The Sieve of Eratosthenes in class (C++)

#include <conio.h>
#include <iostream>
using namespace std;

class sieve_Erastotenes
{
private:
int *first_table;
int size;
public:
sieve_Erastotenes(int x)
{
int i;
size=x;
first_table=new int[size+1];
for(i=1;i<=size;i++)
 first_table[i]=i;
}
bool is_True(int x)
{
if(first_table[x]==0)
 return true;
else
 return false;

}
void Read()
{
int i,j;
i=1;
while(i<size)
{
for(i++;is_True(i);i++);
j=2;
while(i*j<=size)
{
first_table[i*j]=0;
j++;
}
}
}
void Write()
{
int i;
for(i=2;i<=size;i++)
 if(!is_True(i))
  cout<<first_table[i]<<endl;
}

~sieve_Erastotenes()
{
delete first_table;
}

};

 int _tmain(int argc, _TCHAR* argv[])
{
  int limit_numbers;
  cin>>limit_numbers;
  cout<<"The first numbers from 2 to "<<limit_numbers<<endl;
  sieve_Erastotenes SE(limit_numbers);
  SE.Read();
  SE.Write();


 getch();
return 0;
}