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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 · 7 marks

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1Multiple choice1 markStored Program Computers Swap Remove

Identify the function of the control unit in the fetch-decode-execute cycle.

[1 mark]
  • ADecodes instructions
  • BPerforms arithmetic operations
  • CStores data and instructions
  • DTemporarily stores data being processed
Mark scheme
  • A Decodes instructions (1)
  • The only correct answer is A. The correct answer is Decodes instructions.
  • B is not correct because the arithmetic logic unit performs arithmetic operations
  • C is not correct because main memory stores data and instructions
  • D is not correct because registers temporarily store data being processed
Example answers and how they were marked
Full marks1/1

A Decodes instructions

Why: Correct option: the control unit decodes instructions during the fetch-decode-execute cycle (1).

No marks0/1

C Stores data and instructions

Why: Main memory stores data and instructions, not the control unit; this is a common distractor, so no mark.

No marks0/1

B Performs arithmetic operations

Why: Arithmetic operations are performed by the ALU, not the control unit; a common confusion between CPU components, so no mark.

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.

3Short 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.

4Describe2 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.

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