What are unions in C++?

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 more than one object from its list of members.

A structure contains an ordered group of data objects. Unlike the elements of an array, the data objects within a structure can have varied data types. Each data object in a structure is a member or field. A union is an object similar to a structure except that all of its members start at the same location in memory .

A structure is a user-defined data type available in C that allows to combining data items of different kinds. Structures are used to represent a record. A union is a special data type available in C that allows storing different data types in the same memory location.12 Eyl 2021