Question

In the stack implementation of the LRU algorithm, a stack can be maintained in a manner :

a) whenever a page is used, it is removed from the stack and put on top
b) the bottom of the stack is the LRU page
c) the top of the stack contains the LRU page and all new pages are added to the top
d) None of the mentioned

Answer 1

In the LRU algorithm's stack implementation, used pages are moved to the top of the stack, and the bottom of the stack holds the LRU page.

Step-by-step explanation:

In the stack implementation of the Least Recently Used (LRU) algorithm, the correct way to maintain the stack is that whenever a page is referenced or used, it is removed from its current position in the stack and put on the top. This is because the top of the stack represents the most recently used page.

Conversely, the bottom of the stack holds the Least Recently Used page, indicating that if a page needs to be swapped out due to a shortage of memory, the page at the bottom will be selected.

Thus, option (b) 'the bottom of the stack is the LRU page' correctly describes the LRU stack protocol. Option (a) 'whenever a page is used, it is removed from the stack and put on top' also correctly states the operational mechanism of updating the stack when a page is used.