CS 481:  Operating System Principles



            Assignment # 5:  Due Date = Friday, 10/23/98


1. The following is a snapshot of a system with four resource types and with 
   five processes currently executing.

              Allocation               Max
              A  B  C  D           A  B  C  D
        P0    0  0  1  2           0  0  1  2
        P1    1  0  0  0           1  7  5  0
        P2    1  3  5  4           2  3  5  6
        P3    0  6  3  2           0  6  5  2
        P4    0  0  1  4           0  6  5  6
    
    The vector, available, is (1 5 2 0).

    (a) Is the system in a safe state? If so, how many different "safe
        sequences" exist?
    
    (b) If a request from P1 for (0 4 2 0) arrives, can the request be
        immediately granted?


2.  Assume that the average process runs for a time T before blocking
    on I/O. The process switching time is S. For round robin scheduling
    with quantum Q, derive expressions for CPU efficiency in each of the
    following cases:
  
      (i)   Q = infinity.
      (ii)  Q > T
      (iii) S < Q < T
      (iv)  Q = S
 

      
3.  Chapter 7, Problem 2.




Kindly have all answers printed out.