UNIVERSITY OF HOUSTON
                 Department of Computer Science

                   COSC 6360-Operating Systems
                             MIDTERM
                          April 2, 1992

Be concise but complete.

1.   What does Berkeley UNIX to protect its file systems  against
     irrecoverable disk failures? (10 points)

2.   What is an i-node? (5 points) How would you  define  i-nodes
     today  if  you had a chance to redesign the UNIX file system
     from scratch ? Justify your answer. (5 points)

3.

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

(b)  Which ones are best suited to implement 1) a  file  transfer
     protocol  such  as  ftp  and 2) a name server?  Justify both
     answers in a few words. (10 points)

4.   In a recent paper, A. Tanenbaum argues that Mach  is  not  a
     true  distributed system because its message passing mechan-
     ism is optimized towards intra-host message passing.  Is  he
     factually true?  (10 points)

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

5.   How does the current Berkeley UNIX page  replacement  policy
     differs  from  that descibed by Babaoglu and Joy? (6 points)
     What factor motivated this change (4 points).

6.   Sketch a modified MULTICS virtual memory  architecture  that
     would by handle much larger segments (say, one to four Giga-
     words)?  What would be the impact of this change on the per-
     formance of the virtual memory? (20 points)

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

7.   Briefly explain the positions of the two sides of the nested
     monitor call controversy (10 points).

8.   How does the Cedar RPC implements  complicated  remote  pro-
     cedure calls?  (10 points)