CS 3733 Operating Systems, Spring 2009 Exam 1 Comments

Grade Distibution:
90-100: 1
80-89: 3
70-79: 6
60-69: 3
50-59: 5
below 50: 2
Average: 67

1. The question was about the contents of the file.
   Part of the explanation concerns what each process writes, but you need to say what is in the file.
   The number of possibilities is not so large that you cannot list them all. The important aspects of the answer are that the file offset is shared, and each write can return either 1 or 2. The file will contain 2, 3, or 4 bytes.
   Do not say that the two processes share (or do not share) the same file descriptor. The important thing shared is the system file table entry.
2. Most people did not answer the question that was asked. Only one student got full credit on this. Most got 5 points or less. Here, there are only 6 possibilities and you should be able to list them all.
3. Avoid using expressions such as "at the same time" or "simultaneously" when discussing critical sections and mutual exclusion.
   When there is only one CPU, only one thing happens at a time so we never have simultaneous execution.
   You need to distinguish between "simultaneously" and "concurrently".
   In giving an example of busy waiting using a while loop, don't forget the semicolon. It is important.
4. This we discussed in class.
5. To get credit, you must give an explanation.
6. This was just like your Assignment 2.
   Most people did well on this one.