Union in C

A union is a special data type that allows storing different data types in the same memory location. We can illustrate a union with many members, but only one member can contain a value at any given time.

Unions provide an efficient way of using the same memory location for different data types.

The union statement defines a new data with more than one member for the program. The format of statement is as follows:

Syntax:

union union_name {
   data_type member 1;
	data_type member 2; 
	.
	.
	data_type member n;
} [one or more union variables];

Advantage of union

Union occupies less memory.

Disadvantage of union

Last entered data only available in the union because it overwrites previous data memory.

Example:

#include <stdio.h>
#include <stdlib.h>     
union student      
{   int id;      
    char name[50];      
    float mark1;      
}s; 

void main( )    
{    
	s.id=101;
	printf( "Student 1 id : %d\n", s.id); 
    strcpy(s.name, "Arunkumar");
    printf( "Student 1 name : %s\n", s.name);
    s.mark1=89;   
    printf( "Student 1 mark1 : %f\n", s.mark1); 
}