Notice: Practice session group 1 meets on Tuesday 4.12 at 14-16 (A318), not at 12-14 as normally.
Notice 2: Practice session Thursday groups 3 and 4 meet in week 50 on Friday 7.12 at 8-10 (B453) or Monday 10.12 at 8-10 (B453) due to 6.12 being the Independence day. Students in groups 3 and 4 can attend the session that suits them best.

Notice 3: There are altogether 33 homework points (hwp). The compulsory 1 point towards your grade is achieved with 10 hwp, and 12 points towards your grade is given for 27 hwp. For example, doing all 5 problems in HW 6 will give you 3 points toward your grade and will thus increase your grade by one step (e.g., grade 1+/3 becomes 2-/3).

Computer Organization I, Fall 2001, HW 6

1. Java programs (byte code) can be executed in (at least) four different ways: interpretation, ordinary compilation, Just-In-Time compilation and directly on a Java processor.
   1. Give examples on situation where interpretation would be better than any other way. Give reasoning for your examples.
   2. Give similar examples and reasoning to situations where the other ways to execute Java programs would be the best choise.
   3. What would be the best choise to execute (Java) programming laboratory exercise? Why?
   4. Which prosesses are needed in the system at the time when your Java program MyProg is executed with 1) interpretetation, 2) ordinary compilation, 3) Just-In-Time compilation, or 4) Java processor?

    

2. Java virtual machine. Assume the following. X, Y and Z are local variables nr 3, 4, and 5. Tbl points to a 20 element array and it (Tbl) is stored into local variable nr 6.
   1. Give machine instructions to increase value of X by 5.
   2. Give machine instructions to assign value Y+Z to X.
   3. Give machine instructions to assign value of Tbl[3] to Y

    

3. Executing Java programs. Under what circumstances would a program written in Java be faster/slower than a similar program implemented in C or C++? Why?

    

4. Self-modifying code. Some processors, including ttk-91, one can interpret the contents of given memory location both as code and as data. This makes it possible to create self-modifying programs. In a self-modifying program one modifies instructions before they are executed. In some cases this may lead to faster code than conventional approaches. For example, some often executed selection can be completely left out, if (instead of executing selection code) one has modified the instruction sequence to be executed. In general, self-modifying code leads to complex programs that are difficult to understand and very difficult to debug.

   Make a self-modifying ttk-91 program, that has a code sequence that

   1. before modification would compute the sum of variables X and Y, and
   2. after modification will compute the product of variables X and Y.
      I.e., an ADD instruction has been changed to MUL instruction.

   The modification can be made, e.g., by replacing the complete instruction, or by editing that instruction. Which method did you use? Can you do the modification with the other method?
   Hint: instruction "A     ADD  R2, R3" can be loaded into R1 with ordinary "LOAD   R1, A" instruction.

    

5. [1 hwp] Fill in the Student Feedback form (only in Finnish, sorry). Give extra care in your answers to questions 14 and 19. Bring answers to the following additional questions also to the practice session for discussion.

   In question 14 ("Miten kurssia voisi kehittää? or "How the course could be made better") answer also to the following: 

   1. How many hours have you used for this class altogether up to now?
      For lectures? Practices sessions? Self study?
   2. What proportion of the lectures did you attend to?  (100%, 90%, ...)
   3. If you attended most lectures, did you learn the basic material there, or did you have to study hard from the books.
   4. Did you use the English language books? How much?

   In question  19 ("Muita kommentteja ..." or "Other comments ...") answer also to the following: 

   1. Did you gain enough from the practice sessions? Why?
   2. Did it bother you that no "model solutions" were given, because answers for similar questions or examples were available in the Web?
      

Be prepared to show all Koksi related and other programming homeworks using a PC at the practice session. Please bring both a listing and on a diskette all the programs you made for this practice session.