some error plz remove

[deepak_kr_mehta]

hello sir
sir when i run this following programme it will showing me error.plz assist me to remove it

#include<iostream.h>
#include<conio.h>
class student
{
int id;
mutable int j;//it will showing error 1. declaration missing //2. undefined symbol hpublic:
void set(int i)
{
id=i;
j=90;// cannot modify}
void print()
{
cout<<id<<j;
}
};
void main()
{
student s1;
s1.set(5);
s1.print();
}

sir after place mutable it will showing me same error with extra syntex error.
plz sir correct it.
thanx
from
deepak kr.

[Valmont]

Experiment with this code:

#include<iostream>

class student
{
private:
  int id;
  mutable int j;
public:
  student(int id, int j) : id(id), j(j) {}
public:
  void set(int i) const
  {
    j=i;  // can modify
  }

  void print() const
  {
    std::cout<<id<<" "<<j;
  }
};

int main()
{
  const student s1(1,1);
  s1.set(5);
  s1.print();
  
  std::cin.get();
  return 0;
}

Next time, format your code decently so it becomes readable. Also add the code between code tags. In general, READ the sticky topic I posted in the link below:
[READ THIS FIRST] About the standard C++ forum.