What are Nested Structures?

In C programming, a structure is a user-defined data type that allows you to group together variables of different data types under a single name. A nested structure is a structure that is declared inside another structure. This allows you to create more complex and organized data representations.

Defining Nested Structures

Here's how you can define nested structures in C:

 #include <stdio.h>

// Define the inner structure (Address)
struct Address {
    char street[50];
    char city[50];
    char state[3];
    char zip[10];
};

// Define the outer structure (Employee)
struct Employee {
    char name[50];
    int age;
    float salary;
    struct Address address; // Nested structure - Address is a member of Employee
};

int main() {
    struct Employee emp;

    // Accessing members of the nested structure
    strcpy(emp.name, "John Doe");
    emp.age = 30;
    emp.salary = 50000.0;

    strcpy(emp.address.street, "123 Main Street");
    strcpy(emp.address.city, "Anytown");
    strcpy(emp.address.state, "CA");
    strcpy(emp.address.zip, "91234");


    printf("Employee Name: %s\n", emp.name);
    printf("Employee Age: %d\n", emp.age);
    printf("Employee Salary: %.2f\n", emp.salary);
    printf("Employee Address: %s, %s, %s %s\n", emp.address.street, emp.address.city, emp.address.state, emp.address.zip);


    return 0;
} 

In this example, the Address structure is defined *inside* the Employee structure. The Employee structure now contains a member called address, which is of type struct Address.

Accessing Members of Nested Structures

To access the members of a nested structure, you use the dot operator (.) multiple times, following the hierarchy of the structures.

In the example above, to access the street member of the Address structure within the Employee structure, you would use the following syntax: emp.address.street

Each dot operator allows you to drill down into the respective structure until you reach the desired member. So, emp accesses the Employee structure, emp.address accesses the Address structure within Employee, and emp.address.street finally accesses the street member of the Address structure.

Why Use Nested Structures?

• Organization: Nested structures help organize related data into logical groups.
• Reusability: You can reuse the inner structure in multiple outer structures.
• Readability: They improve the readability of your code by making it easier to understand the relationships between different pieces of data.