Embedded Everywhere

The computers nobody calls computers

Think about how many things in an ordinary house have a processor in them, and then think about how few of them anybody would describe as a computer. Far more processors sit inside ordinary objects than inside the machines people actually call computers. What makes those worth a name of their own is not what they are made of. The processor in a washing machine is a processor, the same as any other. It is what the thing is FOR that puts it in a different category. ⚠️ And there is one warning to take into the exam before anything else. A question on this topic almost never wants only a definition. An answer that defines the term and stops will score badly, however accurate it is. What earns the marks is a specific, real example that you can say something about. This module is mostly about making examples do that work.

Words for the two kinds

Five terms. The first two only mean anything against each other, so learn them as a pair rather than separately.

Dedicated against general-purpose

Neither term means much on its own. Set them side by side and the third column gives you a question that settles any example you are handed.

How to answer with an example

A definition on its own cannot be checked. Anybody can write one down from memory without understanding a thing, and examiners know it, which is why this topic is marked the way it is. Three short clauses will do it. Name a real device. Say what the one job is. Say who cannot change what it does. ⚠️ That third clause is the one nearly everybody leaves out, and it is the one that actually proves your point - it is the difference between describing a machine and explaining why it belongs in this category. ⚠️ Choose an example you can say something about. Naming a device and then having nothing to add about its job is worth no more than the definition was. ⚠️ And watch for the reason that is not a reason. How small a thing is, or how cheap, tells you nothing at all about which of the two kinds it is. If that is the only argument you have, you have not applied the test.

Match each device to the one job it was built for

The reason that is not a reason

A student argues that a device must be an embedded system "because it is small". Why does that argument not work?

• Size does not decide it. Being built into something to do one job the owner cannot change is what decides it
• The argument is fine, because embedded systems really are always small
• It is wrong because embedded systems are always large
• It is wrong because only the processor inside is small, not the whole device

True about embedded systems

Select the TWO statements that are true.

• It is built into a larger device to carry out one particular job
• It usually starts working straight away, because there is no general operating system to load first
• Its owner can install new programs on it whenever they choose
• Any computer smaller than a laptop counts as one

One example, done properly

A weak answer: "A washing machine is an embedded system." That is true, and it is worth almost nothing, because it names a device and stops. A strong answer, in three clauses: "A washing machine contains an embedded system. Its one job is to run a wash programme - reading sensors for water level and temperature, and switching the valve, heater, motor and pump in a fixed order. The person who owns it can choose between programmes, but cannot install a new one or make the machine do something else. That is why it belongs in this category rather than the other one." ⚠️ Name the device, name the job, say who cannot change it. The third clause is the one people leave out, and it is the one doing the actual work. ⚠️ And here is the example NOT to give. A smartphone feels like a good answer: it is small, it is full of electronics, it is not a desktop. But its owner installs whatever they like on it, which is exactly the thing an embedded system does not allow. Offering a phone here tells an examiner you have reached for size instead of applying the test.

Complete the embedded systems paragraph

A computer built into a larger device to carry out one particular job is an _____. A machine that runs many different programs, chosen and installed by whoever is using it, is a _____. Having only one job to do and no general operating system to load, an embedded system can usually _____. What decides which of the two kinds a device is, is not how big it is but its _____.

Which kind is it

Five devices, three lives. Apply the test rather than guessing from the size of the thing.

Order what the controller does

A washing machine is part way through a wash programme. Put these stages into the order they happen.

• Sensors report the current water level and temperature
• The controller compares those readings with what the chosen programme requires
• It switches the valve, the heater or the motor accordingly
• The programme moves on to its next stage
• The last stage finishes and the machine stops

Spot the true embedded systems facts

Tap the TWO statements that are true.

• An embedded system is built into a larger device to do one particular job
• A smartphone is general-purpose, because its owner installs whatever programs they like
• A device counts as embedded if it is smaller than a laptop
• An embedded system runs a full operating system so that new programs can be added to it

Three device calls

Three answers to look at. Choose the response you could defend in writing.

• Asked to explain what an embedded system is, a student writes only "a computer inside another device" and scores one mark out of three. What is missing?
• Asked for an example of an embedded system, a classmate offers a smartphone. Is that a good choice?
• Why is a dedicated controller a sensible design for a washing machine, rather than putting a general-purpose computer inside it?

Explain embedded systems with a real example

A friend has learned the definition of an embedded system by heart and keeps scoring one mark out of three or four. Write them the answer that would score properly.

• Explain what makes a system embedded rather than general-purpose
• Name one specific device and say what the single job of its embedded system is
• Say who can and cannot change what that device does, and why that settles the question
• Give two reasons a dedicated system is a sensible design choice for that device
• Finish by explaining why size is not the test, using an example that would be judged wrongly if it were