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4.2 Fundamentals of data structures

7 dot points across 7 inquiry questions. Click any dot point for a focused answer with worked past exam questions where available.

How are arrays, records and fields used to store structured data?

Understand arrays (one, two and three dimensional), records and fields, and the difference between static and dynamic data structures.
A focused answer to AQA A-Level Computer Science 4.2.1, covering one, two and three dimensional arrays, records and fields, indexing, and the difference between static and dynamic data structures.
8 min answer →

What is a dictionary and how does it relate to a hash table?

Understand a dictionary as an abstract data type of key-value pairs, its operations, how it is typically implemented using a hash table, and when a dictionary is appropriate.
A focused answer to AQA A-Level Computer Science 4.2.7, covering the dictionary abstract data type of key-value pairs, its operations, its typical implementation using a hash table, and when to use a dictionary.
7 min answer →

What is a graph and how is it represented in a computer?

Understand graphs, vertices and edges, directed, undirected and weighted graphs, and how a graph is represented as an adjacency matrix or an adjacency list.
A focused answer to AQA A-Level Computer Science 4.2.4, covering graphs, vertices and edges, directed, undirected and weighted graphs, and the adjacency matrix and adjacency list representations with their trade-offs.
8 min answer →

How does a hash table give near-instant lookup, and how are collisions handled?

Understand a hash table, the role of a hashing algorithm, how a key maps to an index, the meaning of a collision, and collision-resolution methods such as rehashing and chaining.
A focused answer to AQA A-Level Computer Science 4.2.6, covering hash tables, hashing algorithms, mapping a key to an index, collisions, load factor, and collision-resolution methods including rehashing and chaining.
8 min answer →

How does a queue work and where is it used?

Understand the queue abstract data type, FIFO behaviour, linear, circular and priority queues, and the enqueue and dequeue operations using front and rear pointers.
A focused answer to AQA A-Level Computer Science 4.2.2, covering the queue abstract data type, FIFO behaviour, linear, circular and priority queues, and the enqueue and dequeue operations with front and rear pointers.
8 min answer →

How does a stack work and why is it used for calls and recursion?

Understand the stack abstract data type, LIFO behaviour, the push, pop and peek operations using a stack pointer, and the use of stacks for subroutine calls and recursion.
A focused answer to AQA A-Level Computer Science 4.2.3, covering the stack abstract data type, LIFO behaviour, the push, pop and peek operations with a stack pointer, overflow and underflow, and the use of the call stack.
8 min answer →

What is a tree and how is a binary search tree used?

Understand trees as a connected, undirected graph with no cycles, the terms root, child, parent, leaf and subtree, and the structure and use of a binary search tree.
A focused answer to AQA A-Level Computer Science 4.2.5, covering trees as connected acyclic graphs, the terminology root, child, parent and leaf, binary trees, and the structure and use of a binary search tree.
8 min answer →