Sun, 17 Nov 2019, 23:04 correction to your PL3 grade
My students, Due to a miscommunication between me and the TA responsible for grading PL3, you received a 0 on test cases that failed because you tried to read a value from memory location x0000. Memory locations x0000 to x2FFF are priviliged, which means a user program can not access them except in very explicit situations which we have not studied as yet. The case in point: The first word of each node of your linked list is a pointer. Some of you tried to load from the address specified by the pointer instead of first examining the pointer to see if it contained the null pointer (x0000). As a result, you got an access control violation since your user program does not have the right to access M[x0000]. The correct approach would be to first examine the pointer. If it is x0000, you know you are at the end of the list and so you would not try to access M[x0000]. Since the concept of privilege is new to you, and I had told you in class that you can ignore access control violations (ACV) until we discuss them in class, I do not want any points taken off for this mistake. Your PL3 submission is being regraded, and some of you will see an increase in your PL3 grade. Some of you know that we have provided a switch on the Simulator which kills the distinction between privileged and non-privileged in case some professor somewhere (certainly not at UT) wants to teach 306 without dealing with the issue of privilege. However, at UT we want you to understand the concept of privilege. So, although we have provided a switch that removes the distinction between privilege and non-privilege, that switch is not for students in our classes at UT. If, for some reason, you feel it is easier for you to set this switch to remove the privileged/non-privileged distinction in order to get started with the program, I will not tell you not to do it. HOWEVER, please be sure the program still works after you set that switch back to recognizing the distinction between privileged and non-privilege. When we grade the program, we will have the switch set to understanding the privilege distintion. And, in the future, not understanding that distinction will result in an unpleasant cost. Finally, I am sending you this message because I do not want you to be discouraged by thinking you lost points for something that is probably not your fault. You will not lose points for it. But right now, you should not be taking time to think about it. Save that for after 5pm on Wednesday after you have taken exam 2. Between now and then, preparing for exam 2 is what needs your attention. Good luck with the exam on Wednesday. Yale Patt