IGCSE Computer Science – Hardware & Systems Vocabulary

A comprehensive set of vocabulary flashcards covering CPU architecture, storage, sensors, networks and related hardware concepts from the lecture notes.

Central Processing Unit (CPU)

A hardware component that processes all data and instructions during the fetch-decode-execute cycle

Microprocessor

Smaller-scale integrated circuit that performs many CPU functions in dedicated devices.

Embedded System

Computer system built into a device to perform a dedicated function, e.g., washing machine control.

Fetch-Decode-Execute Cycle

Repeating process a CPU uses to retrieve, interpret and run each instruction.

Von Neumann Architecture

Computer design in which programs and data share the same memory and buses.

Program Counter (PC)

CPU register that holds the address of the next instruction to be fetched.

Memory Address Register (MAR)

Register that stores the address in RAM of the data or instruction to be accessed.

Memory Data Register (MDR)

Register that temporarily holds the data or instruction fetched from or written to memory.

Current Instruction Register (CIR)

Register within the control unit that holds the instruction currently being decoded/executed.

Control Unit (CU)

CPU component that coordinates activities and decodes instructions.

Arithmetic Logic Unit (ALU)

Part of the CPU that performs mathematical and logical operations.

Accumulator (ACC)

Special ALU register that stores interim results of calculations.

Address Bus

Set of wires that carries memory addresses between CPU and RAM.

Data Bus

Set of wires that transmits data and instructions between components.

Control Bus

Wires that carry control signals to coordinate CPU and peripheral operations.

Core (CPU)

Independent processing unit capable of running its own fetch-decode-execute cycle.

Clock Speed

Number of cycles a CPU performs each second, measured in hertz (Hz/GHz).

Cache (CPU)

Fast on-chip memory storing frequently used data/instructions to speed processing.

Input Device

Hardware used to enter data into a computer, e.g., keyboard or scanner.

Output Device

Hardware that presents processed data, e.g., monitor, printer, speaker.

Sensor

Input device that captures analogue data from its immediate environment for processing.

Acoustic Sensor

Sensor that measures sound levels in the environment.

Accelerometer

Sensor that detects static or dynamic acceleration forces, e.g., phone orientation detection.

Flow Sensor

Sensor measuring rate of liquid, gas or steam movement through a pipe or channel.

Gas Sensor

Sensor that detects presence or concentration of a specific gas, e.g., carbon monoxide.

Humidity Sensor

Sensor measuring moisture content in the air.

Infra-Red Sensor

Sensor detecting IR radiation; often used for motion or heat detection.

Level Sensor

Sensor that checks whether a substance (often liquid) reaches a set height or volume.

Light Sensor

Sensor measuring ambient or direct light levels for automatic lighting systems.

Magnetic Field Sensor

Sensor that detects disturbances in magnetic fields, e.g., vehicle counting loops.

Moisture Sensor

Sensor measuring water content in materials such as soil.

pH Sensor

Sensor determining alkalinity or acidity of a substance.

Pressure Sensor

Sensor measuring force exerted by solids, liquids or gases.

Proximity Sensor

Sensor that detects how close an object is without physical contact.

Temperature Sensor

Sensor that measures heat energy of an object or environment.

Primary Storage

Memory directly accessed by the CPU (RAM and ROM).

Secondary Storage

Non-volatile storage not directly accessed by CPU, e.g., HDD, SSD, optical disc.

Random Access Memory (RAM)

Volatile primary memory holding data and programs currently in use.

Read Only Memory (ROM)

Non-volatile primary memory containing permanent start-up instructions (BIOS).

Magnetic Storage

Secondary storage that uses magnetised spots on spinning platters to store bits, e.g., HDD.

Optical Storage

Secondary storage that uses lasers to read/write pits and lands on disks such as CDs or DVDs.

Solid-State Storage

Secondary storage using semiconductor transistors (flash memory) with no moving parts.

Semiconductor Chip

Electronic circuit on silicon containing transistors for solid-state storage or processing.

Virtual Memory

Hard-drive section used as temporary extension of RAM when RAM is full.

Page (Virtual Memory)

Block of data moved between RAM and virtual memory during paging.

Cloud Storage

Remote data storage service provided by third-party servers accessed via the Internet.

Server

Computer that provides services or resources to other machines on a network.

Network

Two or more devices connected to share data and resources.

Network Interface Card (NIC)

Hardware inside a device that enables connection to a network (wired or wireless).

Media Access Control (MAC) Address

Unique hardware identifier burned into every NIC by the manufacturer.

Router

Network device that forwards data packets toward their destination using address information.

Data Packet

Structured unit of data transmitted across a network containing payload and addressing info.

Internet Protocol (IP) Address

Logical address assigned to a device for identification on a network.

IPv4

32-bit IP address format written as four decimal numbers separated by dots (e.g., 192.168.1.1).

IPv6

128-bit IP address format written in hexadecimal segments separated by colons.

Static IP Address

IP address that remains constant each time a device connects to the network.

Dynamic IP Address

IP address that may change each time a device joins a network.

Transmission Media

Cabling or wireless channel through which data travels in a network.

Hard Disk Drive (HDD)

Magnetic storage device with spinning platters and read/write heads.

Optical Disc (CD/DVD/Blu-ray)

Removable optical media on which lasers burn pits to represent data.

Solid State Drive (SSD)

High-speed solid-state storage device using NAND flash memory.

USB Flash Memory Drive

Portable solid-state storage device that plugs into a USB port.

Actuator

Output component that produces physical movement or action, often controlled by a sensor system.

Digital Light Processing (DLP) Projector

Output device that creates images using micro-mirrors and light projection.

Liquid Crystal Display (LCD)

Flat-panel output technology that uses liquid crystals modulated by electric current to display images.

Light Emitting Diode (LED) Screen

Display that uses LEDs as backlight or pixels for visual output.

3D Printer

Output device that builds three-dimensional objects layer by layer from digital models.

Instruction Set

Complete list of machine-code commands a CPU can understand and execute.

Overclocking

Running a CPU at a higher clock speed than the manufacturer’s specification to increase performance.