3 days ago · In C++, a union is a user-defined data types that allow you to store different types of data in the same memory location but unlike structures, where each member gets its own memory, union members share the same memory space making unions more memory-efficient for specific use cases.

In this tutorial, we will learn what is a union in C++ and its use when compared with structure. We will understand it using a few examples in C++. Union in C++. A union is a user-defined data type in C++. Syntax for union declaration: union union_name { datatype1 var_name1; datatype2 var_name2; . . datatypen var_namen;};

Feb 22, 2010 · The main purpose of using "union" in C/C++ is to provide a datatype that could store anything. union a { char a; int b; float c; }; std::variant<int ,char,float,double,long> v; // std::variant in c++17 for instance , union a would allow to store either of char, int , float.

Aug 14, 2024 · union A {int x; int y [4];}; struct B {A a;}; union C {B b; int k;}; int f {C c; // does not start lifetime of any union member c. b. a. y [3] = 4; // OK: "c.b.a.y[3]", names union members c.b and c.b.a.y; // This creates objects to hold union members c.b and c.b.a.y return c. b. a. y [3]; // OK: c.b.a.y refers to newly created object} struct X ...

Apr 3, 2023 · In C++17 and later, the std::variant class is a type-safe alternative for a union. A union is a user-defined type in which all members share the same memory location. This definition means that at any given time, a union can contain no …

May 6, 2025 · Cpp. Copy Code Run Code. Output: The code shows how union members are assigned and accessed in C++, since all the members share the same memory, thus, each new assignment overwrites the previous one, and then the result is printed to the console. 2. Accessing Union Members

In C++, a union is a special data type that allows storing different data types in the same memory location. Unlike structures and classes, which allocate separate memory for each member, a union allocates a single memory block large enough to hold the largest member only.

To declare a union, use the union keyword followed by the tag_name (union name) and then declare the union members with their data types inside the curly brackets. Close the declaration with a semicolon. Below is the syntax to declare a union −. dataType1 member1; . dataType2 member2; // more members };

Jun 15, 2023 · The syntax of using Union in C++ language is written below: union <Name of the union> { Define the members; } variable names ; Explanation: Name of the union – One can use any name as the union’s name. After writing the union, name the union according to the requirement. Define the members − Here, the coder has to define the member variables.

Apr 16, 2020 · Unions provide multiple ways of viewing the same memory location, allowing for more efficient use of memory. Most of the uses of unions are covered by object-oriented features of C++, so it is more common in C.