Structure stores the different types of elements i.e heterogeneous elements. The struct keyword is used to define structure.
Syntax

struct structure_name

{

data_type member1;

data_type memeberN;

};

Watch this C Programming & Data Structure Video by Intellipaat:

Declaring structure variable
You can declare structure variable in two ways:-

1. By struct keyword within main() function

2. By declaring variable at the time of defining structure.

Example

#include <stdio.h>

#include <string.h>

struct student

{

int rollno;

char name[60];

}s1;  //declaring s1 variable for structure

void main( )

{

//store first employee information

s1.rollno=1;

strcpy(s1.name, “intellipaat”);//copying string into char array

//printing first employee information

printf( “Rollno : %d\n”, s1.rollno);

printf( “Name : %s\n”, s1.name);

}

Output
Rollno : 1
Name : intellipaat

What are Unions in C?

Union also stores the different types of elements i.e heterogeneous elements. The union keyword is used to define structure. Union takes the memory of largest member only so occupies less memory than structures.
Syntax

union union_name

{

data_type member1;

data_type memeberN;

};

Example

#include <stdio.h>

#include <string.h>

union student

{

int rollno;

char name[60];

}s1;  //declaring s1 variable for union

void main( )

{

//store first employee information

s1.rollno=1;

strcpy(s1.name, “intellipaat”);//copying string into char array

//printing first employee information

printf( “Rollno : %d\n”, s1.rollno);

printf( “Name : %s\n”, s1.name);

}

Output
Rollno : 3546656
Name : intellipaat
Rollno takes garbage value because name has large memory size. So only name will have actual value.