Pointers and Arrays in C++

Arrays and pointers are closely related in C++. In most expressions, an array name automatically "decays" into a pointer to its first element. This close relationship is why array elements can be accessed both with the familiar arr[i] syntax and with pointer notation *(arr + i) — they compile to the same thing.

When an array arr is used in most expressions (as a function argument, assigned to a pointer, used in arithmetic), it decays into a pointer to its first element: arr behaves the same as &arr[0]. This is why int* p = arr; compiles without needing &arr[0] explicitly. Because of this decay, indexing an array with arr[i] is defined in the language as shorthand for *(arr + i) — first move the pointer i elements forward using pointer arithmetic, then dereference it. Both forms give identical results and even allow the unusual-looking but valid i[arr], since addition is commutative. One key difference: unlike a real pointer, the array name itself is not a modifiable variable — you cannot reassign arr to point elsewhere, though a pointer copy of it (p) can be reassigned freely.