#include <fstream> //for file streams
#include <iostream>
using namespace std;
////////////////////////////////////////////////////////////////
class person //class of persons
{
   protected:
     char name[40]; //person’s name
     int age; //person’s age
  public:
    void getData(void) { 
      cout << "\n Enter last name: "; cin >> name;
      cout << "Enter age: "; cin >> age;
    }
    void showData(void) {
      cout << "\n Name: " << name;
      cout << "\n Age: " << age;
    }
    void diskIn(int);
    void diskOut(); //write to file
    static int diskCount(); //return number of
};
void person::diskIn(int pn) //read person number pn
{ //from file
  ifstream infile; //make stream
  infile.open("PERSFILE.DAT", ios::binary); //open it
  infile.seekg( (pn-1)*sizeof(person) ); //move file ptr
  infile.read( (char*)this, sizeof(*this) ); //read one person
}
//--------------------------------------------------------------
void person::diskOut() //write person to end of file
{
  ofstream outfile; //make stream
  //open it
  outfile.open("PERSFILE.DAT", ios::app | ios::binary);
  outfile.write( (char*)this, sizeof(*this) ); //write to it
}
//--------------------------------------------------------------
int person::diskCount() //return number of persons
{ //in file
  ifstream infile;
  infile.open("PERSFILE.DAT", ios::binary);
  infile.seekg(0, ios::end); //go to 0 bytes from end
  //calculate number of persons
  return (int)infile.tellg() / sizeof(person);
}
////////////////////////////////////////////////
main()
{
  person p; //make an empty person
  char ch;
  p.diskIn(5);
  p.showData();
  /*
  do { //save persons to disk
    cout << "Enter data for person:";
    p.getData(); //get data
    p.diskOut(); //write to disk
    cout << "Do another (y/n)? ";
    cin >> ch;
    } while(ch=='y'); //until user enters ‘n’
    
  int n = person::diskCount(); //how many persons in file?
  cout << "There are " << n << " persons in file\n";
  for(int j=0; j<n; j++) //for each one,
  {
    cout << "\nPerson " << j+1;
    p.diskIn(j); //read person from disk
    p.showData(); //display person
  }
  cout << endl;*/
  system("pause");
}