******** fig2.9 **********

	int
	binary_search( input_type a[], input_type x, unsigned int n )
	{
		int low, mid, high;	/* Can't be unsigned; why? */

/*1*/		low = 0; high = n-1;
		while( low <= high )
		{
/*2*/			mid = (low + high)/2;
/*3*/			if( a[mid] < x )
/*4*/				low = mid + 1;
			else
/*5*/			if( a[mid] > x )
/*6*/				high = mid - 1;	
			else
/*7*/				return( mid );	/* found */
		}
/*8*/		return( NOT_FOUND );
	}