One of the goals of this question is to give you practice with context switching and thread queue manipulation in Nachos. Consider the following test program for an implementation of KThread. join in Nachos. It begins when the main Nachos thread calls KThread. selfTest. You do not need to know the details of how join is implemented. All you need to know is that when a parent thread calls join on a child thread, the parent does one of two things: (1) if the child is still running, the parent blocks until the child finishes (at which point the parent is placed on the ready queue);
(2) if the child has finished, the parent continues to execute without blocking. Assume join uses a wait queue of some kind in its implementation.