#include <stdio.h>
#include <math.h>

//use them bits! set them up as defines
#define set_bit( mem, index )   (((char *)( mem ))[ index  / 8] |= ( 1 << ( index  % 8 )))
#define test_bit( mem, index )  (((char *)( mem ))[ index  / 8] & ( 1 << ( index  % 8 )))
#define clear_bit( mem, index ) (((char *)( mem ))[ index  / 8] &= ~( 1 << ( index  % 8 )))

int main()
{
   
   int limit = 100;
   
   int i, j, sqrt_limit;
  
   //allocate the memory 
   void *primes = malloc (limit/8+1);
   if (primes ==NULL) return;
  
   //setup the sieve 
   for (i=2;i<=limit;i++)
      set_bit(primes,i);

   printf("List created\n");

   sqrt_limit=(int)sqrt(limit);
   
   //see comments in prime2.c
   for (i=2;i<=sqrt_limit;i++) 
      if (test_bit(primes,i))      
         for (j=i*2;j<=limit;j+=i)
            clear_bit(primes,j);

   for (i=2;i<=limit;i++)
      if (test_bit(primes,i))
         printf("%d ",i);
   
   free (primes);
   return 1;
}