Apage-replacement algorithm should minimize the number of page faults. we can achieve this minimization by distributing heavily used pages evenly over all of memory, rather than having them compete for a small number of page frames. we can associate with each page frame a counter of the number of pages associated with that frame. then, to replace a page, we can search for the page frame wit the smallest counter.

define a page-replacement algorithm using this basic idea. specifically address these problems:

i. what is the initial value of the counters.

ii. when are counters increased

iii. when are counters decreased

iv. how is the page to be replaced selected?

b. how many pages faults occur for your algorithm for the following reference string with four page frames?

1,2,3,4,5,3,4,1,6,7,8,7,8,9,7,8,9,5 ,4,5,4,2