Computer Organisation I

Exercise 3, week 15, Tuesday 6.4.

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. Alternatively to bringing the diskette, you can store your programs to the fs file server.

Question 1: Memory referencing
Return the answer to this question day before your meeting! This answer will grant you one point equal to the points of the course exam.
Write a short essey or report (10 to 30 lines long) about the memory references caused by the TTK-91 machine instructions. How many memory references can execution of any ttk-91 machine instructions cause? Which instruction causes the maximum numebr of references? Which causes the minimum? Please consider the whole instruction cycle. Which matters most here, the opcode, the addressing mode, or both? Why? Justify you answers in the text
Write your answer to a plain text file, which you must then send to the course assistant using the web-page http://db.cs.helsinki.fi/~tuohinie/tito/ .
The web-page asks first you to choose your small group. Then you have to write your name and upload the text file containing your report.
You have to return the answer at the latest 24 hours before the small group session's starting time. A late delivery is not possible.
Question 2: Table
Write a ttk-91 symbolic assembly language program that
1. Allocates space for a 20 element table (1-dimensional array) Tbl[20]. The indexing starts at zero.
2. Initializes Tbl at execution time so that Tbl[i] = i*i
3. Computes the sum of elements in Tbl so that index register R1 has always the index of current element. Current element is thus loaded to R3 with machine instruction "LOAD R3, Tbl(R1)".
4. Prints the sum (2470) computed above
5. Tehtävä 3: Subroutine with parameters
  Complete the program lh_arvop.k91 (in the Koksi example directory) by implementing subroutine Simple(A, B, C), which prints the sum of its three parameters. All parameters are value parameters.
  Check your program by compiling and running it in Koksi. Please remember to bring your solution (to all Koksi questions) also in electronic form to the small group session.
6. Question 4: Subroutine with reference parameters
  Complete the program lh_kutsu.k91 (in the Koksi example directory) by implementing subroutine SUBR(X, A, B), which modifies parameter X into the difference of value parameters A and B. Parameter X is given as call-by-reference parameter.
  Check your program by compiling and running it in Koksi.
7. Question 5: Constants in machine language instructions
  The address field of ttk-91 machine instruction has only 16 bits. This limits the size of constants used in instructions.
  1. What is the largest positive number that can be given as constant in an instruction?
  2. What is the smallest negative number that can be given as constant in an instruction?
  3. What should you do, if you need a bigger constant? E.g., 500000?
  4. And what should you do, if you need a large constant with indexed address mode? For example, you need to read the value from (R1)+666666?
8. Question 6: Data representation.
  1. What is decimal number 43.234 in binary?
  2. What is binary number 101010.1010 in decimal?
  3. What are the 16-bit Big-Endian binary representations of decimal numbers +23 and -75 in following formats:
    1. sign and magnitude
    2. two's complement
    3. one's complement
    4. biased by 32767
  4. What is the IEEE floating point standard representation of decimal number 33.125?
  5. Assume that programming language MyLan has both boolean and floating point data types. For example, one can use variables of type boolean or float in it.
    Ttk-91 does not have such data types. Could one make a MyLan compiler that would allow us to execute MyLan programs in ttk-91? If the answer is yes, why? If the answer is no, why not?
Tiina.Niklander@cs.helsinki.fi