Use the technical terms associated with arrays

10.2 Arrays 📚

Arrays are like a row of lockers where each locker holds a single value. They are a fundamental data structure in computer science that lets us store a collection of items of the same type in a single variable.

Key Technical Terms

Mathematical view of an array:

$$A : \{0,1,\dots,n-1\} \to \text{Type}$$

For example, if A[0] = 10, then the first element is 10.

Creating and Using Arrays

1. Declare an array: int[] scores = new int[5]; – creates space for 5 integers.
2. Assign values: scores[0] = 88; scores[1] = 92; …
3. Read values: int first = scores[0];
4. Check size: int n = scores.length;

Example: Locker Analogy 🚪

Imagine a row of 5 lockers labelled 0 to 4. Each locker can hold one book (an element). The whole row is the array books[5]. If you want the third book, you look at locker 2 (zero‑based).

Multi‑dimensional Arrays: The Spreadsheet 📊

A 2‑D array is like a spreadsheet with rows and columns.

Access the element in the second row, first column: matrix[1][0] → 30.

Common Array Operations

• Get element: array[i]
• Set element: array[i] = value;
• Find length: array.length
• Loop through: for (int i = 0; i < array.length; i++) { … }
• Reverse: swap first and last, second and second‑last, etc.

Pitfalls to Avoid ⚠️

• Index Out of Bounds: array[5] in a 5‑element array causes an error.
• Off‑by‑one errors: forgetting that the last valid index is size-1.
• Assuming arrays are always dynamic – many languages require a fixed size.

Quick Quiz

1. What is the index of the first element in a zero‑based array?
2. How many elements can you access in an array of size 10?
3. Write the code to create a 3‑row, 4‑column integer matrix.

Answer Key (for teachers):

• Index 0.
• 10 elements (indices 0–9).
• int[][] matrix = new int[3][4];

Summary

Arrays give you a fast, organised way to store and retrieve data. Remember the key terms: array, element, index, size, bounds, zero‑based indexing, static vs dynamic, multi‑dimensional, jagged, slice, and out‑of‑bounds errors. Mastering these will help you tackle more advanced data structures later.