C program for LFU page replacement algorithm

Introduction to LFU page replacement :

                      The least frequently used(LFU) page-replacement algorithm requires that the page with the smallest count be replaced. The reason for this selection is that an actively used page should have a large reference count. A problem arises, however, when a page is used heavily during the initial phase of a process but then is never used again. Since it was used heavily, it has a large count and remains in memory even though it is no longer needed. One solution is to shift the counts right by1bit at regular intervals,forming an exponentially decaying average usage count.

C program for LFU page replacement :

#include<stdio.h>

void print(int frameno,int frame[])

{

            int j;

            for(j=0;j<frameno;j++)

            printf("%d\t",frame[j]);

            printf("\n");

}         

int main()

{

            int i,j,k,n,page[50],frameno,frame[10],move=0,flag,count=0,count1[10]={0},

                        repindex,leastcount;

            float rate;

            printf("Enter the number of pages\n");

            scanf("%d",&n);

            printf("Enter the page reference numbers\n");

            for(i=0;i<n;i++)

            scanf("%d",&page[i]);

            printf("Enter the number of frames\n");

            scanf("%d",&frameno);

            for(i=0;i<frameno;i++)

            frame[i]=-1;

            printf("Page reference string\tFrames\n");

            for(i=0;i<n;i++)

            {

                        printf("%d\t\t\t",page[i]);

                        flag=0;

                        for(j=0;j<frameno;j++)

                        {

                                    if(page[i]==frame[j])

                                    {

                                                flag=1;

                                                count1[j]++;

                                                printf("No replacement\n");

                                                break;

                                    }

                        }

                        if(flag==0&&count<frameno)

                        {

                                    frame[move]=page[i];

                                    count1[move]=1;

                                    move=(move+1)%frameno;

                                    count++;

                                    print(frameno,frame);

                        }

                        else if(flag==0)

                        {

                                    repindex=0;

                                    leastcount=count1[0];

                                    for(j=1;j<frameno;j++)

                                    {

                                                if(count1[j]<leastcount)

                                                {

                                                            repindex=j;

                                                            leastcount=count1[j];

                                                }

                                    }

                                   

                                    frame[repindex]=page[i];

                                    count1[repindex]=1;

                                    count++;

                                    print(frameno,frame);

                        }

            }

            rate=(float)count/(float)n;

            printf("Number of page faults is %d\n",count);

            printf("Fault rate is %f\n",rate);

            return 0;

}

 OUTPUT :