Within the 16-bit Windows subsystem, the applications (threads) are scheduled non-preemptively. Because the applications share memory, a single input queue, and are scheduled non-preemptively, an ill-behaved application can cause the subsystem to lock up. This will not affect the rest of Windows NT, since Windows NT treats the 16-bit Windows subsystem as a whole just like any other 32-bit Windows NT-based application. The subsystem is scheduled preemptively along with all of the other 32-bit applications.