The search function does not work - c++

Question

Here is my code. It's homework but i have done it all. But the search function does not work. I know Im doing something wrong in it. The user has to enter a name to search and it should display the whole entry. There is an error at the void search function which says "error C2120: 'void' illegal with all types"
// Awholenew world.cpp : Defines the entry point for the console application.
//
#include "stdafx.h"
#include<process.h>
#include<iomanip>
#include<stdio.h>
#include<string.h>
#include<fstream>
#include<sstream>
#include<iostream>
#include<conio.h>
#include<stdlib.h>
using namespace std;
struct main
{
char FName[20];
char Last[20];
char Address[30];
long Phone;
int ID;
long CNIC;
}obj;
class Main
{
public:
virtual void init()
{
cin.getline(obj.FName,20);
cout << "Enter Name: ";
cin.getline(obj.Last,20);
cout << "Enter Address: ";
cin.getline(obj.Address, 30);
cout << "Enter Phone: ";
cin>>obj.Phone;
}
void view()
{
cout << "Name: " << obj.Last<< endl;
cout << "Address: " << obj.Address << endl;
cout << "Phone: " << obj.Phone << endl;
cout << "CNIC: " << obj.CNIC << endl;
cout << "ID: " << obj.ID << endl;
}
virtual void search()
{
char choice4;
char Target[20];
int Found=0;
fstream fin;
if (fin.open("Main.txt", ios::in| ios::out) == NULL)
cout<<"File is empty" << endl;
else
cout<<"Enter Name: " << endl;
cin.getline(Target, 20);
while(!fin.eof() && Found ==0)
{
fin<< endl << obj.Last << endl <<obj.Address <<endl <<obj.Phone << endl << obj.CNIC << endl << obj.ID;
if (strcmp(Target, obj.Last) == 0)
Found =1;
}
if(Found)
{
Main::view();
}
else if (!Found)
printf("**There is no such Entry**\n");
fin.close();
}
void display()
{
char BUFFER[100];
ifstream fin("Main.txt");
while (!fin.eof())
{
fin.getline(BUFFER, 100);
cout << BUFFER << endl;
}
}
};
class Teacher : public Main
{
public:
void tinit()
{
ofstream fin("Main.txt", ios::app);
Main::init();
cout << "Enter CNIC of Teacher" << endl;
cin>>obj.CNIC;
fin<< endl << obj.Last << endl << obj.Address << endl << obj.Phone << endl << "Teacher CNIC: " << obj.CNIC << endl;
}
};
class Student : public Main
{
public:
void sinit()
{
ofstream fin("Main.txt", ios::app);
Main::init();
cout << "Enter ID of Student" << endl;
cin>>obj.Phone;
fin<< endl << obj.Last <<endl << obj.Address << endl << obj.Phone << endl << "Student ID" << obj.ID << endl;
}
};
class Employee : public Main
{
public:
void einit()
{
ofstream fin("Main.txt", ios::app);
Main::init();
cout << "Enter Employee CNIC" << endl;
cin>>obj.CNIC;
fin << endl << obj.Last <<endl << obj.Address << endl << obj.Phone << endl << "Employee CNIC: " << obj.CNIC << endl;
}
};
int _tmain(int argc, _TCHAR* argv[])
{
Main* myarr[100];
Teacher* tearr[100];
Student* starr[100];
Employee* emarr[100];
int var=0;
int choice;
char input;
start:
printf("===============MAIN MENU===============");
printf("\n[1]Insert\n[2]Display All\n[3]Search\n[4]Exit\n");
printf("=======================================");
printf("\n\nEnter Your Choice: ");
cin >> choice;
switch(choice)
{
case 1:
label:
cout<< "Enter Choice s/t/e" << endl;
cin >> input;
if (input == 't')
tearr[var]->tinit();
if (input == 's')
starr[var]->sinit();
if (input == 'e')
emarr[var]->einit();
cout << " Enter another (y/n)? ";
cin >> input;
if (input == 'y')
goto label;
else
goto start;
break;
case 2:
myarr[var]->display();
break;
case 3:
myarr[var]->search();
break;
case 4:
cout << "Are you sure? y/n" << endl;
char in;
cin>>in;
if (in=='y')
getch();
else goto start;
break;
default:
return 0;
break;
return 0;
}
}

Answer 1

One problem I can see is:
fstream fin;
if (fin.open("Main.txt", ios::in| ios::out) == NULL)
The function fstream::open is declared as:
void open ( const char * filename,
ios_base:openmode mode = ios_base::in | ios_base::out );
as you can see its return type is void, so you cannot use it in the if expression.

Answer 2

The most glaring thing I noticed is that it looks like the struct of type 'main' stored in the obj variable is outside of any particular class instance. This means that every single object of type Main, Employee, Student or Teacher is only writing to a single obj outside of its own scope. ALL Employees, Teachers, Students, 'Mains' will be sharing whatever FName, Last, Address values you wrote last.
What you probably want is for each instance of Main to have its own FName, Last, Address, etc...
class Main
{
struct main
{
char FName[20];
char Last[20];
char Address[30];
long Phone;
int ID;
long CNIC;
}obj;
public:
virtual void init()
{
... rest of code here

Answer 3

please reduce your post to the main problem. if you just list everything in a single "code" block. noone can understand what you do.
1: don't use "goto" !(!!!!!)
2: you sould realy use bool instead of int for flags
3: don't use main / Main for structs or class names. it's actually reserved for the mainmathod (on some systems) and it is confusing to have one class and one struct with the same name (ignoring the case)
4: you're accessing the function Main::view(); in your search method. but on which object ? normaly you should load the data to an object and accessing it via this->view();
5: the whole concept appear wired. why are you using a textfile and a polymorphic class hierarchy ? the textfile dumps the hierarchy. maybe you should reconsider your class concept.