UNIVERSITY OF HOUSTON
                 Department of Computer Science
                                
          COSC 4330--Fundamentals of Operating Systems
                             MIDTERM
                        October 13, 1994


This exam is closed book.  You can have one sheet of notes.

1.   For each of the statements below, indicate in one sentence 
     whether the statement is true or false (2 points), and why 
     (3 points).
     
     (a)  An OS that allows people to reboot the system from a 
          floppy drive without entering first a password is not
          secure.
   
     (b)  Servers should always use blocking receives.
      
     (c)  A process that relinquishes the CPU after it has ex-
          hausted its time slice goes to the waiting_suspended
          state.
             
     (d)  Most modern operating systems use preemptive
          scheduling.
          
2.   What is the major disadvantage of the master-slave approach
     in operating systems for multiprocessor architectures?  (10
     points)

3.   Contrast the respective advantages and disadvantages of 
     user-level and kernel-level threads.  (20 points)
     
4.   What is the difference between blocking and  non-blocking
     reads? (10 points)
  
5    Which features of the multi-level scheduling algorithm with
     feedback ensure that CPU-bound jobs will end in one of the low
     priority queues?  (10 points)
   
6.   Consider the two program fragments one and two, which access the
     same shared variable total_amount, which is initially equal to
     500
     
     one:                          two:
     total_amount += 100           total_amount += 20
     total_amount -= 10
     
     What are all the possible values for total_amount after the
     two  fragments  have  been  executed  exactly  one  time in
     parallel? (10 points)

7.   In the VMS scheduling policy,
     
     (a)  which events decrease the priority of a process?
          (5 points)
     
     (b)  which events increase it? (5 points)

8.   What  is the major advantage of remote procedure calls over
     the conventional message passing approach?  (10 points)
     



--IMPORTANT----IMPORTANT----IMPORTANT----IMPORTANT----IMPORTANT--
Please do not try to answer these questions by yourself BEFORE
having a clear idea of what's on the test for which you are
studying.

Materials covered in each test DO VARY from semester to semester
because the pace of the course can change, some materials are be
added and other deleted almost every semester.
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