← IGCSE Computer Science Paper 1

Devices that use embedded systems

A computer built into a device to do one set job, such as in a washing machine, car engine control, alarm, automatic lighting or vending machine.

Part of: IGCSE Computer Science 0478 — 3.1 Computer Architecture — Module 32

Understanding Devices that use embedded systems in IGCSE Computer Science Paper 1

What it does: The alarm's embedded system checks its sensor and triggers the siren. It does one fixed job, which is typical of an embedded system. The vending machine's embedded system runs one set task: compare the money paid with the price and then release the product. A washing machine has a built-in computer that controls its wash programs, water level and spin speed. Engine management systems use sensors and a microprocessor to control the fuel mix and ignition timing. They do one fixed job. Automatic lighting has sensors as inputs, an embedded system to process the data, and the lights as outputs.

Common mistakes: The washing machine program uses an IF, so it must end with ENDIF, not ENDWHILE. The microwave should keep counting down while seconds is greater than 0. With < 0 the loop never runs. It should be WHILE seconds > 0 DO.

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This module's key terms are also in a printable crossword (Modules 240–251) and word search (Modules 240–261).

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Learning
Duo
Which device contains an embedded system?
A printed textbookA washing machine
Matches
A vending machine is a general-purpose computer because it has a processor
↓
A processor does not make a device general-purpose. A vending machine has an embedded system that does one set job: selling items.
Applying
Meanings
Term
embedded system
Meaning
A computer built into a device to do one set job, such as in a washing machine, car engine control, alarm, automatic lighting or vending machine.
Practice
IF door_closed = TRUE THEN
Testing
Gaps
IF doorClosed = TRUE
Check Answer
Spots
3 START motor
4ENDWHILE

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Quick Questions

1. Which device contains an embedded system?
A. A washing machine ✓
B. A printed textbook
A washing machine has a built-in computer that controls its wash programs, water level and spin speed.
2. What job does an embedded system do in a microwave oven?
A. Lets the user install new games and apps
B. Controls the cooking time and power level ✓
A microwave's embedded system does one set job: it controls the timer and power. It is not a general-purpose computer.
3. Which is a use of an embedded system in a car?
A. Editing documents for the driver
B. Engine management that controls fuel and ignition ✓
Engine management systems use sensors and a microprocessor to control the fuel mix and ignition timing. They do one fixed job.
4. Which statement about an alarm system is correct?
A. It uses an embedded system to read sensors and sound the alarm ✓
B. It has no processor and works by magic
A security alarm has an embedded system that reads input from sensors, decides if there is an intruder, and triggers the siren.
5. How does an automatic lighting system use an embedded system?
A. It switches lights on or off based on light or movement sensor data ✓
B. It lets the user browse the internet on the light switch
Automatic lighting has sensors as inputs, an embedded system to process the data, and the lights as outputs.

Match the Pairs

Washing machine or microwave → A domestic appliance that uses an embedded system to control its timer, temperature and programs
Car engine management → An embedded system in a car that controls fuel injection and engine timing using sensor data
An embedded system in a security system uses sensors and sounds a siren when it detects movement → IF motion_sensor = TRUE THEN sound_alarm
An embedded system in a vending machine checks the money inserted and releases the chosen item → IF money >= price THEN release_item
A vending machine is a general-purpose computer because it has a processor → A processor does not make a device general-purpose. A vending machine has an embedded system that does one set job: selling items.
Automatic lighting is controlled by the user running different programs on it → Automatic lighting uses an embedded system with a fixed program. Users do not install or run different programs on it.

Key Term

embedded system
A computer built into a device to do one set job, such as in a washing machine, car engine control, alarm, automatic lighting or vending machine.

Fill in the Blanks

1. IF doorClosed = TRUE THEN OUTPUT "Start wash" ENDIF
Hint: Type the keyword that follows the condition in this washing machine IF statement.
2. IF fuelLevel < 10 THEN OUTPUT "Low fuel" ENDIF
Hint: Type the comparison operator meaning 'less than' in this car engine check.
3. IF movement = TRUE THEN OUTPUT "ALARM" ENDIF
Hint: Type the pseudocode keyword that sends a message out from the alarm system.
4. IF lightLevel < 30 THEN OUTPUT "Lamp on" ENDIF
Hint: Type the keyword that closes the IF statement in this automatic lighting program.
5. WHILE moneyIn < price INPUT coin ENDWHILE
Hint: Type the loop keyword that keeps repeating as long as the vending machine has not received enough money.

Spot the Error

Question 1
A INPUT door FROM sensor
B IF door = 'closed' THEN
C START motor
D ENDWHILE
Line D — The washing machine program uses an IF, so it must end with ENDIF, not ENDWHILE.
Question 2
A INPUT seconds FROM keypad
B WHILE seconds < 0 DO
C seconds <- seconds - 1
D ENDWHILE
E TURN OFF magnetron
Line B — The microwave should keep counting down while seconds is greater than 0. With < 0 the loop never runs. It should be WHILE seconds > 0 DO.
Question 3
A INPUT temp FROM engine_sensor
B IF temp > 100 THEN
C TURN OFF cooling_fan
D ENDIF
Line C — The engine management system should switch the fan ON when the engine is too hot, not OFF. It should be TURN ON cooling_fan.
Question 4
A INPUT motion FROM sensor
B IF motion = TRUE
C SOUND siren
D ENDIF
Line B — The IF statement is missing THEN. It should be IF motion = TRUE THEN.
Question 5
A INPUT light FROM sensor
B IF light < 20 THEN
C lamp <- ON
D ELSE:
E lamp <- OFF
F ENDIF
Line D — Pseudocode ELSE has no colon after it. The automatic lighting program should use just ELSE.

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