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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 · 12 marks

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1Describe2 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.

2Describe2 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.

3Explain2 marksFetch Decode Execute Cycle Swap Remove

The CPU carries out the fetch-decode-execute cycle.

Explain one reason why the address bus is used in the fetch stage of the fetch-decode-execute cycle.

[2 marks]
Mark scheme

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

  • The address bus carries the address of the next instruction (1) so the CPU can locate/fetch it from main memory/RAM (1)
  • The address bus carries the address of the memory location to be read (1) so the instruction/data stored there can be located/accessed (1)
  • The CPU needs to know where the next instruction is stored (1) so the address bus sends the address to main memory/RAM (1)

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

Allow 'from the program counter/PC' as part of the point for one mark, e.g. the address bus carries the address from the program counter (1), but the second mark needs the destination or purpose (e.g. to locate/fetch the instruction in main memory/RAM).

Do not award the second mark for naming the program counter/PC alone.

Do not accept answers that say the address bus carries data/instructions from main memory to the CPU, as these travel on the data bus.

Do not accept answers that say the address bus stores the address.

Do not allow an answer that only restates that the address bus carries addresses without saying which address or why it is needed.

Example answers and how they were marked
Full marks2/2

The address bus carries the address of the next instruction from the program counter to main memory, so that the CPU can locate the instruction that is to be fetched.

Why: Linked point (1) and reason (1).

Some marks1/2

The address bus carries the address of the next instruction from the program counter.

Why: Point only (1); the second mark is not awarded because the destination/purpose of locating or fetching the instruction is missing.

No marks0/2

It carries the instruction from main memory back to the CPU so that it can be decoded.

Why: Misconception: instructions travel on the data bus, which the mark scheme's Do not accept line covers.

4Discuss6 marksFetch Decode Execute Cycle Swap Remove

A small robotics company is designing a new robot. The robot's computer uses von Neumann architecture. The engineers are explaining how programs are stored and run.

Discuss how the von Neumann stored program concept and main memory (RAM) are used during the fetch-decode-execute cycle.

Your answer should include:

  • what is meant by the stored program concept
  • the role of RAM in the cycle
  • why the stored program concept is useful.
[6 marks]
Mark scheme

Indicative content

Stored program concept

  • Instructions and data are stored together in the same main memory (RAM).
  • Instructions are fetched one at a time from memory and executed in sequence.
  • The program can be changed by loading different instructions into RAM.
  • The CPU can only execute instructions that are in main memory.

Role of RAM

  • RAM holds the program instructions and the data being used.
  • The address of the next instruction is held in the program counter (PC).
  • The instruction is fetched from RAM using the address bus.
  • The data bus carries the instruction from RAM to the CPU.
  • RAM is volatile, so programs are lost when power is off.
  • RAM is directly accessible by the CPU, unlike secondary storage.

Benefits

  • The same hardware can run many different programs.
  • Programs can be loaded and changed quickly.
  • No need to rewire the computer for a new task.
  • Makes general-purpose computers possible.

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)
Example answers and how they were marked
Full marks6/6

The von Neumann stored program concept means that both the program instructions and the data are stored together in the same main memory, RAM. During the fetch-decode-execute cycle, the CPU fetches an instruction from RAM, decodes it in the control unit, and then executes it. The program counter holds the address of the next instruction, and this address is sent along the address bus to RAM. RAM then returns the instruction along the data bus to the CPU. RAM is volatile, so it only holds the program while the robot is powered on. The stored program concept is useful because the robot's computer can run different programs without changing any hardware; new instructions can simply be loaded into RAM. This makes the computer general-purpose and flexible.

Why: Comprehensive understanding: defines stored program concept, explains RAM role with PC, address bus and data bus, applies to robot, and gives benefits. Sustained lines of reasoning. Level 3.

Some marks3/6

The stored program concept is when instructions and data are stored in RAM. The CPU fetches instructions from RAM. The program counter keeps the address of the next instruction. RAM holds the program. The benefit is that you can change the program without rewiring the computer.

Why: Adequate understanding: correct basic points about stored program concept and RAM, with some linkage, but little development or application to the robot's fetch-decode-execute cycle. Level 2.

Some marks1/6

The von Neumann stored program concept is that the CPU uses RAM to store the program. The fetch-decode-execute cycle fetches, decodes and executes. RAM is random access memory. The benefit is that it is fast.

Why: Basic independent points only; no real linkage or application to the robot. Level 1.

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