// Source: "Software Design ...", John A Robinson, Newnes, 2004, page 223.
int search(int x, int array[], int num_in_array)
	{
	int middle;
	int start = 0;
	int end = num_in_array - 1;
	while(end >= start)
		{
 		middle = (start + end)/2;
		if (array[middle] == x)
			return(middle);
		if (array[middle] < x)
			start = middle + 1;
		else
			end = middle - 1;
		}
	return(-1);
	}