What are nested structures in C language?

Structure within structure (or) Nested structures

A structure inside another structure is called nested structure.

Consider the following example,

struct emp{
   int eno;
   char ename[30];
   float sal;
   float da;
   float hra;
   float ea;
}e;

All the items comes under allowances can be grouped together and declared under a sub – structure as shown below.

stuct emp{
   int eno;
   char ename[30];
   float sal;
   struct allowance{
      float da;
      float hra;
      float ea;
   }a;
}e;

The inner most member in a nested structure can be accessed by changing all the concerned structure variables (from outer most to inner most) with the member using dot operator.

Program

Following program is to demonstrate nested structure (structure within the structure) −

 Live Demo

#include<stdio.h>
//Declaring outer and inter structures//
struct Person//Main Structure//{
   char Name[500];
   int Age;
   char Gender;
   char temp;//To clear buffer//
   struct Address//Nested Structure//{
      char Apartment[500];
      char Street[500];
      char City[100];
      char State[100];
      int Zipcode;
   }a[20];//Nested Structure Variable//
   }p[20];//Main Structure Variable//
void main(){
   //Declaring variable for For loop//
   int i;
   //Reading User I/p//
   for (i=1;i<3;i++){//Declaring function to accept 2 people's data//
      printf("Enter the Name of person %d : ",i);
      gets(p[i].Name);
      printf("Enter the Age of person %d : ",i);
      scanf("%d",&p[i].Age);
      scanf("%c",&p[i].temp);//Clearing Buffer//
      printf("Enter the Gender of person %d : ",i);
      scanf("%c",&p[i].Gender);
      scanf("%c",&p[i].temp);//Clearing Buffer//
      printf("Enter the City of person %d : ",i);
      gets(p[i].a[i].City);
      printf("Enter the State of person %d : ",i);
      gets(p[i].a[i].State);
      printf("Enter the Zip Code of person %d : ",i);
      scanf("%d",&p[i].a[i].Zipcode);
      scanf("%c",&p[i].temp);//Clearing Buffer//
   }
   //Printing O/p//
   for (i=1;i<3;i++){
      printf("The Name of person %d is : %s
",i,p[i].Name);
      printf("The Age of person %d is : %d
",i,p[i].Age);
      printf("The Gender of person %d is : %c
",i,p[i].Gender);
      printf("The City of person %d is : %s
",i,p[i].a[i].City);
      printf("The State of person %d is : %s
",i,p[i].a[i].State);
      printf("The Zip code of person %d is : %d
",i,p[i].a[i].Zipcode);
   }
}

Output

Enter the Name of person 1 : Enter the Age of person 1 : Enter the Gender of person 1 : Enter the City of person 1 : Enter the State of person 1 : Enter the Zip Code of person 1 : Enter the Name of person 2 : Enter the Age of person 2 : Enter the Gender of person 2 : Enter the City of person 2 : Enter the State of person 2 : Enter the Zip Code of person 2 : The Name of person 1 is :
The Age of person 1 is : 0
The Gender of person 1 is :
The City of person 1 is :
The State of person 1 is :
The Zip code of person 1 is : 0
The Name of person 2 is :
The Age of person 2 is : 0
The Gender of person 2 is :
The City of person 2 is :
The State of person 2 is :
The Zip code of person 2 is : 0