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Edexcel GCSE Computer Science (1CP2) Exam Questions

Build a practice paper from 604 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 marksStored Program Computers Swap Remove

The central processing unit (CPU) contains an arithmetic logic unit (ALU).

State two types of operation carried out by the ALU.

[2 marks]
Mark scheme

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

  • An arithmetic operation, e.g. addition/subtraction/multiplication/division (1)
  • A logical operation, e.g. comparing two values (is A > B?) / using AND, OR, NOT (1)

Do not accept decoding instructions, fetching instructions or controlling the timing of the CPU, as these are carried out by the control unit.

Example answers and how they were marked
Full marks2/2

It carries out arithmetic operations such as addition and subtraction, and logical operations such as comparing two values to see if one is greater than the other.

Why: Arithmetic operation (1) and logical operation (1).

Some marks1/2

It adds numbers together and works out the result.

Why: Arithmetic operation, addition (1). No logical operation.

No marks0/2

It decodes the instructions that have been fetched from main memory.

Why: Decoding and fetching are the control unit's role; the mark scheme's do-not-accept line covers this.

2Describe2 marksTranslators Swap Remove

Source code can contain syntax errors.

Describe how a compiler and an interpreter differ in the way they deal with syntax errors.

[2 marks]
Mark scheme

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

  • The compiler reports all syntax errors after translation has finished (1) whereas the interpreter stops at the first error it finds (1)
  • The interpreter reports a syntax error as soon as it finds one (1) and does not translate/execute any more of the program (1)
  • The compiler continues translating after an error (1) and reports the errors at the end (1)
  • The interpreter stops translating when it reaches an error (1) but the compiler finishes translating before reporting errors (1)

Do not accept answers about fixing/correcting errors or about object code.

Do not award 'the compiler finds more errors' without saying errors are reported at the end.

Example answers and how they were marked
Full marks2/2

A compiler reports all the syntax errors at the end of translation, whereas an interpreter stops and reports the error as soon as it finds one.

Why: Compiler reports errors at the end (1) and interpreter stops/reports at the first error (1).

Some marks1/2

An interpreter stops translating when it finds a syntax error.

Why: Interpreter stops at the first error (1); no comparison with when the compiler reports errors.

No marks0/2

A compiler reports a syntax error immediately, before translating the rest of the program.

Why: Reverses the compiler's behaviour; it finishes translating before reporting errors.

3Explain2 marksTopologies Swap Remove

A bus topology uses one main cable shared by all devices.

Explain why a bus topology can be a security risk.

[2 marks]
Mark scheme

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

  • All devices receive every data packet (1) because the main cable is shared by all nodes (1)
  • Data can be read by any device on the network (1) because there is no central switch to send it only to the destination (1)
  • A device can intercept/capture data not meant for it (1) because all transmissions travel along the same cable (1)
  • Any device can view all data on the cable (1) so data is not private/secure (1)

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

Do not accept 'it is easy to hack' without saying data can be seen/intercepted on the shared cable.

Do not accept 'the central switch can be hacked' because a bus topology has no central switch.

Example answers and how they were marked
Full marks2/2

Any device on the bus can see all the data (1) because every packet travels along the same shared cable (1).

Why: Linked point (1) and reason (1): data is visible to all devices because the cable is shared.

Some marks1/2

All devices can see the data.

Why: Awarded 1 mark for stating that all devices can see the data, but no linked reason about the shared cable is given.

No marks0/2

It is less secure because the central switch can be hacked.

Why: No credit: a bus topology has no central switch; the answer gives a misconception and no valid point about the shared cable.

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