Suppose We Want an Array to Satisfy the Condition

Suppose we want an array to satisfy the condition,
a[0] <= a[1] <= a[2] <= ...
And suppose this code is written to implement a test of this condition
#include <iostream>
using namespace std;
int main()
{
double array[10] = { 1,2,3,4,5,6,7,8,9,10 };
// assume the array is filled somehow.
for(int i=0;i < 10;i++)
if (array[i] > array[i+1])
cout << "Array elements " << i << " and "
<< i + 1 << " are out of order.\n";
}
When this is run,we sometimes get the following puzzling output:
Array elements 9 and 10 are out of order.
Even more puzzling,sometimes we don't get this output.
Why?