Bsc CSIT Semester 4 – Operating System – Unit 4: Memory Management (8 Hrs.)

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-Remaining-Time-Next (SRTN)
   • d) Round-Robin (quantum = 2)
   • e) Round-Robin (quantum = 1)

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

   • What is the turnaround time for each algorithm?

   OR

   What do you mean by disk management? What is the major difference between error handling and formatting?

2. How many page faults occur for each of the following page replacement algorithms for the reference string
   
   Code

   Copy

   0 1 7 2 3 2 7 1 0 3

   with four page frames and eight pages?
   Suppose all frames are initially empty.
   • a) Optimal replacement
   • b) FIFO replacement
   • c) LRU replacement
   • d) Clock replacement

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

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 assuming 4 page frames?
a) LRU page replacement
b) FIFO page replacement
c) Optimal page replacement
d) Clock replacement

Differentiate between internal and external fragmentation with example.

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

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

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 and uses LRU replacement?

What is Fragmentation? Differentiate between internal and external fragmentation.

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

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

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, 4, 3, 1, 2, 4, 6, 3, 2, 1, 4, 2. Assume the memory size is 3.

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 size 175 KB and 125 KB will be loaded, if we used Best-Fit, and Worst-Fit Strategy?

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

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.

Define working set. How does clock replacement algorithm works?

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

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) 10 MB

(b) 10 MB

For first fit, next fit and best fit.

Write short notes on:

a. Virtual Memory

b. Race Condition

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.