UNIVERSITY OF HOUSTON
                 Department of Computer Science
                                
                  COSC 6360--Operating Systems
                       MIDTERM EXAMINATION
                         March 15, 1995
                                
This exam is closed book.  You can have two sheets (i.e. four
pages) of notes.

1.   What is the purpose of  the UNIX set user-ID bit?  (5
     points)  What is its major drawback?  (5 points)  Which
     precaution(s) should be taken by anyone using it? (5
     points)

     THIS QUESTION WAS RELATED TO A PAPER THAT IS NOT ANYMORE IN THE
     READING LIST.  IT WILL BE NOT BE ASKED AGAIN.

2.   Does it make sense to allow different block sizes in the
     same file system?  Justify your answer in or two sentences.
     (5 points)

3.   How does Mach handle memory inheritance? (3×5 points)

4.   What are the undesirable effects of letting  the hand of the
     CLOCK-1 page replacement policy move (a) too fast and (b)
     too slow and what has been done about it? (2×5 points)

5.   According to Presotto and Ritchie, what are the two major
     drawbacks of BSD 4.2 sockets?  (2×5 points)  What solution
     do they propose?  (5 points)

     THIS QUESTION WAS RELATED TO A PAPER THAT IS NOT ANYMORE IN THE
     READING LIST.  IT WILL BE NOT BE ASKED AGAIN.

6.   What is the primary function of  the MULTICS Active Segment
     Table? (5 points)  What  does each Active Segment Table
     Entry contain? (5 points) Which other data structures are
     attached to each ASTE? (5 points)

     THIS QUESTION WAS RELATED TO A PAPER THAT IS NOT ANYMORE IN THE
     READING LIST.  IT WILL BE NOT BE ASKED AGAIN.

7.   Why did the designers of RVM decide to insulate their design
     from the virtual memory subsystem? (5 points)  How did this
     decision affect the design of RVM? (5 points)

8.   What is the following CSP command doing (6 points) and when
    will it terminate (4 points)?

     *[hungry > tired; waiter ? food ® eat(food) € cashier ? bill
     ® cashier ! cash)]

9.   How did the designers of scheduler activations  divide the
     processor scheduling tasks between the kernel and the user-
     level thread system? (5 points)