Static Arrays

A static array is a fixed-size sequence of elements stored in contiguous memory. The size is decided up front and can't change.

Key Properties

• Contiguous memory — every element sits right next to the previous one
• Fixed size — allocated once, never grows
• O(1) random access — jump to any index instantly

Reading and Writing

Because elements are laid out contiguously, the address of arr[i] is easy to compute:

address(arr[i]) = base_address + i * size_of_element

That formula takes constant time, which is why reads and writes are O(1):

int[] nums = new int[5];
nums[2] = 42;        // O(1) write
int x = nums[2];     // O(1) read

Insertion and Deletion

The catch: inserting or deleting anywhere except the end is slow. To insert at index i, you have to shift every element from i onward one slot to the right. That's O(n).

| Operation | Time | |---|---| | Read / write by index | O(1) | | Insert at end (if space) | O(1) | | Insert in middle | O(n) | | Delete from middle | O(n) |

Note: Languages like Java and C use static arrays directly. Python and JavaScript give you dynamic arrays by default — we'll see those next.