BSC CSIT Semester 4 – Operating System () Questions & Answers | Past TU Exam Papers

Question 1

1) For the processes listed in the following table, draw a Gantt chart illustrating their execution using: - a) First-Come-First-Serve (FCFS) - b) Shortest-Job-First (SJF) - c) Shortest-Remai

Marks: 10

Year: 2070 Final TU

Given processes (arrival, burst): A(0.000, 3), B(1.001, 6), C(4.001, 4), D(6.002, 2) 1) FCFS (non‑preemptive) - Order: A → B → C → D - Completion times: A=3.000, B=9.000, C=13.000, D=15.000 - TAT

Question 2

2) How many page faults occur for each of the following page replacement algorithms for the reference string 0 1 7 2 3 2 7 1 0 3 with four page frames and eight pages? Suppose all frames are

Marks: 10

Year: 2070 Final TU

Page Replacement Algorithms and Page Faults Given: - Reference string: 0 1 7 2 3 2 7 1 0 3 - Number of page frames: 4 - Total pages: 8 - All frames are initially empty. --- 1. a) Optimal Page

Question 3

What are Segmentation and Paging? Why are they sometimes combined into one scheme?

Marks: 5

Year: 2070 Final TU

Segmentation and Paging in Operating Systems 1. Segmentation - Definition: Memory management scheme that divides logical memory into variable-sized segments based on the program’s logical divisions (

Question 4

What is page fault? Consider the following page reference string; 3, 3, 5, 4, 7, 1, 5, 5, 1, 4, 3, 7, 6, 3, 4, 1. How many page faults would occur for each of the following page replacement algorithms

Marks: 10

Year: 2071 Final TU

Page Faults and Page Replacement Algorithms 1. Definition of Page Fault A page fault occurs when a process tries to access a page that is not currently in main memory. - The operating system then l

Question 5

Differentiate between internal and external fragmentation with example.

Marks: 5

Year: 2071 Final TU

Question 6

What are the segmentation and paging? Why they are combined into one scheme?

Marks: 5

Year: 2071 Final TU

Segmentation and Paging in Memory Management 1. Segmentation - Definition: Segmentation is a memory management scheme where a program is divided into logical units called segments. - Key Points:

Question 7

Write short notes: (Any two)\ a) Best Fit vs. Worst Fit\ b) Swapping\ c) Semaphores

Marks: 5

Year: 2071 Final TU

Question 8

Given a references to the following pages by program,\ 1, 2, 3, 4, 2, 1, 5, 6, 2, 1, 2, 3, 7, 6, 3, 2, 1, 2, 3, 6.\ How many page faults will occur if the program has three page frames available to it

Marks: 5

Year: 2072 Final TU

Problem: LRU Page Replacement Given: - Page reference string: 1, 2, 3, 4, 2, 1, 5, 6, 2, 1, 2, 3, 7, 6, 3, 2, 1, 2, 3, 6 - Number of page frames = 3 - Replacement policy = LRU (Least Recently Us

Question 9

What is Fragmentation? Differentiate between internal and external fragmentation.

Marks: 5

Year: 2072 Final TU

Fragmentation in Operating Systems Definition: - Fragmentation occurs when memory is broken into small pieces over time due to allocation and deallocation. - It causes wasted memory, which cannot be u

Question 10

How Second Chance page replacement algorithm differs from FIFO page replacement policy? Discuss the concept of Belady’s anomaly with suitable example.

Marks: 10

Year: 2076 Final TU

Second Chance Page Replacement vs FIFO FIFO (First-In-First-Out) Page Replacement: - The page that has been in memory for the longest time is removed first. - It does not consider whether the page was

Question 11

Why program relocation and protection is important? Explain the technique of achieving program relocation and protection.

Marks: 5

Year: 2076 Final TU

Why Program Relocation and Protection are Important ✅ Program Relocation Program relocation is required because a program cannot always be loaded into the same memory location every time. It ensure

Question 12

Why OPR is best but not pratically fessible page replacement algorithm? Calculate the number of page faults for OPR, LRU and Clock page replacement algorithm for the reference string: 1, 3, 4, 2, 3, 5

Marks: 10

Year: 2078 Final TU

Optimal Page Replacement (OPR) and Practical Feasibility 1. Why OPR is the Best but Not Practically Feasible - Optimal Page Replacement (OPR): - Replaces the page that will not be used for the lon

Question 13

Differentiate between internal and external fragmentation? Suppose that we have memory of 100 KB with 5 partitions of size 150 KB, 200 KB, 250 KB, 100 KB, and 300 KB. Where the processes A and B of si

Marks: 5

Year: 2078 Final TU

Internal vs External Fragmentation | Aspect | Internal Fragmentation | External Fragmentation | |-----------------------------|-----

Question 14

Why do we need virtual memory? Describe the sructure of a page table.

Marks: 5

Year: 2080 Final TU

Virtual Memory 1. Why Do We Need Virtual Memory? Virtual memory is a technique that allows a process to use more memory than physically available by temporarily storing data on disk. Benefits: 1. P

Question 15

Find the number of page fault using FIFO and LRU for the reference string \(4, 7, 6, 1, 7, 6, 1, 2, 7, 2\) with frame size 3.

Marks: 5

Year: 2080 Final TU

Page Replacement Example Reference String: 4, 7, 6, 1, 7, 6, 1, 2, 7, 2 Number of Frames: 3 --- 1. FIFO (First-In-First-Out) Stepwise Simulation: | Time | Pages in Frame (FIFO Order) | Page Fault?

Question 16

Define working set. How does clock replacement algorithm works?

Marks: 5

Year: 2080 Final TU

Working Set and Clock Page Replacement Algorithm 1. Working Set - Definition: The working set of a process is the set of pages that a process has actively used in the recent past (typically last

Question 17

Explain the translation of logical address into physical address using segment table with necessary diagram. List advantages and disadvantages of segmentation.

Marks: 10

Year: 2081 Final TU

Translation of Logical Address to Physical Address Using Segment Table In segmentation, the logical address is divided into two parts: - Segment Number (s) - Offset (d) within that segment Each proces

Question 18

Consider a swapping system in which memory consists of the following hole sizes in memory order: 15 MB, 2 MB, 10 MB, 6 MB, 8 MB and 20 MB. Which hole is taken for successive segment requests of: (a)

Marks: 5

Year: 2081 Final TU

Swapping Allocation: First Fit, Next Fit and Best Fit Given Holes in order: 15 MB, 2 MB, 10 MB, 6 MB, 8 MB, 20 MB Requests: (a) 10 MB (b) 10 MB --- 1. First Fit Allocation First Fit selects

Question 19

Write short notes on: a. Virtual Memory b. Race Condition

Marks: 5

Year: 2081 Final TU

Short Notes a) Virtual Memory Definition: Virtual memory is a memory management technique where the logical memory (used by programs) is separated from physical memory (RAM). It allows execution o

Question 20

Consider the page references 7,0,1,2,0,3,0,4,2,3,0,3,2, Find the number of page fault using OPR and FIFO, with 4 page frame.

Marks: 5

Year: 2079 Final TU

Given Page Reference String 7, 0, 1, 2, 0, 3, 0, 4, 2, 3, 0, 3, 2 Number of page frames = 4 --- 1. FIFO (First-In-First-Out) Page Replacement Algorithm: Replace the oldest page in memory when a new

Processes	Arrival Time	CPU Time
A	0.000	3
B	1.001	6
C	4.001	4
D	6.002	2