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Edexcel GCSE Computer Science (1CP2) Exam Questions

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3 questions · 9 marks

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1Multiple choice1 markStored Program Computers Swap Remove

Identify the component of the CPU that carries out arithmetic and logical operations.

[1 mark]
  • AArithmetic logic unit
  • BControl unit
  • CMain memory
  • DRegister
Mark scheme
  • A Arithmetic logic unit (1)
  • The only correct answer is A. The correct answer is arithmetic logic unit.
  • B is not correct because the control unit decodes instructions and controls the CPU
  • C is not correct because main memory is not part of the CPU and stores data and instructions
  • D is not correct because a register stores small amounts of data within the CPU
Example answers and how they were marked
Full marks1/1

A Arithmetic logic unit

Why: Correct option: the arithmetic logic unit carries out arithmetic and logical operations (1).

No marks0/1

B Control unit

Why: Control unit is a CPU component but its role is to decode and control, not perform arithmetic or logical operations, so no mark.

No marks0/1

D Register

Why: Register stores data but does not carry out operations; a common misconception that any CPU component performs calculations, so no mark.

2Explain2 marksFetch Decode Execute Cycle Swap Remove

The control unit is part of the CPU.

Explain the role of the control unit in the fetch-decode-execute cycle.

[2 marks]
Mark scheme

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

  • Decodes/interprets/translates the instruction (1) to work out what the instruction is/what operation is required (1)
  • Sends control signals to the other components (1) so that the correct component carries out the instruction (1), e.g. the ALU/main memory
  • Controls the fetch of the instruction from main memory (1) because the address of the next instruction is sent via the address bus (1)
  • Controls the fetch of the next instruction from main memory (1) by sending a control signal/read signal to main memory (1)

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

For the decode point, 'decodes the instruction' alone gains 1 mark; a second mark needs the purpose of decoding, i.e. working out what the instruction is/what operation is required.

Do not accept 'it controls the CPU' on its own, without naming a task in the cycle.

Do not accept 'it fetches the instruction from memory' on its own, as this describes the fetch step rather than the control unit's role; credit only if linked to controlling/signalling the fetch.

Do not accept carrying out arithmetic/logical operations, as these are carried out by the ALU, or holding the address of the next instruction, as this is the program counter.

Do not accept storing the instruction in a register (e.g. MAR/MDR), as this is not the role of the control unit.

Example answers and how they were marked
Full marks2/2

The control unit decodes each instruction, working out what it means, so that the CPU knows which component should carry it out.

Why: Linked point (1) and reason (1): decodes/interprets the instruction, and works out what it is/what operation is required.

Some marks1/2

It decodes the instruction that has been fetched from main memory.

Why: Decode point only (1); it does not explain the purpose of decoding, i.e. working out what the instruction is/what operation is required.

No marks0/2

It adds the two numbers together and stores the result in a register.

Why: Misconception: arithmetic is carried out by the ALU, which the mark scheme's Do not accept line covers.

3Discuss6 marksPrimary Memory Swap Remove

An employee is writing a report on a laptop. There is a power cut and the laptop turns off. When power is restored, the employee cannot find the report file.

Discuss the role of RAM in this situation.

Your answer should include:

  • why the report was lost
  • the difference between RAM and secondary storage
  • how the employee could prevent this in future.
[6 marks]
Mark scheme

Indicative content

Why the report was lost

  • The report was being created and edited in RAM, which is volatile.
  • Volatile memory loses its contents when the power supply is removed.
  • The power cut removed the power, so the data in RAM was lost.
  • The report had not been saved to secondary storage before the power cut.
  • Only data that had been saved to secondary storage would remain after the power cut.

The difference between RAM and secondary storage

  • RAM is volatile and holds data temporarily while the computer is on.
  • Secondary storage is non-volatile and keeps data permanently when the power is off.
  • RAM is directly accessible by the CPU and is much faster than secondary storage.
  • Secondary storage has a larger capacity and is cheaper per gigabyte than RAM.
  • RAM holds the programs and data currently in use; secondary storage holds files for long-term storage.

How the employee could prevent this in future

  • The employee should save the report regularly to secondary storage, such as the hard drive or a USB flash drive.
  • The employee could enable autosave or autosave/recovery features in the word processor.
  • The employee could use cloud storage that saves changes automatically.
  • The employee could use an uninterruptible power supply (UPS) or battery to keep the laptop on during a power cut.
  • The employee should not rely on RAM to keep work permanently.

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)

Additional guidance

  • Level 3 responses must explain that RAM is volatile and contrast this with non-volatile secondary storage.
  • Do not award marks for stating that the report was lost from secondary storage unless it had been saved there.
Example answers and how they were marked
Full marks6/6

The report was lost because it was being held in RAM, which is volatile memory. RAM only keeps its contents while the computer has power. When the power cut happened, the laptop turned off and everything in RAM was lost, including the unsaved report. RAM is different from secondary storage because secondary storage is non-volatile and keeps data permanently even when the power is off. For example, the hard drive would still contain the report if it had been saved. RAM is also much faster than secondary storage and is used for programs and data currently in use. To prevent this in future, the employee should save the report regularly to the hard drive or use autosave. They could also save to cloud storage, which saves automatically, or use a UPS to keep the laptop running during a power cut.

Why: Comprehensive understanding of RAM volatility, clear contrast with non-volatile secondary storage, and well-linked prevention methods applied to the employee's situation.

Some marks4/6

The report was lost because it was in RAM. RAM is temporary memory and it loses data when the power goes off. Secondary storage is permanent, so if the employee had saved the report it would still be there. RAM is faster than secondary storage. To prevent it, they should save their work.

Why: Adequate understanding shown through the volatility of RAM and the difference from permanent secondary storage, but the answer lacks detail about why the report was specifically lost and gives only a brief prevention method.

No marks0/6

The report was lost from the hard drive because the power cut erased it. RAM is permanent storage, so the report should have been saved there. The employee should buy more RAM to stop this happening again.

Why: No creditworthy points. The answer wrongly says the report was lost from the hard drive and that RAM is permanent storage, and it suggests more RAM will prevent power-loss data loss. These are misconceptions.

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