unicode of char misused for int

Question

I'm writing a program that reads student grade whether it was a char or an int and store it in a union, then it prints the students whose grades are A or >90.

But when I try to do that I get an unexpected output because the program doesn't know which one (the char or the int) I want to compare.

#include <stdio.h>
#include <stdlib.h>

union StuGrade {
    char charGrade;
    int intGrade;
};

struct Student {
    int ID;
    int typeOfGrade;
    union StuGrade grade;
};

int main () {
    const int size = 5; 
    struct Student *sList[size]; 

    for (int i = 0; i < size; i++) {
        sList[i] = (struct Student *)calloc(1, sizeof(struct Student));
        if (!sList[i]) {
            puts("Error allocating memory");
            return 1;
        }
        printf("Enter ID: "); 
        scanf("%d", &(sList[i]->ID)); 
        printf("0 for char grade or 1 for int grade: "); 
        scanf("%d", &(sList[i]->typeOfGrade));

        if (sList[i]->typeOfGrade) { 
            printf("Enter an int grade: ");
            scanf("%d", &(sList[i]->grade.intGrade)); 
        } else { 
            printf("Enter a char grade: ");
            scanf(" %c", &(sList[i]->grade.charGrade)); 
        }
    } //end for loop

    printf("\n***Student(s) who take grade 'A' is/are***\n");
    for (int i = 0; i < size; i++) {
        if (sList[i]->grade.charGrade == 'A') 
            printf("ID: %d \nGrade: %c \n", sList[i]->ID, sList[i]->grade.charGrade);
        else if (sList[i]->grade.intGrade >= 90) 
            printf("ID: %d \nGrade: %d \n", sList[i]->ID, sList[i]->grade.intGrade);
    }
    for (int i = 0; i < size; i++)
        free(sList[i]);
    return 0;
}

And this is the output:

Enter ID: 1
0 for char grade or 1 for int grade: 0
Enter a char grade: A
Enter ID: 2
0 for char grade or 1 for int grade: 0
Enter a char grade: b
Enter ID: 3
0 for char grade or 1 for int grade: 1
Enter an int grade: 99
Enter ID: 4
0 for char grade or 1 for int grade: 1
Enter an int grade: 84
Enter ID: 5
0 for char grade or 1 for int grade: 1
Enter an int grade: 65

***Student(s) who take grade 'A' is/are***
ID: 1 
Grade: A 
ID: 2 
Grade: 98 
ID: 3 
Grade: 99 
ID: 5 
Grade: A 

Answer 1

Use the type of grade in the comparison:

  if (sList[i]->typeOfGrade == 0 && sList[i]->grade.charGrade == 'A') 
     printf("ID: %d \nGrade: %c \n", sList[i]->ID, sList[i]->grade.charGrade);
  else if (sList[i]->typeOfGrade == 1 && sList[i]->grade.intGrade >= 90) 
     printf("ID: %d \nGrade: %d \n", sList[i]->ID, sList[i]->grade.intGrade);