← IGCSE Computer Science Paper 1

Embedded system

A computer system built into a larger device to perform one dedicated function, usually running a fixed program. Examples: a washing machine controller or a microwave timer.

Part of: IGCSE Computer Science 0478 — 3.1 Computer Architecture — Module 31, IGCSE Computer Science 0478 — 6.1 Automated Systems — Module 9

Understanding Embedded system in IGCSE Computer Science Paper 1

What it does: The washing machine controller always runs the same fixed wash program, which shows a dedicated function. The chip sits inside the thermostat as part of the larger device, showing it is built in, small and cheap. A microwave has a small computer system inside it that controls the timer and power level. A chair has no computer system. Embedded systems are part of the device they control, such as a washing machine or a car engine. The program is stored in the device and is usually fixed, because the system only has one job to do. A dedicated function means the system is designed for one specific job, such as controlling a thermostat.

Common mistakes: The microwave timer should count down while time is greater than 0. With < 0 the loop never runs, so the dedicated timer task never happens. It should be WHILE time > 0. The washing machine controller must assign a value to the heater output using the assignment arrow. It should be heater ← ON.

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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 statement describes an embedded system?
A computer system built into a device to do one dedicated functionA computer system designed to run many different applications
Matches
embedded_system = runs_any_software_the_user_installs
↓
An embedded system has one dedicated function and usually a fixed program. Running any software the user installs describes a general-purpose computer.
Applying
Meanings
Term
embedded system
Meaning
A computer system built into a larger device to perform one dedicated function, usually running a fixed program. Examples: a washing machine controller or a microwave timer.
Practice
// Embedded system: microwave timer
Testing
Gaps
A microwave timer is an
Check Answer
Spots
1time ← 30
2WHILE time < 0

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Quick Questions

1. Which statement describes an embedded system?
A. A computer system built into a device to do one dedicated function ✓
B. A computer system designed to run many different applications
An embedded system is built into a larger device and performs one dedicated function, unlike a general-purpose computer.
2. Which device contains an embedded system?
A. A wooden chair
B. A microwave oven with a timer controller ✓
A microwave has a small computer system inside it that controls the timer and power level. A chair has no computer system.
3. An embedded system is usually...
A. A separate computer that the user installs software on
B. Built into a larger device ✓
Embedded systems are part of the device they control, such as a washing machine or a car engine.
4. What kind of program does an embedded system usually run?
A. A fixed program that rarely changes ✓
B. Any program the user chooses to download
The program is stored in the device and is usually fixed, because the system only has one job to do.
5. How many main tasks does an embedded system normally perform?
A. One dedicated function ✓
B. Many different general tasks
A dedicated function means the system is designed for one specific job, such as controlling a thermostat.

Match the Pairs

embedded system → A computer system built into a larger device to perform one dedicated function, usually running a fixed program
microwave timer controller → An embedded system inside a microwave that only controls the cooking time and power
An embedded system has a dedicated function and usually runs a fixed program stored in the device → washing_machine_controller = run("wash_program")
An embedded system is built into a larger device and is usually small and low cost → device = Thermostat(embedded_chip = True)
embedded_system = runs_any_software_the_user_installs → An embedded system has one dedicated function and usually a fixed program. Running any software the user installs describes a general-purpose computer.
embedded_system = separate_desktop_computer → An embedded system is built into a larger device, not a separate stand-alone computer like a desktop.

Key Term

embedded system
A computer system built into a larger device to perform one dedicated function, usually running a fixed program. Examples: a washing machine controller or a microwave timer.

Fill in the Blanks

1. A microwave timer is an embedded system
Hint: Type the two-word term for a computer system built into a device to do one job
2. An embedded system is built into a device
Hint: Type the two words describing how the system is placed inside a larger device
3. Most embedded systems run a fixed program
Hint: Type the word meaning the program is not normally changed by the user
4. Embedded systems have one dedicated function
Hint: Type the word meaning set aside for a single specific purpose
5. Embedded systems are small and low cost
Hint: Type the word describing how much these systems usually cost

Spot the Error

Question 1
A time ← 30
B WHILE time < 0
C time ← time - 1
D ENDWHILE
E buzzer ← ON
Line B — The microwave timer should count down while time is greater than 0. With < 0 the loop never runs, so the dedicated timer task never happens. It should be WHILE time > 0.
Question 2
A INPUT temp FROM sensor
B IF temp < 40 THEN
C heater ON
D ENDIF
Line C — The washing machine controller must assign a value to the heater output using the assignment arrow. It should be heater ← ON.
Question 3
A REPEAT
B INPUT temp FROM sensor
C IF temp > 25
D fan ← ON
E ENDIF
F UNTIL FALSE
Line C — The IF statement is missing THEN. This embedded thermostat program should read IF temp > 25 THEN.
Question 4
A WHILE TRUE
B INPUT door FROM sensor
C IF door = OPEN THEN
D siren ← OFF
E ENDIF
F ENDWHILE
Line D — The alarm's one dedicated function is to sound when the door opens. Setting the siren to OFF means the alarm never sounds. It should be siren ← ON.
Question 5
A // Program is rewritten daily
B WHILE power = ON
C RUN wash_program
D ENDWHILE
Line A — An embedded system usually runs a fixed program stored in ROM, so it is not rewritten daily. The comment should say the program is fixed and stored in ROM.

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