Computer Science 281

Final Exam

 

Name ___________________________

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Wednesday, May 15

190 pts. (will be normalized to 200 in the gradebook)

I.             Data Representation

a.      (10 pts.)           Write down (in hexadecimal) the internal representation of the integer –13.  Be sure to provide all hexadecimal digits.

 

 

 

 

 

 

 

 

 

 

 

 

b.      (10 pts.)           Write down (again in hex) the internal representation of the double precision number –13.0.  You need write down only the digits in the first word of the representation.

 

 

 

 

 

 

 

 

 

 

c.      (10 pts.)           The assembly language statement

 

         string:   .asciz    "This is a string"

 

         Will cause data to be placed in memory at the address known as 'string'.  What will be placed here?  How is the end of the string indicated?

II.      Data Structures

 

a.         (15 pts.)           The following function (written in C) adds two four-by-four arrays together and places the result in result in a third.  Implement this procedure (as a complete procedure) in assembly language:

           

            void addit(int a[4][4], int b[4][4], int c[4][4]) {

                        int i,j;

                                      for (i = 0; i < 3; ++i)

                        for (j = 0; j < 3; ++j)

                              c[i][j] = a[i][j] + b[i][j];

                  }

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

      b.         (15 pts.)           Suppose that we have

 

                                    struct partstruct {

                                                char      pno[12];

                                                int         qty;

                                                cost      double;

                                                struct partstruct *next;

                                                }

 

and that %i0 points to the address of one of these structures.  These records form a linked list of records.

 

i)          Write the assembly language statements which will place the qty of the current record (i.e., the one pointed to by %i0)  into %o0.

 

 

 

 

 

 

 

ii)         Write the assembly language statements which will place the address of the next record in the linked list into %i0.

 

 

 

 

 

 

 

iii)         What might cause a problem if the array pno were 10 entries long instead of 12?

 

 

III.       Control structures

 

Iteration was pretty well covered in the preceding set of questions, but let's have a simple if-then-else question with a call-by-location twist.

 

1.         (15 pts).  The integer function max takes two arguments, each of which is the address of an integer.  It returns the larger of the two (the larger value – not the address of the memory location containing the larger value).

 

IV.       Some miscellaneous questions:

 

a.         (15 pts.)           You are camping with friends during the summer months, and while relaxing at the end of the day the conversation turns (as it so often does) to programming and to programming languages.  You mention that you have just finished a course on assembly language programming (dropping, for the moment, mention of architecture).  A friend, who knows something of programming, asks why anyone would study that.  Give a good one paragraph answer.

 

 

b.         (15 pts.)           Another friend has finished the first two semesters of computer science using C++ and a very supportive development tool (Visual C++, for example).  Your friend is moving to unix, and is a bit confused by the use of gcc to compile and link programs.  Give a good one paragraph explanation, perhaps including a diagram.

 

c.         (10 pts.)           What is pipelining?

 

 

 

 

 

 

 

 

d.         (10 pts.)           What is the difference between an annulled branch and one that is not annulled, and what does that have to do with pipelining?

 

 

 

 

 

 

 

 

e.         (5 pts.) Give an example of a synthetic instruction, explaining why it is synthetic

 

 

 

 

 

 

f.          (10 pts.)           Do one of the following.  Give your answer both in binary and in hex.

i)          The instruction  sub %r3, -1, %r5 is a format three  instruction with op = 10, op3 = 000100.  How would this instruction assemble? 

ii)         The instruction ble  prev is a branch instruction with op = 00, cond = 0010, and op2 (as an integer branch) = 010.  prev labels an instruction 4 instructions back from this instruction.  How would this instruction assemble?

 

V.        Floating point

 

a.         (20 pts.)           Write a complete assembly language routine which will accept three double precision floating point numbers (a, b, and c) as arguments, and which will return

 

 

 

 

VI.          Some architecture

 

a.            (15 pts.)        Use NAND and NOR gates and inverters to construct a circuit with two inputs A0 and A1  and four outputs (O0 – O3).  O0 – O3 are data lines coming out.  A0 and A1 determine which output line should be active (A1 = 1 and A0 = 0 should select O2 for example).  If an output is selected, then it should be a 1 and all others should be 0.

 

 

 

 

b.            (15 pts. each)            Look at the diagrams (from Tanenbaum) labeled Diagram A and Diagram B on the last two pages of this exam.  Pick one, describe what it does, identify and describe subsystems (which are labeled in diagram A and should be circled in diagram B), and say what the inputs and outputs do.

 

 

Diagram A

(please do not remove this page)

 

 

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Diagram B

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