Data Structures: Arrays, Records, Stacks and Queues

A data structure is an organised way of storing and managing data so that it can be accessed and modified efficiently. Choosing the right data structure is essential for writing effective programs.

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Arrays

An array is a collection of elements of the same data type, stored in contiguous (consecutive) memory locations. Each element is accessed using an index (a number that indicates its position).

Key Features of Arrays

• Fixed size — the size of an array is usually defined when it is created
• Same data type — all elements must be the same type (e.g., all integers or all strings)
• Indexed — elements are accessed by their position (index), usually starting from 0

Example

names = ["Alice", "Bob", "Charlie", "Diana"]

Index	0	1	2	3
Value	Alice	Bob	Charlie	Diana

• names[0] returns "Alice"
• names[2] returns "Charlie"

One-Dimensional and Two-Dimensional Arrays

A one-dimensional (1D) array is a single list of values:

scores = [85, 92, 78, 90]