IMPLEMENTATION OF LRU PAGE REPLACEMENT ALGORITHM

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 IMPLEMENTATION OF LRU PAGE REPLACEMENT ALGORITHM

AIM:

To write a c program to implement LRU page replacement algorithm

ALGORITHM :

1. Start the process

2. Declare the size

3. Get the number of pages to be inserted

4. Get the value

5. Declare counter and stack

6. Select the least recently used page by counter value

7. Stack them according the selection.

8.  Display the values

9. Stop the process

PROGRAM:
#include<stdio.h>
main()
{
int q[20],p[50],c=0,c1,d,f,i,j,k=0,n,r,t,b[20],c2[20];
printf("Enter no of pages:");
scanf("%d",&n);
printf("Enter the reference string:");
for(i=0;i<n;i++)
            scanf("%d",&p[i]);
printf("Enter no of frames:");
scanf("%d",&f);
q[k]=p[k];
printf("\n\t%d\n",q[k]);
c++;
k++;
for(i=1;i<n;i++)
            {
                        c1=0;
                        for(j=0;j<f;j++)
                        {
                                    if(p[i]!=q[j])
                                    c1++;
                        }
                        if(c1==f)
                        {
                                    c++;
                                    if(k<f)
                                    {
                                                q[k]=p[i];
                                                k++;
                                                for(j=0;j<k;j++)
                                                printf("\t%d",q[j]);
                                                printf("\n");
                                    }
                                    else
                                    {
                                                for(r=0;r<f;r++)
                                                {
                                                            c2[r]=0;
                                                            for(j=i-1;j<n;j--)
                                                            {
                                                            if(q[r]!=p[j])
                                                            c2[r]++;
                                                            else
                                                            break;
                                                }
                                    }
                                    for(r=0;r<f;r++)
                                     b[r]=c2[r];
                                    for(r=0;r<f;r++)
                                    {
                                                for(j=r;j<f;j++)
                                                {
                                                            if(b[r]<b[j])
                                                            {
                                                                        t=b[r];
                                                                        b[r]=b[j];
                                                                        b[j]=t;
                                                            }
                                                }
                                    }
                                    for(r=0;r<f;r++)
                                    {
                                                if(c2[r]==b[0])
                                                q[r]=p[i];
                                                printf("\t%d",q[r]);
                                    }
                                    printf("\n");
                        }
            }
}
printf("\nThe no of page faults is %d",c);
}

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