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Explanatory Question

What is a union?

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Answer with Explanation

  • 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.