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Edexcel GCSE Computer Science (1CP2) Exam Questions

Build a practice paper from 693 exam-style questions, each with its mark scheme and example answers. Print it, or answer it on paper and then open the mark schemes. Or browse the questions by topic.

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3 questions · 5 marks

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1Multiple choice1 markSecondary Memory Swap Remove

A company stores films on optical media.

Identify the optical storage medium that can store the most data.

[1 mark]
  • ABlu-ray Disc
  • BCD
  • CDVD
  • DMagnetic tape
Mark scheme
  • A Blu-ray Disc (1)
  • The only correct answer is A. The correct answer is Blu-ray Disc.
  • B is not correct because a CD stores less data than a Blu-ray Disc, up to about 700 MB
  • C is not correct because a DVD stores less data than a Blu-ray Disc, up to about 4.7 GB (single-layer) or 8.4 GB (dual-layer)
  • D is not correct because magnetic tape is not an optical storage medium
Example answers and how they were marked
Full marks1/1

A Blu-ray Disc

Why: Correct option (1): a Blu-ray Disc has the greatest capacity of the optical media.

No marks0/1

C DVD

Why: Near miss scoring 0: a DVD is optical but stores less than a Blu-ray Disc (mark scheme line C). Only A is credited.

No marks0/1

D Magnetic tape

Why: Misconception scoring 0: candidates pick tape for its large capacity but magnetic tape is not an optical storage medium (mark scheme line D).

2Describe2 marksFetch Decode Execute Cycle Swap Remove

The control unit is one component of the CPU.

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

[2 marks]
Mark scheme

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

  • Decodes instructions (1) to determine what action/operation is required (1)
  • Sends control signals (1) along the control bus to coordinate/control the actions of other components (1)
  • Controls the fetch stage (1) by causing the next instruction to be fetched from main memory/RAM (1)
  • Controls the execute stage (1) by telling the ALU/other components when to carry out the required operation (1)

Do not accept responses relating to how the control unit affects performance, such as increasing clock speed.

Do not accept responses that describe the role of the ALU, registers or clock instead of the control unit.

Do not accept responses about the ALU performing calculations unless the control unit controlling the ALU is also stated.

Example answers and how they were marked
Full marks2/2

The control unit decodes instructions to determine what action is required.

Why: Linked point (1) and development (1): decodes instructions and determines the required action.

Some marks1/2

The control unit controls the fetch stage of the cycle.

Why: Point only (1): controls the fetch stage, but no linked development.

No marks0/2

The control unit carries out arithmetic and logical operations on data.

Why: No creditworthy point: describes the role of the ALU, which the mark scheme rejects.

3Describe2 marksStored Program Computers Swap Remove

The control unit (CU) is a component inside the CPU.

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

[2 marks]
Mark scheme

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

  • Decodes each (fetched) instruction (1) to work out which operation is needed / which components should carry it out (1)
  • Coordinates/directs the other components (1) by sending control signals along the control bus (1)
  • Fetches the next instruction (1) by sending its address to main memory along the address bus (1)
  • Sends a read/write control signal to main memory (1) so that the instruction or data is transferred during the fetch/execute stage (1)

Do not accept answers about synchronising the CPU or timing the cycles (that is the role of the clock).

Do not accept answers about carrying out arithmetic or logical operations (that is the ALU).

Do not accept answers about holding data or the results of instructions (that is registers/main memory).

Do not accept generic answers that only say the CU controls the CPU or processes instructions, with no linked development.

Only award one mark for a response that only repeats that the CU sends control signals; the second mark needs a linked outcome such as coordination, a memory read/write, or fetching an instruction.

Do not accept 'during the decode stage' as the development for the decoding point, as it restates the question.

Example answers and how they were marked
Full marks2/2

It decodes the instruction that has been fetched so that it knows which operation the CPU must carry out and which components should do it.

Why: Decoding named with the acceptable wording 'each (fetched) instruction' (1), plus the linked development that this identifies the operation and components (1).

Some marks1/2

It decodes each instruction during the decode stage of the cycle.

Why: Earns (1) for decoding the instruction. 'During the decode stage' restates the question and is not accepted as a development, so the second mark is not earned.

No marks0/2

It carries out the calculations and comparisons when the instruction is executed.

Why: Calculations and comparisons are the ALU's role, which the 'Do not accept' line rules out, so no mark is earned.

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