What is a union?

C Programming Language > Union in C Language > Union in C

Long Question

598

Answer:

The union is a user-defined data type that allows storing multiple types of data in a single unit. However, it doesn't occupy the sum of the memory of all members. It holds the memory of the largest member only.
In union, we can access only one variable at a time as it allocates one common space for all the members of a union.

Syntax of union


union union_name  
{  
Member_variable1;  
Member_variable2;  
.  
.  
Member_variable n;  
}[union variables];

Let's see a simple example


#include<stdio.h>  
union data  
{  
    int a;      //union members declaration.  
    float b;  
    char ch;  
};  
int main()  
{  
  union data d;       //union variable.  
  d.a=3;  
  d.b=5.6;  
  d.ch='a';  
  printf("value of a is %d",d.a);  
  printf("\n");  
  printf("value of b is %f",d.b);  
  printf("\n");  
  printf("value of ch is %c",d.ch);  
  return 0;  
}

Output:

value of a is 1085485921
value of b is 5.600022
value of ch is a

In the above example, the value of a and b gets corrupted, and only variable ch shows the actual output. This is because all the members of a union share the common memory space. Hence, the variable ch whose value is currently updated.

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