error in c++

[saneha]

#include<iostream.h>

using namespace std;

class Student

{

private:

int rollNo;

public:

void setRollNo(int aRollNo);

};

void Student::setRollNo(int aRollNo){

if(aRollNo>0){

cout<<"you are a student of vitual university";

}

else{

cout<<"you are not student of virtual univerity";

}

}

int main()

{

Student astudent;

astudent.setRollNo(500);

system("pause");

return 0;

}