University of Calgary Department of Electrical and Computer Engineering ENCM 335 Instructor: Steve Norman

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1 page 1 of 6 University of Calgary Department of Electrical and Computer Engineering ENCM 335 Instructor: Steve Norman Fall 2018 MIDTERM TEST Thursday, November 1 6:30pm to 8:30pm Please do not write your U of C ID number on this cover page. Name (printed): Signature: General Instructions Marks will be recorded on page 2 of this question paper. When you are told to start the test, the first thing you should do is to put your name and U of C ID number in the appropriate spaces at the top of page 2. No calculators or other electronics may be used during the test. The test is closed-book. You may not refer to books or notes during the test. Some problems are relatively easy and some are relatively difficult. Go after the easy marks first. To reduce distraction to other students, you are not allowed to leave during the last ten minutes of the test. Write all answers on the question paper and hand in the question paper when you are done. Please print or write your answers legibly. What cannot be read cannot be marked. If you write anything you do not want marked, put a large X through it and write rough work beside it. You may use the backs of pages for rough work.

2 ENCM 335 Fall 2018: Midterm Test page 2 of 6 Name (printed): Problem Mark 1 / 10 2 / 19 U of Calgary ID number: 3 / 10 4 / 8 TOTAL / 47 PROBLEM 1 (total of 10 marks). Part a. (5 marks.) Make a diagram of memory for the second time the program gets to point one. int f1(const int *b, const int *c) { int s = 0; do { c--; s += *c; while (c!= b); return s; int f2(const int *d, const int *e) { return f1(d, e); void f3(int *a, int n) { int i; for (i = 0; i < n; i++) a[i] += n i; int a[ ] = {10, 20, 30, 40; int k; f3(a, 4); k = f2(a, a + 4); Part b. (5 marks.) Make a diagram of memory for point one. struct foo { char c[3]; int d; ; struct bar { char a[3]; struct foo b; ; void quux(struct bar *e) { char *f = e->b.c; char *g = e->a; f++; *f = Y ; g[1] = Z ; return; struct bar x = {"pq", {"rs", 34; quux(&x);

3 ENCM 335 Fall 2018: Midterm Test page 3 of 6 PROBLEM 2 (total of 19 marks). Write complete function definitions to implement the given function interfaces. Part a. (4 marks.) The purpose of this function is to convert a number of milliseconds to a description in minutes, seconds, and thousandths of a second. For example, ms is 2 minutes, 3 seconds, and 456 thousandths of a seccond. void milli2mst(int ms, int *min, int *sec, int *thou); // REQUIRES: ms > 0. Pointer parameters point to appropriate variables. // PROMISES: *min, *sec, and *thou contain the time in ms represesented // as minutes, seconds, and thousandths of a second. Part b. (6 marks.) The standard C library tolower function was used in Lab 4. Its prototype is int tolower(int c); In this part, your code may call tolower but no other library functions. int c_i_match(const char *s, const char *t); // REQUIRES: s and t point to beginnings of strings // PROMISES: Returns 1 if the strings match, disregarding the cases // of letters; returns 0 otherwise. // EXAMPLES: // c_i_match("abc!", "Abc!") and c_i_match("hi!", "Hi!) would have // values of 1, but c_i_match("wxy", "wxz") and c_i_match("abc", "abcd") // would have values of There are more parts on the next page...

4 ENCM 335 Fall 2018: Midterm Test page 4 of 6 PROBLEM 2 (continued) Part c. (5 marks.) Full marks will be given only for code that is reasonably efficient. void accumulate(const int *a, int *s, int n); // REQUIRES: n > 0. Array elements a[0]... a[n-1] and s[0]... s[n-1] // exist. // PROMISES: For each i from 0 to n-1, s[i] is the sum of a[0]... a[i]. Part d. (4 marks.) The cross product of vectors u and v is defined to be u v = u y v z u z v y u z v x u x v z u x v y u y v x struct vec { double x; double y; double z; ; typedef struct vec vec_t; vec_t cross_product(const vec_t *u, const vec_t *v); // REQUIRES: u and v point to vector objects. // PROMISES: Returns cross product of *u and *v.

5 ENCM 335 Fall 2018: Midterm Test page 5 of 6 PROBLEM 3 (10 marks) Here is some brief documentation for some functions related to text file operations with the standard C library: FILE *fopen(const char *path, const char *mode); path gives the name of the file; for mode we ve seen examples of "r" for input, and "w" and "a" for output. A return value of NULL indicates failure to open the file. int fclose(file *fp); fp must correspond to an open file. The return value is 0 for success and EOF to indicate some kind of error. int fprintf(file *fp, const char *fmt,...); This function works like printf, but sends output to the file associated with fp. You don t need to worry about the return value of fprintf in this problem. Consider the main function below. If write_array is coded correctly, the output files will be as shown. a.txt int main(void) { list of 7 integers... int a[ ] = {10, 20, 30, 40, 50, 60, 70; 10, 20, 30, 40, 50, int b[ ] = {-1, -2, -3, -4, -5; 60, 70 int r1, r2;... end of list r1 = write_array("a.txt", a, 7); r2 = write_array("b.txt", b, 5); if (r1 == 0 && r2 == 0) printf("both writes worked.\n"); b.txt else printf("something went wrong.\n"); list of 5 integers... -1, -2, -3, -4, end of list Write a definition for write_array. Integers should be be printed 5 per line, wih a comma after every integer except the last. The return value should be 0 for success, 1 if the file could not be opened, and 2 if there was a problem closing the file. Of course, the function should work for all reasonable array sizes, not just the example values of 5 and 7 elements!

6 ENCM 335 Fall 2018: Midterm Test page 6 of 6 PROBLEM 4 (total of 8 marks). Part a. (2 marks.) The program below contains an incorrect solution to a Quiz 2 problem. In the space beside the listing, explain precisely why r1 correctly gets a value of 1 but r2 incorrectly gets a value of 0. struct date { int year; char month[4]; int day; ; int same_date(const struct date *a, const struct date *b) { if (a->year!= b->year a->month!= b->month a->day!= b->day) return 1; struct date a = {2018, "nov", 1, b = {2018, "nov", 1; int r1, r2; r1 = same_date(&a, &a); r2 = same_date(&a, &b); Part b. (3 marks.) In a call to fwrite or fread, the second argument is the size of an array element, and the third argument is a count of array elements. Assume that all calls to library functions in the following program are completely successful. Fill in the tables to show the contents of arrays b and c at point one. #include <stdio.h> int a[ ] = {10, 20, 30, 40, b[3], c[3]; FILE *fp = fopen("foo.dat", "wb"); fwrite((void *) a, sizeof(int), 4, fp); fwrite((void *) a, sizeof(int), 4, fp); fclose(fp); fp = fopen("foo.dat", "rb"); fread((void *) b, sizeof(int), 3, fp); fread((void *) c, sizeof(int), 2, fp); fclose(fp); b[0] b[1] b[2] c[0] c[1] c[2] Part c. (3 marks.) Assume that the call to malloc succeeds. In the space beside the listing, make a memory diagram for point one, showing stack, static storage, and heap. #include <stdlib.h> double *clone(const double *s, int n) { double *r = malloc(sizeof(double) * n); int i; for (i = 0; i < n; i++) r[i] = s[i]; return r; double x[4] = {1.5, 3.5, 4.5; double *p; p = clone(x, 3);