Computer Science 0478 Revision Notes - Unit 3 Hardware

Vocabulary-style flashcards covering Unit 3 Hardware, including computer architecture, storage, input/output devices, and sensors for IGCSE Computer Science 0478.

CPU

A component in the computer used to process data and execute instructions within computer applications, serving as the core component of the computer setup.

Microprocessor

An integrated circuit that is multi-functional.

Architecture

A design of a computer.

Von neumann architecture

An architecture that allows main memory to both store data and instructions in the same place.

Register

High speed memory within the CPU.

Cache

Small, fast memory on the integrated circuit of the CPU used as temporary storage and quick access to frequently executed instructions.

Control Unit (CU)

Fetches instructions and sends signals to other computer components through the control bus.

Program Counter (PC)

Keeps track of the address of the next instruction to be executed.

Accumulator (ACC)

Stores results from the ALU temporarily.

Current instruction register (CIR)

Stores the current instruction being executed or decoded.

Memory Address Register (MAR)

Stores the address of the instruction to be executed.

Arithmetic and logic Unit (ALU)

Performs calculations and expressions within the CPU.

Address Bus

The bus through which the address stored in the Program Counter is sent to the RAM.

Data Bus

The bus through which contents stored in a known address are transferred to the Memory Address Register.

Control Bus

The bus used by the Control Unit to send signals to other computer components.

Fetch Stage (F-E-D Cycle)

The process where the PC address is copied to the MAR, sent to RAM, the PC is incremented, and data is transferred to the CIR.

Decode Stage (F-E-D Cycle)

The process where the instruction is decoded by the ALU and the control unit.

Execute Stage (F-E-D Cycle)

The process where the control unit executes instructions and results are stored in the ACC.

Clock Speed

The number of Fetch-Execute-Decode cycles that can be executed per second, measured in $GHz$.

Core

A copy of a CPU that has its own CU, ALU, ACC, and general use registers, allowing for multi-tasking.

Buses

Parallel wires in a computer circuit that connect components together.

Instruction Sets

Lists of all commands a CPU could use and process through machine language.

Opcode

The operation code that indicates what function should be performed, such as ADD, SUB, LDA, STA, or HLT.

Operand

The part of an instruction that indicates the location or what task the instruction will carry out.

Embedded System

A computer system with a specific function that is small, uses less power, and has a lower cost.

Primary Storage

Storage directly connected to the main processing unit that is expensive and high in speed, such as RAM or ROM.

RAM (Random Access Memory)

Volatile memory used to temporarily store data, files, and operating system parts currently in use.

ROM (Read-Only Memory)

Non-volatile memory that stores the bootstrap, BIOS, and previous programs used by the last boot.

Volatile Memory

Temporary memory that requires power to operate and loses contents when powered off.

Non-volatile Memory

Memory where data can be retained without power.

Bootstrap

A program stored in ROM used during the computer's startup process.

Secondary Storage

Non-volatile storage not directly accessed by the CPU, used for long-term storage, backups, and archiving.

Magnetic Storage (HDD)

Storage containing multiple platters of metal discs coated with a magnetic layer where data is stored in sectors and tracks.

Read-write heads

Components in an HDD that read or change the direction of magnetic coating using magnets or resistive force.

Solid-state drive (SSD)

Durable storage where electrons are stored inside a floating gate with insulation layers.

Floating Gate

A component in SSDs where electrons are forced in or out by applying voltage to a control gate to represent data.

NAND / NOR Tech

The technologies used in SSD, SD cards, and USB drives.

Optical Storage

Storage that uses lasers to read pits and lands, such as CD, DVD, and Blu ray.

Pits and Lands

The physical features on optical discs used by lasers to read data.

Virtual Memory

Memory allocated from secondary storage to extend RAM usage to avoid crashing and reduce the need for physical RAM.

Page

A fixed length of data block used in virtual memory.

Cloud Storage

Data storage owned by third-party servers over the internet.

Public Cloud

Cloud storage where the client and provider are not the same company.

Private Cloud

A dedicated storage system with a firewall used by a client and storage provider that is associated.

Hybrid Cloud

A combination of public and private clouds, often keeping confidential data in private clouds.

Input Devices

Devices that transfer analogue real-world data from the source to the computer.

Keyboard mechanism

A peg pushes through an insulation layer to create a circuit with $2$ conducting membranes when a key is pressed.

Optical Mouse

Works by shining a red LED onto a surface, which is reflected and detected by a CMOS sensor.

Digital Signal Processor (DSP)

In an optical mouse, it calculates mouse coordinates based on reflected light pulses transformed into digital signals.

Microphone

Converts sound waves into digital signals by vibrating a diaphragm and a copper coil within a magnetic field.

Resistive Touchscreen

Composed of $2$ layers of electrically resistive material that complete a circuit when pushed together.

Capacitive Touchscreen

Uses a transparent electrode layer and glass substrate to detect changes in the electrostatic field from human skin conductive touch.

Infra red touchscreen

Uses LEDs to shine infrared rays across a screen forming a grid to detect interruptions by a finger.

Barcode Reader

Uses infrared light and a sensor to sense reflected or absorbed light from long guard bars and data bars.

UPC-A

Universal Product Code version 'A' used in retail with $12$ digits from 0-9.

Code 128

A type of barcode used in transport and shipment tracking.

QR Code

A 2D data arrangement with $3$ large boxes for self-alignment and built-in error checking.

2D Scanner

Shines bright light through a document and uses sensors to convert reflected intensity into electric signals for a digital image.

3D Scanner

Scans solid objects at several points along $x, y, z$ coordinates to produce a three-dimensional image.

Digital Camera

Uses a CCD sensor made of millions of light-sensitive pixels to convert light into electricity.

Charge-coupled device (CCD)

A light-sensitive cell in digital cameras composed of millions of tiny sensors acting as photodiodes.

Pixel

Short for picture element, representing the small components that collectively form a digital image.

Analog-to-Digital Converter (ADC)

A component that converts electrical charges (analogue) into digital image arrays or digital signals.

Output Devices

Hardware components that convert digital data from processors into analogue data.

Digital-to-Analogue Converter (DAC)

Used to convert digital data into analogue signals for output devices.

Actuator

An output device that converts input into mechanical energy to power a mechanism that moves.

LCD Screen

Liquid crystal displays that control light passing through RGB subpixels via liquid crystals.

LED Screen

Screen using Light Emitting Diodes as a backlight instead of fluorescent light used in standard LCDs.

DLP Projectors

Projectors where light shines through a color wheel and reflects off millions of micro mirrors on a DMD chip.

DMD chip

A single chip containing micro mirrors used in DLP projectors to change shades of color.

LCD Projectors

Projectors that shine light through dichroic mirrors and an LCD array to control color and brightness.

Dichroic mirror

A mirror in LCD projectors that reflects only red, green, or blue light.

Thermal Bubble

Inkjet printer technology where heat vaporises ink to create a bubble that pushes a drop out of the nozzle.

Piezoelectric Crystal

Inkjet technology where a crystal vibrates to push ink out of the reservoir.

Laser Printer

Uses a laser to apply electrostatic charges to a print drum, which then picks up toner to transfer to paper.

Heated Fuser

Component in a laser printer that presses against the page to melt toner so it does not smear.

3D Printer

Device that ejects plastic filament through a nozzle to create objects piece-by-piece or via binder printing.

Sensor

An input hardware device that measures physical properties and represents them as data.

Feedback loop

A system where a sensor constantly takes readings for a microprocessor to analyze and adjust mechanisms.

Accelerometer

A sensor that measures acceleration rate, tilt, and vibration.

Proximity Sensor

A sensor used to measure distance and monitor the position of objects in robotics or safety systems.