Computer Organisation I

Exercise 2, week 14, 29.3. - 2.4.2004

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: Fibonacci
  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 TTK-91 symbolic assembly language program that computes the n'th Fibonacci number. Your program could be a translation from C program

          int n, i, prev, fib, next;  /* variables n, i, prev, fib, next */
          main () {                   /* main program */
              scanf ("%d", &n); /* read an integer into n */
  
              i = 1;
              prev = 0;
              fib = 1; 
              
              while (i < n) {
                  next = prev+fib;
                  prev = fib;
                  fib = next;
                  
                  i++;
                  }
  
              printf ( "%d %d \n", n, fib);  /* print n, fib */
          }
  
  /* scanf command simply read one integer and
  printf command prints two integers */
  

  You can keep variable values either in memory or in device registers.

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  The answers can be only returned 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 your symbolic assembler file. The same you use as source code to koksi simulator.

  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.

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• Question 2: High level language vs. assemble language..

  Assume that we have program Simple that is written with some high level language (C, Java, Pascal), and that it has been translated into TTK-91 machine language.

  What data in program Simple (e.g., variable values) would one want to keep ...

  1. in device registers all the time
  2. in memory all the time
  3. sometimes in device registers and sometimes in memory
  4. nowhere (not in the registers or in the memory)
  ... during program execution? Why? Give examples.

  d) is not a trick question!

   

• Tehtävä 3: Into symbolic assembly language

  Write a TTK-91 symbolic assembly language program that does the same as C program

          int x=7, y=33, z=5;  /* variables x, y, z */
          main () {           /* main program */
              y = 4;
              x = 52 - y * z;
              if (x < 40) {
                  y = x - 34;
                  }
              else {
                  y = x / y + 4;
                  z = 23;
                  }
              printf ( "%d %d %d \n", x, y, z)  /* print x, y, z */
          }
  
  /* printf command simply prints three integers */
  

  
  Check your program by compiling and running it in Koksi. Please remember to bring your solution also in electronic form to the small group session.
  Although the program uses fixed initial values to the variable and you could be tempted to implement only the part necessary, please implement the whole program. This allows you to easily experiment the programs behavior when you change the values to for example (x=3, y=1, z=4).

   

• Question 4: Constants

  Constants (e.g., value MAXID=78) can locate in many different places during program execution. Write TTK-91 symbolic assembly language instructions with which one would add value of constant MAXID to R1, and where MAXID value (78) is taken from

  1. memory (memory location)
  2. register
  3. machine instruction

  Give an example where case (a) would be best suitable. Similarly, for cases (b) and (c). Give reasoning for your examples.

   

• Question 5: Records and memory references. Personnel register record type has been defined with pseudoinstructions
  

  	# record person:        3 integer fields 
  	Id   	EQU  0   # relative address within record
  	Age     EQU  1
  	Salary  EQU  2
     

  Records Pekka and Jussi have been allocated from memory with initialized data and record Maija has been allocated with uninitialized data with pseudoinstructions
  

  	Pekka	DC   3214   # ID     =  3214
  		DC     35   # AGE    =    35
   		DC  12345   # SALARY = 12345
  	Jussi	DC   8888
  		DC     54
   		DC  14321
  	Maija	DS      3   # initial values not defined
      

  Example: If R4 points to the beginning of record Pekka, then Pekka's salary is obtained to register R5 with machine instruction "LOAD   R5, Salary(R4)".

  Write a TTK-91 symbolic assembly language program to

  1. Print the values of all fields in the record pointed by R1, when R1 is first set to point to Jussi's record with machine instruction "LOAD   R1, =Jussi".
  2. Sets Maija's id to 7458, age to 32, and salary to the same as what Jussi has currently.
  3. Prints the sum of Pekka's, Jussi's and Maija's current salaries.
  4. Print the current age of the youngest person of these three.
  
  Check your program by compiling and running it in Koksi. Please remember to bring your solution also in electronic form to the small group session.

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  Tiina.Niklander@cs.helsinki.fi