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Edexcel GCSE Computer Science (1CP2) Exam Questions

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4 questions · 11 marks

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1Multiple choice1 markStored Program Computers Swap Remove

Identify the function of the control unit in the fetch-decode-execute cycle.

[1 mark]
  • ADecodes instructions
  • BPerforms arithmetic operations
  • CStores data and instructions
  • DTemporarily stores data being processed
Mark scheme
  • A Decodes instructions (1)
  • The only correct answer is A. The correct answer is Decodes instructions.
  • B is not correct because the arithmetic logic unit performs arithmetic operations
  • C is not correct because main memory stores data and instructions
  • D is not correct because registers temporarily store data being processed
Example answers and how they were marked
Full marks1/1

A Decodes instructions

Why: Correct option: the control unit decodes instructions during the fetch-decode-execute cycle (1).

No marks0/1

C Stores data and instructions

Why: Main memory stores data and instructions, not the control unit; this is a common distractor, so no mark.

No marks0/1

B Performs arithmetic operations

Why: Arithmetic operations are performed by the ALU, not the control unit; a common confusion between CPU components, so no mark.

2Short recall2 marksStored Program Computers Swap Remove

The central processing unit (CPU) contains an arithmetic logic unit (ALU).

State two types of operation carried out by the ALU.

[2 marks]
Mark scheme

Award one mark for any of the following up to a maximum of two marks:

  • An arithmetic operation, e.g. addition/subtraction/multiplication/division (1)
  • A logical operation, e.g. comparing two values (is A > B?) / using AND, OR, NOT (1)

Do not accept decoding instructions, fetching instructions or controlling the timing of the CPU, as these are carried out by the control unit.

Example answers and how they were marked
Full marks2/2

It carries out arithmetic operations such as addition and subtraction, and logical operations such as comparing two values to see if one is greater than the other.

Why: Arithmetic operation (1) and logical operation (1).

Some marks1/2

It adds numbers together and works out the result.

Why: Arithmetic operation, addition (1). No logical operation.

No marks0/2

It decodes the instructions that have been fetched from main memory.

Why: Decoding and fetching are the control unit's role; the mark scheme's do-not-accept line covers this.

3Describe2 marksSecondary Memory Swap Remove

Computers use secondary storage.

Describe the role of secondary storage.

[2 marks]
Mark scheme

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

  • Stores programs (including the operating system) and data that are not currently in use (1) so that they can be loaded into RAM/main memory when needed (1)
  • Keeps files/programs/data when the power is turned off (1) which happens because it is non-volatile (1)
  • Stores files/data for backup or archiving (1) so that they can be recovered if the originals are lost/corrupted (1)

A correct role on its own earns one mark; the second mark requires a linked development.

Accept either order if both the role and the link are given.

Do not accept 'it is non-volatile' on its own, unless it is linked to keeping data when the power is turned off.

Do not accept answers that only name a storage type (magnetic, optical, solid state) without describing a role.

Do not accept responses that describe primary storage/RAM, e.g. storing the data/instructions the CPU is currently working on, or that secondary storage makes the computer run faster.

Example answers and how they were marked
Full marks2/2

Secondary storage stores programs and data that are not currently in use so that they can be loaded into RAM when they are needed.

Why: Role point (1) linked to loading into RAM when needed (1).

Some marks1/2

It stores files and programs that are not currently in use.

Why: Correct role on its own earns one mark (1); no linked development, so the second mark is not awarded.

No marks0/2

It holds the data and instructions the CPU is working on so the computer runs faster.

Why: Describes primary storage/RAM and a speed benefit, which the mark scheme does not accept; no role of secondary storage is given.

4Discuss6 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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