c

ofstream out;
 out.open("clientData.data",ios::ate);
 if(out.is_open())
 {
  BankData bd ={0,"","",0.0};
  for(int i= 0;i<100;++i){
   out.write(reinterpret_cast<const char*>(&bd),sizeof(bd));
  }
 }

 BankData bd;
 cout<<"please num id 1-100"<<endl;
 cin>>bd.accountID;

 while(bd.accountID>0&&bd.accountID<=100){

  cout<<"input fist name , last name and balance"<<endl;
  cin>>bd.firstName>>bd.lastName>>bd.balance;

  out.seekp((bd.accountID-1)*sizeof(bd));
  out.write(reinterpret_cast<const char*>(&bd),sizeof(bd));

  cout<<"please num id 1-100"<<endl;
  cin>>bd.accountID;
 }

 out.close();

 BankData bd;
 ifstream in("clientData.data");
 if(!in)
 {
  cerr<<"file not open"<<endl;
  exit(1);
 }
 
 cout<<" input num id to look"<<endl;
 cin>>bd.accountID;

 while(!in.eof()&&bd.accountID>0&&bd.accountID<101){
  
  in.seekg((bd.accountID-1)*sizeof(bd));

  in.read(reinterpret_cast<char*>(&bd),sizeof(bd));
  
  cout<<" first name ,last name , balance is:"<<bd.firstName<<"  "<<bd.lastName<<"  "<<bd.balance<<endl;
  
  
  cout<<" input num id to look"<<endl;
  cin>>bd.accountID;

 }

 in.close();