Write the simulation program for demand paging and show the page scheduling and total number of page faults according to SECOND CHANCE page replacement algorithm. Assume the memory of ‘n’ frames.

#include<stdio.h>
int refstring[20],pt[10],u[10],nof,nor;
void accept()
{
int i;
printf("\nEnter the reference string:");
for(i=0;i<nor;i++)
{
printf("[%d]=",i);
scanf("%d",&refstring[i]);
}
}
int search(int s)
{
int i;
for(i=0;i<nof;i++)
if(pt[i]==s)
return(i);
return(-1);
}
void second_chance()
{

int i,j,k,faults=0,sp=0;
for(i=0;i<nor;i++)
{
printf("%d",refstring[i]);
k=search(refstring[i]);
if(k==-1)
{
while(1)
{
if(u[sp]==0)
                                       {
       pt[sp]=refstring[i];
u[sp]=1;
sp=(sp+1)%nof;
faults++;
break;
}
else
{
u[sp]=0;
sp=(sp+1)%nof;
}
}
}
for(j=0;j<nof;j++)
{
printf("\n%3d%3d",pt[j],u[j]);
if(j==sp)
printf("*");
}
}
printf("\t");
printf("Total page faults=%d\n",faults);
}
int main()
{
clrscr();
printf("Enter length of reference string:");
scanf("%d",&nor);
printf("Enter the no. of frames:");
scanf("%d",&nof);
accept();
second_chance();
getch();
}