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Edexcel GCSE Computer Science (1CP2) Exam Questions

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4 questions · 11 marks

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1Short recall1 markSecondary Memory Swap Remove

Data is stored on optical discs as pits and lands.

Name the component in an optical disc drive that reads this data.

[1 mark]
Mark scheme

Award one mark for:

  • Laser (1)

Allow laser beam

Do not accept read/write head

Do not accept pits

Do not accept lands

Do not accept reflective surface

Do not accept magnet/magnetic

Example answers and how they were marked
Full marks1/1

Laser

Why: Laser is the creditworthy answer (1).

No marks0/1

A read/write head

Why: Read/write head is not accepted by the mark scheme; it reads magnetic media, not optical discs, so no marks are awarded.

No marks0/1

Pits and lands

Why: Pits and lands are what the laser reads, not the component that reads the data, so the mark scheme does not accept them.

2Describe2 marksSecondary Memory Swap Remove

A laptop uses a solid state drive (SSD) for secondary storage.

Describe how data is stored on a solid state drive.

[2 marks]
Mark scheme

Award up to two marks for a linked description such as:

  • Data is stored on (flash) memory chips/cells (1) as a pattern of electrical charges (1)
  • A current/voltage forces electrons through a barrier (1) so that they are trapped (or not trapped) to hold/represent a value (1)
  • Cells with a trapped charge and cells with no trapped charge (1) represent 1s and 0s/binary (1)
  • The trapped charge remains when the power is turned off (1) so the data is not lost/it is non-volatile (1)

Do not accept responses that describe magnetic storage, e.g. magnetised platters, spinning disks or read/write heads, or optical storage, e.g. lasers, pits and lands.

Do not award a mark for 'it is solid state' or 'it has no moving parts' without a description of how the data is stored.

Do not award a mark for restating the stem, e.g. 'a laptop uses an SSD' or 'an SSD uses flash memory'.

'Data is stored as electrical charges' on its own, with no reference to memory chips/cells or to how the charge is held, earns a maximum of one mark (1).

A response that only describes electrons being trapped, with no link to how the value/data is represented, earns one mark (1). The second mark needs a link such as trapped and not trapped charge representing 1s and 0s, or the trapped charge being kept so the data is not lost.

Example answers and how they were marked
Full marks2/2

A current is used to force electrons through a barrier so that they become trapped, and a cell with a trapped charge or a cell with no trapped charge represents a 1 or a 0.

Why: Linked description: a current forces electrons through a barrier (1) and trapped/not trapped charge represents 1s and 0s (1).

Some marks1/2

The data is stored in flash memory chips.

Why: Gives the creditworthy point that data is stored on flash memory chips (1) but does not develop it, e.g. by saying the data is held as electrical charges or by describing trapped electrons.

No marks0/2

The data is stored as magnetised areas on a spinning platter.

Why: This describes magnetic storage, which the mark scheme says not to accept for a solid state drive.

3Explain2 marksFetch Decode Execute Cycle Swap Remove

The CPU carries out the fetch-decode-execute cycle.

Explain one reason why the address bus is used in the fetch stage of the fetch-decode-execute cycle.

[2 marks]
Mark scheme

Award up to two marks for a linked explanation such as:

  • The address bus carries the address of the next instruction (1) so the CPU can locate/fetch it from main memory/RAM (1)
  • The address bus carries the address of the memory location to be read (1) so the instruction/data stored there can be located/accessed (1)
  • The CPU needs to know where the next instruction is stored (1) so the address bus sends the address to main memory/RAM (1)

For both marks, the expansion must follow/associate with the statement.

Allow 'from the program counter/PC' as part of the point for one mark, e.g. the address bus carries the address from the program counter (1), but the second mark needs the destination or purpose (e.g. to locate/fetch the instruction in main memory/RAM).

Do not award the second mark for naming the program counter/PC alone.

Do not accept answers that say the address bus carries data/instructions from main memory to the CPU, as these travel on the data bus.

Do not accept answers that say the address bus stores the address.

Do not allow an answer that only restates that the address bus carries addresses without saying which address or why it is needed.

Example answers and how they were marked
Full marks2/2

The address bus carries the address of the next instruction from the program counter to main memory, so that the CPU can locate the instruction that is to be fetched.

Why: Linked point (1) and reason (1).

Some marks1/2

The address bus carries the address of the next instruction from the program counter.

Why: Point only (1); the second mark is not awarded because the destination/purpose of locating or fetching the instruction is missing.

No marks0/2

It carries the instruction from main memory back to the CPU so that it can be decoded.

Why: Misconception: instructions travel on the data bus, which the mark scheme's Do not accept line covers.

4Discuss6 marksEmbedded Systems Swap Remove

A supermarket is replacing its staffed checkouts with self-service checkouts. Each checkout has a touchscreen, a barcode scanner and weighing scales. The supermarket wants the checkouts to be reliable and quick to respond.

Discuss why the supermarket should use embedded systems in its self-service checkouts rather than general-purpose computers.

Your answer should consider:

  • the characteristics of embedded systems
  • what self-service checkouts use embedded systems for
  • how embedded systems compare with general-purpose computers

You do not need to consider the cost of the materials used in the checkout.

[6 marks]
Mark scheme

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.

Example answers and how they were marked
Full marks6/6

An embedded system performs a single, dedicated task, so each self-service checkout is built only to scan items, weigh them and show prices. This suits the supermarket because the checkout does one job well instead of being used for anything else. The checkout uses its embedded system to read the barcode scanner, so the correct price is found quickly, and to read the weighing scales, so the weight of the items can be checked against the product that was scanned. It also controls the touchscreen that shows the customer what to do.

Embedded systems have limited processing resources and storage, which is more than enough for these tasks. Because they use a simple operating system held in ROM, they are less likely to fail while a customer is using them, so customers do not need a member of staff. They also have low power consumption, so a row of checkouts can run all day without using much electricity, and they are small and low cost per unit, so the supermarket can afford one at every till.

A general-purpose computer, by contrast, runs many programs and loads a full operating system, so it can slow down or need restarting and it is more expensive and bigger than the checkout needs. The embedded system runs fixed firmware, so customers cannot install software on the checkout, which keeps it reliable and quick to respond, and this is why it meets the supermarket's requirements better.

Why: Comprehensive understanding with sustained lines of reasoning: characteristics (single dedicated task, limited resources, simple operating system in ROM, low power, small and low cost) and uses (scanner, scales, touchscreen) are all applied to the checkout, and each is compared with a general-purpose computer. Meets the Level 3 guidance for a 6-mark answer.

Some marks2/6

Embedded systems are small and cheap. The checkout needs to scan items and weigh them. An embedded system can do this. It is reliable. A general-purpose computer could also do it but might crash more.

Why: Basic, independent points with little linkage or application: one characteristic (small and cheap), one use (scanning and weighing) and a brief comparison (a general-purpose computer might crash more). No line of reasoning is developed, so it is Level 1, top of the band, not Level 2.

No marks0/6

Embedded systems are better than normal computers because they are faster and can run lots of different programs. The checkout needs to be fast so it should use an embedded system.

Why: Level 0. Both claims are misconceptions that the mark scheme tells examiners not to accept (embedded systems have limited processing resources and run a single, dedicated program), and the last sentence only repeats the stem's requirement for quick responses, so there is no rewardable content.

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