Like structure, Union in c language is a user-defined data type that is used to store the different type of elements.
At once, only one member of the union can occupy the memory. In
other words, the size of the union in any instance is equal to the size of its
largest element.
Unions provide an efficient way of using the same
memory location for multiple-purpose.
Defining union
The union keyword
is used to define the union. Let's see the syntax to define union in c.
union union_name
{
data_type
member1;
data_type
member2;
.
.
data_type
memeberN;
};
The example to define union for an employee in c.
union employee
{ int id;
char name[50];
float salary;
};
Declaring union variable
There are
two ways to declare union variable:
- By union keyword within main() function
- By declaring a variable at the time of defining the union.
{
int
id;
char name[50];
float salary;
};
After defining structure write below code inside the main() function.
union employee e1, e2;
The variables e1 and e2 can be used to access the values stored in the union.
Second Method:
union employee
{
int id;
char name[50];
float salary;
}e1,e2;
If number
of variables is not fixed, use the first method. It provides the flexibility to
declare the union variable as many times as required
Accessing members of the Union
There are two ways to access union members:
- By
. (member or dot operator)
- By
-> (structure pointer operator)
A pointer can be created to
a union. If a pointer to union is created, members are accessed using
arrow ( -> ) operator.
Example:
#include <stdio.h>
#include <string.h>
union employee
{ int id;
char name[50];
}e1; //declaring e1
variable for union
int main( )
{
//store first
employee information
e1.id=101;
strcpy(e1.name, "Ashraf");//copying
string into char array
//printing first
employee information
printf(
"employee 1 id : %d\n", e1.id);
printf(
"employee 1 name : %s\n", e1.name);
return 0;
}
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