C Nested Structures

C Nested Structures

One structure can be nested within another structure.

In programming, we usally deal with collection of ints, chars and floats rather than isolated entities.

Example an entity book is a collection of things like a title, an author, total pages, date of publication and price etc..

Structure is user defined data type which combines dissimilar data types into an entity.

Nested Strucure syntax,

struct <struct-name1>
{
  //data-type member1;
  //data-type member2;
  ...
  //data-type membern;
};
struct <struct-name2>
{
  //data-type member1;
  //data-type member2;
  ...
  //data-type membern;
  // <struct-name1> inner;
};

C Program for nested structures

Sample nested structure c program,

#include<stdio.h>                                                          
                                                                                
void main()                                                                     
{                                                                               
  struct person                                                                 
  {                                                                             
    char *firstname, *lastname;                                                 
  };                                                                            
  struct book                                                                   
  {                                                                             
    int id;                                                                     
    char *title;                                                                
    struct person author;                                                       
    float price;                                                                
  }b2, b1 = {1, "book1", {"author1 fn", "lastname1"}, 20.5};                    
  b2.id = 2;                                                                    
  b2.title = "book2";                                                           
  b2.author.firstname = "author2 fn";                                           
  b2.author.lastname = "lastname2";                                             
  b2.price = 35.0;                                                              
  printf("\nbook id\ttitle \t auther \t price \n");                             
  printf("%d\t%s\t%s %s\t%f\n", b1.id, b1.title, b1.author.firstname, b1.author.lastname, b1.price);
  printf("%d\t%s\t%s %s\t%f\n", b2.id, b2.title, b2.author.firstname, b2.author.lastname, b2.price);
} 

Output:

$ cc structure.c
$ ./a.out 

book id	title 	 auther 	 price 
1	book1	author1 fn lastname1	20.500000
2	book2	author2 fn lastname2	35.000000

Sample c program to copy the nested structure variable to another same structure variable.

here nested structure with string variable using pointers (firstname and last name),

#include<stdio.h>                                                             
                                                                                
void main()                                                                     
{                                                                               
  struct person                                                                 
  {                                                                             
    char *firstname, *lastname;                                                 
  };                                                                            
  struct book                                                                   
  {                                                                             
    int id;                                                                     
    char *title;                                                                
    struct person author;                                                       
    float price;                                                                
  }b2, b1 = {1, "book1", {"author1 fn", "lastname1"}, 20.5};                    
  b2 = b1;                                                                      
  b2.id = 2;                                                                    
  b2.title = "book2";                                                           
  b2.price = 35.0;                                                              
  printf("\nbook id\ttitle \t auther \t price \n");                             
  printf("%d\t%s\t%s %s\t%f\n", b1.id, b1.title, b1.author.firstname, b1.author.lastname, b1.price);
  printf("%d\t%s\t%s %s\t%f\n", b2.id, b2.title, b2.author.firstname, b2.author.lastname, b2.price);
}  

Output:

$ cc structure.c
$ ./a.out 

book id	title 	 auther 	 price 
1	book1	author1 fn lastname1	20.500000
2	book2	author1 fn lastname1	35.000000

here nested structure with string variable using array,

#include<stdio.h>                                                                   
                                                                                
void main()                                                                     
{                                                                               
  struct person                                                                 
  {                                                                             
    char firstname[20], lastname[20];                                           
  };                                                                            
  struct book                                                                   
  {                                                                             
    int id;                                                                     
    char *title;                                                                
    struct person author;                                                       
    float price;                                                                
  }b2, b1 = {1, "book1", {"author1 fn", "lastname1"}, 20.5};                    
  b2 = b1;                                                                      
  b2.id = 2;                                                                    
  b2.title = "book2";                                                           
  b2.price = 35.0;                                                              
  printf("\nbook id\ttitle \t auther \t price \n");                             
  printf("%d\t%s\t%s %s\t%f\n", b1.id, b1.title, b1.author.firstname, b1.author.lastname, b1.price);
  printf("%d\t%s\t%s %s\t%f\n", b2.id, b2.title, b2.author.firstname, b2.author.lastname, b2.price);
}                                                                               

Output:

$ cc structure.c
$ ./a.out 

book id	title 	 auther 	 price 
1	book1	author1 fn lastname1	20.500000
2	book2	author1 fn lastname1	35.000000