Embedded systems
What is an embedded system?
An embedded system is a computer system built inside a larger device to do one dedicated job. You can't usually see it, and you can't install new programs on it.
Embedded systems are everywhere:
- a washing machine that runs its wash programs and checks the water level
- a microwave that times the cooking and controls the power
- a central heating thermostat that switches the boiler on and off
- a car's engine management and anti-lock brakes: a car has dozens of embedded systems
- traffic lights, a fitness tracker and a digital camera
A laptop, by contrast, is a general-purpose computer: it can run all sorts of programs, and you choose which.
Key terms
Characteristics of embedded systems
| Embedded system | General-purpose computer | |
|---|---|---|
| Job | One dedicated job | Many jobs |
| Size | Usually small, to fit inside the device | Larger |
| Power | Uses little power: some run for years on a battery | Uses more power |
| Cost | Cheap to make in large numbers | More expensive |
| Reliability | Very reliable: runs for years without restarting | Needs restarts and updates |
| Software | Stored as firmware in ROM or flash memory; rarely changed | Programs installed and changed by the user |
| Input | Simple: buttons, or sensors such as a temperature sensor | Keyboard, mouse, touch screen |
Because an embedded system only does one job, its hardware and software can be designed just for that job, which is why it can be so small, cheap and reliable.
Key terms
Spotting an embedded system
Ask: is the computer part of a bigger device, doing one job?
- A smart speaker's volume buttons and microphone are controlled by embedded systems inside it.
- A dishwasher has an embedded system: it runs set wash programs and reads its water and temperature sensors.
- A desktop PC isn't one: it's a general-purpose computer.
Exam tip
When asked for a characteristic, link it to the device in the question: 'a fitness tracker's embedded system uses little power, so its battery lasts for days'.