Nested Structure in C

C provides us the feature of nesting one structure within another structure by using which, complex data types are created. For example, we may need to store the address of an entity employee in a structure. The attribute address may also have the subparts as street number, city, state, and pin code. Hence, to store the address of the employee, we need to store the address of the employee into a separate structure and nest the structure address into the structure employee. Consider the following program.

#include<stdio.h>  
struct address   
{  
    char city[20];  
    int pin;  
    char phone[14];  
};  
struct employee  
{  
    char name[20];  
    struct address add;  
};  
void main ()  
{  
    struct employee emp;  
    printf("Enter employee information?\n");  
    scanf("%s %s %d %s",emp.name,emp.add.city, &emp.add.pin, emp.add.phone);  
    printf("Printing the employee information....\n");  
    printf("name: %s\nCity: %s\nPincode: %d\nPhone: %s",emp.name,emp.add.city,emp.add.pin,emp.add.phone);  
}  
Output
Enter employee information?

Arun            

Delhi           

110001       

1234567890    

Printing the employee information....   

name: Arun      

City: Delhi  

Pincode: 110001

Phone: 1234567890


The structure can be nested in the following ways.

• By separate structure
• By Embedded structure

1) Separate structure
Here, we create two structures, but the dependent structure should be used inside the main structure as a member. Consider the following example.


struct Date  
{  
   int dd;  
   int mm;  
   int yyyy;   
};  
struct Employee  
{     
   int id;  
   char name[20];  
   struct Date doj;  
}emp1;  
As you can see, doj (date of joining) is the variable of type Date. Here doj is used as a member in Employee structure. In this way, we can use Date structure in many structures.



2) Embedded structure
The embedded structure enables us to declare the structure inside the structure. Hence, it requires less line of codes but it can not be used in multiple data structures. Consider the following example.

struct Employee  
{     
   int id;  
   char name[20];  
   struct Date  
    {  
      int dd;  
      int mm;  
      int yyyy;   
    }doj;  
}emp1;  

Accessing Nested Structure

We can access the member of the nested structure by Outer_Structure.Nested_Structure.member as given below:

e1.doj.dd  
e1.doj.mm  
e1.doj.yyyy  

C Nested Structure example
Let's see a simple example of the nested structure in C language.

#include <stdio.h>  
#include <string.h>  
struct Employee  
{     
   int id;  
   char name[20];  
   struct Date  
    {  
      int dd;  
      int mm;  
      int yyyy;   
    }doj;  
}e1;  
int main( )  
{  
   //storing employee information  
   e1.id=101;  
   strcpy(e1.name, "Sonoo Jaiswal");//copying string into char array  
   e1.doj.dd=10;  
   e1.doj.mm=11;  
   e1.doj.yyyy=2014;  
  
   //printing first employee information  
   printf( "employee id : %d\n", e1.id);  
   printf( "employee name : %s\n", e1.name);  
   printf( "employee date of joining (dd/mm/yyyy) : %d/%d/%d\n", e1.doj.dd,e1.doj.mm,e1.doj.yyyy);  
   return 0;  
}  
Output:

employee id : 101
employee name : Sonoo Jaiswal
employee date of joining (dd/mm/yyyy) : 10/11/2014

Passing structure to function

Just like other variables, a structure can also be passed to a function. We may pass the structure members into the function or pass the structure variable at once. Consider the following example to pass the structure variable employee to a function display() which is used to display the details of an employee.

#include<stdio.h>  
struct address   
{  
    char city[20];  
    int pin;  
    char phone[14];  
};  
struct employee  
{  
    char name[20];  
    struct address add;  
};  
void display(struct employee);  
void main ()  
{  
    struct employee emp;  
    printf("Enter employee information?\n");  
    scanf("%s %s %d %s",emp.name,emp.add.city, &emp.add.pin, emp.add.phone);  
    display(emp);  
}  
void display(struct employee emp)  
{  
  printf("Printing the details....\n");  
  printf("%s %s %d %s",emp.name,emp.add.city,emp.add.pin,emp.add.phone);  
}