Union in C Programming Language

Union in C Programming Language

In this tutorial, We will learn about unions in C programming language.

Introduction

A union is a user-defined data type. In union, all members share the same memory location. For example in the following C program, both A and B share the same location. If we change A, we can see the changes being reflected in B.

 #include <stdio.h>  
 union test  
 {  
   int A, B;  
 };  
 int main()  
 {  
   // A union variable t  
   union test t;  
   t.A = 2; // t.B also gets value 2  
   printf ("After making A = 2:\n A = %d, B = %d\n\n",  
        t.A, t.B);  
   t.B = 10; // t.A is also updated to 10  
   printf ("After making Y = 'A':\n A = %d, B = %d\n\n",  
        t.A, t.B);  
   return 0;  
 }  

Declare Union in C
Like the structure, we use keyword union in order to declare a union in C programming language.

 union test  
 {  
   int A, B;  
 };  

Access Union in C
Like the structure, we use the dot operator to access a member of a union.

• Declare a variable of union type
• use the dot operator to access a member of a union

 int main()  
 {  
   // Dclaring union test type variable t
   union test t;  
   t.A = 2; //Accesing A with dot operator
   printf ("A = %d\n", t.A);  
   return 0;  
 }  

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