C Programming Part 3: I/O and Operators

Topics

  • printf function and format specifiers
  • sscanf, and sprintf
  • Operators

Class Slides

Resources

Study Questions

  1. (T or F) printf("%c\n", 'a'); will print the character a.
  2. (T or F) printf("%s\n", 'a'); will print the character a.
  3. (T or F) printf("%.*s", 5, "hello there\n"); prints out hello.

  4. (T or F) For printf(), the formatting argument G may generate the same results as the formatting argument f.

  5. The following program prints out hello there! when executed (T or F). 
     int main() {
   char array[20];
   sprintf(array, "%s", "hello there!");
 }
  6. (T or F) sscanf() reads characters from standard input.

  7. What does the following program print when executed and when you type 2 2 2 and press enter (or carriage return).

     #include <stdio.h>

 int main() {
   int month, day, year;
   printf("%d\n", scanf("%d %d %d", &month, &day, &year));
 }
  8. What does the following program print when executed? Why? 
    #include <stdio.h>
#include <string.h>
#define LENGTH 100
int main() {
  char string1[LENGTH] = "hello ";
  char string2[LENGTH] = "there";
  strcpy(string1, string2);
  printf("%s\n", string1);
}
  9. What does the following program print when executed? Why? 
    #include <stdio.h>
#include <string.h>
#define LENGTH 100
int main() {
  char string1[LENGTH] = "hello ";
  char string2[LENGTH] = "there";
  strcat(string1, string2);
  printf("%ld\n", strlen(string1));
}
  10. What does the program below print out? 
     int main() {
     int i=9;
     int j = ((0 > 1) && (i=14));
     printf("%d\n", i);
 }
  11. What does the program below print out? 
     int main() {
     int i=9;
     int j = ((0 > 1) || (i=14));
     printf("%d\n", j);
 }
  12. What does the following program print out? 
     #include <stdio.h>

 int main() {
     int i = 0 < 1;
     printf("%d\n", i);
 }
  13. What does the following program print out? 
     #include <stdio.h>
 #include <math.h>

 int main() {
     int n = 16;
     printf("%d\n", sqrt(n));
 }
  14. What is the first value printed out by the program shown below? 
     #include <stdio.h>

 int main() {
 int j = 4;
     printf("%d\n", j++);
     printf("%d\n", ++j);
 }

  15. What is the second value printed out by the program shown above?

  16. What is the value printed out by the program shown below? 
     #include <stdio.h>
 int main() {
     printf("%d\n", 0xf0 | 0xf == 0xff);
 }
  17. What is the value printed out by the program shown below? 
     #include <stdio.h>
 int main() {
     printf("%d\n", (0xf0 | 0xf) == 0xff);
 }
  18. What is the value printed out by the program shown below? 
     #include <stdio.h>
 int main() {
     int i = 4;
     int x = 1;
     printf("%d\n", x/i);
 }
  19. What is the value printed out by the program shown below? 
     #include <stdio.h>
 int main() {
     int i = 4;
     double x = 1;
     printf("%d\n", x/i);
 }
  20. What is the value printed out by the program shown below? 
     #include <stdio.h>
 int main() {
     int i = 4;
     double x = 1;
     printf("%f\n", x/i);
 }
  21. Study this program. Try commenting out the s[j] = '\0'; statement. What happens? 
     #include <stdio.h>
 // Work an example of this in class (pg. 47)
 void squeeze(char s[], int c) {
     int i, j;
     for (i = j = 0; s[i] != '\0'; i++)
         if (s[i] != c)
         s[j++] = s[i];
     s[j] = '\0';
 }

 int main() {
     char str[20] = "hello there!";
     char c = 'e';
     squeeze(str, c);
     printf("%s\n", str);
 }
  22. What does this code print? 
     #include <stdio.h>
 #include <ctype.h>

 int main() {
 printf("%d\n", isdigit('9'));
 }
  23. What does this code print? 
     #include <stdio.h>
 #include <ctype.h>

 int main() {
 printf("%d\n", isdigit("9"));
 }