C++ program to update the record in binary mode

#include<iostream>
#include<conio.h>
#include<fstream>
#include<process.h>

using namespace std;

class rec
{
    protected:
        int roll;
        int long phon;
        char name[20];

    public:
        input()
        {
            std::cout<<"Enter the name = ";
            std::cin>>name;
            std::cout<<"Enter the roll # = ";
            std::cin>>roll;
            std::cout<<"Enter the phone # = ";
            std::cin>>phon;
        }

        dis()
        {
            std::cout<<name<<"t"<<roll<<"t"<<phon<<std::endl;
        }
};

int main()
{
    system("cls");

    int recn,n;
    rec r;

    fstream fir("new.cpp",ios::binary|ios::in|ios::out);

    if(!fir)
    {
        std::cout<<"File opening error"<<std::endl;
        getch();
        exit(0);
    }

    fir.seekg(0,ios::end);

    int endp = fir.tellg();
    n = endp/sizeof(r);

    std::cout<<"Number of records in file = "<<n<<std::endl;
    std::cout<<"Enter any key"<<std::endl;

    getch();

    std::cout<<"Enter record Number you want to update = ";
    std::cin>>recn;

    long int pos = (recn-1)*sizeof(r);
    fir.seekg(pos);

    std::cout<<"You are modify the record "<<std::endl;

    fir.read((char*)&r, sizeof(r));
    r.dis();

    std::cout<<"Now enter new entry"<<std::endl;
    fir.seekg(pos);
    r.input();

    fir.write((char*)&r, sizeof(r));
    std::cout<<"Record has updated successfully";

    getch();
    return 0;
}

Number of records in file = 2
Enter any key
Enter record Number you want to update = 1
You are modify the record
ABC     1   12345
Now enter new entry
Enter the name = A
Enter the roll # = 1
Enter the phone # = 12345

Record has updated successfully