Worksheet: C0

Worksheets are self-guided activities that reinforce lectures. They are not graded for accuracy, only for completion. Worksheets are due by Sunday night before the next lecture.

• Github Classroom Link: https://classroom.github.com/a/pijY0GkE

Questions

1. Write a program called youshotme.c that prints out the following message:

   You shot me! Ugh. Oh. Ow. Ow.
   .
   .
   .
    .-.
   (o o)
   | O \
    \   \
     `~~~'
   

   Add the program to your repo.

2. Compile the program above with gcc.

   • What gcc command did you use?
   • Did you have any errors? If so, note them and how you fixed them.
   • If you had no errors, introduce one (like removing a ;) and note the error message.

3. The following program should not compile… fix it and explain why.

   int main(){
     printf("Why oh why does this program fail to compile?!?!\n");
   }
   

4. We were expecting the following output

   They're not equal :-| 
   They're not equal :-| 
   They're not equal :-| 
   They're not equal :-| 
   They're not equal :-| 
   They're equal :-) 
   They're not equal :-| 
   They're not equal :-| 
   They're not equal :-| 
   They're not equal :-| 
   

   But it’s not working :( … Can you fix the program below to get it to work?

   int main(){
     int a = 10;
     int b = 5;
     while(a > 0){
       if(a = b){
         printf("They're equal :-) \n");
       }else{
         printf("They're not equal :-| \n");
       }
       a-=1;
     }
   }
   

   Describe what was wrong?

5. What value(s) is/are true in C? What value(s) is/are false in C?

6. Convert the following code snippet into a function deceleration and definition.

   int minus(int a, int b){return a-b;}
   

7. The following three programs will not compile when trying

   gcc main.c one.c two.c
   

   Fix the issues. The programs are below:

   //funcs.h
   void printOne();
   void printTwo();
   

      //one.c
      void printOne(){
        printf("one\n");
      }
   

      //two.c
      void printTwo(){
        printf("two\n");
      }
   

      //main.c
   
      int main(){
       for(int i=0;i<10;i++){
          if(i%2){
            printOne();
          }else{
            printTwo();
          }
       }
      }
   

8. Below are Java print statements. Write the C equivalent print statement.

   int a = 5;
   int b = 2;
   float c = 4.4;
   System.out.println("a = "+a+" b="+b+" c="+c);
   

9. What is the differences between fopen() file mode w and w+?

10. The C program below doesn’t write anything to a file.

    int main(){
      FILE * stream = fopen("helloworld.txt", "r");
      fprintf(stream, "Hello World!\n");
      fclose(stream);
    }
    

    Fix the program and describe the error(s).

11. What is the output of this C program?

    int main(){
       float f = 3.14;
       int n = 10;
       printf("%d %f\n",f,n);
    }
    

    Was it what you expected or not? Try and describe the process by which the output was achieved.

12. Consider the format directive %.3g, use man 3 printf to describe what the output would be if the input was 3.141592

13. You’re opening a file, and you get an error!?! Provide two preferred ways to report the error to stderr, as in …

    if( fopen( /* ... */) == NULL){
      // WHAT GOES HERE?!
    }
    

14. Fix and describe the error in the code below.

    printf("Enter a number: ");
    
    int num;
    scanf("%d", num);
        
    printf("You entered %d\n", num);
    

15. Fix and describe the error in the code below.

    printf("Enter a number: ");
    
    int num;
    scanf("%f", &num);
        
    printf("You entered %d\n", num);