Unions in C++

A union in C++ is a data structure that allows storing different types of data in the same memory location.

Unlike structures (structs), where each member has its own storage area, in unions, all members share the same memory area.

This means that a union can have multiple members, but only one member can hold a value at any given time.

Basic Syntax

The basic syntax for defining a union is similar to that of a structure (struct), but using the union keyword instead of struct.

union UnionName {
    data_type1 member1;
    data_type2 member2;
    // More members
};

For example,

union Data {
    int integer;
    float floating;
    char character;
};

Accessing Union Members

To access union members, the same syntax is used as for accessing members of a structure (struct), using the dot operator (.).

Data data;
data.integer = 10;
std::cout << "Value of the integer: " << data.integer << std::endl;

Size of a Union

The size of a union is equal to the size of the largest member. This is because the union reserves enough memory space to store the largest member, and all other members share the same memory location.

union Data {
    int integer;
    char string[10];
};

std::cout << "Size of the union Data: " << sizeof(Data) << std::endl; // Will print the size of an int

Using Unions to Save Memory

Unions can be used to save memory when different types of data need to be stored in the same memory location, but only one needs to be accessed at a given time.

union Value {
    int integer;
    float floating;
};

Value v;
v.integer = 10;
std::cout << "Value of the integer: " << v.integer << std::endl;