Make sure the version number is marked on your scantron sheet. This is Version 1

Transcription

1 Last Name First Name McGill ID Make sure the version number is marked on your scantron sheet. This is Version 1 McGill University COMP Computers in Engineering Mid-Term Examination Tuesday, March 11, :00 8:00 P. M. Faculty standard calculators allowed. Grading: Question Points/Question Total marks marks marks Total 105 (The extra 5 marks can be viewed as bonus marks.)

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3 Question 1 Which of the following statements (a-d) is false? a) Programs written in a high level language are translated into assembly or machine level programs before being executed. b) Compilers do not translate comments. c) A compiler is a specialized text editor that uses indentation or colours to make the code easier to read d) A program is stored in memory by a loader before being executed e) All of these statements are true. Question 2 An array is: a) A group of variables with a single name and all of the same types b) A collection of values of various types stored in adjacent memory locations c) A variable that contains multiple values of the same type d) A collection of variables, each with its own name but all of the same type Question 3 Which of the following symbols can be used in a variable name in C? a) & (ampersand) b) * (asterisk) c) _ (underscore) d) (pipeline) e) (hyphen) Question 4 The expression means: X == Y a) The value of X is the same as the value of Y b) The address of X is the same as the address of Y c) The value stored in Y should be copied to X d) The value stored in X should be copied to Y Computers in Engineering 3 of 16 March 11, 2014

4 Question 5 The C function free() is used to a) Close a file that has been opened by the program b) Reclaim dynamically allocated storage c) Reset the counter for determining how many operations a program performs d) Restart a random number generator e) None of the above Question 6 Consider the two statements: char *p; p = (char*) malloc(100); Which statement is equivalent? a) char p = * malloc(100); b) char *p = (char) malloc(100); c) char p = (char *)malloc (100); d) char *p = (char *)(malloc *)(100); e) char *p = (char*) malloc(100); Question 7 Suppose A and B are arrays, i and j are integers. What is the following assignment equivalent to? A[i++] = B[j++] a) i = i+1; j = j+1; A[i]=B[j]; b) A[i]=B[j]; i = i+1; j = j+1; c) j = j+1; A[i]=B[j]; i = i+1; d) i = i+1; A[i]=B[j]; j = j+1; Question 8 What is the value of the following expression? 4/3 == 4/4 a) 1 b) 0 c) It is not a valid C expression Computers in Engineering 4 of 16 March 11, 2014

5 Question 9 The following values were in an array after each pass of a sorting algorithm. Which sorting algorithm was used? a) Bubblesort b) Optimized bubblesort c) Selection sort d) Insertion sort e) Mergesort Question 10 What is the decimal representation of the binary number ? a) 106 b) 202 c) 226 d) 234 e) 238 Question 11 Suppose the variable x has the value Which of the following expressions will round it off to 2.0 a) (int)x b) floor (x) c) (int)(x + 0.5) d) floor (x + 0.5) e) (float)x * 2 Computers in Engineering 5 of 16 March 11, 2014

6 Question 12 Zeller s formula used in assignment 2 converts months from the usual representation of 1 for January, 2 for February, etc. to a representation M where 1 represents March, 2 represents April, etc until 10 represents December while January and February are months 11 and 12. An eager COMP 208 student converts the standard representation using the following formula: M = (month + 10) % 12; a) This formula is correct b) This formula works for every month except January c) This formula works for every month except February d) This formula only works for January and February but none of the other months e) This formula works for every month except December Question 13 What does the following function do? int foo (int x[],int size) { int i; for (i=size-1; i>0; i--) if (x[i]<x[i-1]) return 0; return 1; a) It always returns 0 b) It sorts the list x c) It determines the size of list x d) It returns true if the list x is sorted and false otherwise e) It is syntactically incorrect Question 14 How many passes will an optimized bubble sort algorithm make when sorting the following data? {40, 53, 75, 4, 63, 65, 49, 78, 60, 64 a) 1 b) 4 c) 7 d) 9 e) 10 Computers in Engineering 6 of 16 March 11, 2014

7 Question 15 How many times will the following program output Hello? #include<stdio.h> void main() { int i, j; for (i=1;i<=5;i++) for (j=1;j<=i;j++) printf("hello\n"); a) 1 b) 5 c) 10 d) 15 e) 25 Question 16 What is the output of the following program? #include <stdio.h> void main() { int min = 0, max = 0, i = 0; int a[6] = {2,1,3,1,5,4; for(i = 0; i<6; i++) if (a[i] > max) max = a[i]; else if (a[i] < min) min = a[i]; printf("%d,%d\n",min, max); return; a) 5,0 b) 0,5 c) 5,1 d) 1,5 e) 0,0 Computers in Engineering 7 of 16 March 11, 2014

8 Question 17 The following function is intended to implement a bubble sort algorithm that sorts the array x of length size into ascending order by making passes through the array from right to left. The limits for the control variable of the inner loop are missing. void bubble (int x[],int size) { int i, j, k; for (i=0; i<size-1; i++){ for ( *** MISSING CODE *** ){ if (x[j]<x[j-1]) swap(&x[j],&x[j-1]); bubble_cost++; for (k=0;k<size;k++) printf("%d ",x[k]); printf("\n"); What should replace the missing code so that the algorithm is correct? a) j=size; j>i; j-- b) j=size-1; j>0; j c) j=0; j<size-1; j++ d) j=i; j<size-1;j++ e) j=size-1; j>i; j-- Question 18 What is the output of the following program? #include <stdio.h> int f(int *x){ *x = *x * 2; return *x; void main(){ int y = 2; f(&y); printf("%d\n",f(&y)); return; a) 1 b) 2 c) 4 d) 6 e) 8 Computers in Engineering 8 of 16 March 11, 2014

9 Question 19 What is the output of the following program? #include<stdio.h> int main() { char a = '*', b = '+'; int i = 0, j = 1; while(i<=10){ if(i%2 == 0) printf("%c", a); else printf("%c", b); a) +++* b) ***+ c) ++* d) **+ e) *+* j = j + 2; i = i + j; printf("\n"); return 0; Question 20 What is the output of the following program? #include <stdio.h> void newswap (int* a, int b) { int temp = *a; *a = b; b = temp; void main() { int a = 10, b = 30; newswap(&a,b); printf ("%d %d\n", a, b); a) b) c) d) e) a is an address and cannot be output as an integer Computers in Engineering 9 of 16 March 11, 2014

10 Question 21 What is the output of the following program? #include <stdio.h> void main() { int i, a[8]; for (i=0; i<8; i++){ if (i%2) a[i] = i*i + 1; else a[i] = i*i -1; for (i=0; i<8; i++) if (a[i]%5 == 0) printf("%d ", a[i]); printf("\n"); a) b) c) d) e) Question 22 What is the output of the following C program? void main() { int a[5] = {2, 3, 9, 7, 0; a[a[4]] = a[a[1]]; a[1] = 6; a[a[2]-a[1]] = a[2]; printf ("%d %d\n", a[a[0]-a[1]], a[3]); a) 6 9 b) 7 6 c) 9 7 d) 2 7 e) 2 6 Computers in Engineering 10 of 16 March 11, 2014

11 Question 23 What is the output of the following program? #include <stdio.h> void main() { int i, n = 26, d[5]; for (i=4; i>=0; i--) { d[i] = n - 2 * (n/2); n=n/2; for (i=0; i<5; i++) printf ("%d", d[i]); printf("\n"); a) b) c) 1011 d) e) Question 24 What does the following recursive C function compute when given two non-negative integer arguments? int f (int n, int m){ if (m==0) return 0; else return n + f(n, m-1); a) n b) m c) n+m d) n*m e) n m Computers in Engineering 11 of 16 March 11, 2014

12 Question 25 What is the output of the following recursive C program? #include <stdio.h> int abc (int *, int, int); void main() { int a[14] ={2, 68, 70, 9, 24, 24, 83, 76, 17, 65, 6, 4, 28 ; printf ("%d\n",abc(a,0,13)); int abc (int x[], int l, int r) { int mid, a, b; if (l == r) return x[r]; mid = (l+r)/2; a = abc(x, l, mid); b = abc(x,mid+1, r); return a>b?a:b; a) 2 b) 83 c) 6 d) 28 e) The program is infinite and does not terminate Computers in Engineering 12 of 16 March 11, 2014

13 Answer the programming questions on the pages provided below. Question 26 (Programming) Given any positive integer, n, we can generate a sequence of integers as follows: If n is odd and not equal to 1, the next value in the sequence is 3n+1. If n is even, the next value in the sequence is n/2. If n is 1, the sequence terminates. There is a longstanding unproven conjecture that, for any starting value of n, the sequence eventually terminates. Write a program that reads a number and outputs the sequence of numbers generated as described. Also output the length of the sequence. Since the conjecture is unproven, just to be on the safe side your program should terminate if the length of the sequence is over 1000 (whether or not it reaches the value 1). For example, If the input is 3, the output should be the following values (not necessarily on one line): 3, 10, 5, 16, 8, 4, 2, 1 The length of the sequence is 8 Question 27 (Programming) Picture a school hallway with 500 lockers. Initially all of the lockers are closed. Then 500 students enter the hallway, one after the other. The first student opens all the lockers. Student number 2 closes every other locker starting with the second. Student 3 changes the state of every third locker beginning with the third. That is, if the locker is open the student shuts it and if it is closed the student opens it. In general student number i changes the state of every i th locker beginning with the i th. Write a program which outputs the numbers of the lockers that are open at the end of this process. You should use an array of 501 integers (int lockers[501]) to represent the lockers. Do not use the variable lockers[0] but start the process with lockers[1]. (Observation: This is not part of the question but it turns out that the lockers that are open are those whose index is a perfect square 1, 4, 9, 16, 25, 36,.) Answer the programming questions on the following pages. Computers in Engineering 13 of 16 March 11, 2014

14 Answer to question 26 Computers in Engineering 14 of 16 March 11, 2014

15 Answer to question 27 Computers in Engineering 15 of 16 March 11, 2014

16 Additional page for your answers (if needed). Computers in Engineering 16 of 16 March 11, 2014