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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 · 6 marks

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1Short recall2 marksSecondary Memory Swap Remove

Computers have both primary storage and secondary storage.

Define the term secondary storage.

[2 marks]
Mark scheme

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

  • (Storage that is) non-volatile / keeps its data when the power is turned off (1)
  • (Storage that is) used to store programs and data/files (for later use) (1)
  • (Storage that is) not directly accessible by the CPU / not directly accessed by the CPU (1)

Allow both the non-volatile point and the stores programs and data point from one sentence if each idea is clearly stated, e.g. 'non-volatile storage that holds programs and data'.

Allow accessed via the CPU / must be copied into RAM before the CPU can use it for the third point.

Do not accept volatile / loses its data when the power is turned off.

Do not accept a description of primary storage, such as RAM or ROM.

Do not accept capacity.

Do not accept an example device on its own (e.g. hard disk drive).

Example answers and how they were marked
Full marks2/2

Secondary storage is non-volatile, so it does not lose data when the power is turned off. It is used to store programs and data files for later use.

Why: Non-volatile / keeps data when the power is off (1) and used to store programs and data files (1), each idea clearly stated.

Some marks1/2

Secondary storage is used to store programs and data files.

Why: Stores programs and data/files (1), but nothing is said about it being non-volatile or not directly accessible by the CPU.

No marks0/2

Secondary storage is volatile memory that holds the data the CPU is using at the moment.

Why: Describes primary storage (RAM) and says it is volatile, which the mark scheme says not to accept, so no marks are awarded.

2Describe2 marksFetch Decode Execute Cycle Swap Remove

The control unit is one component of 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 instructions (1) to determine what action/operation is required (1)
  • Sends control signals (1) along the control bus to coordinate/control the actions of other components (1)
  • Controls the fetch stage (1) by causing the next instruction to be fetched from main memory/RAM (1)
  • Controls the execute stage (1) by telling the ALU/other components when to carry out the required operation (1)

Do not accept responses relating to how the control unit affects performance, such as increasing clock speed.

Do not accept responses that describe the role of the ALU, registers or clock instead of the control unit.

Do not accept responses about the ALU performing calculations unless the control unit controlling the ALU is also stated.

Example answers and how they were marked
Full marks2/2

The control unit decodes instructions to determine what action is required.

Why: Linked point (1) and development (1): decodes instructions and determines the required action.

Some marks1/2

The control unit controls the fetch stage of the cycle.

Why: Point only (1): controls the fetch stage, but no linked development.

No marks0/2

The control unit carries out arithmetic and logical operations on data.

Why: No creditworthy point: describes the role of the ALU, which the mark scheme rejects.

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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