Arrays and Lists

An array (called a list in Python) is a data structure that stores multiple values under a single identifier. Arrays are essential for managing collections of data efficiently and are a key topic in GCSE Computer Science (AQA 3.2 / OCR J277 2.2).

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What Is an Array?

An array is an ordered collection of elements of the same data type, stored in contiguous memory locations. Each element is accessed by its index (position number).

Index	0	1	2	3	4
Value	"Alice"	"Bob"	"Charlie"	"Diana"	"Eve"

Key Point: In most programming languages (including Python), array indices start at 0. This is called zero-based indexing. In AQA pseudocode, indices also start at 0.

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Declaring Arrays

Pseudocode

names ← ["Alice", "Bob", "Charlie", "Diana", "Eve"]
scores ← [85, 72, 91, 64, 78]

Python

names = ["Alice", "Bob", "Charlie", "Diana", "Eve"]
scores = [85, 72, 91, 64, 78]

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Accessing Elements

Use the index to read or modify a specific element:

Pseudocode