# Pointers & Arrays — C Programming

Source: https://www.geekswithgeeks.com/en/c/c-pointers-arrays

> An array name decays into a pointer to its first element.

## Array name = address of element 0

In most expressions, an array's name **decays** into a pointer to its first element. That's why `arr` and `&arr[0]` are interchangeable, and `arr[i]` is really `*(arr + i)`.

## Same result, two notations

Indexing and pointer-offset dereferencing give identical results.

```c
int arr[4] = {1, 2, 3, 4};
printf("%d\n", arr[2]);
printf("%d\n", *(arr + 2));  // same thing
```

Output:

```
3
3
```

## But arrays aren't pointers

`sizeof(arr)` gives the whole array's byte size, while `sizeof` on a pointer gives just the pointer's size (usually 8 bytes). Decay only happens when the array is *used*, not when it's `sizeof`'d.