CSC231 Final Exam Fall 2017

This exam is one-week, take-home, and is due on December 20, at 11:55 p.m. It must be done individually.
It is open books, open notes, and open Web.
There won't be any office hours or TA hours during the exam period.
This exam is given under the rules of the honor code. It has to be done individually. You have access to all your notes, to books, and to the Web. You cannot, however, discuss the details of the exam with anybody other than your instructor. Questions regarding the exam can only be asked in class, or using Piazza. Do not post code on Piazza. Do not suggest or imply possible solutions in your posts on Piazza.
All six problems are worth the same number of points (16.6/100).
If you use material not in the class Web page or the on-line textbook we used for class, you need to list references to them in the header of your program.

Problem 1: Assembly Cow

• Get a fresh copy of 231Lib.asm..
• Make a copy of it under the name 231Lib2.asm
• Add a new function to 231Lib2.asm called _printCow() that gets a message in ecx, edx (similarly to _printString), and that prints a message with a cow, similarly to the bash command cowsay. See below for an example.
• The message will always be at most 80 characters, and at least 1 character in length, and will be printed on one line only. Your program will not be tested with message shorter than 1 and longer than 80 characters.
• Use the Linux cowsay command to see examples of outputs (/usr/games/cowsay your message).

cs231a@aurora ~ $ /usr/games/cowsay Hello CSC231
 ______________
< Hello CSC231 >
 --------------
        \   ^__^
         \  (oo)\_______
            (__)\       )\/\
                ||----w |
                ||     ||
cs231a@aurora ~ $

• You should get the same output as shown above if you do this in your test program:

Hello		db	"Hello CSC231"
HelloLen	equ	$-Hello

		
		mov	ecx, Hello
		mov	edx, HelloLen
		call	_printCow

• Your function should not modify any of the registers.
• You are allowed to add other functions to your 231Lib2.asm file.

Submission

You need to submit 231Lib2.asm on Moodle. It will be tested with a separate main program.

Problem 2: C function

Write a C program and its header file containing a function called zap2() that will work similarly to the zap() function of Homework 9, but will replace all occurrences of the second string in the first string. The C program should be called final.c and the header file final.h.

zap2() will return 1 if one or more substitutions occur, and 0 otherwise. Note that zap2() does not return the number of substitutions, just 1 or 0.

For example, zap2( "Mississippi", "ss" ) will change the first string in "Mi--i--ippi", and will return 1. zap2( "Mississipi", "tt" ) will not change the first string and will return 0.

You may add other helper function(s) in your final.c and final.h files. Your C file should not contain a main function, as it will be linked with a test program that will contain main().

Submission

• Submit your file in the Problem 3 section of the final exam on Moodle.

Solution Zap Function from HW 9

int zap( char *s1, char *s2 ) {
  int i, ret=0;
  char *p = strstr( s1, s2 );

  if ( p!=NULL ) {
    ret = 1;
    for ( i=0; i<strlen( s2 ); i++ )
      *(p++) = '-';
  }
  return ret;
}

Problem 3: Bash Script

• Write a bash script called finalFact.sh that contains a recursive function called fact that will compute the factorial of a number passed on the command line.

cs231a@aurora ~/handout $ ./finalFact.sh 4
fact( 4 ) = 24
cs231a@aurora ~/handout $ ./finalFact.sh 5
fact( 5 ) = 120
cs231a@aurora ~/handout $ ./finalFact.sh 6
fact( 6 ) = 208
cs231a@aurora ~/handout $ for i in 1 2 3 5 6 7 8 9 10 ; do 
> ./finalFact.sh $i 
> done
fact( 1 ) = 1
fact( 2 ) = 2
fact( 3 ) = 6
fact( 4 ) = 24
fact( 5 ) = 120
fact( 6 ) = 208
fact( 7 ) = 176
fact( 8 ) = 128
fact( 9 ) = 128
fact( 10 ) = 0

Output Format

Your script should include only one echo, of this form:

echo "fact( $n ) = $?"

Question

In the header of your program, explain why the program returns 0 for fact(10). If you are not sure, suggest the most likely reason.

Submission

Submit your program in the Problem 3 section on Moodle.

Problem 4: Fixed-Point Formats

Answer the questions in the Problem 4 section of the final exam on Moodle.

Problem 5: Floating-Point Format

Assume that we want to create a 16-bit floating point format similar to the IEEE floating point format we have seen in class. This format uses all the rules we have studied as being intrinsic to the 32-bit format, including the exceptions, and the biased exponent.
In this 16-bit format, the sign, exponent, and mantissa are defined as follows:

• The most significant bit is the sign bit: 0 for positive, 1 for negative
• The next 4 bits are the exponent. The stored exponent is offset by a bias relative to the true exponent.
• The lower 11 bits are the mantissa, and we assume that the mantissa contains a hidden 1. All numbers, as with the 32-bit format, are normalized as 1.bbb...bbb x 2^(true exponent).

Questions

Section 5 of the Final Exam section on Moodle contains several questions relating to this format.

Problem 6: Linked Lists in C

Your assignment is to complete the function makeList() in the program below, so that it outputs the correct information. Several examples of how the finished program should work are given below.

Incomplete Program

// makeList.c
// D. Thiebaut
// program to complete for CSC231, Final Exam
// 
// Example:
//  gcc -o makeList makeList.c
//  ./makeList 100 200 300 1000 
// 1
// 2
// -5
// 10
// 20
// -30
// 5
// 
// 100
// 200
// 300
// 1000
//
//
#include <stdio.h>
#include <stdlib.h>
#include <ctype.h>

//--- structure used to implement the node ---
//--- of the linked-list  ---                    
struct node {
  int item;
  struct node* next;
};
typedef struct node node_t;


//--------------------------------------------------
// makeList( array, arraySize ): takes the contents
// of the array and stores it, in the same order, in
// a singly linked list.
//--------------------------------------------------
node_t *makeList( int* table, int n ) {
  
  // add your code here...

  return NULL;  // you probably want to remove this line!
}

//--------------------------------------------------
int main( int argc, char *argv[] ) {
  int i, x, A[] = { 1, 2, -5, 10, 20, -30, 5 };
  int *B;

  //--- make a linked list with A and print it in same order ---
  node_t *p, *head = makeList( A, sizeof(A)/sizeof(int) );
  
  for ( p=head; p!=NULL; p=p->next ) {
    printf( "%d\n", p->item );
  }


  //--- if user entered ints on the command line, put them ---
  //--- in array B and put B in linked list.  Then print   ---
  //--- linked list.                                       ---
  if ( argc > 1 ) {
    printf( "\n" );

    //--- create array B with same number of cells as ints on command line---
    B = (int *) malloc( (argc-1) * sizeof( int ) );

    //--- convert strings taken from command line in true integers ---
    for ( i=1; i<argc; i++ )  {
      B[i-1] = atoi( argv[i] );
      //printf( "B[%d] = %d\n", i-1, B[i-1] );
    }

    //--- make linked list out of B, and print linked list ---
    head = makeList( B, argc-1 );
    for ( p=head; p!=NULL; p=p->next ) {
      printf( "%d\n", p->item );
    }   
  }
}

Examples

cs231a@aurora ~ $ gcc -o makeList makeList.c
cs231a@aurora ~ $ ./makeList 
1
2
-5
10
20
-30
5
cs231a@aurora ~ $ ./makeList 100 200 300 1000 
1
2
-5
10
20
-30
5

100
200
300
1000
cs231a@aurora ~ $ ./makeList 100
1
2
-5
10
20
-30
5

100
cs231a@aurora ~ $ ./makeList hello there
1
2
-5
10
20
-30
5

0
0

Submission

• Submit your code on Moodle, in the Problem 6 section.

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