the lowest 2 bits of handle values are no longer unused, and 0 is now a valid handle value. the first 64 handles are now reserved, and will not be automatically allocated by the kernel. however, they are still valid handles, and other handles can be moved to this area using an as-yet-unwritten function. this is to allow support for standard POSIX file descriptors, which require the values 0, 1, and 2.