pointers

Pointers are variables that store memory addresses rather than actual values. They enable indirect access to data, dynamic memory management, and the construction of data structures such as linked lists and trees. In low-level languages, a pointer's type indicates the type of value it can address, and the pointer itself occupies space that holds another address.

Common operations include obtaining the address of a variable, via the address-of operator, and dereferencing to read or modify the pointed-to value. Pointer arithmetic allows navigation through arrays by adding or subtracting integer offsets. A null pointer represents the absence of a valid address.

In languages like C and C++, pointers can reference any object, can be incremented or decremented, and can be cast between types. Function pointers store addresses of functions for indirect invocation. Void pointers are untyped and require casting to a concrete type before use.

Safety concerns include dangling pointers (pointing to freed memory), memory leaks from unreleased allocations, and undefined behavior from invalid dereferencing. Mitigations include disciplined memory management, bounds checking where provided, and language features such as smart pointers that automate lifetime management.

Many modern languages provide reference types that behave like pointers but with stronger safety guarantees, or restrict direct pointer manipulation. In C++, smart pointers such as unique_ptr and shared_ptr help manage ownership, while languages with managed runtimes separate memory management from user code.