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++  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;          // Assign an integer value

cout << u.integer;       // 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.



Storage Classes in C++ In

Preprocessors in C++ A preprocessor

Standard Template Library in C++

Exception Handling in C++ Exception

Destructors in C++ A destructor

Constructors in C++ A constructor

Inheritance in C++ Inheritance is

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