Indicative content
Characteristics of embedded systems
- An embedded system performs a single, dedicated task, so each self-service checkout is built only to scan, weigh and price items and cannot be used for any other job.
- An embedded system has limited processing resources and storage, which is enough for the checkout to scan barcodes, weigh items and display prices.
- An embedded system normally has a simple operating system held in ROM, so a checkout is less likely to fail while a customer is using it.
- Embedded systems have low power consumption, so a row of checkouts can be left running all day without using much electricity.
- Embedded systems are small and low cost per unit, so one can be built into each checkout unit and the supermarket can afford one at every till.
- An embedded system has a limited user interface, so the checkout only shows its own screens to the customer.
- The firmware of an embedded system is not normally changed by the customer, although a technician can update it when the supermarket changes the checkout's software.
Uses of embedded systems in the checkout
- The checkout uses an embedded system to read the barcode scanner, so the correct price for each item is found quickly.
- The checkout uses an embedded system to read the weighing scales, so the weight of the items can be checked against the product that was scanned.
- The checkout uses an embedded system to control the touchscreen that shows the customer what to do and how much to pay.
- The checkout uses an embedded system to respond quickly to each scan, because it only carries out the checkout's own tasks, which keeps the queues moving.
- The checkout uses an embedded system so that it keeps working for long periods without being restarted, which means customers can use it without a member of staff.
Comparison with general-purpose computers
- A general-purpose computer can run many different programs, whereas the checkout's embedded system runs one dedicated program, so it cannot be used for other jobs.
- A general-purpose computer loads a full operating system when it starts and has other software running, so it can slow down or need restarting, whereas the checkout is not slowed down by other programs.
- A general-purpose computer has far more processing power and memory than the checkout needs, so using one would be more expensive and would take up more space than an embedded system.
- A general-purpose computer is designed for users to install new software, but the checkout's embedded system runs fixed firmware, so customers cannot change what the checkout does.
Levels
- Level 0 (0 marks): No rewardable content.
- Level 1 (1–2 marks): Basic, independent points are made, showing elements of understanding of key concepts/principles of computer science. (AO1) The discussion will contain basic information with little linkage between points made or application to the context. (AO2)
- Level 2 (3–4 marks): Demonstrates adequate understanding of key concepts/principles of computer science. (AO1) The discussion shows some linkages and lines of reasoning with some structure and application to the context. (AO2)
- Level 3 (5–6 marks): Demonstrates comprehensive understanding of key concepts/principles of computer science to support the discussion being presented. (AO1) The discussion is well developed, with sustained lines of reasoning that are coherent and logically structured, and which clearly apply to the context. (AO2)
Level 3 responses must consider both the characteristics of embedded systems and what the checkout uses them for, and must make a comparison with a general-purpose computer. Answers that only list characteristics or checkout tasks without linking them to the checkout are limited to Level 1.
Do not accept claims that embedded systems are faster than general-purpose computers or that they can run many different programs, as embedded systems have limited processing resources and carry out a single, dedicated task.