A student writes: I am having difficult understanding question number two. Are we supposed = to list what happens during each instruction phase using a certain = opcode? If so, are we supposed to know how the BR and LD+ opcodes work = becuase they were not mentioned in lecture or during the TA session so I = am not familiar with what they do or how they work. Also, for the = upcoming exam, which opcodes are we supposed to be familiar with? < Thanks for the question. I have gotten the same question about this problem set from three of you. So, you are clearly not alone on this. So, let me explain briefly tonight, since you got a lot of work still to do. On the exam, you are only responsible for what I have covered in class through Wednesday. However, I felt that after we went through the ADD so carefully in class on Wednesday, you would be able to read about the branch and the load instructions in the book. So, yes, I would like you to take a shot at it. You note that some of the questions on Problem Set 4 I postponed 'til Problem set 5. Those I decided should wait until I cover the material in class. Some I left on the problem set. Those I felt were within your capability to read in the book, without benefit of being covered in lecture or in discussion section. Good luck with the problem set and with the exam on Wednesday. Yale Patt