COSC 4330                FIRST MIDTERM              March 1, 2000


This exam is closed book.  You can have one sheet of notes.
     
1.   Answer in one sentence to each of the following questions:
     (5x5 points)
     
     (a)  What is the  major disadvantage of datagrams over virtual
          circuits?

     (b)   Why is memory protection always implemented in hardware?

     (c)  What is the major advantage of monolithic kernels over
          microkernels?

     (d)  What is the major disadvantage of non-preemptive scheduling
          policies?

     (e)  Why is the fork() system call so expensive?

2.   What  is  the major disadvantage of the master-slave approach  in
     operating  systems for multiprocessor architectures?  (5  points)
     What is its only advantage? (5 points)
 
3.   How many lines of output will the following program print out? (5
     points)?

     main(){
          fork(); printf("Hi!\n"); fork();
     }
                            The program will print ____________ lines.
                                                                      
4.   Contrast  the  respective advantages and disadvantages  of  user-
     level and kernel-level threads.  (20 points)
     
5.   How can you simulate blocking sends using only non-blocking sends and
     non-blocking receives? (10 points)
6.   List the two state transitions leaving the waiting state and
     indicate what events can cause them (2×5 points)

7.   Consider  the  following system V scheduler, which  contains  two
     errors: (4x5 points)
     
          #ts_quantum ts_tqexp ts_slpret ts_maxwait ts_lwait LEVEL
               800        0        1        4000        0    #  0
               400        0        2        2000        2    #  1
               200        1        3        1000        3    #  2
               100        3        3         500        3    #  3
          
      On level ___ parameter ______________ should be set to _____
      On level ___ parameter ______________ should be set to _____