WJEC A-Level Computer Science Unit 1 Fundamentals of Computer Science: a complete overview of data, hardware, software, algorithms, networks and the law

What Unit 1 actually demands

Unit 1 Fundamentals of Computer Science is the broad foundation of the whole course. It moves from the lowest level (how data and instructions are represented in binary) up through data structures, logic, algorithms and programming principles, then out to systems software, hardware architecture, databases, networking, and the legal and ethical context. The unit rewards precise definitions, confident number-base and two's complement work, and the ability to trace algorithms and the fetch-execute cycle by hand.

This guide walks through the ten topics of the unit, then sets out the exam patterns WJEC repeats. Each topic has a matching dot-point page with worked exam questions; this overview ties them together.

Data representation

Everything is stored in binary. WJEC expects fluent conversion between denary, binary and hexadecimal, signed integers in two's complement, binary addition and shifts, and how characters (ASCII, Unicode), sound (sample rate and bit depth) and images (resolution and colour depth) are encoded. The recurring theme is the trade-off between quality and file size.

Data structures

The common structures are arrays and records, the abstract data types stack (last-in first-out) and queue (first-in first-out), lists, binary trees and hash tables. WJEC expects you to trace operations by hand and to justify which structure suits a problem, for example a stack for the call stack or a hash table for fast lookup.

Logical operations

Boolean logic links binary data to physical circuits. The gates (NOT, AND, OR, NAND, NOR, XOR) each have a truth table, Boolean expressions are simplified with identities including De Morgan's laws, and simplification means fewer gates and so cheaper, faster circuits.

Algorithms and programs

Algorithms are designed in pseudocode before coding. The standard searching algorithms are linear and binary search, and the standard sorts are bubble, insertion and merge sort. Efficiency is judged by how the operation count grows with input size, captured by Big-O notation (O(n), O(log n), O(n squared), O(n log n)).

Principles of programming

Programs are built from data types and variables, the three control structures (sequence, selection, iteration), and subroutines (procedures and functions) with parameters passed by value or by reference. Recursion (a routine that calls itself with a base case) is a key idea, often examined by tracing a factorial or sum routine.

Software and systems

Software divides into system software (the operating system and utilities) and application software. The operating system manages memory, processes and CPU scheduling, files and devices. Translators are the compiler, interpreter and assembler. Modes of operation include batch, real-time and multi-user.

Hardware and architecture

The von Neumann architecture stores instructions and data together. The CPU has a control unit, an ALU and registers (program counter, MAR, MDR, current instruction register, accumulator), and the fetch-execute cycle drives execution. Storage forms a hierarchy from registers and cache through RAM to secondary storage, and performance depends on clock speed, cores and cache size.

Organisation of data

Data is held in files (records of fields) or, better, in relational databases linked by primary and foreign keys. Normalisation removes redundancy and anomalies, SQL queries and edits the data (SELECT, INSERT, UPDATE, DELETE, WHERE), and validation (reasonableness) is distinguished from verification (correctness of entry).

Communication and the internet

Networks connect computers: a LAN covers a small area, a WAN spans large distances, and the internet is the largest WAN. Topologies (star, bus, mesh), transmission media and methods, protocols and the TCP/IP stack, and packet switching all feature, with the roles of IP (addressing and routing) and TCP (reliable, ordered delivery) a favourite question.

Security, integrity and the law

Threats include malware, hacking and phishing, countered by antivirus, firewalls, passwords and backups. Encryption scrambles data with a key so intercepted data is unreadable. The legal context covers data protection, computer misuse and copyright legislation, alongside ethical duties around privacy and responsible use.

How Unit 1 is examined

Unit 1 is a written paper contributing 62.5 per cent of the AS and 25 per cent of the full A level. Questions come straight from the specification statements and mix short factual recall with extended explanation. Drill the binary and two's complement conversions, the algorithm traces, the truth tables and the fetch-execute cycle until they are automatic, and learn the definitions precisely because mark schemes reward exact wording.

The ten topics, dot point by dot point

Each topic has a dot-point answer page with worked exam questions and cross-links. Browse them from this unit overview and the subject hub.

For the official specification

WJEC publishes the full specification, past papers and mark schemes at wjec.co.uk. Always revise from the current specification and WJEC's own past papers, because question style is board-specific.