GCSE Computer Science

Overview

For parents: Each exam board teaches Computer Science slightly differently. Ask the school which board they use — it's the key to revising the right content.

Topics

Computer Science key terms

Original definitions for core course vocabulary, informed by the references below. Not an official or exhaustive board-specific glossary.

40 of 40 terms

Bit

A binary digit with a value of either 0 or 1.

Data representation

Byte

A group of eight bits.

Data representation

Binary

A base-2 number system that uses only the digits 0 and 1.

Data representation

Hexadecimal

A base-16 number system using digits 0–9 and letters A–F.

Data representation

Overflow

An error condition in which a calculated value exceeds the range representable using the allocated bits.

Data representation

Character set

A defined collection of characters with a unique code assigned to each character.

Data representation

Pixel

The smallest individually represented picture element in a bitmap image.

Data representation

Colour depth

The number of bits used to represent the colour of each pixel.

Data representation

Sampling rate

The number of measurements of an analogue signal taken per second when digitising it.

Data representation

Lossless compression

Reducing a file's size in a way that allows the original data to be reconstructed exactly.

Data representation

Central processing unit

The processor that executes instructions and controls the processing of data in a computer.

Computer systems

Arithmetic logic unit

The part of the processor that performs arithmetic calculations and logical operations.

Computer systems

Control unit

The part of the processor that coordinates instruction execution and directs the movement of data and control signals.

Computer systems

Register

A small, fast storage location within the processor used to hold data, addresses or instructions temporarily.

Computer systems

Random access memory

Volatile main memory that holds programs and data currently in use.

Computer systems

Read-only memory

Non-volatile memory used to retain instructions or data that are not normally changed during operation.

Computer systems

Cache memory

Small, fast memory that stores frequently or recently used data and instructions to reduce processor waiting time.

Computer systems

Secondary storage

Non-volatile storage used to retain programs and data when power is switched off.

Computer systems

Operating system

System software that manages hardware resources and provides services and an interface for users and applications.

Computer systems

Embedded system

A computer system built into a larger device to perform a dedicated function.

Computer systems

Local area network

A network connecting devices over a relatively small geographical area, such as one school site.

Networks and security

Wide area network

A network spanning a large geographical area, often linking multiple local networks.

Networks and security

Packet

A unit of transmitted data containing a payload and control information such as addressing details.

Networks and security

Protocol

An agreed set of rules governing communication between devices.

Networks and security

IP address

An address used to identify a network interface and route data on an IP network.

Networks and security

Domain name system

A distributed system that translates domain names into IP addresses.

Networks and security

Encryption

Transforming readable data into an encoded form using an algorithm and a key to protect confidentiality.

Networks and security

Firewall

Hardware or software that monitors and filters network traffic according to security rules.

Networks and security

Phishing

A deceptive attempt to obtain sensitive information by impersonating a trusted person or organisation.

Networks and security

Malware

Software deliberately designed to damage systems, disrupt operation or gain unauthorised access.

Networks and security

Algorithm

A finite, ordered set of unambiguous steps for solving a problem or completing a task.

Algorithms and programming

Decomposition

Breaking a complex problem into smaller, more manageable subproblems.

Algorithms and programming

Abstraction

Removing unnecessary detail to focus on the features needed to solve a problem.

Algorithms and programming

Variable

A named storage location whose value can change during program execution.

Algorithms and programming

Constant

A named value that is not intended to change during program execution.

Algorithms and programming

Selection

A programming construct that chooses which instructions to execute according to a condition.

Algorithms and programming

Iteration

Repeated execution of a set of instructions, controlled by a count or condition.

Algorithms and programming

Array

An indexed collection of elements of the same data type stored under one identifier.

Algorithms and programming

Validation

Checking whether input data meets specified rules, without proving that it is factually correct.

Algorithms and programming

Verification

Checking that data has been copied or entered accurately, for example by double entry or visual comparison.

Algorithms and programming

Exams

Add your exam dates in My Exams and see a countdown for every paper on your dashboard.

Revision

Tell GCSE.es which Computer Science topics feel weak. Your dashboard then picks a short, timed next step — learn the key idea, check yourself, review mistakes.

Practice

• ✓ Key terms you tap to reveal
• ✓ Quick multiple-choice quizzes
• ✓ 3, 6, 9 and 12-mark exam-style questions
• ✓ Marking with feedback and a model answer

Available free inside your GCSE journey. Questions are written by GCSE.es, not taken from real past papers.

Resources

Short, focused tasks for the Computer Science topics you find hardest — learn the key idea, check yourself, then try a marked exam-style question.