Reference type

In Object-oriented programming, a reference type is a data type that can only be accessed by references. Unlike objects of value types, objects of reference types cannot be directly embedded into composite objects and are always dynamically allocated. They are usually destroyed automatically after they become unreachable.

Immutable objects are usually of a reference type, where supported.

Language and platform support

* C++ has no built-in support for reference types. However this behavior can be emulated by restricting access to a type's constructor.
* The .NET Framework makes a clear distinction between value and reference types, and allows creation of user-defined types for both kinds.
** In C#, the struct keyword defines a value type, while the class keyword defines a reference type.
** In C++/CLI, the keyword pairs value class and value struct define managed value types, while the ref class and ref struct pairs define managed reference types.
* On the Java platform, all composite and user-defined types are reference types. Only primitive types are value types.
* Windows COM objects are reference-counted reference types.