Input, output and sensors — GCSE Computer Science practice questions

Question 1

A public library is putting in a terminal where visitors can search the catalogue for books. It must be easy to use for visitors who are blind.

Which pair of devices is the most suitable?

Accepted Answer

C: Braille keyboard (input) and loudspeaker giving spoken results (output). A blind visitor needs to enter a search by touch or voice and receive the results by sound or touch. A Braille keyboard lets them type by feeling the raised dots, and a loudspeaker reads the results aloud. The other pairs all rely on seeing a screen, a pointer or printed text for at least one of the two devices.

Question 2

When a student borrows a book, the librarian scans the barcode on its back cover.

Which statement describes how the barcode scanner reads the barcode?

Accepted Answer

B: It shines light on the barcode; the dark bars reflect less light than the white gaps, and a sensor turns the pattern of reflected light into a digital code. A barcode scanner shines light (often a red laser or LED) across the code. The black bars reflect little light and the white spaces reflect a lot, so a light sensor picks up a pattern of strong and weak reflections. This pattern is converted into a digital code that identifies the book.

Question 3

Each system below uses sensors and a microprocessor.

Which one is a **control** system rather than a monitoring system?

Accepted Answer

C: A school heating system that switches the radiators on when a classroom's temperature falls below 19 °C. A control system uses the sensor readings to change the conditions automatically: the heating system switches the radiators on, which raises the temperature it is measuring. The other three only collect, display or log readings and warn people; an alarm or a text message does not change the wind, the heart rate or the river level, so they are monitoring systems.