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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 markPrimary Memory Swap Remove

RAM is the main memory of a computer.

Identify the effect on the contents of RAM when the computer is switched off.

[1 mark]
  • AThey are lost
  • BThey are stored permanently
  • CThey are saved to secondary storage
  • DThey are written to ROM
Mark scheme
  • A They are lost (1)
  • The only correct answer is A. The correct answer is They are lost
  • B is not correct because RAM is volatile and its contents are lost when the power is switched off, so they are not stored permanently
  • C is not correct because RAM is volatile and its contents are lost when the power is switched off, so they are not saved to secondary storage
  • D is not correct because ROM is read-only memory that holds the start-up instructions, so the contents of RAM are not written to it
Example answers and how they were marked
Full marks1/1

A They are lost

Why: Selected the correct option. RAM is volatile, so its contents are lost when the power is switched off (1).

No marks0/1

C They are saved to secondary storage

Why: Near miss: thinks RAM contents are automatically saved, but RAM is volatile and its contents are not saved to secondary storage (0).

No marks0/1

B They are stored permanently

Why: Misconception: thinks RAM is non-volatile and keeps data permanently, but RAM is volatile and loses its contents when the power is switched off (0).

2Multiple 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.

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.

4Explain2 marksEmbedded Systems Swap Remove

A greenhouse uses an embedded system to keep the plants healthy.

Explain how the embedded system controls the temperature in the greenhouse.

[2 marks]
Mark scheme

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

  • A temperature sensor measures/reads the temperature in the greenhouse (1) which the processor compares with the value stored in the system (1)
  • The heater is switched on (1) when the temperature reading goes below the value stored in the system (1)
  • A fan/vent/window is opened/a cooler is switched on (1) when the temperature reading goes above the value stored in the system (1)
  • The temperature is checked/measured continuously (1) so the heater/fan is switched on or off as soon as the temperature changes (1)

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

Allow one mark for a correct point on its own without a linked reason, e.g. 'a temperature sensor measures the temperature'.

Do not award 'the embedded system controls/keeps the temperature correct' as this repeats the question.

Do not accept naming a device without saying what it does, e.g. 'the greenhouse has a thermostat'.

Example answers and how they were marked
Full marks2/2

A temperature sensor measures the temperature in the greenhouse, which the processor compares with the value stored in the system.

Why: Point (1): the input and what it measures. Reason (1): the linked statement about what the processor does with the reading.

Some marks1/2

The embedded system uses a temperature sensor that measures the temperature in the greenhouse.

Why: A correct point on its own (1); no linked statement about what the system does with the reading, so the second mark is not awarded.

No marks0/2

The embedded system controls the temperature so the plants do not get too cold.

Why: Rewords the question without saying how the temperature is measured or changed, so no mark is awarded.

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