Pointer: How to find Data in Memory
Introduction
Un pointer est un type de donnée qui stocke uniquement une adresse mémoire.
On les retrouve principalement dans les langages de programmation bas niveau ou compilés, où la gestion de la mémoire est explicite.
IMPORTANT
A pointer only holds a memory address and an expected interpretation of what is stored there.
It does NOT guarantee that:
the memory is still allocated
the value at that address is valid
This leads to cases like dangling pointers, which point to freed or invalid memory.
Types of pointers
1. Pointeur vers valeur unique (Scalar / Raw Pointer)
Pointer vers une seule valeur en mémoire.
{
addr: memory_address
}2. Pointeur de liste (Slice / Fat Pointer)
Used to represent a sequence of values in memory.
Memory can be contiguous or represented as a view depending on the system.
{
addr: memory_address,
len: number_of_elements,
stride: bytes_between_elements
}Metadata depends on the language and memory model.
3. Pointeur Null (Null Pointer)
A null pointer is a special pointer value that explicitly represents no valid memory address.
It does not point to unknown memory; it points to nothing.
It is often used to indicate:
- absence of value
- uninitialized pointer state
- optional data
Dereferencing
A pointer has one key operation: dereferencing.
Dereferencing means accessing the value stored at the memory address pointed to by the pointer.
*ptr → value at addr(ptr)Depending on the language, dereferencing may allow:
- read access
- write access
- ownership / memory deallocation (in ownership systems)
TL;DR
- pointer → GPS coordinate
- dereference → arriving at the location
- **slice pointer **→ GPS + size (and possibly stride metadata)
- null pointer → “no location”
A pointer is not “data”, it is a tag that indicate where you could find it in memory*