#include<iostream.h>
#include<conio.h>
#include<fstream.h>
 
class inventory
{
char b_name[15];
char p_name[15];
float isbn;
int pur;
float p_cost;
float s_cost;
int hand;
public:
 
void getdata()
	{
	cout<<"ENTER ISBN :";cin>>isbn;
	cout<<"ENTER BOOK :";cin>>b_name;
	cout<<"ENTER PUBLSHER :";cin>>p_name;
	cout<<"ENTER PURCHASE COST :";cin>>p_cost;
	cout<<"ENTER SALE COST :";cin>>s_cost;
	}
 
void inhand()
	{
	cout<<"ENTER QUANTITY PURCHASED :";cin>>pur;
	hand=pur;
	}
 
void sale()
	{
	hand=hand-1;
	}
 
void show()
	{
	cout<<"\nISBN :"<<isbn<<"\nBOOK :"<<b_name<<"\nPUBLISHER :"<<p_name;
	cout<<"\nQUANTITY PURCHASE :"<<pur<<"\nQUANTITY IN HAND :"<<hand;
	cout<<"\nPURCHASE COST :"<<p_cost<<"\nSALE COST :"<<s_cost;
	}
};
 
void main()
{
clrscr();
char c;
inventory inv;
fstream file;
file.open("inv_dat.txt",ios::ate);
cout<<"\n\n\n\t\t\"MENU\"";
cout<<"\nPRESS \"1\" to print all the records.";
cout<<"\nPRESS \"2\" to delete a record.";
cout<<"\nPRESS \"3\" to update a record.";
cout<<"\nPRESS \"4\" to enter a new record.";
cout<<"\nPRESS \"5\" to sell a book.";
cout<<"\nPRESS \"5\" to calculate profit in this month.";
cout<<"\nPRESS \"0\" for EXIT";
char choice='0';
cout<<"\n\n\"ENTER CHOICE\" :";cin>>choice;
switch (choice)
{
case'1':
	{
	file.open("inv_dat.txt",ios::in);
	file.seekg(0);
	file.read((char*)&inv,sizeof(inv));
	do
		{
		inv.show();
		cout<<endl;
		file.read((char*)&inv,sizeof(inv));
		}
	while(!file.eof());
	getch();
	};break;
case '2':
	{
	file.open("inv_dat.txt",ios::in|ios::out|ios::ate);
	file.seekg(0,ios::end);
	int n,pos;
	cout<<"The records present are :"<<file.tellg()/sizeof(inv);
	cout<<"\nEnter ISBN no. of the record you want to delete :";
	cin>>n;
	pos=(n-1) *sizeof(inv);
	file.seekp(pos);
	file.write((char *)&inv,sizeof(inv));
	getch();
	};break;
case '3':
	{
	file.open("inv_dat.txt",ios::in|ios::out|ios::ate);
	int n,pos;
	cout<<"Enter ISBN no. of the record you want to update";
	cin>>n;
	pos=(n-1) *sizeof(inv);
	file.seekp(pos);
	cout<<"\n\" ENTER NEW DATA \"\n";
	inv.getdata();
	inv.inhand();
	file.write((char *)&inv,sizeof(inv));
	file<<flush;
	getch();
	};break;
case '4':
{
file.open("inv_dat.txt",ios::app);
 
do
	{
	inv.getdata();
	inv.inhand();
	file.write((char*)&inv,sizeof(inv));
	cout<<"\n\nWnat to enter another object(y/n):" ;cin>>c;
	}
while (c=='y');
};break;
case '5':
	{
	file.open("inv_dat.txt",ios::in|ios::out);
	int n,pos;
	cout<<"\n Enter the ISBN no of the Book you want to sell :";
	cin>>n;
	pos=(n-1) *sizeof(inv);
	file.seekp(pos);
	file.read((char*)&inv,sizeof(inv));
	inv.sale();
	file.write((char*)&inv,sizeof(inv));
	file<<flush;
	getch();
	};break;
 
 
default:getch();
}
}

for(int i = 0; i < number_of_records; i++)
{
    if(i == record_number_i_want_to_delete)
        continue; // this skips the rest of the loop and effectively goes back to the top
    // copy record[i] or whatever...
}