UNIVERSITY OF HOUSTON
                 Department of Computer Science
                                
           COSC 4330—Fundamentals of Operating Systems
                       MIDTERM EXAMINATION
                          June 22, 1995

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)  FCFS is  a  terrible  scheduling  policy   for
          interactive systems  

     (b)  A  process that has exceeded its quantum  of  CPU
          time is put in the waiting state. 

     (c)  Any  scheduling policy that maximizes the  system
          throughput will also minimize the system response time.
     
     (d)  Peterson's algorithm assumes that each C statement
          is executed in an atomic fashion.
2.   What  is the major motivation for the microkernel approach in
      kernel design? (5 points)

3.   What  is  the  major  advantage  of  kernel-level threads over
     user-level threads? (5 points)

4.   What are the tasks performed by the server stub in a remote
     procedure call? (10 points)

5.   What is the major difference between datagrams and virtual
     circuits? (10 points)

6.   Why  did  the  designers of UNIX  chose  to  have separate
     fork() and exec() system calls instead of a  single
     fork_and_exec()? (10 points)

7.   What  does the VMS scheduling policy do to favor I/O-bound
     processes  over  other  regular  processes? (10 points)

8.   Give one major motivation to use kernel-supported semaphores
     instead of any user-level solution? (10 points)

9.   What is wrong with the following solution to the mutual
     exclusion problem? (20 points)

                    // Global variables
                    #define FALSE 0
                    #define TRUE  1
                    int reserved[2];
                    reserved[0] = TRUE;
                    reserved[1] = FALSE;
                    
                    
  void enter_region(int pid)
  {
     int other; // other process
     other = 1 - pid;
     while (reserved[other]);
  } // enter_region
  
   void leave_region(int pid)
  {
     int other; // other process
     other = 1 - pid;
     reserved[other] = TRUE;
     reserved[pid] = FALSE;
     } // leave_region

--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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