Computing Glossary

Every key term across Key Stage 3, GCSE and A Level computing, each defined in one sentence you could write in an exam.

Definitions written the way a mark scheme wants them: one sentence, precise, and using the vocabulary the examiner is looking for. Type in the box to filter, and cover the definition and say it out loud before you read it.

Abstraction All: Removing detail that is not relevant to the problem being solved, so that only what matters remains.
ACID KS5: Atomicity, Consistency, Isolation and Durability, the guarantees a reliable database transaction provides.
Algorithm All: A finite sequence of unambiguous, correctly ordered steps that solves a problem.
ALU KS4: Arithmetic Logic Unit. Performs all arithmetic and logical operations inside the processor.
Amdahl's law KS5: The principle that the speedup from parallel processing is limited by the fraction of a task that must remain sequential.
ASCII KS3: A 7 bit character set representing 128 characters, sufficient for English text.
Bandwidth KS4: The amount of data that can be transmitted over a connection in a given time.
Big O notation KS5: A description of how an algorithm's time or memory use grows as its input grows, in the worst case.
Binary KS3: Base 2. A number system using only 0 and 1, matching the two states of electronic components.
Binary search KS4: Finding an item in sorted data by repeatedly halving the search range. O(log n).
Bit KS3: A binary digit, either 0 or 1. The smallest unit of data.
Boolean KS3: A data type with exactly two values, true and false.
Bubble sort KS4: Repeatedly comparing adjacent items and swapping them if out of order. Simple but O(n squared).
Byte KS3: Eight bits.
Cache KS4: Small, very fast memory close to the processor holding recently and frequently used data and instructions.
Casting KS3: Converting a value from one data type to another, such as int() or str() in Python.
CIR KS5: Current Instruction Register. Holds the instruction currently being decoded and executed.
Client server KS4: A network model where central servers provide resources to client computers.
Colour depth KS3: The number of bits used to store the colour of each pixel. n bits gives 2 to the power n colours.
Compiler KS4: A translator converting an entire program to machine code before execution, producing an executable.
Compression KS4: Reducing file size, either lossily by discarding data or losslessly by encoding it more efficiently.
Concurrency KS5: Carrying out parts of a task at the same time, or appearing to by switching rapidly between them.
Constant KS3: A named value fixed when set and not changeable afterwards.
Control Unit KS4: The processor component that decodes instructions and generates the control signals coordinating everything else.
Cookie KS3: A small file stored on a device by a website, used to remember settings or to track browsing.
Data Protection Act 2018 KS3: UK legislation governing how organisations collect, store and use personal data.
De Morgan's laws KS5: The rules that the negation of an AND is the OR of the negations, and vice versa.
Deadlock KS5: A state where two processes each hold a resource the other needs, so neither can proceed.
Decomposition All: Breaking a large problem into smaller sub problems that are easier to solve and test.
Defensive design KS4: Writing a program so it continues to work correctly despite unexpected input or misuse.
Denary KS3: Base 10, the everyday number system. Also called decimal.
Digital divide KS3: The gap between those with reliable access to technology and the internet and those without.
Dijkstra's algorithm KS5: An algorithm finding the shortest path in a weighted graph with non negative weights.
DNS KS4: Domain Name System. Resolves human readable domain names into IP addresses.
Encapsulation KS5: Bundling data with the methods that act on it and controlling access, so an object protects its own state.
Encryption KS4: Scrambling data with a key so that intercepted data cannot be understood.
Fetch decode execute KS4: The cycle a processor repeats continuously to run instructions.
Firewall KS4: Hardware or software inspecting network traffic and blocking anything that does not meet its rules.
Hash function KS5: A function producing a fixed size output from any input, designed to be one way.
Hash table KS5: A structure using a hash function to map keys directly to array positions, giving average constant time lookup.
Heuristic KS5: A rule of thumb producing a good enough solution quickly, without guaranteeing the optimal one.
Hexadecimal KS3: Base 16, using 0 to 9 and A to F. One hex digit represents four bits.
HTTPS KS4: The encrypted version of HTTP, protecting web traffic from being read if intercepted.
Interpreter KS4: A translator converting and executing a program one statement at a time, each time it runs.
Interrupt KS5: A signal requesting the processor's attention, checked at the end of each fetch decode execute cycle.
IP address KS4: An address identifying a device on a network, assigned by the network and used for routing between networks.
Iteration KS3: Repeating a set of instructions, either a fixed number of times or until a condition is met.
Linked list KS5: A structure of nodes each holding data and a pointer to the next, allowing dynamic size and cheap insertion.
Lossless compression KS4: Compression that reduces size without losing any data, so the original is restored exactly.
Lossy compression KS4: Compression that permanently removes data, giving much smaller files at the cost of quality.
MAC address KS4: A unique address assigned to network hardware by its manufacturer, used within a local network.
Malware KS3: Any software written with the intention of causing harm.
Merge sort KS4: A divide and conquer sort with consistent O(n log n) time but O(n) additional space.
Metadata KS4: Data about data, such as the dimensions and colour depth stored with an image.
MOD KS3: The modulus operator, which returns the remainder after a division.
Normalisation KS5: Organising a database to remove redundancy and eliminate update, insertion and deletion anomalies.
Object KS5: A specific instance created from a class, holding its own data and sharing the class's methods.
Operating system KS4: System software managing hardware and software and providing an environment for applications.
Overflow KS4: An error where a result requires more bits than are available, so the stored value is wrong.
Packet KS3: A small unit of data sent across a network, carrying addresses and a sequence number.
PageRank KS5: An algorithm ranking pages by importance derived from the weighted link structure of the web.
Paging KS5: Dividing memory into fixed size pages mapped to equally sized physical frames.
Peer to peer KS4: A network model where every computer is equal, acting as both client and server.
Phishing KS3: A fraudulent message imitating a trusted organisation to obtain personal information.
Pipelining KS5: Overlapping the fetch, decode and execute stages of consecutive instructions to raise throughput.
Pixel KS3: Picture element. The smallest single point of colour in a bitmap image.
Polymorphism KS5: Objects of different classes responding to the same method call, each in their own way.
Precondition KS5: A condition that must be true before a subroutine is called for it to work correctly.
Protocol KS4: An agreed set of rules governing how data is transmitted between devices.
RAM KS3: Random access memory. Volatile main memory holding the operating system, running programs and data in use.
Recursion KS5: A subroutine calling itself, with a base case that stops the process.
RISC KS5: Reduced Instruction Set Computer. Few simple fixed length instructions, pipelining well and using less power.
ROM KS3: Read only memory. Non volatile memory holding the boot program available at switch on.
Sampling KS3: Measuring the amplitude of a sound wave at regular intervals and storing each value in binary.
Selection KS3: Choosing between different paths through a program based on a condition.
SQL KS4: Structured Query Language, used to search and manipulate data held in a database.
Stack KS5: A last in first out data structure supporting push and pop. Used for the call stack and backtracking.
Subroutine KS4: A named block of code performing one task, callable from elsewhere. A function returns a value, a procedure does not.
Two's complement KS5: A signed integer representation where the most significant bit carries a negative place value.
Unicode KS3: A character set using 16 or more bits per character, covering over a million characters from all major scripts.
Validation KS3: Checking that input data is sensible and in the expected format before the program uses it.
Variable KS3: A named memory location holding a value that can change while the program runs.
Virtual memory KS4: An area of secondary storage used as an extension of RAM when physical memory is full.
Von Neumann architecture KS4: A design where instructions and data share one memory, fetched one instruction at a time.