GCSE Computer Science Revision: Systems Architecture, Data Representation, and Networks

Comprehensive vocabulary flashcards covering computer hardware, CPU architecture, memory, secondary storage, operating systems, utilities, data representation (binary, hex, characters, images, sound), compression, and network types and topologies.

Hardware

The physical components that make up a computer system, such as the CPU, motherboard, monitor, and printer.

Software

The programs or applications that a computer system runs, such as an operating system, a word processor, or a video game.

Peripherals

External pieces of hardware connected to a computer system, such as the keyboard, mouse, and printer.

Embedded System

A dedicated computer built into a larger device (such as a dishwasher, microwave, or TV) to monitor and control machinery to achieve a specific task.

Motherboard

The main circuit board in the computer where all the internal hardware components are connected.

Central Processing Unit (CPU)

The 'brain' of the computer system that processes all of the data and program instructions that make the system work.

Control Unit (CU)

The part of the CPU in overall control; it manages the fetching, decoding, and execution of instructions and directs data flow inside and outside the CPU.

Arithmetic Logic Unit (ALU)

The CPU component that performs simple calculations, comparisons, logic operations (AND, OR, NOT), and binary shifts, and contains the accumulator register.

Cache Memory

Very fast, low-capacity, expensive memory located in the CPU that stores regularly used data so the CPU can access it quickly, organized into levels L1, L2, and L3.

Registers

Extremely fast, temporary memory locations inside the CPU that hold tiny bits of data immediately needed by the processor.

Von Neumann Architecture

A computer architecture proposed in 1945 where programs and data are stored together in memory addresses, utilizing a single shared memory for both instructions and data.

Program Counter (PC)

A CPU register that holds the memory address of the instruction to be fetched for each execution cycle, incrementing each time.

Memory Address Register (MAR)

A CPU register that holds any memory address about to be used by the CPU, pointing either to data or to a CPU instruction.

Memory Data Register (MDR)

A CPU register that holds the actual data or instruction fetched from memory, or waiting to be written to memory.

Accumulator

A register in the ALU that temporarily stores the intermediate results of arithmetic and logic operations.

Fetch-Execute Cycle

The continuous cycle where the CPU fetches an instruction from memory using the PC and MAR, decodes it with the CU, and executes it (e.g., using the ALU).

RAM (Random Access Memory)

High-speed, volatile main memory where all data, files, and programs are loaded and stored while they are being actively used by the computer.

Volatile Memory

Temporary storage that requires continuous electrical power to retain its data, losing all contents when the power is switched off.

Non-Volatile Memory

Permanent storage that keeps its contents intact even when the computer system has no electrical power.

Virtual Memory

A designated space on secondary storage used as extra temporary RAM when physical RAM is full, temporarily holding inactive application data.

ROM (Read Only Memory)

Non-volatile memory factory-built into a motherboard chip that can only be read from, containing the instructions needed to boot the computer (the BIOS).

BIOS (Basic Input Output System)

Firmware stored in ROM that runs self-checks, detects hardware, and copies the operating system into RAM when the computer powers on.

Clock Speed

The number of instructions a single processor core can carry out per second, measured in Hertz ($\text{Hz}$) or Gigahertz ($\text{GHz}$).

Overclocking

Configuring a CPU to run at a higher clock speed than its factory-set rate, which risks overheating, crashes, and permanent hardware damage.

CPU Core

An independent processing unit within a CPU capable of processing data and executing instructions independently of other cores.

GPU (Graphics Processing Unit)

A specialised electronic circuit designed to process graphics and images, relieving processing load from the CPU.

Primary Storage

Fast memory areas directly and quickly accessible by the CPU, including registers, cache, ROM, and RAM.

Secondary Storage

Non-volatile long-term storage where operating systems, applications, and user files are stored when not in use, featuring slower read/write speeds than primary storage.

Hard Disk Drive (HDD)

Traditional magnetic internal storage made of spinning magnetised metal disks read and written to by a moving arm.

Solid State Drive (SSD)

Fast, shock-proof, non-volatile secondary storage with no moving parts that relies on flash memory.

Optical Disc

Secondary storage media, such as CDs ($\approx 700\,\text{MB}$), DVDs ($\approx 4.7\,\text{GB}$), and Blu-ray discs ($\approx 25\,\text{GB}$), that read data from microscopic surface indentations using lasers.

Magnetic Tape

High-capacity, sequential-access secondary storage medium housed in cassettes that provides an extremely low cost per gigabyte, used primarily for archiving.

Operating System (OS)

Complex systems software that manages computer hardware, controls resources, provides a user interface, and provides a platform to execute applications.

Device Driver

Software that acts as a translator for the signals passing between the operating system and internal hardware or external peripherals.

Graphical User Interface (GUI)

A visual, interactive user interface designed for everyday users that relies on windows, icons, menus, and pointers (WIMP) or touchscreen gestures.

Command-Line Interface (CLI)

A text-based user interface where the user enters specific typed commands, requiring fewer system resources than a GUI.

Multi-Tasking Operating System

An operating system capable of running multiple applications concurrently by managing memory and dividing CPU processing time among processes.

Memory Buffer

Temporary storage areas used by the OS to manage the flow of data between components or devices that send, receive, and process data at differing speeds.

Multi-User Operating System

An operating system (such as a UNIX server on a mainframe) that allows several different users to access the computer and its resources simultaneously.

Single-User Operating System

An operating system that allows only one user to use the computer system at any single time, even if multiple user accounts are set up.

Defragmentation

Utility software that reorganises data on a magnetic hard drive to put fragmented files back together into contiguous blocks and collect all free space together.

Encryption Software

Utility software that scrambles data using a key to prevent unauthorised third parties from reading it, allowing only intended readers with the key to decrypt it.

Bit

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

Nibble

A data unit consisting of $4\,\text{bits}$, capable of representing $2^4 = 16$ different values.

Byte

A data unit consisting of $8\,\text{bits}$, capable of representing $2^8 = 256$ different values.

Overflow Error

An error that occurs during binary arithmetic when a calculation yields a result requiring more bits than the CPU has available to store it.

Overflow Flag

An indicator used by computers to signal that an overflow error has occurred during an arithmetic calculation.

Binary Shift

An operation that shifts all bits in a binary number left or right, doubling the value for each position shifted left or halving it for each position shifted right.

Hexadecimal

A base-$16$ numbering system using sixteen characters ($0\text{--}9$ and $\text{A--F}$) where each hex character represents a $4\,\text{bit}$ binary nibble.

Character Set

A defined collection of characters that a computer system recognises and translates from their binary representation.

ASCII

A standard $7\,\text{bit}$ character set (stored in $1\,\text{byte}$ with a leading $0$) representing $128$ characters, including the English alphabet, numbers, symbols, and commands.

Unicode

A comprehensive character set using multiple bytes per character to represent every possible symbol and character across all major world languages.

Bitmap Image

A type of digital image made up of a grid of tiny dots called pixels, where the colour of each pixel is represented by a binary code.

Colour Depth

The number of bits used to represent the colour of each pixel in an image, allowing $\text{Total number of colours} = 2^n$ (where $n$ is bits per pixel).

Image Resolution

The number of pixels that make up an image, frequently expressed as $\text{width} \times \text{height}$.

Metadata

Supplementary data stored inside an image file (such as file format, width, height, colour depth, resolution, and date) that enables computers to recreate it accurately.

Sampling

The process of converting a continuous analogue sound wave into digital data by measuring the amplitude of the wave at regular intervals.

Sample Rate

The number of audio amplitude samples captured per second, measured in Hertz ($\text{Hz}$) or kilohertz ($\text{kHz}$).

Bit Depth (Audio)

The number of bits available to store the amplitude value for each recorded audio sample.

Data Compression

The process of reducing file sizes while keeping the compressed file as true to the original file as possible.

Lossy Compression

A compression technique that permanently removes data from a file to dramatically reduce file size and bandwidth requirements, causing a slight loss in quality.

Lossless Compression

A compression technique that temporarily removes data to store the file and restores it perfectly to its original state upon decompression, with no reduction in quality.

Local Area Network (LAN)

A network that covers a small geographical area on a single site, using hardware entirely owned and maintained by the organisation using it.

Wide Area Network (WAN)

A network that connects geographically separate LANs, typically by hiring telecommunications infrastructure such as telephone lines or satellite links.

Network Interface Controller (NIC)

An internal hardware component built into or connected to a device that enables it to establish a wired or wireless network connection.

Network Switch

A hardware device that connects devices on a LAN, receiving data in units called frames and transmitting them directly to the device with the matching MAC address.

Router

A networking device responsible for transmitting data packets between different networks, such as connecting a LAN to the Internet.

Twisted Pair Cable

Ethernet cables, such as CAT 5e and CAT 6, containing four pairs of copper wires twisted together to reduce internal interference.

Fibre Optic Cable

High-performance cables that transmit data as pulses of light over very large distances without experiencing electrical interference or loss of signal quality.

Wireless Access Point (WAP)

A networking device that functions as a wireless switch, allowing Wi-Fi-enabled devices to connect wirelessly to a network.

Bandwidth

The amount of data that can be transferred across a network within a given period of time, typically measured in megabits per second ($\text{Mbps}$).

Client-Server Network

A centralised network model managed by a server that hosts shared files, programs, and user credentials, fulfilling requests sent by client devices.

Peer-to-Peer (P2P) Network

A decentralised network model where all connected devices have equal status and share files directly with one another without a central server.

Star Topology

A network layout where all devices are individually connected to a single central switch that controls and directs network traffic.

Mesh Topology

A decentralised network layout where devices are connected directly or indirectly to one another without a central switch, routing data along the fastest path.