How to use structure and union in C?

Answer 1

union test {
    int x, y;
};

int main()
{
    // A union variable t
    union test t;
    t.x = 2; // t.y also gets value 2
    printf("After making x = 2:\n x = %d, y = %d\n\n",
           t.x, t.y);
    t.y = 10; // t.x is also updated to 10
    printf("After making y = 10:\n x = %d, y = %d\n\n",
           t.x, t.y);
    return 0;
}

struct Point
{
   int x, y;
};

int main()
{
   struct Point p1 = {0, 1};
   // Accessing members of point p1
   p1.x = 20;
   printf ("x = %d, y = %d", p1.x, p1.y);
   return 0;
}

Answer 2

Have a look at the links.

https://www.geeksforgeeks.org/difference-structure-union-c/

https://www.tutorialspoint.com/cprogramming/c_unions.htm
https://www.tutorialspoint.com/cprogramming/c_structures.htm