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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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3 questions · 5 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).

2Describe2 marksFetch Decode Execute Cycle Swap Remove

A computer has an address bus.

Describe the purpose of the address bus in the fetch-decode-execute cycle.

[2 marks]
Mark scheme

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

  • Carries the address of a memory location (1) that the CPU needs to access/read from or write to (1)
  • Transfers the address of the next instruction (1) to main memory so it can be fetched (1)
  • Carries the address of data/instructions (1) from the CPU to main memory (1) so the correct location is found
  • Is used by the CPU to specify/identify a location in memory (1) by carrying its address along the bus (1)

Award one mark for a correct point even if not developed, e.g. 'it carries the address of a memory location'.

Accept 'the address of the next instruction' without mentioning the program counter, if it is linked to being sent to main memory/to be fetched.

Do not accept responses about carrying data or control signals.

Do not accept responses that say the address bus sends/transfers instructions or data without referring to addresses.

Do not accept vague responses such as 'it carries addresses' without saying what the address is for.

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 it can be fetched.

Why: Linked point (1) and development (1): transfers the address of the next instruction to main memory to be fetched. 'From the program counter' is an accepted extra detail, not required.

Some marks1/2

The address bus carries the address of a memory location.

Why: Correct point (1) but no linked development, e.g. that the CPU needs to access it.

No marks0/2

The address bus carries data between the CPU and RAM.

Why: No creditworthy point: confuses the address bus with the data bus.

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.

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