COSC 4330                   MIDTERM                            7/28/98

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)  The First Come First Served policy minimizes the average waiting
          time of all processes.
     
     (b)  Time-sharing systems are not true real-time systems.

     (c)  It is a good idea to increase the priority of CPU-bound
          processes.

     (d)  In a multiprogramming system, there can be many programs in the
          system but there is never more than a single process.
      
     (e)  Programs that transfer entire files from one machine to another
          should use datagrams rather than streams.

     (f)  Accessing a disk drive is 1,000 times slower than accessing the
          main memory.

2    Answer  in one sentence or less to each of the following questions (5
     points)
     
     (a)  What is the value returned by the wait() system call?
    
     (b)  Give one good reason for a process to interrupt itself:

     (c)  Can you simulate a non-blocking receive using blocking receives?

     (d)  What is the major disadvantage of layered kernels?

3.   What is the major advantage of kernel-supported threads over user-
     level threads ? ( 10 points)
 
4.   What  is  the  major  motivation for swapping processes  out?  (5
     points)  What can you do to avoid excessive swapping? (5 points)
     
5    What events will increase or decrease the priority of a process in
     VMS and by how much?(10 points)    
  
6.   What does the scheduling policy of UNIX System V.4 do to avoid
     process starvation? (10 points)

7.   How would you select the time slice in a Round Robin scheduling
     policy? (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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