Nested Structure in C

Nested Structure

A nested structure is a structure that contains another structure as one of its members.
This means that a nested structure can be defined within another structure.

Example of a nested structure:

struct date {
    int day;
    int month;
    int year;
};

struct person {
    char name[50];
    int age;
    struct date birthdate;
};

Explanation

The person structure contains a nested date structure as one of its members.
The date structure has three members: day, month, and year.
The person structure has three members: name, age, and birthdate, where birthdate is of type date.

Acessing members of the nested structure

To access the members of the nested structure, you can use the dot operator twice, once for the outer structure and once for the inner structure.

For example:

    john.birthdate.day = 1;
    john.birthdate.month = 1;
    john.birthdate.year = 2000;

Example of nested structure

#include <stdio.h>

struct date
{
    int day;
    int month;
    int year;
};

struct person
{
    char name[50];
    int age;
    struct date birthdate;
};

int main()
{
    struct person john;

    // assign values to the members of the john structure
    strcpy(john.name, "John");
    john.age = 25;
    john.birthdate.day = 1;
    john.birthdate.month = 1;
    john.birthdate.year = 2000;

    // access the members of the john structure and print them out
    printf("Name: %s\n", john.name);
    printf("Age: %d\n", john.age);
    printf("Birthdate: %d/%d/%d\n", john.birthdate.day, john.birthdate.month,
           john.birthdate.year);

    return 0;
}

Output:

Explanation

We define a nested structure called date within the person structure.
We then declare a person variable called john and assign values to its members, including the birthdate member which is a nested structure.
We then use the dot operator twice to access the day, month, and year members of the birthdate structure, and print them out using printf().

Output:

Name: John
Age: 25
Birthdate: 1/1/2000

When to use nested strutures

We use nested structures in C when we need to represent more complex data structures that have multiple levels of abstraction.
A nested structure is particularly useful when one or more members of a structure are themselves structures.

For example:

Consider a program that manages a company's employee database. Each employee may have a personal information structure, an employment information structure, and a salary structure, each with its own set of members. We could use nested structures to represent each employee's record, with the employee structure containing the personal, employment, and salary structures as members.

Nested structure for representing an employee record:

struct personal_info {
    char name[50];
    char address[100];
    char phone[20];
};

struct employment_info {
    char job_title[50];
    char department[50];
    char hire_date[20];
};

struct salary_info {
    double base_salary;
    double bonus;
    double tax_rate;
};

struct employee {
    int employee_id;
    struct personal_info personal;
    struct employment_info employment;
    struct salary_info salary;
};

Explanation

We have defined four structures: personal_info, employment_info, salary_info, and employee.
The employee structure contains the personal_info, employment_info, and salary_info structures as members.