Structure and Unions

• A Structure is like a suitcase with separate compartments for your shoes, clothes, and toiletries. You can carry everything at the same time.

• A Union is like a magic box that can only hold one item at a time. If you put your shoes in, the clothes have to come out.

• 1. Structures (struct)

  #include <stdio.h>
  #include <string.h>
  
  struct Student {
      char name[20];
      int id;
      float gpa;
  };
  
  int main() {
      struct Student s1;
  
      // Assigning values
      strcpy(s1.name, "Alice");
      s1.id = 101;
      s1.gpa = 3.8;
  
      printf("--- Structure Output ---\n");
      printf("Name: %s\n", s1.name);
      printf("ID: %d\n", s1.id);
      printf("GPA: %.2f\n", s1.gpa);
  
      return 0;
  }

Expected Output:

--- Structure Output ---
Name: Alice
ID: 101
GPA: 3.80

2. Unions (union)

#include <stdio.h>

union Data {
    int i;
    float f;
    char str[20];
};

int main() {
    union Data d1;

    // Warning: Only one member can hold a value at a time!
    d1.i = 10;
    printf("--- Union Output ---\n");
    printf("After setting i: %d\n", d1.i);

    d1.f = 220.5;
    printf("After setting f: %.1f\n", d1.f);
    
    // Notice that 'i' is now corrupted because 'f' took its place
    printf("Value of i now: %d (Corrupted!)\n", d1.i);

    return 0;
}

Expected Output:

--- Union Output ---
After setting i: 10
After setting f: 220.5
Value of i now: 1130135552 (Corrupted!)