binary search on c, the while loop

Question

There's something that I don't get with the binary search code on C.

int binarySearch(int a[], int n, int x)
{
   int low=0, mid, high=n-1;
   while(low <= high)
   {
        mid = (low + high) / 2;
        if (x < a[mid])
            high = mid - 1;
        else if (x > a[mid])
         low = mid + 1;
       else
         return mid;
   }
   return -1;
}

Why does the while loop while(left<=right) can't be written: while(left<right)? Will this change effect things?

Solution

Take a simple case of

int a[1] = {5};
printf("%d\n", binarySearch(a, 1, 5));

With while(low < high), code prints -1 (did not find - wrong answer).

With while(low <= high), code prints 0 (found - right answer).