C++ Unions
A union in C++ is a composite data type that allows you to store different types of data in the same memory location. Unlike a struct, where each member has its own memory location, a union shares the memory among its members. This means that only one member of the union can hold a value at a given time, making unions suitable for situations where you want to conserve memory while storing data of different types.
In the below PDF we discuss about Unions in C++Â in detail in simple language, Hope this will help in better understanding.
Declaring a Union:
 To declare a union in C++, you use the union keyword, followed by the union’s name and a list of member variables enclosed in curly braces. Here’s a simple example:
union MyUnion {
  int integer;
  double floatingPoint;
  char character;
};
In this example, MyUnion can hold an integer, a double, or a character, but not all of them simultaneously.
Accessing Union Members:
You can access the members of a union using the dot (.) operator, just like you would with a struct. However, remember that only one member can hold a value at a time. Here’s an example of accessing union members:
MyUnion u;
u.integer = 42;Â Â Â Â Â // Assign an integer value
cout << u.integer;Â Â Â Â // Access the integer member
In this case, the integer member of the union holds the value 42, and you can access it using u.integer.
Size and Memory Allocation:
 The size of a union is determined by the member with the largest size. For example, if a union has an integer, a double, and a character, its size will be equal to the size of a double since that’s the largest member.
cout << sizeof(MyUnion); // Prints the size of MyUnion
In memory, all members share the same location, so changing one member may affect the values of the others.
Related Question
A union in C++ is a user-defined data type that allows you to store different data types in a single memory location. Unlike structures, which allocate memory for each member separately, unions share the same memory location for all their members.
You declare a union in C++ using the union keyword
The size of a union in C++ is determined by the size of its largest member variable. It allocates enough memory to accommodate the largest member variable.
You can access the members of a union using the dot (.) operator, just like you would with structures.
No, a union in C++ can only contain data members (variables). It cannot have member functions like classes.
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