执行程序时，当主存没有可用页面时，为了选择淘汰主存中的哪一页面，腾出1个空闲块以便存放新调入的页面。淘汰哪个页面的首要问题是选择何种置换算法。该程序采用LRU方法选择，依置换策略选择一个可置换的页面并计算它们的缺页率以便比较。

-implementation procedures, when the main pages can be no deposit, in order to choose out of the main deposit which pages, spare a spare block transferred to the new store pages. Which pages out of the first problem is the choice of replacement algorithm. The program LRU Methods, according to choose a replacement strategy may replacement pages and calculation of their missing pages rate to facilitate comparison.