CS 3733 Operating Systems, Spring 2011 Exam 2 Comments

Grade Distribution:
90-100: 6
80-89: 9
70-79: 10
60-69: 5
below 60: 2
Average: 77

• For problem 1, you should be using the correct terms: generated, delivered, pending, etc. For part e, you needed to mention a signal handler. If the default action is taken, the signal has not been caught.
• For the first 3 parts of problem 2, you only need to answer the question. You do not need to say what else the code does, only how it affects the process signal mask.
• In Problem 2f), SIGUSR1 may or may not be in maskunblocked. For full credit, you need to explain how this might affect the running of the code segment.
• Problem 3c asks about the behavior of the code, not how individual variables are set. There are basically two issues. One is that with this code when it gets past line 6, SIGUSR1 is blocked, whereas in the other code it is only blocked if it was blocked originally. Also, in this code, only SIGUSR1 is blocked while the process is suspended, while in the other code, all previously blocked signals are also blocked. Note that line 4 of this code affects the signal mask in exactly the same way that line 6 does in the previous code because SIG_BLOCK is used. Other signals in the process signal mask are unchanged.
• In Problem 4, your answer should distinguish connection-oriented from connectionless communication. There are 2 steps, establish a connection, and communicate on a dedicated channel. The client must initiate the connection request, but once the connection is made, there is no distinction between the client and the server. The server can request information from the client.
• In Problem 5, It is not sufficient to say that a serial server handle can only handle one client at a time. This is true of any program running on a single CPU. The distinction is that with a serial server, the current connection must be closed before another connection request can be handled. When describing an implementation of a parallel server, it is not sufficient to just say "fork a child." You need to describe what each of the two processes does.
• For Problem 6, a number of people had trouble multiplying 3 by .9.
• For Problem 7h, you needed to describe how the physical address is constructed from the frame number and the offset.