Anonymous Unions in C++

Unions in C++ are special type of classes. We can declare member functions and variables with in the union in c++ (all 'C' features of union remain same). 

But in the unions all the data members share the same memory location.

    Union members are public by default as like structures.

     Anonymous unions are the special type unions with the no name and so we can not create object for that union. All the member data in the anonymous unions share same memory location. We can directly access the these members without any dot operator with in the block where these unions declared. 

      The scope of the anonymous union members restricted to the block where it declared and these members can be treated as the local varibles to that block, so there shouldn't be any conflict between the names of the variables defined with in the unions and variables defined with in the block.

For example:

 #include<iostream>  
 #include<cstring>  
 using namespace std;  
 int main()  
 {  
   union   
   {  
     int i;  
     char ch[4];  
   };  
   i = 56;  
   cout<<"i val: "<<i<<" ch val:"<<ch<<endl;  
   memcpy(ch,"1",sizeof(ch));  
   cout<<"i val: "<<i<<" ch val:"<<ch<<endl;  
   return 0;  
 }  

Output:

i val: 56 ch val:8

i val: 49 ch val:1

Here union member data i and ch are having same scope as the variables declared with in the main block. Here i and ch share the same memory location so when we set ivalue ch value is also same. Ascii values 48 to 57 represents 0 to 9 decimal numbers.

Note: Alls the restrictions applicable to the unions in c++ are also applicable to anonymous unions

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