Edexcel GCSE Computer Science (1CP2) Exam Questions

• B The destination IP address (1)
• The only correct answer is B. The correct answer is the destination IP address.
• A is not correct because a domain name is converted to an IP address by a DNS server before routing begins
• C is not correct because the sender's MAC address is only used to deliver the packet on the local network
• D is not correct because the file name is not used to route packets

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

• Each user/file is given permissions/access rights (1) so other users cannot read/write/open/change that user's files (1)
• A user may be given read-only/read access to a file (1) so they cannot edit/delete/change it (1)
• Each file is given permissions/access rights for different users (1) so the operating system allows/refuses access depending on which user is logged in (1)
• The operating system checks a user's permissions/access rights when a file is opened (1) so a user with read-only/read access cannot save/delete changes (1)

Do not accept responses about asking for a password/username, as this checks who the user is, not what they are allowed to do.

Do not accept 'files are protected/safe' or 'access rights protect files' without saying how access is limited (e.g. read-only access, permissions for different users).

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

• Instructions can manipulate/control the hardware/memory/registers directly (1) so the driver can control the specific device it is written for (1)
• The code is written for one specific processor/architecture (1) so it works with the exact hardware it will control (1)
• The programmer controls exactly how memory/registers are used (1) so the code is efficient and needs little memory, which suits a device that has limited memory (1)
• Each instruction maps to one machine code instruction (1) so the driver code is small enough to fit in the memory of the device (1)

Extra detail, such as naming the device the driver controls, is not needed to earn the marks.

Do not accept 'it is closer to machine code' on its own: it must be developed to show how this helps the driver, e.g. it can control the hardware directly.

Do not accept 'it is faster/quicker' with no link to the hardware/device, e.g. the device responds quickly.

Do not accept 'it is easier to learn', 'it is easier to debug' or 'it takes less time to write'.

Indicative content

How RAM is used when editing video

• The editing software and the video project being worked on are loaded into RAM so that the CPU can access them quickly.
• RAM holds the frames, effects and timeline data that the CPU is processing as part of the fetch-decode-execute cycle.
• The CPU fetches the instructions and the video data it needs from RAM, which is much faster than fetching them from secondary storage.
• Having more RAM means that more of the 4K video project and its effects can be held in memory at the same time.
• RAM is also used by the operating system and any other open software, so not all of the RAM is available to the editing software.

Why too little RAM causes poor performance

• If there is not enough RAM, the operating system uses virtual memory on secondary storage for data that will not fit in RAM.
• Virtual memory is much slower than RAM, so the editor waits longer for 4K video to load and for effects to be applied.
• Data has to be swapped between RAM and virtual memory, which is extra work that slows the computer down.
• The editing software may freeze or close if it runs out of memory while working on the 4K video.
• Playback of the 4K video is not smooth because the frames cannot all be held in RAM ready for the CPU.

Why adding more RAM may not always improve performance

• If the computer already has enough RAM for the editing software, the extra RAM will not be used and performance will hardly change.
• The clock speed and the number of cores of the CPU decide how quickly instructions are processed, so a slow CPU will still limit how quickly the video is edited.
• A slow secondary storage drive will still limit how quickly the 4K video files can be loaded into RAM.
• Adding RAM only improves performance if a shortage of RAM was the reason for the computer being slow.

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)

Additional guidance

• Level 3 responses must explain how RAM is used when editing video and give a developed reason why adding more RAM may not always improve performance; responses that only explain how RAM is used, or only why too little RAM causes poor performance, are limited to Level 2.
• Accept 'paging' or 'swap file' as equivalent to virtual memory, but do not accept 'cache' or 'ROM'; do not credit statements that adding RAM increases the CPU clock speed or makes the CPU faster, or that 'RAM is volatile' explains poor performance, as these are not linked to the question asked.