UNIVERSITY OF HOUSTON
               Department of Computer Science

       COSC 4330: Fundamentals of Operating Systems
                       SECOND MIDTERM

CLOSED BOOK You may have with you one sheet of notes.

1.   What is the difference between a PUBLIC mailbox  and  a
     PRIVATE mailbox?  (10 points)

2.   What  is  the  difference  between  BLOCKING  and  NON-
     BLOCKING RECEIVE primitives?  (10 points)

3.   What problem can arise when  the  acknowledgment  of  a
     message  never  reaches  the  sender of the message? (5
     points) What should be done to avoid this  problem?  (5
     points)

4.   What happens when a procedure inside a monitor  does  a
     WAIT operation on some condition variable? (10 points)

5.   A good  scheduling  policy  should  be  FAIR,  minimize
     RESPONSE  TIME for interactive users, and maximize sys-
     tem THROUGHPUT.  How does the ROUND ROBIN  policy  fare
     with  respect  to  these  three  criteria (3x5 points)?
     What can be done to improve that policy? (5 points)

6.   Which are the major disadvantages of (a)  multiprogram-
     ming  with  FIXED  partitions  and (b) multiprogramming
     with VARIABLE partitions? (2x10 points)

7.   A workstation has a maximum memory size  of  128  Mega-
     bytes.   The  memory  is  byte  addressable and virtual
     addresses have 32 bits.  Given a page size of  8  Kilo-
     bytes, what are the number of bits:

     (a)  in a page number? (5 points)            bits

     (b)  in a frame number? (5 points)            bits

8.   What is the function of the MODIFIED or DIRTY  bit?  (5
     points)  What  would happen if the MODIFIED bit was not
     implemented in a given architecture? (5 points)


--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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