Edexcel GCSE Computer Science (1CP2) Exam Questions

• A Address bus (1)
• The only correct answer is A. The correct answer is address bus. Do not accept 'address' on its own.
• B is not correct because the control bus carries control signals in both directions between the CPU and other components
• C is not correct because the data bus carries data in both directions between the CPU and main memory
• D is not correct because the system bus is the collection of all three buses

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

• Reduces/makes the size of a file smaller (1)
• No data is lost/removed (during compression) (1)
• The original file/data can be recreated/restored exactly (1)

Allow 'the compressed file takes up less storage space' for the first mark.

The second and third bullets are two ways of making the same point: award a maximum of one mark for them, so a response that says no data is lost and that the original file can be restored, but does not say the file is smaller, scores one mark.

Do not accept descriptions of lossy compression, e.g. 'it removes data that is not needed to make the file smaller'.

Ignore reference to download/transmission times, bandwidth and streaming, as these are benefits of compression and not part of the definition.

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

• Each router chooses the best route at the time (1) so when a route becomes busy/congested or fails, later packets are forwarded along a different path (1)
• Routers forward each packet separately (1) so the path a packet takes depends on the traffic conditions when that packet arrives (1)
• A router may send a packet to a different next router (1) if its routing table shows a better/less congested route for that packet (1)
• Traffic on the internet changes (1) so no single path is kept for the file and each packet can use whichever route is best when it is sent (1)

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

Allow reference to a routing table, or to how a router decides the route, as part of the linked reason.

Do not accept 'the packets have different IP addresses' because all packets from the same file have the same destination IP address, even though their routes can differ.

Do not accept 'the internet is busy' or 'there is a lot of traffic' on its own without linking this to the router choosing a different route.

Do not accept 'different routers send the packets' on its own without a reason why a different router/route is chosen.

Do not accept an answer that only says the packets take different routes without explaining why.

Indicative content

Allocating space

• The operating system checks that there is enough free space before a file is saved, so a large photograph does not make the save fail.
• The operating system finds free space on the disk and allocates it to the new file, so the file's data has somewhere to be written.
• Disk space is allocated so that a file is not written on top of data that already belongs to another file.
• When a file is deleted, the operating system marks its space as free so it can be used again by the next document that is saved.

Keeping track

• The operating system keeps a record of the name, size and location of every file, so it knows where each file is stored.
• The record is updated whenever a file is saved, renamed or deleted, so it still matches what is on the disk.
• The operating system uses this record to find a file again, so an employee can open a document or photograph that was saved earlier.
• The record lets the operating system tell the two employees' documents and photographs apart, even though they are all on the same disk.

Without this management

• Two files could be given the same space, so one document would overwrite another and the work would be lost.
• The operating system would not know where a file is stored, so a saved document could not be found and opened again.
• Space used by deleted files might never be freed, so the disk would fill up and new files could not be saved.

Levels

• Level 0 (0 marks): No rewardable content.
• Level 1 (1–2 marks): Basic, independent points are made, showing elements of understanding of key concepts/principles of computer science. (AO1) The discussion will contain basic information with little linkage between points made or application to the context. (AO2)
• Level 2 (3–4 marks): Demonstrates adequate understanding of key concepts/principles of computer science. (AO1) The discussion shows some linkages and lines of reasoning with some structure and application to the context. (AO2)
• Level 3 (5–6 marks): Demonstrates comprehensive understanding of key concepts/principles of computer science to support the discussion being presented. (AO1) The discussion is well developed, with sustained lines of reasoning that are coherent and logically structured, and which clearly apply to the context. (AO2)

Level 3 responses must cover both the allocation of space and the tracking of files, with at least one consequence of no management linked to its cause. Reference to a file being split across blocks that are not next to each other, or to the record holding the location of each block, is Level 3 detail and is not required.

Basic, unlinked points with no application to the business's documents or photographs, and a consequence such as 'files would be lost' with no cause given, are limited to Level 1; to reach Level 2 a point must be linked to a reason (for example, the record is kept so a document can be found again) and be applied to the context. Do not accept defragmentation, process scheduling, user management, peripheral management, or backup and antivirus scanning, as file management.