Unexpected Output using Struct Array in C

Question

So I have a struct, and within that struct I have a array of chars that is meant to store a phone number. Format being xxxxxxxxxx (with x being a digit from 0-9). Then, I'm running a for loop to format the display of those ten digits while printing.

 #include <stdio.h>
 
 
void clear(void);
 
struct Student {
    int idNumber;
    char firstName[25];
    char lastName[25];
    char cellNumber[15];
    char grade, grade2;
    char semester[11], semester2[11];
    char course[10], course2[10];
};
 
int main() {
 
    struct Student studentArr[2];
 
    for (int x = 0; x < 2; x++){
 
        printf("For student %d...\n", x+1);
        printf("Enter student number: \n");
        scanf("%d", &studentArr[x].idNumber);
        printf("%d", studentArr[x].idNumber);
        printf("Enter student's first name: \n");
        scanf("%s", studentArr[x].firstName);
        printf("%s", studentArr[x].firstName);
        printf("Enter student's last name: \n");
        scanf("%s", studentArr[x].lastName);
        printf("%s", studentArr[x].lastName);
        printf("Enter student's cell number: \n");
        scanf("%s", studentArr[x].cellNumber);
        printf("%c", &studentArr[x].cellNumber[1]);
        printf("(");
        //print("%s", studentArr[x].cellNumber);
        for(int i = 0; i < 3; i++) {
            printf("%s", &studentArr[x].cellNumber[i]);}
        printf(")");
        for(int i = 3; i < 6; i++){
            printf("%s", &studentArr[x].cellNumber[i]);}
        printf("-");
        for(int i = 6; i < 10; i++){
            printf("%s", &studentArr[x].cellNumber[i]);}
        printf("Enter course %d: \n", x+1);
        scanf("%s", studentArr[x].course);
        printf("%s", studentArr[x].course);
        printf("Enter semster for course %d: \n", x+1);
        scanf("%s", studentArr[x].semester);
        printf("%s", studentArr[x].semester);
        printf("Enter letter grade for course %d: \n", x+1);
        scanf("%s", studentArr[x].grade);
        printf("%s", studentArr[x].grade);
        clear();
       
    }
 
}
 
void clear(void) {
 
    while(getchar() != '\n');
}

Here is the output:

As you can see, the output for the phone number is completely messed up, also I'm ending up with a segmentation fault.

EDIT: Switched the %s to %c and now am getting this output and not prompt for user entry: Letters instead of numbers

Answer 1

You should ensure your compiler warnings are on. If you didn't get warnings, then you should ensure you're using a good compiler like Clang.

When I compiled your code, I got these errors:

$cc phone.c -o phone
phone.c:34:22: warning: format specifies type 'int' but the argument has type 'char *' [-Wformat]
        printf("%c", &studentArr[x].cellNumber[1]);
                ~~   ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
                %s
phone.c:52:21: warning: format specifies type 'char *' but the argument has type 'int' [-Wformat]
        scanf("%s", studentArr[x].grade);
               ~~   ^~~~~~~~~~~~~~~~~~~
phone.c:53:22: warning: format specifies type 'char *' but the argument has type 'char' [-Wformat]
        printf("%s", studentArr[x].grade);
                ~~   ^~~~~~~~~~~~~~~~~~~
                %c
3 warnings generated.

These clue you in to what mistakes you may have made.

In this case, you got a little confused between characters and strings, along with some other issues.

1. Fixing your character/string issues:

   You made the error of passing a pointer to a character where you should've just passed the char itself. To fix this, you should delete the ampersand, changing this:

   printf("%c", &studentArr[x].cellNumber[i]);
   

   to this:

   printf("%c", studentArr[x].cellNumber[i]);
   

   for each of your three lines.

2. You also probably want to print a '1' first, not the index 1 of the phone string (otherwise input 5555555555 outputs 5(555)555-5555).

   So, change this:

   printf("%c", &studentArr[x].cellNumber[1]);
   

   to this:

   printf("%c", '1');    // or printf("1");
   

   After you do #1 and #2, you will get output like this:

   gregEnter student's last name: 
   schmit
   schmitEnter student's cell number: 
   6306089561
   1(630)608-9561Enter course 1:
   

3. There are still errors in your code. From here, you should compile and inspect warnings, and then search for the errors you get, as they are well documented.