i 'm doing my assignment but i have some problem with this.can anyone help me to solve this problem .

here is my code:
Code:
#include<fstream.h>
#include<stdlib.h>
class variable
{
 protected:
  struct student
  {
   char name[100],course[100],id[10],gender;
   int  dob,mob,yob,age,ic;
   double cgpa,marks[10];
  }std[100];
  int i;
};
class student:public variable
{
 private:
 public:
  void reg()
  {
   i=1;
   std[i].dob=std[i].mob=std[i].yob=0;
   cout<<"Enter Student Name   : ";
   cin.ignore();
   cin.getline(std[i].name,100);
   cout<<"Enter Student IC     : ";
   cin.ignore();
   cin>>std[i].ic;
   cout<<"Enter Student Gender : ";
   cin.ignore();
   cin>>std[i].gender;
   cout<<"Enter Student Course : ";
   cin.ignore();
   cin.get(std[i].course,100);
   cout<<"Student Borthday     : "<<endl;;
   cout<<"Date  : ";
   cin.ignore();
   cin>>std[i].dob;
   cout<<"Month : ";
   cin.ignore();
   cin>>std[i].mob;
   cout<<"Year  : ";
   cin.ignore();
   cin>>std[i].yob;
   i++;
  }
  void dpl()
  {
   for(int a=1;a<=i;a++)
   {
     cout<<"Student Name     : "<<std[a].name<<endl;
     cout<<"Student ID       : "<<std[a].id<<endl;
     cout<<"Student IC       : "<<std[a].ic<<endl;
     cout<<"Student Gender   : "<<std[a].gender<<endl;
     cout<<"Student Course   : "<<std[a].course<<endl;
     cout<<"Student Birthday : "<<std[a].dob<<"/"<<std[a].mob<<"/"<<std[a].yob<<endl;
     cout<<"============================================="<<endl;
   }
  }
};
class exam:public student
{
};
class slt_menu:public exam
{
 private:
  int choice;
  char reply;
 public:
  void mainmenu()
  {
   cout<<"\t\t\t*******************************************"<<endl;
   cout<<"\t\t\t*           Extreme Technology            *"<<endl;
   cout<<"\t\t\t*                 Collage                 *"<<endl;
   cout<<"\t\t\t*          Student Detail System          *"<<endl;
   cout<<"\t\t\t*******************************************"<<endl;
   cout<<"\n\t\t\t1.Student Data System"<<endl;
   cout<<"\t\t\t2.Student Examination System"<<endl;
   cout<<"\t\t\t3.Exit From This Program"<<endl;
   cout<<"\n\t\t\tEnter Your Choice : ";
   do{
   cin>>choice;
    switch(choice)
    {
     case 1:
     {
      smenu();
      break;
     }
     case 2:
     {
      cout<<"****";
      break;
     }
     case 3:
     {
      exit(1);
      break;
     }
     default:
     {
      cout<<"\t\t\tYou Have Enter Invalid Input!!!Enter Again!!!"<<endl;
      cout<<"\t\t\tEnter Your Choice Again : ";
     }
    }
   }
   while(choice!=1 || choice !=2 ||choice !=3);
  }
  void smenu()
  {
   student st;
   cout<<"\t\t\t~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~"<<endl;
   cout<<"\t\t\t~               Student Data              ~"<<endl;
   cout<<"\t\t\t~                  System                 ~"<<endl;        
   cout<<"\t\t\t~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~"<<endl;
   cout<<"\n\t\t\t1.Student Registration"<<endl;
   cout<<"\t\t\t2.Display Student Detail"<<endl;
   cout<<"\t\t\t3.Seacrh  Student Detail"<<endl;
   cout<<"\t\t\t4.Return To Main Menu"<<endl;
   cout<<"\n\t\t\tEnter YOur Choice : ";
   cin>>choice;
   do{ 
    switch(choice)
    {
     case 1:
     {
      do{
       reg();
       cout<<"Do You Wish To Add More Data??"<<endl;
       cin>>reply;
      }while(reply=='Y'||reply=='y');{}
      cout<<"Do You Want To Save & Return To Main Menu"<<endl;
      cin>>reply;
      if(reply=='Y'||reply=='y')
      {
       ofstream input("student_details.txt");
       input.write((char*)&st,sizeof(student));
       input.close();
       mainmenu();
      }  
      break;
     }
     case 2:
     {
      ifstream toread("student_details.txt");
      toread.read((char*)&st,sizeof(student));
      while(toread)
      {
       toread.read((char*)&st,sizeof(student));
      }
      toread.close();
      dpl();
     }
     case 3:
     {
      
     }
     case 4:
     {
      mainmenu();
     }
     default:
     {
      cout<<"\t\t\tYou Have Enter Invalid Input!!!Enter Again!!!"<<endl;
      cout<<"\t\t\tEnter Your Choice Again : ";
      cin>>choice;
     }
    }
   }while(choice!=1||choice!=2||choice!=3||choice!=4);
  }
};
void main()
{
 slt_menu m;
 m.mainmenu();
}
can anyone help me ???