STRUCTURE:

A structure is a collection of variables of different types under a single name or in other words structure is a user defined data type. Structures can be used like any other variable. We can make a struct array or used as pointers.

SYNTAX:

struct structure_name{
type1 id_list1 ;
type2 id_list2 ;
.
.
.
typen id_listn ;
} struct_type ;
EXAMPLE:
struct number{
int num;
char name[10];
};

STRUCTURES WITH FUNCTIONS:

• Stucture variables are passed by value by default.
• To pass a structure by reference, pass its address. Arrays of structures—like all other arrays—are automatically passed by reference.
• To pass an array by value, create a structure with the array as a member. Structures are passed by value, so the array is passed by value.

Implementation of Structure in C:

#include<stdio.h> 
#include<string.h> 

//structure declaration 
struct employee { 
   char name[25]; 
   int id_number; 
   int age; float salary; 
} emp1 = {"Dummy1",1,24,20000}; 

int main() 
{ 
   struct employee emp2; 
/* Structure variable declaration. There is now an emp2 variable that has modifiable variables inside it.*/ 
/* Structure members can be accessed using direct component selection operator or dot operator as shown in the following statements */ 

   strcpy(emp2.name,"Dummy2"); 
   emp2.age = 22; 
   emp2.id_number = 2; 
   emp2.salary = 12000.21; 
   struct employee emp3; 

/* Initialize the structure variable emp3 from input data as follows */ 
   
   printf("Enter the name of employee: " ); 
   gets(emp3.name); 
   printf("Enter the id number of employee: " ); 
   scanf("%d",&emp3.id_number); 
   printf("Enter the age of employee: " ); 
   scanf("%d",&emp3.age); 
   printf("Enter the salary of employee: " ); 
   scanf("%f",&emp3.salary); 

/*A new copy of a structure’s value can be made by simply assigning one structure to another as in the following statement */ 
  
   struct employee emp4 = emp1;

//Displaying the content for each employee 

   printf("\n%s is %d years old and has %d id number and %.2f salary.\n",emp1.name, emp1.age, emp1.id_number,emp1.salary); 
   printf("\n%s is %d years old and has %d id number and %.2f salary.\n",emp2.name, emp2.age, emp2.id_number,emp2.salary);
   printf("\n%s is %d years old and has %d id number and %.2f salary.\n",emp3.name, emp3.age, emp3.id_number,emp3.salary);  
   printf("\n%s is %d years old and has %d id number and %.2f salary.\n",emp4.name, emp4.age, emp4.id_number,emp4.salary); 

   return 0; 

}