C Programming Part 4: Arrays & Structs

Topics

• Arrays
• Character Arrays
• Structs

Class Slides

• Slides

Resources

• https://en.wikibooks.org/wiki/C_Programming/Arrays_and_strings
• https://en.wikibooks.org/wiki/C_Programming/Advanced_data_types#Structs
  • Note: You can skip the material about pointers to structs.

Study Questions

1. How do you declare arrays in C? How do you initialize them?
2. If you decare an array like this: int values[10]={3};, what is the value of values[5]?
3. (T/F) If you access an array element outside the array bounds, C has runtime code that will catch the error.
4. (T/F) sizeof() returns the number of elements in the array.
5. (T/F) If you have an array uint32_t vals[10], what is the value of sizeof(vals)?
6. (T/F) C has a string datatype.
7. If you declare a string (char array) like this: char str[10] = "hi";, what is the size of the array (in bytes)? What is returned by strlen(str)?
8. How do you define a new struct? Is the struct keyword optional?
9. In the following code, how many struct variables are declared? How many struct types are defined?

    struct mystruct {
        int int_member;
        double double_member;
        char string_member[25];
    } s;
    struct mystruct t;
   

10. In the following code, how many struct variables are declared? How many struct types are defined?

     typedef struct {
         int int_member;
         double double_member;
         char string_member[25];
     } mystruct;
    

11. Assuming you declared a struct variable using the struct above (mystruct s;), how would you write printf statements to print out each member of the struct?

12. What does this program print?

     #include <stdio.h>
    
     struct point {
         int x;
         int y;
     };
    
     struct point makePoint(int x1, int y1) {
         struct point temp;
         temp.x = x1;
         temp.y = y1;
         return temp;
     }
    
     void printPoint(struct point p) {
         printf("(%d, %d)\n", p.x, p.y);
     }
    
     int main() {
         struct point p1 = makePoint(3, 4);
         struct point p2 = p1;
         printPoint(p2);
     }
    

13. What does this program print?

     #include <stdio.h>
    
     struct point {
         int x;
         int y;
     };
    
     struct point makePoint(int x1, int y1) {
         struct point temp;
         temp.x = x1;
         temp.y = y1;
         return temp;
     }
    
     void printPoint(struct point p) {
         printf("(%d, %d)\n", p.x, p.y);
     }
    
     int main() {
         struct point p1 = makePoint(3, 4);
         struct point p2 = p1;
         p1.x = p1.y;
         printPoint(p2);
     }
    

14. What does this program print?

     #include <stdio.h>
    
     struct point {
         int x;
         int y;
     };
    
     void printPoint(struct point p) {
         printf("(%d, %d)\n", p.x, p.y);
     }
    
     void modifyPoint(struct point p) {
         p.x++;
         p.y++;
     }
    
     int main() {
         struct point p1 = {3, 4};
         modifyPoint(p1);
         printPoint(p1);
     }
    

15. What does this program print?

     #include <stdio.h>
     struct point {
         int x;
         int y;
     };
    
     void printPoint(struct point p) {
         printf("(%d, %d)\n", p.x, p.y);
     }
    
     void modifyPoint(struct point p) {
         p.x++;
         p.y++;
     }
    
     int main() {
         struct point p[2] = { {3, 4}, {4, 5} };
         modifyPoint(p[0]);
         printPoint(p[0]);
     }
    

16. What does this program print?

     #include <stdio.h>
     struct point {
         int x;
         int y;
     };
    
     void printPoint(struct point p) {
         printf("(%d, %d)\n", p.x, p.y);
     }
    
     int main() {
         struct point p[2] = { {3, 4}, {4, 5} };
         p[0] = p[1];
         printPoint(p[0]);
     }
    

17. What does this program print?

     #include <stdio.h>
     struct point {
         int x;
         int y;
     };
    
     void printPoint(struct point p) {
         printf("(%d, %d)\n", p.x, p.y);
     }
    
     int main() {
         struct point p[2] = { {3, 4}, {4, 5} };
         printPoint(p[2]);
     }