← IGCSE Computer Science Paper 1

Choosing input devices, output devices and sensors together for a system

A complete system uses input devices or sensors to capture data and output devices or actuators to deliver results, each chosen to suit the task.

Part of: IGCSE Computer Science 0478 — 3.2 Input and Output Devices — Module 51, IGCSE Computer Science 0478 — 6.1 Automated Systems — Module 26, QCE Digital Solutions Unit 3 — Interactions Between Users, Data and Digital Systems — Module 87

Understanding Choosing input devices, output devices and sensors together for a system in IGCSE Computer Science Paper 1

What it does: The infra-red sensor captures data about a person approaching, and the motor is the actuator that opens the door. The sensors capture the weather data automatically and the screen delivers the readings to the user. A barcode scanner reads the product code and the system looks up the price. A microphone captures sound, which is no use for identifying products. A screen displays the results of processing, such as the total. A keyboard is an input device that sends data into the system. A humidity sensor measures water vapour in the air. A magnetic field sensor detects magnets and has nothing to do with moisture.

Common mistakes: The price must be looked up using the barcode data captured by the scanner. A screen is an output device and does not provide data. It should be LOOKUP(code). An automatic door needs an actuator such as a motor to physically open it. A printer cannot move a door. It should be SEND open TO motor.

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Learning
Duo
A supermarket checkout needs to capture the price of each item quickly. Which input device is the best fit?
Barcode scannerMicrophone
Matches
Smart home heating: Input: radiator, Output: temperature sensor
↓
The input and output are swapped: the temperature sensor is the input that captures data and the radiator or heater actuator is the output
Applying
Meanings
Term
inputs and outputs
Meaning
A complete system uses input devices or sensors to capture data and output devices or actuators to deliver results, each chosen to suit the task.
Practice
SYSTEM: Automatic door
Testing
Gaps
Input:
Check Answer
Spots
1INPUT code FROM scanner
2price <- LOOKUP(screen)

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Quick Questions

1. A supermarket checkout needs to capture the price of each item quickly. Which input device is the best fit?
A. Barcode scanner ✓
B. Microphone
A barcode scanner reads the product code and the system looks up the price. A microphone captures sound, which is no use for identifying products.
2. At a supermarket checkout, which is an OUTPUT device that shows the customer what they owe?
A. LCD screen ✓
B. Keyboard
A screen displays the results of processing, such as the total. A keyboard is an input device that sends data into the system.
3. Automatic doors need to detect that a person is standing in front of them. Which sensor is the most suitable?
A. pH sensor
B. Infra-red or proximity sensor ✓
An infra-red or proximity sensor detects movement or nearness. A pH sensor measures acidity, which is not relevant to a door.
4. In an automatic door system, what is the actuator?
A. The motor that opens the door ✓
B. The sensor that detects the person
An actuator is an output component that causes physical movement. The sensor is the input. The microprocessor processes the sensor data and then signals the motor.
5. A weather station records air temperature, rainfall and wind. Where does the data come from?
A. Speakers
B. Sensors ✓
Sensors capture physical data from the environment and send it to a computer. Speakers are output devices that produce sound.

Match the Pairs

Input: barcode scanner, keypad → At a supermarket checkout, these devices capture the product code and the customer's payment details
Output: speaker, receipt printer → At a supermarket checkout, these devices give the beep and the printed receipt as results
An automatic door uses a sensor to detect a person, and the microprocessor then makes an actuator open the door → Input: infra-red sensor | Output: motor actuator
A weather station uses sensors to capture data and a screen to output the results to people → Input: temperature, pressure, humidity sensors | Output: LCD screen
Smart home heating: Input: radiator, Output: temperature sensor → The input and output are swapped: the temperature sensor is the input that captures data and the radiator or heater actuator is the output
Weather station: Input: speaker, Output: keyboard → The devices do not suit the task: a weather station needs sensors as inputs and a screen or printer as output, not a speaker and a keyboard

Key Term

inputs and outputs
A complete system uses input devices or sensors to capture data and output devices or actuators to deliver results, each chosen to suit the task.

Fill in the Blanks

1. Scenario: supermarket checkout Input: barcode scanner Output: receipt printer
Hint: Type the input device that reads the product codes on items at the till.
2. Scenario: automatic door Sensor: infra-red sensor Output: actuator opens the door
Hint: Type the output component that uses a motor to physically move the door.
3. Scenario: weather station Measures sunshine: light sensor Output: screen shows the readings
Hint: Type the kind of sensor that measures how bright it is.
4. Scenario: smart home heating Sensor: temperature sensor Output: heater switched on
Hint: Type the kind of sensor that measures how hot or cold the room is.
5. Scenario: smart home alarm Inputs: motion sensor, keypad Outputs: siren, flashing light
Hint: Type the label for the devices that deliver results to the user.

Spot the Error

Question 1
A INPUT code FROM scanner
B price <- LOOKUP(screen)
C OUTPUT price TO screen
D OUTPUT receipt TO printer
Line B — The price must be looked up using the barcode data captured by the scanner. A screen is an output device and does not provide data. It should be LOOKUP(code).
Question 2
A READ s FROM infra-red sensor
B IF s = movement THEN
C SEND open TO printer
D ENDIF
Line C — An automatic door needs an actuator such as a motor to physically open it. A printer cannot move a door. It should be SEND open TO motor.
Question 3
A temp <- READ(temp sensor)
B hum <- READ(humidity sensor)
C OUTPUT temp, hum TO keyboard
Line C — A keyboard is an input device, so it cannot show the weather readings. The results should go to an output device such as a screen.
Question 4
A lux <- READ(light sensor)
B IF lux > 20 THEN
C SWITCH lamp ON
D ENDIF
Line B — The lamp should switch on when it is dark, which means the light level is low. The condition should be lux < 20, not lux > 20.
Question 5
A System: smart doorbell
B Input: button
C Input: camera
D Output: microphone
Line D — A microphone is an input device because it captures sound. The doorbell needs an output device such as a speaker to make the sound.

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