Computer Science GCSE
Computer Science GCSE glossary
117 key terms for Computer Science GCSE, A to Z, each linked to the topic pages that use it.
A
- Abstraction
- The process of removing unnecessary details and focusing only on the essential characteristics of a problem.AQA, Pearson Edexcel
- Acceptable Use Policy (AUP)
- A document stipulating constraints and practices that a user must agree to for access to a corporate network or the internet.Pearson Edexcel
- Algorithm
- A precise, step-by-step sequence of instructions used to solve a problem or complete a task.AQA, Pearson Edexcel
- Algorithmic Bias
- Systematic and repeatable errors in a computer system that create unfair outcomes, often due to prejudiced training data.Pearson Edexcel
- AND Operator
- A logical operator that returns a value of TRUE only if both of its operands are TRUE.Pearson Edexcel
- Append Mode
- A file handling mode that opens a file and adds new data to the end of it, preserving existing content.Pearson Edexcel
- Argument
- The actual value or data passed into a subprogram when it is called.Pearson Edexcel
- Array
- A structured data type that stores a fixed-size, ordered collection of elements of the same data type under a single identifier.Pearson Edexcel
- Assignment
- The process of storing a value in a variable, typically using the single `=` operator.AQA
- Audit Trail
- A security-relevant chronological record that provides documentary evidence of the sequence of activities that have affected at any time a specific operation,…Pearson Edexcel
- Authentication
- The process of verifying the identity of a user or system, typically using credentials like a username and password.Pearson Edexcel
B
- Bandwidth
- The maximum amount of data that can be transmitted across a network connection in a given amount of time, usually measured in bits per second (bps).Pearson Edexcel
- Binary
- A Base-2 number system that uses only two digits, 0 and 1, to represent all data and instructions in a computer.Pearson Edexcel
- Bit
- The fundamental unit of data in computing, represented as a 0 or a 1.Pearson Edexcel
- Bit Depth (Audio)
- The number of bits used to record the amplitude of a single audio sample.Pearson Edexcel
- Boolean
- A primitive data type that can only hold one of two possible values: True or False.AQA, Pearson Edexcel
- Boolean Expression
- A logical statement that evaluates to either True or False.Pearson Edexcel
- Boolean Logic
- A form of algebra in which all values are reduced to either TRUE (1) or FALSE (0).Pearson Edexcel
- Brute Force Attack
- A trial-and-error method used to obtain information such as a user password, by systematically trying every possible combination.Pearson Edexcel
- Byte
- A group of 8 bits, typically used to represent a single character of text.Pearson Edexcel
C
- Carbon Footprint
- The total amount of greenhouse gases (including carbon dioxide) generated by our actions, including the manufacture and use of devices.Pearson Edexcel
- Casting
- Converting data from one type to another, such as converting a string input into an integer.Pearson Edexcel
- Character Set
- A defined list of characters recognized by the computer hardware and software, where each character is represented by a unique binary number.Pearson Edexcel
- Clock Speed
- The number of fetch-decode-execute cycles the CPU can perform per second, measured in Hertz (usually GHz).Pearson Edexcel
- Code Review
- Systematic examination of computer source code intended to find and fix mistakes overlooked in the initial development phase.Pearson Edexcel
- Colour Depth
- The number of bits used to represent the colour of a single pixel in a bitmap image.Pearson Edexcel
- Compression
- The process of encoding data so that it requires fewer bits to store or transmit than the original representation.Pearson Edexcel
- Computational Thinking
- The use of computers to solve problems, involving logical reasoning, algorithms, decomposition, and abstraction.Pearson Edexcel
- Concatenation
- The process of joining two or more strings together to form a single longer string.Pearson Edexcel
- Condition
- An expression that evaluates to True or False, determining the flow of control in an algorithm.AQA
- Constant
- A named memory location used to store data that cannot be changed while the program is running (usually written in UPPERCASE in Python).Pearson Edexcel
D
- Data Centre
- A large facility used to house computer systems, servers, and associated components like telecommunications and storage systems.Pearson Edexcel
- Data Protection Act 2018
- UK legislation that controls how personal information is used by organisations, businesses, or the government.Pearson Edexcel
- Data Type
- A classification that dictates what kind of data a variable can hold and what operations can be performed on it.Pearson Edexcel
- Decomposition
- Breaking down a large, complex problem into smaller, more manageable sub-problems.AQA, Pearson Edexcel
- Defragmentation
- The process of reorganising data on a magnetic hard drive so that related pieces of data are put back together, improving read/write speeds.Pearson Edexcel
- Denary
- The standard Base-10 number system used by humans, utilizing digits 0-9.Pearson Edexcel
- Denial of Service (DoS) Attack
- A cyber-attack in which the perpetrator seeks to make a machine or network resource unavailable to its intended users by temporarily or indefinitely…Pearson Edexcel
- Device Driver
- A computer program that operates or controls a particular type of device that is attached to a computer.Pearson Edexcel
- Digital Divide
- The gap between demographics and regions that have access to modern information and communications technology, and those that don't.Pearson Edexcel
E
- E-Waste
- Discarded electronic devices and components that are broken, obsolete, or no longer wanted.Pearson Edexcel
- Embedded System
- A computer system built into a larger machine to perform a specific, dedicated function.Pearson Edexcel
- Encryption
- The process of converting readable data (plaintext) into an unreadable format (ciphertext) to prevent unauthorised access.Pearson Edexcel
F
- Firewall
- A network security device or software that monitors and filters incoming and outgoing network traffic based on an organisation's previously established…Pearson Edexcel
- Flowchart
- A visual representation of an algorithm using standard shapes to denote different types of instructions.AQA
- Function
- A subprogram that performs a task and returns a value to the calling code.Pearson Edexcel
G
- GDPR
- General Data Protection Regulation; a legal framework that sets guidelines for the collection and processing of personal information.Pearson Edexcel
H
- Hexadecimal
- A Base-16 number system utilizing digits 0-9 and letters A-F, commonly used as a shorthand for binary.Pearson Edexcel
I
- Integer
- A primitive data type used to store positive or negative whole numbers, including zero.Pearson Edexcel
- Integer Division
- Division in which the fractional part (remainder) is discarded, returning only the whole number quotient.Pearson Edexcel
- Intellectual Property (IP)
- Creations of the mind, such as inventions, literary and artistic works, designs, and symbols.Pearson Edexcel
- IP Address
- A unique string of numbers assigned to each device connected to a computer network that uses the Internet Protocol for communication.Pearson Edexcel
- Iteration
- A programming construct where a block of code is repeated either a set number of times (count-controlled) or until a condition is met (condition-controlled).AQA, Pearson Edexcel
K
- Kibibyte (KiB)
- A unit of data storage equal to 1024 bytes ($2^{10}$ bytes).Pearson Edexcel
L
- Latency
- The time delay between the moment data is transmitted and the moment it is received.Pearson Edexcel
- Legal Liability
- Being legally responsible for something, such as damages or injuries caused by a product or system.Pearson Edexcel
- Local Area Network (LAN)
- A network covering a small geographical area where the hardware is owned by the organisation using it.Pearson Edexcel
- Local Variable
- A variable declared inside a subprogram that is only accessible within that subprogram.Pearson Edexcel
- Logic Error
- An error that occurs when a program runs but produces incorrect or unexpected output due to a flaw in the algorithm.Pearson Edexcel
- Logic Gate
- A physical or simulated device implementing a Boolean function; it performs a logical operation on one or more binary inputs and produces a single binary…Pearson Edexcel
- Lossless Compression
- A data compression algorithm that reduces file size without losing any information, allowing exact reconstruction of the original data.Pearson Edexcel
- Lossy Compression
- A data compression algorithm that permanently discards some data to significantly reduce the file size.Pearson Edexcel
M
- MAC Address
- Media Access Control address.Pearson Edexcel
- Machine Code
- The lowest-level programming language, consisting of binary instructions directly executable by the CPU.Pearson Edexcel
- Malware
- Malicious software designed to disrupt, damage, or gain unauthorised access to a computer system.Pearson Edexcel
- Model
- A simplified representation of a real-world entity or system, created through abstraction.Pearson Edexcel
- Modulus
- An arithmetic operation that finds the remainder after division of one number by another.Pearson Edexcel
- Most Significant Bit (MSB)
- The bit position in a binary number having the greatest value (the leftmost bit).Pearson Edexcel
N
- NOT Operator
- A logical operator that returns the inverse of its given input.Pearson Edexcel
O
- Open Source Software
- Software whose source code is made available to the public, allowing anyone to view, modify, and distribute it.Pearson Edexcel
- Operand
- The value or variable that an operator acts upon.Pearson Edexcel
- Operating System
- System software that manages computer hardware and software resources and provides a user interface.Pearson Edexcel
- Operating System (OS)
- System software that manages computer hardware and software resources and provides common services for computer programs.Pearson Edexcel
- Operator
- A character or set of characters that represents an action or process to be performed on one or more values.Pearson Edexcel
- Operator Precedence
- The set of rules that dictates the order in which different operators are evaluated in a single expression.Pearson Edexcel
- OR Operator
- A logical operator that returns a value of TRUE if at least one of its operands is TRUE.Pearson Edexcel
- Overflow
- An error that occurs when the result of a calculation requires more bits to store than are available in the system.Pearson Edexcel
- Overflow Error
- An error that occurs when the result of a calculation requires more bits to store than are available in the computer's architecture.Pearson Edexcel
P
- Packet
- A small block of data transmitted over a network.Pearson Edexcel
- Parameter
- A variable declared in a subprogram definition that acts as a placeholder for data passed into the subprogram.Pearson Edexcel
- Penetration Testing
- The process of attempting to gain access to resources without knowledge of usernames, passwords and other normal means of access, in order to find…Pearson Edexcel
- Phishing
- A form of social engineering where attackers send fraudulent emails designed to trick people into revealing sensitive information or installing malware.Pearson Edexcel
- Pixel
- The smallest addressable element of a digital image.Pearson Edexcel
- Presence Check
- A validation technique that ensures a field has not been left blank.Pearson Edexcel
- Procedure
- A subprogram that performs a task but does not return a value.Pearson Edexcel
- Proprietary Software
- Software that is legally the property of the creator; users buy a license to use it but cannot modify or distribute the source code.Pearson Edexcel
- Protocol
- A set of rules that govern how devices communicate and transmit data across a network.Pearson Edexcel
- Pseudocode
- A text-based way of representing an algorithm that resembles a simplified programming language but ignores strict syntax rules.AQA
R
- Range Check
- A validation technique that ensures numerical data falls within a specified upper and lower limit.Pearson Edexcel
- Rare Earth Metals
- A group of elements essential for manufacturing modern electronics (e.g., screens, batteries), the mining of which is highly destructive.Pearson Edexcel
- Real / Float
- A primitive data type used to store numbers with a fractional or decimal part.Pearson Edexcel
- Record
- A structured data type that groups together related items of data (fields), which can be of different data types, under a single identifier.Pearson Edexcel
- Register
- A very fast, small capacity memory location situated inside the CPU used to hold temporary data during processing.Pearson Edexcel
- Relational Operator
- A symbol used to compare two values, evaluating to a Boolean (True or False) result.AQA
- Replacement Cycle
- The period of time before a consumer replaces an electronic device with a newer model.Pearson Edexcel
- Robust Program
- A program that can handle unexpected actions or invalid data without crashing.Pearson Edexcel
- Robustness
- The ability of a program to handle unexpected actions or invalid data without crashing.Pearson Edexcel
S
- Sample Rate
- The number of times per second that the amplitude of an analogue sound wave is measured and recorded.Pearson Edexcel
- Scope
- The region of code within which a variable is visible and can be accessed (Global or Local).Pearson Edexcel
- Secondary Storage
- Non-volatile storage used to store programs and data permanently for long-term use.Pearson Edexcel
- Selection
- A programming construct where a decision is made based on a condition, leading to different paths of execution (e.g., IF statements).AQA, Pearson Edexcel
- Sequence
- Programming construct where instructions are executed one after another in order.Pearson Edexcel
- Social Engineering
- The art of manipulating people so they give up confidential information or bypass security procedures.Pearson Edexcel
- Subprogram
- A self-contained block of code (function or procedure) designed to perform a specific task or sub-problem.Pearson Edexcel
- Syntax Error
- An error that occurs when the rules or grammar of the programming language are not followed.Pearson Edexcel
T
- Toxic Leaching
- The process where harmful chemicals from e-waste dissolve in rainwater and contaminate soil and groundwater.Pearson Edexcel
- Trace Table
- A table used to manually track the values of variables as an algorithm executes step-by-step.AQA
- Truth Table
- A mathematical table used in logic to compute the functional values of logical expressions on each of their functional arguments.Pearson Edexcel
- Two's Complement
- A method of representing signed integers (positive and negative numbers) in binary, where the most significant bit acts as a sign bit.Pearson Edexcel
U
- Utility Software
- System software designed to help analyze, configure, optimize or maintain a computer.Pearson Edexcel
V
- Validation
- An automated check to ensure that data entered into a system is sensible, reasonable, and meets specific criteria before processing.Pearson Edexcel
- Variable
- A named memory location used to store data that can change while the program is running.Pearson Edexcel
- Variable Scope
- The region of code within which a variable is visible and can be accessed (Local vs Global).Pearson Edexcel
- Volatile Memory
- Memory that loses its contents when the power is turned off (e.g., RAM).Pearson Edexcel
- Von Neumann Architecture
- A computer architecture where both the program instructions and the data are stored together in the same main memory.Pearson Edexcel
- Vulnerability
- A weakness in a computer system, network, or software that can be exploited by an attacker.Pearson Edexcel
W
- Wide Area Network (WAN)
- A network covering a large geographical area, connecting multiple LANs, typically using leased telecommunications infrastructure.Pearson Edexcel
Where these terms come from
Each definition is one we publish on a Computer Science GCSE topic page or study guide. Open a term to see how each exam board words it and which topic it belongs to. For the full course, go to Computer Science revision or the glossary for every subject.
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