Nested Structures

NESTED STRUCTURES

A structure can be placed within another structure, i.e., a structure may contain another structure as its member. A structure that contains another structure as its member is called a nested structure.

Let us now see how we declare nested structures or structures that contain structures. Although it is possible to declare a nested structure with one declaration, it is not recommended. The easier and clearer way is to declare the structures separately and then group them in a high- level structure. When you do this, take care to check that nesting must be done from inside out (from lowest level to the most inclusive level), i.e., to say, declare the innermost structure, then the next level structure, working towards the outer (most inclusive) structure.

typedef struct

{

char first name [20];

char mid_name [20];

char last name [20];

}NAME;

typedef struct

{

int dd;

int mm;

int yy:

}DATE;

typedef struct student

{

int r_no;

NAME name;

char course [20];

DATE DOB;

float fees;

};

In this example, we see that the structure student contains two other structures-NAME and DATE. Both these structures have their own fields. The structure NAME has three fields: first_name, mid_name, and last_name. The structure DATE also has three fields: dd, mm, and yy, which specify the day, month, and year of the date. To assign values to the structure fields, we will write

student stud1;

{

studl.name.first_name ="Janak";

studl.name.mid_name = "Raj";

studl.name.last_name = "Thareja";

stud1.course = "BCA";

studl.DOB. dd = 15;

stud1.DOB.mm = 09;

studl.DOB.yy = 1990;

studl.fees = 45000;

In case of nested structures we use the dot operator in conjunction with the structure variables to access the members of the innermost as well as the outermost structures. The use of nested structures is illustrated in the following program:

5. Write a program to read and display information of a student using a structure within a structure.

#include <stdio.h>

#include <conio.h>

int main()

{

struct DOB

{

int day;

int month;

int year;

};

struct student

{

int roll_no;

char name [100];

float fees;

struct DOB date;

};

struct student stud1;

clrscr();

printf("\n Enter the roll number: ");

scanf("%d", &stud1.roll_no);

printf("\n Enter the name: ");

scanf("%s", stud1.name);

printf("\n Enter the fees: ");

scanf("%f", &stud1.fees);

printf("\n Enter the DOB: ");

scanf("%d %d %d", &stud1.date.day, &stud1.date.month, &stud1.date. year);

printf("\n *** STUDENT'S DETAILS ***");

printf("\n ROLL No. = %d", stud1.roll_no);

printf("\n NAME %%s", stud1.name);

printf("\n FEES = %f", stud1. fees);

printf("\n DOB %d %d %d", stud1. date.day, stud1.date.month, stud1.date. year);

getch();

return 0;

}

Output

Enter the roll number: 01

Enter the name: Rahul

Enter the fees: 45000

Enter the DOB: 25 09 1991

********STUDENT'S DETAILS ****

ROLL NO. = 01

NAME = Rahul

FEES = 45000.00

DOB = 25-09-1991