CS 3733 Operating Systems, Spring 2001 Assignment 3 Comments

This assignment was graded on a basis of 30 points.

Part 1

• For ring.c the output is unpredictable. It may always be the same on a particular machine, but the order of the output is not determined by the program.
• For ring1.c the output is also unpredictable. The last process will almost always output first (unless the machine is so busy that it is delayed for more than one second by other processes.) The other processes are able to finish at almost the same time and to they can print in almost any order. Most likely, however, the output will be in reverse order.
• For ring2.c the processes output in order unless they are delayed by other processes for more than one second. This is very unlikely. When the first process exits, the prompt is displayed and this will usually be just before the output of the second process.
• For ring3.c the output must be in reverse order since a process cannot output until its child has terminated.

Part 2

• If the scheduling is non-preemptive, with the parent runs after the fork, the processes output in order.
• This may also be the case for other scheduling, but it does not have to be.
• If after the fork the child goes first, the last process will output first. The rest of the order is determined by the scheduling algorithm.
• If the print is not atomic, the output will be jumbled, unless the wait is inserted. The wait forces the processes to print in reverse order.

General Comments

• If the parent of a process exits before the process does, it will be inherited by init which as process ID 1.
• A large number of students got the extra credit, indicating that either it was too easy or the inter-student communication was working very well. The extra credit was worth 2 points out of 30.