← IGCSE Computer Science Paper 1

Choosing a suitable output device for a context

Match the result needed (image, print, sound, 3D, movement) and the situation to the device that suits it best, then justify with 'because'.

Part of: IGCSE Computer Science 0478 — 3.2 Input and Output Devices — Module 31

Understanding Choosing a suitable output device for a context in IGCSE Computer Science Paper 1

What it does: The type of output is a 3D object, and only a 3D printer makes one, so the justification uses 'because'. Movement is the type of output needed, and an actuator produces movement, so it is the suitable device. A projector enlarges the image so a large audience can see it. A small laptop screen is too small for 200 people. Laser printers are fast and have a low cost per page for large print jobs. A 3D printer makes objects, not paper documents. The result needed is sound. A screen shows an image, which a blind user cannot see. A justified answer uses 'because' and gives a reason linked to the situation, such as photo quality and cost. Repeating the device name is not a reason.

Common mistakes: A projector only shows images and cannot produce sound. When the result needed is sound, the device should be a speaker. The IF statement is missing THEN. It should be IF need = "3D object" THEN.

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Learning
Duo
A teacher wants to show a video to a hall of 200 students. Which output device is best?
A laptop LCD screen, because it is cheap to runA projector, because the image can be enlarged for a big audience
Matches
A blind user needs spoken directions, so use an LCD screen because it shows clear text
↓
The result needed is sound, not an image. A speaker should be chosen because it outputs spoken directions.
Applying
Meanings
Term
suitable output device
Meaning
Match the result needed (image, print, sound, 3D, movement) and the situation to the device that suits it best, then justify with 'because'.
Practice
Context: show a film to a large hall
Testing
Gaps
device ← ""
Check Answer
Spots
2IF need = "sound" THEN
3 device ← "projector"

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Quick Questions

1. A teacher wants to show a video to a hall of 200 students. Which output device is best?
A. A projector, because the image can be enlarged for a big audience ✓
B. A laptop LCD screen, because it is cheap to run
A projector enlarges the image so a large audience can see it. A small laptop screen is too small for 200 people.
2. A company needs 500 copies of a black and white report every day at low cost per page. Which is the better choice?
A. A laser printer, because it prints fast and each page is cheap ✓
B. A 3D printer, because it prints in layers
Laser printers are fast and have a low cost per page for large print jobs. A 3D printer makes objects, not paper documents.
3. An engineer wants a physical prototype of a new phone case to hold and test. Which output device should be used?
A. An inkjet printer, because it prints high quality photos
B. A 3D printer, because it builds a solid object layer by layer ✓
A 3D printer outputs a solid object. An inkjet printer only produces flat printed pages.
4. A smart home needs to tell a blind user that someone is at the door. Which output is most suitable?
A. A speaker, because it outputs sound the user can hear ✓
B. An LED screen, because it shows a clear image
The result needed is sound. A screen shows an image, which a blind user cannot see.
5. A greenhouse system must open a window when the temperature gets too high. Which output device is needed?
A. A speaker, because it makes a loud alarm
B. An actuator, because it causes movement ✓
The result needed is movement, so an actuator is used to open the window. A speaker only makes sound.

Match the Pairs

A school needs a printed class set of 300 worksheets cheaply and quickly → Laser printer: fast, low cost per page for large print runs
A teacher must show a lesson to a whole hall of 200 students → Projector: displays a large image that a big audience can see
Result needed is a solid physical model of a new product design, so choose a device that builds objects → 3D printer, because it builds a solid object layer by layer
Result needed is physical movement, such as opening a greenhouse window when it gets too hot → Actuator, because it turns a signal from the microprocessor into movement
A blind user needs spoken directions, so use an LCD screen because it shows clear text → The result needed is sound, not an image. A speaker should be chosen because it outputs spoken directions.
A home user prints a few photos a month, so buy a laser printer because laser printers are always cheapest → The claim is wrong and ignores cost and quality needs. An inkjet printer is cheaper to buy and gives good photo quality for light use.

Key Term

suitable output device
Match the result needed (image, print, sound, 3D, movement) and the situation to the device that suits it best, then justify with 'because'.

Fill in the Blanks

1. IF need = "3D object" THEN device ← "3D printer" ENDIF
Hint: Type the output device that builds a solid object layer by layer.
2. need ← "movement of a robot arm" device ← "actuator"
Hint: Type the output device that turns a control signal into movement.
3. need ← "image for a large audience" device ← "projector"
Hint: Type the output device that shows an image big enough for a whole room.
4. need ← "100 pages, low cost per page" device ← "laser printer"
Hint: Type the printer type with the lowest running cost for large print jobs.
5. need ← "sound" OUTPUT "Use a speaker because sound is needed"
Hint: Type the word that links your choice to the reason in a justified answer.

Spot the Error

Question 1
A need ← "sound"
B IF need = "sound" THEN
C device ← "projector"
D ENDIF
Line C — A projector only shows images and cannot produce sound. When the result needed is sound, the device should be a speaker.
Question 2
A IF need = "3D object"
B device ← "3D printer"
C ENDIF
D OUTPUT device
Line A — The IF statement is missing THEN. It should be IF need = "3D object" THEN.
Question 3
A need ← "movement"
B device ← "LCD screen"
C why ← "it makes things move"
D OUTPUT device,"because",why
Line B — An LCD screen displays images and cannot make anything move. A need for movement is met by an actuator, so the line should be device ← "actuator".
Question 4
A audience = 300
B IF audience > 100 THEN
C device ← "projector"
D ENDIF
Line A — Pseudocode assigns a value with the arrow ←, not =. It should be audience ← 300.
Question 5
A need ← "printed copy"
B IF need = "printed copy" THEN
C device ← "laser printer"
D ENDWHILE
E OUTPUT device
Line D — An IF statement must be closed with ENDIF, not ENDWHILE. Line 4 should be ENDIF.

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