#include<iostream>
#include<string.h>
using namespace std;
class BOOK
{
int BOOK_NO;
string BOOK_TITLE ;
float PRICE;
float TOTAL_COST(int N)
{
float TOTAL;
TOTAL=N*PRICE;
return TOTAL;
}
public:
void INPUT()
{
cout<<"nEnter the Book no.:";
cin>>BOOK_NO;
cout<<"nEnter book title:";
cin>>BOOK_TITLE;
cout<<"nEnter Price:";
cin>>PRICE;
}

…… and rest of code

i hope you have got what you were looking for,,,,