UNIVERSITY OF HOUSTON
                Department of Computer Science

                  COSC 6360-Operating Systems
                            MIDTERM
                       November 5, 1990

Be concise but complete.

1. Explain the function and the purpose of the set user-ID  bit
   in UNIX. (10 points)

2. What makes the choice of an optimal block  size  so  compli-
   cated  in UNIX.  (4 points) How is Berkeley UNIX solving the
   problem? (6 points)

3. What is the difference between stream sockets  and  datagram
   sockets in Berkeley UNIX? (10 points).

4. Describe and compare the page replacement  policies  of  VMS
   and Mach.  (20 points)

5. Explain how Berkeley UNIX implements the page-referenced bit
   (7 points) and give the major limitation of that approach (3
   points)

6. Which steps are taken by  the  MULTICS  supervisor  when  it
   activates a segment? (10 points)

   THIS QUESTION WAS RELATED TO A PAPER THAT IS NOT ANYMORE IN
   THE READING LIST.

7. What is the purpose  of  the  MULTICS  linkage  segment?  (4
   points)  Could this information have been stored in the pro-
   cedure segment?  (6 points)

   THIS QUESTION WAS RELATED TO A PAPER THAT IS NOT ANYMORE IN 
   THE READING LIST.

8. Contrast the advantages and disadvantages  of  shared-memory
   vs. message-based IPC? (14 points) What steps can be taken
   to improve the applicability-or the performance-of either of
   them? (6 points)