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Edexcel GCSE Computer Science (1CP2) Exam Questions

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4 questions · 8 marks

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1Describe2 marksEmbedded Systems Swap Remove

A greenhouse uses an embedded system to control the growing conditions for plants.

Describe how the embedded system controls the growing conditions in the greenhouse.

[2 marks]
Mark scheme

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

  • It reads/monitors the temperature/humidity/light level using sensors (1) to switch the heaters/vents/lamps/watering system on or off when the reading is outside the set range (1)
  • It compares the readings from the sensors with the set values/thresholds stored in its memory (1) to decide whether the conditions need to be changed (1)
  • It monitors the light level using a light sensor (1) and turns the lamps on when the light falls below the level the plants need (1)
  • It monitors the soil moisture using a soil moisture sensor (1) and turns the water pump/irrigation on when the soil is too dry (1)

For the second mark, the action/response must be linked to the sensor reading given in the first point.

Allow named sensors (temperature/humidity/light/soil moisture) and named outputs (heater, fan, vent/window, lamp, irrigation/water pump).

Do not accept answers that only name a sensor or only name an output, e.g. 'it has a temperature sensor and a heater', as there is no link between the reading and the control action.

Do not accept answers where a person switches the equipment on or off, as the embedded system controls the conditions automatically.

Example answers and how they were marked
Full marks2/2

The embedded system reads the temperature using a sensor and switches the heater on when the temperature is below the set value.

Why: Sensor reading point (1) and linked control action (1).

Some marks1/2

The embedded system compares the readings from the sensors with the set values stored in its memory.

Why: First point only (1) - the comparison with stored values - with no linked action.

No marks0/2

The greenhouse has a temperature sensor and a heater.

Why: Only names a sensor and an output, which the mark scheme says is not accepted.

2Describe2 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.

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

A technician increases the amount of RAM in a laptop from 8 GiB to 16 GiB.

Explain one benefit of increasing the amount of RAM in a computer.

[2 marks]
Mark scheme

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

  • More applications/programs can be open/run at the same time (1) because more instructions and data can be held in main memory at once (1)
  • Programs run faster (1) because the CPU does not have to wait for instructions/data to be read/transferred from slower secondary storage (1)
  • The CPU waits/idles for less time (1) because instructions and data can be transferred to the CPU more quickly from RAM (1)

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

Do not accept 'more files/photos/documents can be stored' or 'the computer has more storage' - this is a benefit of secondary storage, not RAM.

Do not accept 'the CPU becomes faster' or 'the clock speed increases'.

Example answers and how they were marked
Full marks2/2

More programs can be open at the same time because more instructions and data can be held in main memory at once.

Why: Linked point (1) for more programs running at the same time and reason (1) for more instructions and data being held in main memory at once.

Some marks1/2

Programs will run faster.

Why: Point (1) only; no linked reason such as the CPU not having to wait for data from slower secondary storage.

No marks0/2

There will be more space to save files and documents on the laptop.

Why: Misconception: the benefit given is a benefit of secondary storage, which the mark scheme's 'Do not accept' line rules out.

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