OCR GCSE (9-1) Computer Science Vocabulary Review

Vocabulary flashcards covering core terms, hardware, networking, protocols, security, software, and computational thinking from the OCR GCSE (9-1) Computer Science J277 specification textbook.

Hardware

The physical components that make up a computer system.

Software

The programs that provide instructions for the computer, telling it what to do.

Central Processing Unit (CPU)

The hardware component made of billions of transistors that processes data, carries out instructions, and controls the components of the computer.

Fetch–Execute cycle

The continuous process in which the CPU fetches instructions from memory, decodes them, and then executes them.

Arithmetic Logic Unit (ALU)

The CPU component responsible for arithmetic operations, logical operations, and binary shift operations.

Control Unit (CU)

The CPU component that coordinates the activity of the CPU by fetching and decoding instructions and sending control signals.

Cache memory

High-speed temporary storage located between main memory and the CPU, used to store repeatedly accessed instructions and data.

Registers

High-speed memory locations within the CPU that hold data, instructions, or addresses temporarily for immediate use during the Fetch–Execute cycle.

Von Neumann architecture

A computer design where data and instructions are stored in the same area of memory and are indistinguishable from each other.

Program Counter (PC)

A CPU register that keeps track of the memory address for the next instruction to be fetched and processed.

Memory Data Register (MDR)

A CPU register used to store any data fetched from memory or any data waiting to be transferred and stored in memory.

Memory Address Register (MAR)

A CPU register that stores the location in memory (address) from which data will be fetched or to which data will be written.

Accumulator (ACC)

A CPU register that stores the results of calculations performed by the ALU or stores input and output values.

Clock speed

The frequency at which a CPU fetches and executes instructions per second, measured in hertz ($Hz$) or gigahertz ($GHz$).

Embedded system

A specialized computer system engineered to perform a dedicated function as part of a larger device.

Random Access Memory (RAM)

Volatile main memory required to hold the operating system, running applications, and active data while the computer is turned on.

Read-Only Memory (ROM)

Non-volatile main memory that stores the permanent instructions and data needed to boot up the computer system.

Virtual memory

An area of secondary storage allocated to temporarily act like RAM when main memory becomes full.

Secondary storage

Non-volatile, high-capacity storage used to store programs, files, and data permanently when the computer is turned off.

Latency

The time delay experienced before a packet of data or disk access operation begins.

Bit

The smallest unit of digital data, representing a single binary digit with a value of $0$ or $1$.

Byte

A unit of digital data storage consisting of $8$ bits.

Nibble

A unit of digital data storage consisting of $4$ bits.

Hexadecimal

A base-$16$ number system using the digits $0$ to $9$ and letters $A$ to $F$ to represent denary values from $0$ to $15$.

Character set

The complete collection of characters available to and recognized by a computer system.

ASCII

American Standard Code for Information Interchange; a $7$-bit character encoding standard representing $128$ unique characters.

Unicode

A universal character encoding standard using $16$ or $32$ bits per character, designed to represent characters across all written languages, symbols, and emojis.

Pixel

The smallest individual picture element or block making up a digital image.

Colour depth

The number of bits used per pixel to represent the range of available colours in an image.

Resolution

The number of pixels per unit of distance in an image, typically measured in dots per inch (DPI).

Metadata

Data about data, stored alongside a file to enable a computer to reconstruct or interpret the file correctly.

Sample rate

The number of sound samples taken per second when converting analogue audio to digital form, measured in hertz ($Hz$).

Bit depth (sound)

The number of bits allocated to store each individual audio sample value.

Lossy compression

A data compression technique where least-noticeable data is permanently removed to reduce file size.

Lossless compression

A data compression technique that reduces file size without losing any original data, allowing the original file to be reconstructed exactly.

Local Area Network (LAN)

A computer network covering a small geographical area on a single site, using hardware owned and maintained by the user organization.

Wide Area Network (WAN)

A network that links together LANs across a wide geographical area, using leased or hired telecommunication connections.

Bandwidth

The amount of data that can be transmitted over a network connection in a given period of time.

Client-server network

A network structure where central server computers manage network security, files, and services for connected client devices.

Peer-to-peer (P2P) network

A network structure where connected devices have equal status and share files directly without relying on a central server.

Network Interface Controller (NIC)

A hardware component inside a device that formats data signals and enables connection to a wired or wireless network.

MAC address

Media Access Control address; a unique $48$-bit hardware identifier assigned to a Network Interface Controller during manufacturing.

Wireless Access Point (WAP)

A network hardware device that allows Wi-Fi devices to connect wirelessly to a wired network.

Switch

A LAN hardware device that connects devices together and forwards data packets exclusively to their intended destination device using MAC addresses.

Router

A network device that connects different networks together by inspecting destination IP addresses and routing data packets.

Domain Name Server (DNS)

A database server that translates human-readable domain names into corresponding IP addresses.

Star topology

A network layout where every device connects individually to a central point, such as a switch or hub.

Mesh topology

A network layout where all devices are connected directly or indirectly to one another without using a central switch.

Protocol

An agreed-upon set of rules defining how data is transmitted between devices across a network.

IP address

A unique address assigned to a device on a network to identify its location for data routing.

Malware

Any malicious software installed without a user's knowledge to disrupt functionality, cause damage, or steal data.

Phishing

A social engineering attack using fake emails and websites to trick individuals into revealing sensitive personal data.

SQL injection

A cyberattack technique where malicious SQL expressions are typed into input fields on online forms to bypass security and access a database.

Penetration testing

An authorized, controlled attack performed on a computer system or network to discover security vulnerabilities.

Firewall

A hardware or software security system that inspects and filters incoming and outgoing network traffic based on configured security rules.

Operating System (OS)

Systems software that manages hardware, resources, user interfaces, memory, files, and running applications on a computer.

Utility software

Systems software that performs specific maintenance or housekeeping tasks to help configure, optimize, or maintain a computer system.

Defragmentation

The process of reorganizing data blocks on a magnetic hard drive so that files are stored in adjacent blocks and free space is consolidated.

Decomposition

The computational thinking principle of breaking down a complex problem into smaller, manageable sub-problems.

Abstraction

The computational thinking principle of removing or hiding unnecessary details to focus on important aspects of a problem.

Algorithmic thinking

The process of defining the step-by-step logic, sequence, and decisions required to solve a problem.