# Operating System

QUESTION 2 24 Marks (a) There are nine (9) fixed partitions of different sizes which are 70 KB, 100 KB, 60 KB, 120 KB, 100 KB, 90 KB, 110 KB, 55 KB and 40 KB. There are several jobs needs to be placed in the memory which are (in order): A (60 KB), B (120 KB), C (40 KB), D (30 KB), E (100 KB), F (55 KB) i. How would the Best-fit and Worst-fit algorithms place all the jobs into the memory partitions. [6] ii. For all the jobs allocation schemes above, is there any job that needs to wait from entering a partition? State the job and allocation scheme. [2] iii. Calculate the size of unused partition and internal fragmentation for Best-fit and Worst-fit algorithms. [4] (b) Consider the page references string: 1, 2, 3, 4, 5, 3, 4, 1, 6, 7, 7, 4, 8, 9,6,8,9 i. Apply the Optimal replacement and find how many page faults would occur. [4] ii. Apply the Least recently used replacement and find how many page faults would occur. [4] iii. Which page replacement show the best result in term of page faults occurred and justify? [1] iv. Based on the previous answer in (iii), how to reduce the page fault number? [1] State 2 methods used in LRU implementation. [2] V