program to implement page replacement algorithm. there are different types of page replacement algorithms for an operating system. I need LRU, Optimal and FIFO now, others are appreciated too.
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#include<stdio.h>
#include <stdlib.h>
int n,nf;
int in[100];
int p[50];
int hit=0;
int i,j,k;
int pg_fault_cnt=0;
//Reference String input function
void getData()
{
printf("Enter length of page reference sequence:\n");
scanf("%d",&n);
printf("Enter the page reference sequence:\n");
for(i=0; i<n; i++)
scanf("%d",&in[i]);
printf("Enter no of frames:\n");
scanf("%d",&nf);
}
void initialize()
{
pg_fault_cnt=0;
for(i=0; i<nf; i++)
p[i]=9999;
}
int isHit(int data)
{
hit=0;
for(j=0; j<nf; j++)
{
if(p[j]==data)
{
hit=1;
break;
}
}
return hit;
}
/*
int getHitIndex(int data)
{
int hit_ind=0;
for(k=0; k<nf; k++)
{
if(p[k]==data)
{
hit_ind=k;
break;
}
}
return hit_ind;
}*/
void display_Pages()
{
for (k=0; k<nf; k++)
{
if(p[k]!=9999)
printf(" %d",p[k]);
}
}
//Display to number of page fault value
void display_Page_Fault_Cnt()
{
printf("Total no of page faults:%d\n",pg_fault_cnt);
}
//page fault for first in first out algorithm
void fifo()
{
initialize();
for(i=0; i<n; i++)
{
printf("\nFor %d :",in[i]);
if(isHit(in[i])==0)
{
for(k=0; k<nf-1; k++)
p[k]=p[k+1];
p[k]=in[i];
pg_fault_cnt++;
display_Pages();
}
else
printf("No page fault");
}
display_Page_Fault_Cnt();
}
//page fault for optimal page replacement algorithm
void optimal()
{
initialize();
int near[50];
for(i=0; i<n; i++)
{
printf("\nFor %d :",in[i]);
if(isHit(in[i])==0)
{
for(j=0; j<nf; j++)
{
int pg=p[j];
int found=0;
for(k=i; k<n; k++)
{
if(pg==in[k])
{
near[j]=k;
found=1;
break;
}
else
found=0;
}
if(!found)
near[j]=9999;
}
int max=-9999;
int replace_index = 0;
for(j=0; j<nf; j++)
{
if(near[j]>max)
{
max=near[j];
replace_index=j;
}
}
p[replace_index]=in[i];
pg_fault_cnt++;
display_Pages();
}
else
printf("No page fault\n");
}
display_Page_Fault_Cnt();
}
//page fault for least recent used algorithm
void lru()
{
initialize();
int least[50];
for(i=0; i<n; i++)
{
printf("\nFor %d :",in[i]);
if(isHit(in[i])==0)
{
for(j=0; j<nf; j++)
{
int pg=p[j];
int found=0;
for(k=i-1; k>=0; k--)
{
if(pg==in[k])
{
least[j]=k;
found=1;
break;
}
else
found=0;
}
if(!found)
least[j]=-9999;
}
int min=9999;
int replace_index=0;
for(j=0; j<nf; j++)
{
if(least[j]<min)
{
min=least[j];
replace_index=j;
}
}
p[replace_index]=in[i];
pg_fault_cnt++;
display_Pages();
}
else
printf("No page fault!\n");
}
display_Page_Fault_Cnt();
}
int main()
{
int choice;
while(1)
{
printf("\nPage Replacement Algorithms\n1.Enter data\n2.FIFO\n3.Optimal\n4.LRU\n5.Exit\nEnter your choice:\n");
scanf("%d",&choice);
switch(choice)
{
case 1:
getData();
break;
case 2:
fifo();
break;
case 3:
optimal();
break;
case 4:
lru();
break;
case 5:
exit(5);
default:
return 0;
}
}
}
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