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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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1Explain2 marksPacket Switching Swap Remove

A router connects a home network to the internet.

Explain how a router uses the destination IP address in a packet header.

[2 marks]
Mark scheme

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

  • The router reads the destination IP address (1) so it knows which network/device the packet is for (1)
  • The router looks up the destination IP address in its routing table (1) to find the next router/route for the packet (1)
  • The router forwards the packet to the next router (1) that leads towards that IP address / is on the best route (1)

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

Do not accept MAC address - routers use the IP address to route packets between networks.

Do not accept 'it finds the exact device' without saying how the router uses the address, e.g. routing table/next router.

Example answers and how they were marked
Full marks2/2

The router looks up the destination IP address in its routing table to find the next router to send the packet to.

Why: Linked point (1) and reason (1): looks up the destination IP address in the routing table to find the next router.

Some marks1/2

It reads the destination IP address.

Why: Reads the destination IP address (1) but gives no linked reason about a routing table or next router.

No marks0/2

It reads the MAC address so it knows which computer sent the packet.

Why: Routers use the IP address to route packets, not the MAC address; no creditworthy point.

2Explain2 marksTopologies Swap Remove

A bus topology has a terminator at each end of its cable.

Explain why terminators are needed in a bus topology.

[2 marks]
Mark scheme

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

  • Terminators absorb the signal at the ends of the cable (1) so it is not reflected back along the bus (1)
  • Terminators prevent signals reflecting/bouncing back (1) so the reflected signal does not corrupt data on the cable (1)
  • Terminators absorb the signal (1) so it does not collide/interfere with data being sent by other devices (1)
  • Terminators stop the signal reflecting back down the cable (1) so data can be transmitted and received without errors (1)

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

Allow 'interfere'/'corrupt' only where the answer says the reflected signal mixes with/collides with data on the cable.

Do not accept 'to stop the signal' on its own, as stopping the signal is not the same as stopping it reflecting back along the cable.

Do not accept 'to terminate the cable/network', 'to end the cable' or 'to stop the cable breaking'.

Do not award responses that only repeat the stem, e.g. 'because there is a terminator at each end'.

Example answers and how they were marked
Full marks2/2

Terminators absorb the signal at each end of the cable so that it does not reflect back along the bus.

Why: Linked point (1) and reason (1): absorbing the signal is linked to it not being reflected back along the bus.

Some marks1/2

Terminators absorb the signal at the ends of the cable.

Why: Awarded 1 mark for the point that the signal is absorbed, but no linked consequence is given.

No marks0/2

They terminate the network so the cable does not break.

Why: No credit: it does not say the signal is absorbed or that reflections are prevented, and the mark scheme rejects 'to terminate the network' and 'to stop the cable breaking'.

3Explain2 marksAddressing Swap Remove

Data is split into packets before it is sent over the internet.

Explain why each device that receives packets over the internet needs a unique IP address.

[2 marks]
Mark scheme

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

  • Data/packets are delivered to the correct/intended device (1) because the destination IP address identifies that device, so a duplicate address would mean packets could be delivered to the wrong device (1)
  • Replies are sent back to the device that requested the data (1) because the sender's IP address identifies that device, so a duplicate address would mean the reply could be sent to the wrong device (1)
  • The device can be identified separately from other devices (1) so packets are not delivered to a different device that has the same address (1)

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

Award one mark for a valid point and a second mark only for a linked reason explaining why a duplicate address would cause a problem.

Do not accept 'it is unique'/'it has its own address' as a point, as this repeats the question.

Do not accept 'so it can connect to the internet' or 'so it can be found' on its own without a link to data/packets being delivered to the correct device.

Allow 'data' for 'packets'.

Example answers and how they were marked
Full marks2/2

Packets are delivered to the correct device because the destination IP address identifies one device, so if two devices had the same address packets could be sent to the wrong one.

Why: Point that packets reach the correct device (1) and linked reason that a duplicate address would cause misdelivery (1).

Some marks1/2

Packets are sent to the correct device because it has its own IP address.

Why: Valid point that packets reach the correct device (1), but the reason only restates uniqueness and does not explain how a duplicate address would cause a problem, so no second mark.

No marks0/2

So that it can connect to the internet.

Why: No link to packets/data being delivered to the correct device; the mark scheme rejects a connection statement on its own.

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