kartik2080 Chaitra
#6Repeated 2 Times[8 Marks]Process Communication and Synchronization
Explain the Dining Philosophers Problem. Provide a deadlock-free solution using semaphores or monitors.
Appeared in:2081 Chaitra2079 Baishakh
#7Repeated 2 Times[8 Marks]Process Communication and Synchronization
Explain the Readers-Writers problem. Provide a synchronization solution using semaphores giving priority to readers.
Appeared in:2082 Shrawan2078 Bhadra
#8Repeated 2 Times[8 Marks]Process Communication and Synchronization
State and explain Banker's Algorithm for deadlock avoidance. Given Allocation, Max, and Available resource matrices for 5 processes and 3 resource types (A, B, C), determine if the system is in a safe state and find a safe sequence.
Appeared in:2082 Kartik2081 Chaitra
#9Repeated 2 Times[6 Marks]Process Communication and Synchronization
Explain Resource Allocation Graph (RAG) and Wait-For Graph (WFG). Explain how deadlock detection is performed in single vs multiple instances of resource types.
Appeared in:2081 Chaitra2079 Chaitra
I/O and Memory Management
8 Questions
#1Asked in 8 Exam Sessions[10 Marks]I/O and Memory Management
Differentiate between internal and external fragmentation. Consider the following page reference string: 7, 0, 1, 2, 0, 3, 0, 4, 2, 3, 0, 3, 2, 1, 2, 0, 1, 7, 0, 1 with 3 (or 4) page frames. Calculate the number of page faults that occur for: (a) FIFO, (b) LRU, and (c) Optimal page replacement algorithms, and identify Belady's Anomaly.
Appeared in:2082 Bhadra2081 Bhadra2080 Baishakh2079 Bhadra2078 Bhadra2076 Chaitra2074 Ashwin2071 Chaitra
#2Asked in 8 Exam Sessions[8 Marks]I/O and Memory Management
Suppose a disk drive has 200 tracks (numbered 0-199). The read/write head is currently serving a request at track 53 (or 60) and previous request was at track 54. The queue of pending requests in FIFO order is: 98, 183, 37, 122, 14, 124, 65, 67. Calculate the total head movement (seek distance in cylinders) for: (a) FCFS, (b) SSTF, (c) SCAN, and (d) C-LOOK algorithms.
Appeared in:2082 Bhadra2081 Bhadra2080 Baishakh2079 Bhadra2078 Bhadra2076 Chaitra2073 Shrawan2070 Ashad
#3Asked in 7 Exam Sessions[8 Marks]I/O and Memory Management
Explain how a logical address is mapped to a physical address in a paging scheme using a Page Table and Translation Lookaside Buffer (TLB). Define Effective Memory Access Time (EMAT) and calculate EMAT for given memory access time and TLB hit ratio.
Appeared in:2082 Bhadra2081 Bhadra2080 Baishakh2078 Bhadra2076 Chaitra2073 Chaitra2071 Chaitra
#4Repeated 6 Times[6 Marks]I/O and Memory Management
What is thrashing in virtual memory? Explain the causes of thrashing and describe how the Working Set model and Page Fault Frequency (PFF) technique detect and prevent thrashing.
Appeared in:2082 Bhadra2081 Bhadra2080 Baishakh2078 Bhadra2075 Ashwin2072 Kartik
#5Repeated 5 Times[6 Marks]I/O and Memory Management
Describe the layered architecture of I/O software. Differentiate between Programmed I/O, Interrupt-Driven I/O, and Direct Memory Access (DMA). What is the role of a device driver?
Appeared in:2082 Bhadra2080 Baishakh2078 Bhadra2076 Ashwin2073 Chaitra
#6Repeated 2 Times[8 Marks]I/O and Memory Management
Explain Paging and Segmentation memory management schemes. Describe the hardware implementation of paging with Translation Lookaside Buffer (TLB) and calculate Effective Memory Access Time (EMAT).
Appeared in:2082 Kartik2081 Chaitra
#7Repeated 2 Times[8 Marks]I/O and Memory Management
Consider the page reference string: $7, 0, 1, 2, 0, 3, 0, 4, 2, 3, 0, 3, 2, 1, 2, 0, 1, 7, 0, 1$. Calculate the number of page faults for 3 frames using: (i) FIFO, (ii) Optimal, and (iii) LRU page replacement algorithms. Explain Belady's Anomaly.
Appeared in:2082 Kartik2080 Chaitra
#8Repeated 2 Times[8 Marks]I/O and Memory Management
Explain disk scheduling algorithms: FCFS, SSTF, SCAN, and C-SCAN. For a disk with 200 cylinders (0 to 199), calculate total head movement for requests: $98, 183, 37, 122, 14, 124, 65, 67$ starting at cylinder 53 moving towards larger cylinder numbers.
Appeared in:2081 Chaitra2078 Bhadra
File Systems
2 Questions
#1Asked in 7 Exam Sessions[8 Marks]File Systems
Describe contiguous, linked list, and indexed allocation methods for file storage with their advantages and disadvantages. Explain the concept of inodes and their pointer hierarchy (direct, single indirect, double indirect, triple indirect) in UNIX/Linux file systems.
Appeared in:2082 Bhadra2081 Bhadra2080 Baishakh2079 Bhadra2076 Chaitra2074 Ashwin2071 Chaitra
#2Repeated 2 Times[8 Marks]File Systems
Explain file allocation methods: Contiguous, Linked, and Indexed allocation with diagrams. Compare them in terms of access speed, external fragmentation, and file size flexibility.
Appeared in:2082 Kartik2081 Chaitra
Security and System Administration
2 Questions
#1Repeated 5 Times[6 Marks]Security and System Administration
Differentiate between Access Control Lists (ACL) and Capability Lists for resource authorization. Explain the principles of protection (Domain of protection) and how encryption/decryption safeguards operating system files.
Appeared in:2082 Bhadra2080 Baishakh2079 Bhadra2076 Chaitra2072 Kartik
#2Repeated 2 Times[6 Marks]Security and System Administration
Explain the Access Matrix model for system protection and its implementation mechanisms: Access Control Lists (ACL) and Capabilities.
5.2Directory structures: Paths and hierarchies (Linux/Windows)
5.3File system implementation: Inodes, allocation methods (Contiguous, linked, indexed)
5.4File system performance: Factors affecting efficiency
5.5Example file systems: NTFS, EXT4, FAT32, NFS
6. Security and System Administration
6.1OS security: Cryptography, multi-factor authentication (MFA), secure boot and sandboxing
6.2Access control: Policies, lists, and OS support
6.3System administration: User management, environment setup and tools (AWK, shell scripts, make)
7. Hypervisors and Virtual Systems
7.1Hypervisors: Type 1 and type 2
7.2Virtual machines: Creating virtual machine in Qemu/Virtual box/VMWare
7.3Container virtualization: Docker and Kubernetes
7.4Power shell and windows subsystem for LINUX (WSL)
7.5Performance optimization and security in virtualized environments
8. Overview of Contemporary OS
8.1Windows and Linux-based OS
8.2Embedded and mobile OS
8.3IoT and RT operating system
8.4Robot and smart card operating system
Examination Scheme & Marks Distribution
Evaluation Structure
Final Board Theory Exam: 60 Marks (Pass mark: 24)
Internal Assessment: 40 Marks (Pass mark: 16)
Practical / Lab Exam: 25 or 50 Marks (Continuous lab evaluation + viva, where applicable)
* This is the general current IOE 60/40 scheme; verify course-specific details in the syllabus above.
Exam Preparation Guidelines
Review the 3 available past examination papers to identify recurring patterns, core problem types, and chapter weightage.
Cross-reference key answers with official syllabus units, standard textbooks, and lecture notes.
Structure answers with labeled diagrams, concise bullet points, and highlight final answers in numerical solutions.
Frequently Asked Questions (Operating System)
Q: How can I download Operating System past question papers?
You can preview or download the Operating System question papers (PDF) directly using the built-in viewer on this page with zero redirects or paywalls.
Q: What is the pass mark for Operating System?
The general current scheme is a 60-mark final theory exam and a 40-mark internal assessment, with pass marks of 24 and 16. Verify the course-specific syllabus above.
Q: Where can I find the complete syllabus for this subject?
The available chapter-wise syllabus and topic breakdown is indexed in the Syllabus section above, with links to the curriculum PDF source.