Union In C Programming

union is a user-defined data type

It is the collection of different data elements

union keyword is used to define a structure

dot operator(.) is used for accessing members.

When a variable is associated with a union, the compiler allocates the memory by considering the size of the   largest memory. So size of union is equal to the size of largest member

Only one member can be accessed at a time.    

Syntax:

union[union name]

{

Member definition;

Member definition;

..

Member definition

};

Example:

union Employee

{

    char name[50]; //1byte memory

    int id;                //2 byte

    float salary;        //4byte   

} e1;

Note:

4 bytes memory is allocated because the compiler allocates the memory in union by considering the size of the   largest memory

Example 1(1^st way):

#include <stdio.h>

#include<string.h>

#include<conio.h>

union Employee

{

    char name[50];

    int id;

    float salary;

};

void main()

{

   union Employee e1;

   e1.id=1;

   clrscr();

  strcpy(e1.name, "Suryosnata");

  e1.salary =35000.45;    

 printf(" Name is: %s \n", e1.name);

 printf(" Id is: %d \n", e1.id);

 printf(" Salary is: %f \n", e1.salary);

 getch();

}

Output:

Name is: sGosnata                                                                                                             

 Id is: 1191753843                                                                                                             

 Salary is: 35000.449219

Example 1(2^nd way):

#include <stdio.h>

#include<conio.h>

union Employee

{

    char name[50];

    int id;

    float salary;

};

void main()

{

union Employee e1={"suryosnata",1,35000.45};

    

   printf(" Name is: %s \n", e1.name);

   printf(" Id is: %d \n", e1.id);

  printf(" Salary is: %f \n", e1.salary);

 getch();

}

Output:

Name is: suryosnata                                                                                                           

 Id is: 2037544307                                                                                                             

 Salary is: 78682374557984041996425324851625984.000000

Example 2(Taking value from user)

#include <stdio.h>

#include<conio.h>

union Employee

{

    char name[50];

    int id;

    float salary;

} e1;

void main()

{

    clrscr();

    printf("Enter  Employee information:\n");

   printf("Enter NAME: ");

    scanf("%s", e1.name);

    printf("Enter ID: ");

    scanf("%d", &e1.id);

    printf("Enter SALARY: ");

    scanf("%f", &e1.salary);

   printf("Employee Information:\n");

    printf("Name: %s\n",e1.name);

    printf("Id: %d\n",e1.id);
    printf("Salary: %f\n", e1.salary);

     getch();

}

Enter Employee information:                                                                                                   

Enter NAME: surya                                                                                                              

Enter ID: 101                                                                                                                  

Enter SALARY: 12456                                                                                                            

Employee Information:                                                                                                          

Name:

Id: 1178771456                                                                                                                 

Salary: 12456.000000  

 Note:

Only salary is displayed here because the compiler allocates the memory by considering the size of the   largest memory (salary is the largest size)