curruption of the heap

#include "StdAfx.h"
#include<iostream>
using namespace std;

class stream
{
	char *name_of_stream;
	int year_of_starting;
	public:
	void set_stream(char *n,int y)
	{
		name_of_stream=n;
		year_of_starting=y;     //error comes at this point
		
	}
	void get_stream()
	{
		cout<<name_of_stream;
		cout<<year_of_starting;
		
	} 
};
class students:public stream
{
	char *stud_name;
	int stud_rollno;
	public:
	void set_data(char *n,int r)
	{
		stud_name=n;
		stud_rollno=r;
	}
	void get_data()
	{
		cout<<stud_name;
		cout<<endl<<stud_rollno;
	}			
};
int main()
{
	students *s;
	int num=0;
	s=new students[num];
	char c;
	char stream[10],name[50];
	int year;
	double rollno;
	do
	{
		cout<<"enter the stream";
		cin>>stream;
		cout<<"enter the year of joining the college"<<endl;
		cin>>year;
		cout<<"enter your name";
		cin>>name;
		cout<<"enter your rollno";
		cin>>rollno;
		(s+num)->set_data(name,rollno);
		(s+num)->set_stream(stream,year);
		num++;
		cout<<"do you want to continue  (y/n)";
		cin>>c;
	}while(c!='n');
	cout<<num;
	for(int i=0;i<num;i++)
	{
		(s+i)->get_data();
		(s+i)->get_stream();
	}
	delete s;
	return 0;
}