Dereference

Dereference is a concept in computer science and programming that describes accessing the value stored at a location referenced by a pointer or reference. It is the operation that retrieves the object itself rather than the reference or address that refers to it. Dereferencing is the counterpart to taking the address or obtaining a reference to a value.

In languages such as C and C++, dereferencing is explicit. The dereference operator (*) applied to a pointer yields the object to which the pointer points, while the arrow operator (->) accesses members of a structure through a pointer. Dereferencing a null or invalid pointer leads to undefined behavior and can cause program crashes. Pointers to pointers and multi-level indirection extend this concept.

Other languages handle dereferencing in different ways. In Rust, the * operator dereferences references and smart pointers, with automatic deref coercions that allow seamless method calls and field access. In Java and many managed languages, dereferencing is implicit when accessing a field or method through an object reference, with the runtime enforcing memory safety. In languages without explicit pointers, dereference occurs behind the scenes whenever an alias is followed to obtain the underlying value.

Dereferencing also appears in data structures and algorithms. An iterator dereferences to yield the element it points to, and in databases or linked data, dereferencing a reference or foreign key retrieves the related record. Across contexts, dereference centers on translating a reference or address into the actual value stored at that location, with implications for safety, performance, and software design.