University of Calgary Department of Electrical and Computer Engineering ENCM 339 Lecture Section 01 Instructor: Steve Norman

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1 page 1 of 6 University of Calgary Department of Electrical and Computer Engineering ENCM 339 Lecture Section 01 Instructor: Steve Norman Fall 2017 MIDTERM TEST Wednesday, November 1 7:00pm to 9:00pm This version of the question paper uses red print to provide an important clarification to Problem 2, part a, and an important correction to Problem 4, part a. There are also some corrections to minor typographical errors. Please do not write your U of C ID number on this cover page. Name (printed): Signature: General Instructions Marks will be recorded on the last page 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 bottom of the last page. 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 339 Fall 2017: Midterm Test for Lecture Section 01 page 2 of 6 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. In this part show all values as numbers do not use character constants such as A. The ASCII codes for uppercase A, B, C, and D are 65, 66, 67, and 68, and the ASCII code for \0 is 0. int foo(const char *left, const char *right) { int result; while (*left!= \0 && *left == *right) { left++; right++; result = *left - *right; // point one return result; int main(void) { int v, w; char x[ ] = "AB"; const char *y = "ABC", *z = "AD"; v = foo(x, y); w = foo(x, z); Part b. (5 marks.) Make a diagram of memory for point one. In this part you may use character constants such as a to show the contents of arrays with char elements. struct small { int w; int x; ; struct big { char y[4]; struct small z; ; void g(char *p, struct small *q) { p[1] = E ; q->x += 100; // point one return; void f(struct big *r) { g(r->y, &r->z); int main(void) { struct big b = { "abc", { 12, 34 ; f(&b);

3 ENCM 339 Fall 2017: Midterm Test for Lecture Section 01 page 3 of 6 PROBLEM 2 (total of 21 marks). Write complete function definitions to implement the given function interfaces. Part a. (3 marks.) Note: There are 12 inches in a foot, and 1 inch is exactly meters. double to_meters(int feet, int inches, int sixteenths); // REQUIRES: The parameters together represent a measurement // in feet, inches, and sixteenths of inches. // PROMISES: Return value is the equivalent number of meters. Clarification: For example, to get the number of meters in 2 feet, 3 5 function call would be to_meters(2, 3, 5). 16 inches, the Part b. (7 marks.) String A is said to be a suffix of string B either if the strings match exactly or if string A is shorter and all of its characters appear in the same order at the end of string B. For example, "ram" is a suffix of "program" and "Hi!" is a suffix of "Hi!", but "cde" is not a suffix of "codec". In this part, you are not allowed to call strlen or any other library function. int suffix(const char *s, const char *t); // REQUIRES: s and t each point to the beginning of a string. // PROMISES: Return value is 1 is the string found with s is // a suffix of the string found with t, and 0 otherwise.... There are more parts on the next page...

4 ENCM 339 Fall 2017: Midterm Test for Lecture Section 01 page 4 of 6 PROBLEM 2 (continued) Part c. (7 marks.) A sequence of numbers is called strictly increasing if each number is greater than the previous number in the sequence, and strictly decreasing if each number is less than the previous number in the sequence. int classify(const int *a, int n); // REQUIRES: n >= 2. Elements a[0]... a[n-1] exist. // PROMISES: Return value is // 1 if a[0]... a[n-1] form a strictly increasing sequence; // -1 if a[0]... a[n-1] form a strictly decreasing sequence; // 0 of neither of the above is true. Part d. (4 marks.) struct item_list{ int count; double item[10]; ; double min_item(const struct item_list *x); // REQUIRES: x points to a struct object with its count member // having a value between 1 and 10. // PROMISES: Return value is the minimum value among item[0]... item[count-1] // within the object that x points to.

5 ENCM 339 Fall 2017: Midterm Test for Lecture Section 01 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 fputc(int c, FILE *fp); A call to fputc writes a single character to an output file. c should contain a character code and fp must correspond to a file open for output. You don t need to worry about the return value of fputc in this problem. Consider the problem of drawing a triangle with space and star characters, where the number of stars in the base is equal the number of lines, and where the right edge of the triangle is a vertical line. For example, a version with four lines is shown to the right of this paragraph. * ** *** **** Complete the function definition below, so that it draws a triangle in a text file, with the name of the file and the number of lines supplied as parameters. Assume that reasonable values for those parameters are obtained in a main function, which you do not have to write. The function should return 0 for success, 1 if it fails to open the file, and 2 if detects a problem when trying to close the file. #include <stdio.h> int draw_triangle(const char *filename, int line_count) {

6 ENCM 339 Fall 2017: Midterm Test for Lecture Section 01 page 6 of 6 PROBLEM 4 (total of 9 marks). Part a. (2 marks.) In the following program listing, line 7 line 6 makes an assignment to the variable a. In the space beside the listing, show how line 7 line 6 will appear in the output of the C preprocessor. 1 #include <stdio.h> 2 #define MACRO1(x, y) x - y 3 #define MACRO2(z) MACRO1(z, 5) * z 4 int main(void) { 5 int a; 6 a = MACRO2(6-2); 7 printf("value of a: %d\n", a); 8 9 Part b. (1 mark.) What is the output of the program of part a? Part c. (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. In the space beside the program listing, write out the program output. #include <stdio.h> int main(void) { int x[ ] = { 100, 200, 300, 400, 500, 600, 700 ; FILE *fp = fopen("foo.dat", "wb"); fwrite(x + 4, sizeof(int), 3, fp); fclose(fp); fp = fopen("foo.dat", "rb"); fread(x, sizeof(int), 2, fp); fclose(fp); for (int i = 0; i < 7; i++) printf("%d\n", x[i]); Part d. (3 marks.) Suppose that this line of text abc is entered as input to the listed program. Use the table to give the values of the local variables of main at point one. #include <stdio.h> int main (void) { int a = 100, b = 101, c = 102, d = 103, e = 104, f = 105; printf("enter a line of input:\n"); a = scanf("%d", &b); c = scanf("%d", &d); e = scanf("%d", &f); // point one a b c d e f MARKS: The space below will be used to record your marks for each question and your overall test mark. Please put your name and U of C ID number in the appropriate boxes. Name (printed): Problem Mark 1 / 10 2 / 21 U of Calgary ID number: 3 / 10 4 / 9 TOTAL / 50