GCSE · Computer Science · AQA · Spec 8525

Embedded systems

There's probably a computer in your washing machine, maybe several. So why can't you use it to watch a video?

Computer Science · Systems architecture

Embedded or general purpose?

For each device, ask one thing: who decides what its computer does? The user, or the machine's one job? Pick a device, then pick a box.

Still to sort

Embedded system (0)

A small computer built into a device to do one set job.

Where the line is: Lots of settings don't make a device general purpose. If every setting serves the same one job, it's still embedded.

General purpose computer (0)

The user chooses the task, and it runs and switches between many applications.

Where the line is: The test isn't how many buttons it has. It's whether the user can choose what job the computer does.

9 of 9 still to sort.

Every one of these devices has a computer inside. The question is what kind.

Why embedded?

Reason it through

Why is a fitness tracker built around an embedded system rather than a general purpose computer?

Link 1 of 4

First link · your turn

Start with the job. What does a fitness tracker's computer need to do?

Locked — reveal the link above first

Computer Science · Structure

Inside one washing machine

A washing machine may have several embedded systems, not just one. Tap each part to see its job.

Tap any part of the diagram to see what it does.

What do you really think?

The washing machine test

Sam's washing machine has a dial with lots of different wash cycles to choose from.

Which of these is closest to what you think about the computer inside it?

It must be a general purpose computer, because you get to choose between lots of cycles.It's embedded, and there's a single computer in there running the whole machine.It isn't really a computer at all. It's just some electronics that follow the dial.It's embedded, because all those cycles are for one job: washing clothes.

How sure are you?

I'm sureI think soI'm guessing

It must be a general purpose computer, because you get to choose between lots of cycles.

This is a common misconception

This is the most tempting mistake, because you really are choosing. But look at what you're choosing between: every cycle is a way of washing clothes. You choose how it washes, never what job the computer does. You can't install an app on it or switch it to a different task. All its settings serve one purpose, so it's embedded.

It's embedded, and there's a single computer in there running the whole machine.

This is a common misconception

Right kind of computer, but not necessarily one of them. Embedded systems are usually part of a larger system, and each controls a set function. A washing machine may have separate embedded systems for the water inlet, the temperature and the cycle.

It isn't really a computer at all. It's just some electronics that follow the dial.

This is a common misconception

An embedded system is a computer: a small one, built into the device to control specific functions. It's easy to overlook because it has little or no user interface and gets on with its job without you.

It's embedded, because all those cycles are for one job: washing clothes.

This matches the evidence

Exactly. The number of settings doesn't matter. What matters is that every setting serves the same single purpose. That's the test to use on any device.

Lots of settings, one purpose: still embedded. General purpose means the user chooses the job, not just how one job is done.

WHAT YOU'VE LEARNED

A quick recap of today's lesson.

The computers hiding inside everyday machines, and how to tell them apart from the ones you control.

What you need to know

An embedded system is a small computer built into a device to control specific functions. It has a specific task, or set of tasks, to complete, and is often found inside a machine.
A general purpose computer is designed to perform many different tasks. The user chooses the task, and it can run several applications and switch between them. Laptops, tablets and smartphones are examples.
Characteristics of embedded systems: focused on one or a few specific tasks, limited or no user interface, limited resources, often work without a user, small in size, use less power and lower cost.
A general purpose computer has a user interface that lets the user select tasks or applications. It costs more because it has more advanced hardware and software.
Embedded systems are usually part of a larger system. Each one controls a set function, so one machine can contain several embedded systems.
Having lots of settings doesn't make a device general purpose. If all the settings serve the same single purpose, the computer is embedded.

The big picture

An embedded system is a small computer built into a device to control specific functions, so it has one set task or a set of tasks to do. A general purpose computer, like a laptop, tablet or smartphone, is designed for many different tasks: the user chooses what it does, and it can run and switch between applications. Embedded systems are focused, have limited or no user interface, are small, low power and lower cost, and are often part of a larger machine that may contain several of them. A device with lots of settings is still embedded if every setting serves the same one purpose.

Key points

1Embedded: one set job. General purpose: the user chooses the job.

2Many settings, one purpose? Still embedded.

3One machine can hide several embedded systems, each with its own set function.

4One set task → limited resources → cheaper, less complex, compact and low power.

5Embedded: washing machines, traffic lights, smart thermostats, fitness trackers. General purpose: laptops, tablets, smartphones.

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Worked example

Problem

A coffee machine lets the user choose between several different drinks and cup sizes. Is the computer that controls it an embedded system or a general purpose computer? Explain your answer.

⚠ Watch out

Deciding a device is general purpose because it has lots of settings or buttons. The real question is whether the user can choose what job the computer does. If every setting serves one purpose, it's embedded.

🧠

Memory hook

Ask "Who's the boss?" If the user is the boss of what the computer does, it's general purpose. If the machine's one job is the boss, it's embedded.

✓

Check yourself

Pick a device in your home that isn't in this lesson. Which kind of computer controls it, and who decides what that computer does?

Flashcards

(14)

What is an embedded system?

A small computer built into a device to control specific functions. It has a specific task, or set of tasks, to complete.

What is a general purpose computer?

A computer designed to perform many different tasks. The user chooses the task, and it can run and switch between applications.

Give three examples of general purpose computers.

Laptops, tablets and smartphones.

What one question tells you whether a device's computer is embedded or general purpose?

Who decides what the computer does? If it's the device's one purpose, it's embedded. If the user chooses the task, it's general purpose.

A device has lots of settings. Does that make it general purpose?

No. If all the settings serve the same single purpose, it's still an embedded system.

What kind of user interface does an embedded system usually have?

A limited one, or none at all. Embedded systems often work without a user.

What kind of user interface does a general purpose computer have?

One that lets the user select tasks or applications.

Why does a general purpose computer usually cost more than an embedded system?

It has more advanced hardware and software.

Why is an embedded system usually cheaper and less complex?

It's dedicated to one set task, so it only needs limited resources.

What does "part of a larger system" mean for an embedded system?

It's built into a bigger machine and controls one set function of it, so one machine can contain several embedded systems.

What does the embedded system in traffic lights control?

The timing of the lights, based on traffic-flow sensors or a set programme.

What does a smart thermostat's embedded system do?

It adjusts the temperature of a home based on the user's settings and its sensors.

Why does a fitness tracker suit an embedded system?

It collects step count, heart rate and sleep data, and an embedded system can be compact and low power for that continuous monitoring.

Name four other devices that contain embedded systems.

Any four from: microwaves, automated robotic arms, coffee machines, robot vacuums, security systems, printers, game controllers.

Tap any card to flip it, or use Study as deck to go through them one at a time. In the full lesson these run as a spaced-repetition deck — you rate each card Hard, Good or Easy and the tricky ones keep coming back until they stick.

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Embedded systems

Embedded or general purpose?

Build the difference, one tick at a time

Inside one washing machine

The washing machine test

More AQA GCSE Computer Science topics