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Edexcel GCSE Computer Science (1CP2) Exam Questions

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4 questions · 11 marks

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1Multiple choice1 markFetch Decode Execute Cycle Swap Remove

Identify the component that stores instructions and data during the fetch-decode-execute cycle.

[1 mark]
  • AArithmetic logic unit
  • BClock
  • CMain memory (RAM)
  • DProgram counter
Mark scheme
  • C Main memory (RAM) (1)
  • The only correct answer is C. The correct answer is main memory (RAM); accept 'main memory', 'RAM' or 'random access memory'.
  • A is not correct because the arithmetic logic unit performs arithmetic and logical operations
  • B is not correct because the clock sends regular pulses to synchronise the components of the CPU
  • D is not correct because the program counter holds the address of the next instruction, not the instructions and data
Example answers and how they were marked
Full marks1/1

C Main memory (RAM)

Why: Correct option: main memory (RAM) stores instructions and data during the fetch-decode-execute cycle (1).

No marks0/1

D Program counter

Why: Near-miss distractor: the program counter holds the address of the next instruction, not the instructions and data (0).

No marks0/1

A Arithmetic logic unit

Why: Misconception: the ALU performs arithmetic and logical operations, so it does not store instructions and data (0).

2Short recall2 marksPrimary Memory Swap Remove

A computer is designed using the von Neumann stored program concept.

Define the term stored program concept.

[2 marks]
Mark scheme

Award one mark for any of the following up to a maximum of two marks:

  • The program instructions and data are stored together in main memory/RAM (1)
  • The same memory is used for both instructions and data (1)
  • The instructions are fetched from main memory and executed by the CPU (1)
  • The instructions are fetched and executed one at a time / in sequence (1)
  • The program can be changed/replaced by loading new instructions into memory, without changing the hardware (1)

Do not accept the program is stored in secondary storage / on the hard disk.

Do not accept the program is stored in the CPU / in registers.

Example answers and how they were marked
Full marks2/2

The program instructions and the data are stored together in main memory, and the CPU fetches the instructions one at a time and executes them.

Why: Creditworthy point that instructions and data are stored in the same main memory (1) and the linked point that the CPU fetches and executes them from memory (1).

Some marks1/2

The program is held in the main memory (RAM) so that the computer can run it.

Why: Earns the point that the program instructions are stored in main memory (1), but does not say that the CPU fetches and executes them, so the second mark is not earned.

No marks0/2

The program is stored on the hard disk and loaded into the CPU when it is run.

Why: Both parts are misconceptions named in the Do not accept lines: the stored program concept keeps the instructions in main memory, not on secondary storage or in the CPU.

3Explain2 marksSecondary Memory Swap Remove

A Blu-ray disc and a CD are the same physical size.

Explain why a Blu-ray disc can store more data than a CD.

[2 marks]
Mark scheme

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

  • The pits and lands on a Blu-ray disc are smaller/closer together (1) because the blue laser has a shorter wavelength than the infrared laser used by a CD (1)
  • More pits and lands can be stored in the same length of track (1) because the blue laser has a shorter wavelength, so it can focus on a smaller area/read smaller details (1)
  • A blue laser can focus on a smaller area (1) so smaller pits and lands can be used, allowing more data to be stored on the disc (1)

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

Do not accept 'a Blu-ray is newer/better' or 'a Blu-ray has more space/bigger storage' without a linked reason about the laser/pits and lands.

Do not accept answers about read/write speed, for example 'a Blu-ray spins faster', because the question asks about the amount of data stored, not how quickly it is read.

Do not award 'a Blu-ray disc can have more layers' on its own as the reason; it must be linked to the smaller pits and lands/shorter wavelength of the laser.

Do not accept 'red laser' for a CD; a CD uses an infrared laser (red is used by DVD).

Example answers and how they were marked
Full marks2/2

A Blu-ray is read with a blue laser which has a shorter wavelength so the pits and lands on the disc can be smaller and more of them fit on the disc.

Why: Linked point (1) shorter wavelength of the blue laser with reason (1) smaller pits and lands so more data fits on the same disc.

Some marks1/2

The pits and lands on a Blu-ray are smaller than the ones on a CD so it can store more data.

Why: Point (1) that the pits and lands are smaller, but the second part repeats the question and does not give the linked reason (shorter wavelength of the blue laser/infrared CD laser), so only one mark.

No marks0/2

A Blu-ray spins faster than a CD so more data can be read from it in the same time.

Why: Do not accept answers about read/write speed; the question asks about the amount of data stored, not how quickly it is read.

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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