#include <fstream> //for file streams
#include <iostream>
using std::fstream;
#include <cstdlib>

using namespace std;
////////////////////////////////////////////////////////////////

class person //class of persons
{
  protected:
    char name[80]; //person’s name
    int age; //person’s age
  public:
    void getData() //get person’s data
    {
      cout << "\n Enter name: "; cin >> name;
      cout << " Enter age: "; cin >> age;
    }
    void showData() //display person’s data
    {
      cout << "\n Name: " << name;
      cout << "\n Age: " << age;
    }
};

int main()
{
  person pers; //create person object
  ifstream infile; //create input file
  infile.open("group.dat", ios::in | ios::binary); //open file
  infile.seekg(0, ios::end); //go to 0 bytes from end
  int endposition = infile.tellg(); //find where we are
  int n = endposition / sizeof(person); //number of persons
  cout << "\nThere are " << n << " persons in file";
  cout << "\nEnter person number: ";
  cin >> n;
  int position = (n-1) * sizeof(person); //number times size
  infile.seekg(position); //bytes from start
  //read one person
  infile.read( reinterpret_cast<char*>(&pers), sizeof(pers) );
  pers.showData(); //display the person
  cout << endl;
  system("pause");
}