Computer Science IGCSE 0478 C3

Chapter 3

What is the primary role of the CPU in a computer?

Processes instructions and data for output. It's the device's brain.

Name three types of devices that have a CPU.

Laptops, Desktops, Mobile Devices.

Describe the data flow involving the CPU when a user interacts with a computer.

User inputs data; CPU processes it; results outputted.

What are the key components that make up a CPU?

Control Unit (CU), Arithmetic and Logic Unit (ALU), Registers, Buses, System Clock.

What are the three main purposes of the CPU?

Processes data/executes instructions, carries out calculations, performs logical operations.

Which computer architecture model includes the CPU as a central component?

Von Neumann architecture.

What is a microprocessor?

An integrated circuit on a single chip containing the CPU and sometimes other components, for compact data processing.

What are the common applications for microprocessors?

General-purpose computer systems and embedded systems.

Who introduced the Von Neumann Architecture and when?

John von Neumann, mid-1940s.

What are the main features of the Von Neumann Architecture?

CPU concept, direct CPU memory access, stored programs/data in memory, ordered instruction execution. It shows how memory, I/O, and processor work together.

What is the function of the Arithmetic and Logic Unit (ALU) within the CPU?

Performs arithmetic and logical operations (AND, OR, NOT).

Describe the function of the Control Unit (CU) in the CPU.

Coordinates and controls CPU activities, decodes/executes instructions, directs timing.

What are Registers in a CPU, and what is their general purpose?

Small storage locations holding data for the fetch-execute cycle.

What is the specific role of the Program Counter (PC) register?

Stores address of next instruction to fetch.

What is the specific role of the Memory Address Register (MAR)?

Stores address of data being fetched/written to memory.

What is the specific role of the Memory Data Register (MDR)?

Stores data fetched from/being written to memory.

What is the specific role of the Current Instruction Register (CIR)?

Stores current instruction being decoded/executed.

What is the specific role of the Accumulator (ACC) register?

Stores ALU calculation results.

What is the purpose of the System Clock in the CPU?

Synchronizes CPU operations using timing signals.

What is the general function of System Buses?

Transfer data and control signals.

Name the three common types of system buses and state their directionality.

Address bus (unidirectional), Data bus (bidirectional), Control bus (bidirectional).

What is RAM (Random Access Memory) in terms of primary memory?

Volatile, primary memory holding current data/instructions, directly accessed by CPU.

Describe the steps in the Fetch Stage of the Fetch-Decode-Execute cycle.

PC sends address to MAR via address bus; MAR sends address to RAM via address bus; RAM sends data to MDR via data bus; MDR sends data to CIR via data bus.

What happens during the Decode Stage of the Fetch-Decode-Execute cycle?

CU decodes instruction using machine code instruction set.

What happens during the Execute Stage of the Fetch-Decode-Execute cycle?

CU sends instructions; ALU performs arithmetic (results to ACC) if needed, using control bus.

What is a Core in a CPU and how does it affect performance?

A processor unit. More cores = more multitasking.

What is Cache in a CPU and how does it affect performance?

Small, fast memory inside CPU. Larger cache = faster data access.

What is Clock Speed in a CPU and how does it affect performance?

CPU speed in GHz. Higher speed = more instructions per second.

What is an instruction set for a CPU?

A list of all commands a CPU can process, in machine code.

What are Opcode and Operand in the context of an instruction set?

Opcode is the operation, Operand is its location.

What is the primary purpose of an embedded system?

To perform a dedicated function.

Name three characteristics of an embedded system.

Has microprocessor, built into larger device, works automatically, user can't reprogram, real-time, small, low power, low cost.

Provide three examples of devices that commonly use embedded systems.

Washing machines, cars, security systems.

How does an embedded system differ from a general-purpose computer?

Embedded performs specific function; general-purpose performs many.

What is an input device and why is it required?

Hardware allowing user interaction, converts inputs to digital data for processing.

What is a barcode scanner and where is it commonly used?

Reads 1D parallel lines; used in supermarkets, warehouses, libraries.

Why are barcode scanners used?

Quick, accurate retrieval of product details for stock/checkout.

What is a digital camera and where is it commonly used?

Captures photos/videos digitally; used in photography, smartphones, webcams.

Why are digital cameras used?

For high-quality visual content.

What is a keyboard and how does it input data?

Inputs text/commands by pressing keys, converting to digital signals.
Q

Where are keyboards commonly used?

Computers, tablets, laptops.

Why are keyboards used?

To type, enter data, control software.

What is a microphone and how does it work?

Captures analogue sound, converts to digital signals for input.
Q

Where are microphones commonly used?

Recording studios, smartphones, computers.

Why are microphones used?

Audio recording, voice communication.

What is an optical mouse and how does it work?

Moves cursor based on hand movements, uses red LED/CMOS sensor.

Where are optical mice commonly used?

Computers, laptops.
Q

Why are optical mice used?

Precise control and navigation.

What is a QR (Quick Response) code scanner and what are QR codes?

Reads 2D matrix of squares (QR codes) for information access.

Where are QR code scanners commonly used?

Retail shops, mobile phones.

Why are QR code scanners used?

Quickly retrieve data (e.g., website links).

How does a Resistive Touch Screen detect touch?

Pressure connects two conductive layers, completing a circuit.

Where are resistive touch screens commonly used?

ATMs, older smartphones/tablets.

Why are resistive touch screens used?

Direct device interaction.

How does an Infra-red Touch Screen detect touch?

Touch interrupts invisible infrared light beams across the screen.
Q

Where are infra-red touch screens commonly used?

Kiosks, large touch displays.
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Why are infra-red touch screens used?

Accurate touch detection, good in various lighting.

How does a Capacitive Touch Screen detect touch?

Changes in electrical charge on the screen surface from touch.

Where are capacitive touch screens commonly used?

Modern smartphones, tablets, touch monitors.
Q

Why are capacitive touch screens used?

Smooth, responsive multi-touch experience.

What is a Two-Dimensional (2D) Scanner and what is its purpose?

Captures flat 2D images, digitizes hard copy documents/photos.

Where are 2D scanners commonly used?

Offices, libraries, schools.

What is a Three-Dimensional (3D) Scanner and what is its purpose?

Captures detailed 3D shapes/dimensions, creates digital object models.

Where are 3D scanners commonly used?

Manufacturing, design, medical imaging.

What is an output device and why is it required?

Hardware receiving info from computer to present to user, enables communication of processed data.

What is an Actuator and what is its function?

Converts energy to motion, performs physical tasks based on instructions.
Q

Where are actuators commonly used?

Factories, robotics.

Why are actuators essential?

Essential in any system requiring movement.

How does an Inkjet Printer work and where is it commonly used?

Sprays tiny ink droplets from a moving print head; used in homes, schools, offices.

What is an advantage of an inkjet printer?

Low cost.

How does a Laser Printer work and where is it commonly used?

Heat from laser fuses toner onto paper; used in offices, schools.

What are the advantages of a laser printer?

High-quality prints, fast speed.

What is a Light Emitting Diode (LED) Screen and how does it display images?

Displays images/video using tiny LEDs, brightness controlled by current.

Where are LED screens commonly used?

Televisions, computer monitors, smartphones.

What are the advantages of an LED screen?

High-quality, bright, energy efficient, thin.

What is a Liquid Crystal Display (LCD) Screen and how does it work?

Uses liquid crystals with a backlight to display images.

Where are LCD screens commonly used?

Televisions, monitors, smartphones, laptops.

What are the advantages of an LCD screen?

Energy efficient, thin, sharp images, lightweight, low power consumption.

What is a Speaker and what is its purpose?

Converts electrical signals to analogue sound waves; essential for sound output.

Where are speakers commonly used?

Televisions, radios, smartphones.

What is a 3D Printer and how does it work?

Adds thin layers of plastic to form 3D objects, based on inkjet/laser tech.

Where are 3D printers commonly used?

Manufacturing, medicine.

Why are 3D printers used?

Create prototypes, custom parts.

What does an Acoustic sensor measure and what is a typical use?

Sound levels; industrial machinery sound changes, noise pollution, security.

What does an Accelerometer measure and what is a typical use?

Acceleration rate, tilt, vibration; vehicle safety features, mobile device orientation.

What does a Flow sensor measure and what is a typical use?

Rate of gas/liquid/powder flow; detecting flow changes in water pipes.

What does a Gas sensor measure and what is a typical use?

Presence of a gas (e.g., carbon monoxide); gas levels in confined spaces, leak fixing.

What does a Humidity sensor measure and what is a typical use?

Levels of water vapour; monitoring humidity in greenhouses.

What does an Infra-red sensor measure and what is a typical use?

Motion or heat source; security systems, emergency services detecting people.

What does a Level sensor measure and what is a typical use?

Liquid levels; petrol in car tank, water in tank, leak detection.

What does a Light sensor measure and what is a typical use?

Light levels; automatically switching on streetlights/headlights.

What does a Magnetic field sensor measure and what is a typical use?

Presence/strength; anti-lock braking, monitoring rotating machinery.

What does a Moisture sensor measure and what is a typical use?

Presence/levels of moisture; soil moisture, dampness in buildings.

What does a pH sensor measure and what is a typical use?

Acidity or alkaline; monitoring soil for growing, chemical processes.

What does a Pressure sensor measure and what is a typical use?

Gas, liquid, or physical pressure; tire pressure, manufacturing pipe pressure.

What does a Proximity sensor measure and what is a typical use?

Distance; object position in robotics, safety systems preventing collisions.

What does a Temperature sensor measure and what is a typical use?

Temperature; maintaining pool temperature, controlling chemical processes.

What is primary storage?

Holds data/instructions CPU needs immediately, volatile (except ROM), small capacity, direct CPU access.

What is secondary storage?

Stores programs/data long-term (even when off), non-volatile, large capacity, not directly CPU accessible.

Is primary storage generally volatile or non-volatile? What's the exception?

Volatile, except for ROM.