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Edexcel GCSE Computer Science (1CP2) Exam Questions

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4 questions · 8 marks

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1Short 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.

2Short recall2 marksStored Program Computers Swap Remove

Computers use 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:

  • Program instructions are stored in main memory/RAM (1)
  • The data used by the program is stored in main memory/RAM (1)
  • The CPU fetches/reads instructions from main memory to execute them (1)
  • The program can be run without the instructions being input again (1)

Allow 'the program is stored in memory' for one mark.

Do not accept answers about programs being stored on secondary storage, such as a hard disk or USB memory stick.

Do not accept answers that only describe the von Neumann architecture (e.g. having a CPU and memory) without stating that instructions are stored in main memory.

Example answers and how they were marked
Full marks2/2

Both the program instructions and the data the program uses are held in the same main memory, and the CPU fetches these instructions from memory to execute them.

Why: Instructions stored in main memory (1) and the CPU fetches instructions from memory to execute them (1).

Some marks1/2

Program instructions are stored in main memory.

Why: Instructions stored in main memory (1). No second point about data being stored in the same memory or about the CPU fetching instructions.

No marks0/2

The program is saved on the hard disk so that it can be loaded into RAM when the user runs it.

Why: A near-miss about secondary storage, which the mark scheme says not to accept; the stored program concept is about instructions being held in main memory.

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.

4Explain2 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.

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