EE 312 Fall 2018 Midterm 1 Version A October 10, 2018

Transcription

1 EE 312 Fall 2018 Midterm 1 Version A October 10, 2018 I promise that all work on this exam is my own, that I have not received assistance on it, and that I am adhering to the University's honor code. Name: EID: Recitation time: Give clear, legible answers. If you give more than one answer, we will randomly choose one to grade, so clearly mark out any answer you do not want us to grade. Write all code in C. The proctors will not answer questions about the course material or about the content of the exam. For the questions on this test, you do not have to handle the possibility that the functions malloc and calloc might return NULL. Put away all electronics and earbuds. You are not allowed to use a calculator. You should only have out pencils. Silence your cellphone and put it away. Scratch paper is attached. Place your final answers on the test, not on scratch paper. Your answer must be legible to receive credit. When you complete the test, show the proctor your UTID, give them the test and the scratch paper, used or not, and leave the room quietly. 100 points are possible. GOOD LUCK

2 1. (10 pts, 2 per answer) Process Memory. Consider the following program: #include<stdio.h> int bad; double doublebad = 1.4; int main() { char ch = 'A'; int num; int *p = malloc(5*sizeof(int)); Where is each value stored in process memory? Circle your answer for each. bad i) run-time stack ii) heap iii) data segment iv) bss segment v) text segment doublebad i) run-time stack ii) heap iii) data segment iv) bss segment v) text segment ch i) run-time stack ii) heap iii) data segment iv) bss segment v) text segment p i) run-time stack ii) heap iii) data segment iv) bss segment v) text segment the array of 5 ints that p points to i) run-time stack ii) heap iii) data segment iv) bss segment v) text segment

3 2. Short Answer. a. (4 pts) What is the output? Place the output in the box to the right of the code. #include<stdio.h> void fun1(int a[]) { printf("zu\n", sizeof(a)); int main() { int arr[] = {3, 1, 8, 6, 9, 0, 2; printf("%zu\n", sizeof(arr)); fun1(arr); b. (6 pts) What is the output? Place the output in the provided box. #include<stdio.h> #include<string.h> int main() { char *s = "helloworld"; int arr[2][3] = {{5, 1, 2,{3, 6, 0; printf("%lu %lu %lu ", sizeof(s), sizeof(*s), sizeof("helloworld")); printf("%lu", strlen(s)); printf("\n%d\n%c", *arr[1], s[*arr[0]]);

4 3. Code Evaluation and Completion. Assume all necessary #includes are provided. a) (5 pts) What is the output? char *s = "sourgrapes"; char arr[] = "pageturner"; for(int i = 0; i < 6; i++) { for(int j = i; j < 2+i; j++) { if(arr[j] > s[j]) arr[j] = s[j+1]; printf("%s", arr); b) (5 pts) What is the output? Note: Draw a picture to the right of the code. Include all the structures and pointers. struct node { int key; struct node *next; ; typedef struct node *link; int main() { link x, y, z, t; x = malloc(sizeof(struct node)); y = malloc(sizeof(struct node)); z = malloc(sizeof(struct node)); xànext = y; yànext = z; zànext = x; xàkey = 3; yàkey = 1; zàkey = 4; for(t = x; tàkey < 20; t = tànext) { tàkey = xàkey + y à key + zàkey; printf( %d\n, tànextàkey); c) (5 pts) What is the output? char var = 'A'; for(int i = 5; i >= 1; i--) { for(int j = 0; j < i; j++) { printf("%c ", (var+j)); printf("\n");

5 d) (6 pts) In the following program, we are using a constant MAX to determine the number of lines and the integer on the last line of output. MAX can take on any integer value from 2 up to 9. Below is the desired output for several values of MAX. Fill in the blanks below to produce the correct output. MAX = 2:.1 2. MAX = 3: const int MAX =... ; // assume MAX has been initialized to a // value between 2 and 9 int main() { for(int line = 1; ; line++) { // Fill in Blank 1 for(int j = 1; j <= ; j++) { // Fill in Blank 2 printf("."); printf("%d", line); MAX = 4: for(int j = 1; j <= ; j++) { // Fill in Blank 3 printf("."); printf("\n"); MAX = 9:

6 4. (10 pts, 5 each) UNIX COMMANDS For the following questions, fill in the blank to indicate what command you would type at a command line prompt on kamek (or one of the other ECE linux machines) to carry out the specified action. You may only use a single command. a. Use a text editor (not an IDE) to create and edit a C program called myprog.c. (Use the text editor you chose earlier this semester.) What command do you type at the command prompt on kamek to edit the file? username@kamek % b. Continuing the question from part a., what command will you type at the command prompt on kamek in order to compile your C program in myprog.c? Your command should create an executable named myprog. username@kamek % c. What unix command would you use to execute an executable named myprog? username@kamek % d. What unix command would you type at the command prompt in order to list all files in your current directory? username@kamek % e. What unix command would you type at the command prompt in order to move into the parent directory of your current directory? username@kamek %

7 PROGRAMMING. Write all code in C. 5. (12 pts) Write a C program that prints the length of each command line argument. For example, if you execute your program with this command: username@kamek%./a.out hello eye goodbyes The output would be: Length of argument 0: 7 Length of argument 1: 5 Length of argument 2: 3 Length of argument 3: 8 Complete the main function below. #include<string.h> int main(int argc, char *argv[]) { // Put your code below

8 6. (17 pts) Write a C function sumrightbelow() that takes a 2D array arr of ints, and the number of rows and columns in arr. The function returns the number of entries in arr that have the following property: the entry is equal to the sum of the entry directly below it and the entry directly to its right. For example, if A is the array below, the call sumrightbelow(4, 3, A) returns 2. Below, I've highlighted entries of A that have the specified property int sumrightbelow(int n, int m, int arr[n][m]) { // put your code below

9 7. (20 pts) Write a function getdifference. The function accepts two parameters, both pointers to linked lists (see the node type below.) The function returns a pointer to another linked list which has the same length as the parameter with the smallest length. The elements in the returned linked list are equal to the corresponding element in the first parameter minus the corresponding element in the second parameter. Examples of results given different inputs: list1: 12 à 5 à 3 à12 à 6 à 2 à NULL list2: 10 à 10 à -5 à NULL returned list: 2 à -5 à 8 à NULL list1: list2: returned list: list1: list2: returned: NULL (i.e., list pointer is NULL because the list is empty) 10 à 10 à -5 à NULL NULL 5 à 6 à -5 à10 à 100 à NULL 5 à 6 à -5 à 13 à 50 à NULL 0 à 0 à 0 à -3 à 50 à NULL Neither of the parameters is altered as a result of a call to the function. The pointers that are passed in, and the lists they point to, remain unchanged. Write the function on the next page. No code on this page will be graded. Do not remove this sheet from the test. Node type: struct node { int data; struct node *next; ;

10 Solution to #7 add your code below struct node *getdifference(struct node *list1, struct node *list2) {

11 Scratch Paper

12 Scratch Paper