CS 3733 Operating Systems, Fall 2005 Midterm Comments

The grade distribution for the midterm exam was as follows:

• 90-98: 8
• 80-89: 9
• 70-79: 3
• 60-69: 6
• 50-59: 1
• below 50: 1

Comments on particular problems

• 3. a) This is about the SFT. You only have to answer the question and not give a long general discussion.
  open always creates a new entry in the SFT, even if one already exists for the file being opened.
• 3. b) Most processes have open files, even if they have not explicitly called open. A process inherits the open files from its parent.
  Perhaps a better description of the answer is:
  For each open file descriptor in the parent, the corresponding entry in the SFT has its count incremented.
• 5. Give the CPU utilization as a fraction.
  If you did not calculate the waiting time correctly, make sure you know how to do it for the final exam.
• 7. Everyone got credit for this one.