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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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4 questions · 6 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.

2Multiple choice1 markStored Program Computers Swap Remove

Identify the bus that carries addresses in one direction only, from the CPU to main memory.

[1 mark]
  • AAddress bus
  • BControl bus
  • CData bus
  • DSystem bus
Mark scheme
  • A Address bus (1)
  • The only correct answer is A. The correct answer is address bus. Do not accept 'address' on its own.
  • B is not correct because the control bus carries control signals in both directions between the CPU and other components
  • C is not correct because the data bus carries data in both directions between the CPU and main memory
  • D is not correct because the system bus is the collection of all three buses
Example answers and how they were marked
Full marks1/1

A Address bus

Why: Correct option: the address bus carries addresses in one direction only, from the CPU to main memory (1).

No marks0/1

C Data bus

Why: The data bus carries data in both directions, so it is not the bus that carries addresses in one direction only from the CPU to main memory; no creditworthy point.

No marks0/1

B Control bus

Why: The control bus carries control signals in both directions, not addresses in one direction only; this is the common control/address bus confusion, so no mark.

3Explain2 marksEmbedded Systems Swap Remove

An engine control unit (ECU) in a car is an embedded system.

Explain one benefit of using an embedded system for the engine control unit instead of a general purpose computer.

[2 marks]
Mark scheme

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

  • (The ECU) is more reliable/less likely to crash (1) because it only runs the one program/has a single purpose (1)
  • (The ECU) cannot be affected by other software/viruses (1) because it cannot run other software/it can only run the program it was made for (1)
  • (The ECU) is cheaper (1) because it has limited processing resources/less memory/simple components (1)
  • (The ECU) uses less power (1) because it has limited processing resources/a simpler processor (1)
  • (The ECU) is smaller (1) because it has fewer components/less memory than a general purpose computer (1)

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

A suitable benefit stated on its own earns one mark.

Do not accept a description or a location given as the reason, e.g. 'because it is part of the car', 'because it is inside the engine', 'because it is embedded'.

Do not accept a description of an embedded system on its own as the benefit, e.g. 'it does one specific job' or 'it is part of the car'.

Do not accept 'it is faster'/'it has a more powerful processor' as embedded systems have limited processing resources.

Example answers and how they were marked
Full marks2/2

It is more reliable than a general purpose computer because it only runs the one program so it will not crash and stop the engine working.

Why: Benefit stated (1) with a linked reason (1); the reason shows why only running one program makes it reliable.

Some marks1/2

It is more reliable because it is part of the car's engine.

Why: Only the benefit earns a mark (1); being part of the car is a location, not a linked reason why it is reliable.

No marks0/2

It is faster than a general purpose computer because it is embedded in the engine.

Why: Misconception that an embedded system is faster; embedded systems have limited processing resources, so neither point nor reason is creditworthy.

4Explain2 marksPrimary Memory Swap Remove

RAM is used to store data while a computer is running.

Explain one reason why the data in RAM is lost when a computer is switched off.

[2 marks]
Mark scheme

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

  • RAM is volatile (memory) (1) because it needs a constant/continuous power supply to hold/store the data it contains (1)
  • Data is held in RAM as electrical states/charges (1) so when the power supply is removed these states cannot be kept/refreshed and the data is lost (1)
  • RAM is used as short-term storage for the data and instructions currently in use (1) because it can only hold them while the computer has power (1)

For both marks, the expansion must follow/associate with the statement and must link the loss of the data to the power supply being removed.

Accept 'RAM is volatile' on its own for the first mark; the second mark is only awarded for a linked reason about the power supply.

Do not accept 'RAM is temporary/short-term memory' or 'RAM is cleared when the computer is switched off' on its own for both marks, as neither gives a reason.

Do not accept answers that say the data is deleted/cleared/erased by the computer or the operating system, or that the data is saved/moved to secondary storage, without saying why the data cannot be kept (e.g. because RAM needs power/is volatile).

Example answers and how they were marked
Full marks2/2

RAM is volatile memory, which means it needs a constant power supply to keep the data it is holding. When the power is switched off, the data is lost.

Why: Linked point (1) for 'RAM is volatile memory' and reason (1) for needing a constant power supply to hold the data.

Some marks1/2

The data in RAM is lost because RAM is volatile memory.

Why: Point (1) for 'RAM is volatile' but no linked reason about the power supply, and the mark scheme states that 'RAM is volatile' alone earns only the first mark.

No marks0/2

The data is deleted from RAM by the operating system when the computer is shut down so that the memory is free for next time.

Why: No creditworthy point: the answer says the data is deleted without saying why it cannot be kept, which the mark scheme's 'Do not accept' line rules out.

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