[Data structure] using bitmap sorting

#include <stdio.h>
#include <stdlib.h>

#define INT_BY_BIT
#define MASK 0x1F
#define SHIFT 5

#define N 1000000

int a[n/int_by_bit+1];
void set_bit (int x) {A[x>>shift] |= 1 << (x & MASK);}
void clear_bit (int x) {A[x>>shift] &= ~ (1<< (x & MASK));}
int test_bit (int x) {return a[x>>shift]& (1<< (x & MASK));}

int main ()
{
//	int a[n/int_by_bit+1];
	int i;
	for (i=0;i<n;i++)
	{
		clear_bit (i);
	}
	while (scanf ("%d", &i)! = EOF)
	{
		set_bit (i);
	}
	for (i=0;i<n;i++)
	{
		if (test_bit (i))
		{
			printf ("%d", I);
			printf ("");
		}
	}
	return 0;
}

1, if a number can occur up to 8 times, how to sort the bitmap.
A: You can use a byte to represent a number

2, if there are 10 million numbers, but the memory is only 1 m, and 10000000 need 1.25M, used how to sort.
A: Can be completed by two sequencing, first Order 1 to 5000000, second order 5000000 to 10000000