SecondChance.cpp

#include<bits/stdc++.h>
using namespace std;

int present(int a[],int nf,int page,int rf_bit[])
{
    for(int i=0;i<nf;i++)
    {
        if(a[i]==page)
        { 
        	int temp = a[i];  
        	for(int k=i;k<nf-1;k++){
        		a[k]=a[k+1];  
			}
			a[nf-1]= temp;   
          	rf_bit[i]=1;
          
          return 1;
        }

    }
    return 0;
}

void printtable(int table_frame[], int nf)
{
	for(int i=0; i<nf; i++)
	{
		if(table_frame[i] == -1)
			printf("-- ");
		else
			printf("%2d ", table_frame[i]);
	}
	printf("||");
}


int main()
{
    int nf;
    cout<<"enter number of frames"<<endl;
    cin>>nf;
    int a[nf],rf_bit[nf];
    for(int i=0;i<nf;i++)
    {
        a[i]=-1;
        rf_bit[i]=0;
    }

    int np;
    cout<<"enter number of pages"<<endl;
    cin>>np;
    int b[np];
    cout<<"enter page requests"<<endl;
    for(int i=0;i<np;i++)
    {
        cin>>b[i];
    }
    int pos=0,count1=0;

    for(int i=0;i<np;i++)
    {
        printf("page table after request from %2d || ",b[i]);
        if(!present(a,nf,b[i],rf_bit))
        {
            //int pos=findpos(a,nf,b,i,np);
            
            while(rf_bit[pos]==1)
            {
                rf_bit[pos]=0;
                pos=(pos+1)%nf;
            }
			if(pos>=nf){
				
				for(int j=0;j<nf-1;j++){
					a[j]=a[j+1];
				}
				a[nf-1]=b[i];
			}
			else{
				 a[pos]=b[i];
			}
           
            printtable(a,nf);
            printf("page fault\n");
            count1++;
            pos++;
            continue;
        }
        
        

        printtable(a,nf);
		printf("\n");
    }

     printf("\nNumber of page faults : %d\n\n", count1);
}