Operating System Long Questions and AnswersHere in this section of Operating System Long Questions and Answers,We have listed out some of the important Long Questions with Answers on Clock Page Replacement Algorithm which will help students to answer it correctly in their University Written Exam.

 

Lists of Long Descriptive type Questions that may be asked in Written Exams.

  • (1) Explain The Clock Page Replacement Algorithm

 

Question-1 Explain The Clock Page Replacement Algorithm

The Clock Page Replacement Algorithm

  • Although second chance is a reasonable algorithm, it is unnecessarily inefficient because it is constantly moving pages around on its list.
  • A better approach is to keep all the page frames on a circular list in the form of a clock, as shown in Fig. below.
  • A hand points to the oldest page.
  • When a page fault occurs, the page being pointed to by the hand is inspected.

Page replacement Algorithm fig-2

Figure – The clock page replacement algorithm.

  • If its R bit is 0, the page is evicted, the new page is inserted into the clock in its place, and the hand is advanced one position. If R is 1, it is cleared and the hand is advanced to the next page.
  • This process is repeated until a page is found with R = 0. Not surprisingly, this algorithm is called clock.
  • It differs from second chance only in the implementation.

 
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