If the array is being accessed using pointer addition, the check is for the value being added to be between 0 and the number of elements in the array, inclusive. An exeption is that no run-time check is made if the compiler can determine that the access is valid. If a multi-dimension array is accessed, the compiler performs checks on each of the subscript expressions, making sure each is within the corresponding bound. So for the following code, the compiler checks that both x and y are between 0 and 9. ALL Do all checks.
NONE Do no checks.