Page Replacement Algorithm FIFO, LRU, OPT

Consider the following page:

When the number of memory blocks is three, what are the number of missing pages of the FIFO, LRU, and OPT replacement algorithms?
A: page missing is defined as that all memory blocks are empty at first, so the pages used for the first time generate a page missing.

The number of page breaks is 16.

The number of page breaks is 15.

The number of page breaks is 11.
In the OPT algorithm, pages accessed in the farthest future are swapped out first. When page 6 is to be transferred, the memory status is 1, 2, and 5. The pages to be transferred after page 6 are 2, 1, 2 ,..., It can be seen that 5 is the least used in the recent period of time. In this case, replace page 6 with the memory.

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