pointer

Pointer refers to a variable that stores a memory address. Unlike a value, a pointer identifies a location in memory where a value resides. Pointers are central to low‑level programming and enable indirect access, dynamic memory management, and the construction of data structures.

In languages such as C and C++, pointers support dereferencing to read or write the value at the referenced address and the address-of operator to obtain a pointer to a value. They can be used for arrays, functions, and dynamically allocated memory. Pointer arithmetic enables navigation through contiguous memory blocks, but can lead to undefined behavior if misused. A null pointer represents a guaranteed non-target; using a null pointer in dereferencing is a common source of runtime errors. Void pointers provide a generic address that can be cast to any object type.

Common pitfalls include dangling pointers (pointing to freed memory), wild pointers (uninitialized pointers), and memory leaks when allocated memory is not released. Safe usage patterns emphasize clear ownership, bounds, and the use of higher-level abstractions.

Many modern languages provide safe abstractions instead of raw pointers. C++ introduces smart pointers that manage lifetime and ownership, such as unique_ptr and shared_ptr. Other languages provide references or handles with managed memory; Rust offers borrowing references and safe pointers with strict ownership rules; Java and C# use references managed by a garbage collector with no pointer arithmetic.

Pointers remain a foundational concept in systems programming, enabling efficient data structures and low-level control, while present risks require disciplined use and safer abstractions.