Nesting Structures and Unions

Program 1: Nested Structures

#include<stdio.h>

typedef struct Small
{
    char a;
    char b;
    int c;
} small;

typedef struct Medium
{
    char a;
    int c;
    char b;

} medium;

typedef struct Big
{
    small member1;
    medium member2;
} big;

int main(){
    big A;

    printf("Size of struct big is %d\n",sizeof(big));
    printf("Size of struct small is %d\n",sizeof(small));
    printf("Size of struct medium is %d\n\n",sizeof(medium));

    printf("Size of A is %d\n",sizeof(A));
    printf("Size of member1 of A is %d\n",sizeof(A.member1));
    printf("Size of member2 of A is %d\n\n",sizeof(A.member2));

    printf("Address of A is %lu\n",&A);
    printf("\nchar a Inside instance A member1: %u",&A.member1.a);
    printf("\nchar b Inside instance A member1: %u",&A.member1.b);
    printf("\nint c Inside instance A member1: %u",&A.member1.c);
    printf("\n");
    printf("\nchar a Inside instance A member2: %u",&A.member2.a);
    printf("\nint c Inside instance A member2: %u",&A.member2.c);
    printf("\nchar b Inside instance A member2: %u",&A.member2.b);

}

Output:

Program 2: structures inside union

#include<stdio.h>

typedef struct Small
{
    char a;
    char b;
    int c;
} small;

typedef struct Medium
{
    char a;
    int c;
    char b;

} medium;

typedef union Big
{
    small member1;
    medium member2;
} big;

int main(){
    big A;

    printf("Size of union big is %d\n",sizeof(big));
    printf("Size of struct small is %d\n",sizeof(small));
    printf("Size of struct medium is %d\n\n",sizeof(medium));

    printf("Size of union big instance A is %d\n",sizeof(A));
    printf("Size of member1 of A is %d\n",sizeof(A.member1));
    printf("Size of member2 of A is %d\n\n",sizeof(A.member2));

    printf("Address of A is %lu\n",&A);
    printf("\nchar a Inside instance A member1: %u",&A.member1.a);
    printf("\nchar b Inside instance A member1: %u",&A.member1.b);
    printf("\nint c Inside instance A member1: %u",&A.member1.c);
    printf("\n");
    printf("\nchar a Inside instance A member2: %u",&A.member2.a);
    printf("\nint c Inside instance A member2: %u",&A.member2.c);
    printf("\nchar b Inside instance A member2: %u",&A.member2.b);

}

Output:

Program 3: Unions inside structure

#include<stdio.h>

typedef union Small
{
    char a;
    char b;
    int c;
} small;

typedef union Medium
{
    char a;
    int c;
    char b;

} medium;

typedef struct Big
{
    small member1;
    medium member2;
} big;

int main(){
    big A;

    printf("Size of struct big is %d\n",sizeof(big));
    printf("Size of union small is %d\n",sizeof(small));
    printf("Size of union medium is %d\n\n",sizeof(medium));

    printf("Size of struct big instance A is %d\n",sizeof(A));
    printf("Size of member1 of A is %d\n",sizeof(A.member1));
    printf("Size of member2 of A is %d\n\n",sizeof(A.member2));

    printf("Address of A is %lu\n",&A);
    printf("\nchar a Inside instance A member1: %u",&A.member1.a);
    printf("\nchar b Inside instance A member1: %u",&A.member1.b);
    printf("\nint c Inside instance A member1: %u",&A.member1.c);
    printf("\n");
    printf("\nchar a Inside instance A member2: %u",&A.member2.a);
    printf("\nint c Inside instance A member2: %u",&A.member2.c);
    printf("\nchar b Inside instance A member2: %u",&A.member2.b);

}

Output:

Program 4: Union inside union

#include<stdio.h>

typedef union Small
{
    char a;
    char b;
    int c;
} small;

typedef union Medium
{
    char a;
    int c;
    char b;

} medium;

typedef union Big
{
    small member1;
    medium member2;
} big;

int main(){
    big A;

    printf("Size of union big is %d\n",sizeof(big));
    printf("Size of union small is %d\n",sizeof(small));
    printf("Size of union medium is %d\n\n",sizeof(medium));

    printf("Size of union big instance A is %d\n",sizeof(A));
    printf("Size of member1 of A is %d\n",sizeof(A.member1));
    printf("Size of member2 of A is %d\n\n",sizeof(A.member2));

    printf("Address of A is %lu\n",&A);
    printf("\nchar a Inside instance A member1: %u",&A.member1.a);
    printf("\nchar b Inside instance A member1: %u",&A.member1.b);
    printf("\nint c Inside instance A member1: %u",&A.member1.c);
    printf("\n");
    printf("\nchar a Inside instance A member2: %u",&A.member2.a);
    printf("\nint c Inside instance A member2: %u",&A.member2.c);
    printf("\nchar b Inside instance A member2: %u",&A.member2.b);

}

Output:

Program 5: Another example of a union inside a structure

#include <stdio.h>
#include <string.h>

union id_proof
{
 char pan_id[11];
 char voter_id[11];
 long long int aadhaar_num;
 char passport_num[9];
};

struct person
{
 char name[25];
 int age;
 char address[50];
 union id_proof identity_proof; // union variable is now the member of the structure
};
int main()
{
struct person acct_holder; // structure variable declaration
// assigning the values to the members of the structure variable acct_holder
strcpy(acct_holder.identity_proof.pan_id, "ABCDE1217F");
strcpy(acct_holder.name, "Rahul");
acct_holder.age=39;
strcpy(acct_holder.address, "Mumbai");
 // displaying the values of the members of the structure
 printf(" Name of the account holder : %s \n", acct_holder.name);
 printf(" Age of the account holder : %d \n", acct_holder.age);
 printf(" Address of the account holder : %s \n", acct_holder.address);
 printf(" Identity Proof number of the holder : %s \n", acct_holder.identity_proof.pan_id);
return 0;
}

Output: