# Pointer Arithmetic — C Programming Fundamentals: Pointers, Memory and Files

Source: https://www.skillbyai.com/en/c/c-pointer-arithmetic

> Move pointers by whole elements with pointer arithmetic and see how it matches array indexing.

## p + 1 skips a whole element

`p + 1` doesn't add 1 byte — it adds `sizeof(*p)` bytes, moving to the **next element** of that type. This is what makes pointer + array indexing work seamlessly.

## Walking an array via pointer

Adding to a pointer and dereferencing it is equivalent to array indexing.

```c
int nums[3] = {5, 10, 15};
int *p = nums;         // points to nums[0]

printf("%d\n", *p);       // 5
printf("%d\n", *(p + 1)); // 10
printf("%d\n", *(p + 2)); // 15
```

Output:

```
5
10
15
```

## Only within (or one past) the array

Pointer arithmetic is only well-defined within an array's bounds, or one element past the end (for comparison, never dereferenced). Going further is undefined behavior.