Module 13: Structures, Unions, Enums & Memory Alignment

typedef struct {
    uint32_t id;
    char name[32];
    double gpa;
} Student;

int main(void) {
    Student s1 = {101, "Alexander", 3.95};

    // 1. Direct variable access uses Dot (.) operator:
    printf("Student: %s, GPA: %.2f\\n", s1.name, s1.gpa);

    // 2. Pointer access uses Arrow (->) operator (*ptr).member:
    Student *ptr = &s1;
    printf("Via pointer: %s\\n", ptr->name); // Identical to (*ptr).name
    return 0;
}

union DataHolder {
    int int_val;       // 4 bytes
    float float_val;   // 4 bytes
    char bytes[4];     // 4 bytes
}; // sizeof(union DataHolder) is exactly 4 bytes!

struct StatusRegister {
    unsigned int is_ready      : 1; // Exactly 1 bit (0 or 1)
    unsigned int error_code    : 3; // Exactly 3 bits (0 to 7)
    unsigned int mode_select   : 2; // Exactly 2 bits (0 to 3)
    unsigned int parity_flag   : 1; // Exactly 1 bit
    unsigned int interrupt_en  : 1; // Exactly 1 bit
}; // Total size fits neatly in 1 single Byte!