Edexcel GCSE Computer Science (1CP2) Exam Questions

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

• The address (of the next instruction) is sent from the CPU to main memory / placed on the address bus (1)
• The (next) instruction is fetched/read from main memory (RAM) (1)
• The instruction is brought/copied into the CPU / received into the MDR (1)
• The program counter (PC) is incremented/updated to hold the address of the next instruction (1)

Allow 'the PC/MAR is placed on the address bus' for the address being sent to main memory.

Allow 'the MDR receives the instruction' for the instruction being brought into the CPU.

Do not award a second mark for the instruction being fetched from main memory and the instruction being brought into the CPU; these are the same point.

Do not award 'the instruction is transferred along the data bus' on its own; this is the same point as the instruction being fetched from main memory.

Do not accept answers about decoding the instruction, e.g. 'the instruction is fetched from RAM and decoded', as decoding happens in the decode stage.

Do not accept answers about the execute stage, e.g. 'the ALU carries out the calculation' or 'the result of a calculation is stored in a register', as these happen in the execute stage.

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

• The compiler translates the whole program/complete source code in one go (1) whereas the interpreter translates one line/statement at a time (1)
• The compiler translates all of the source code before any of it is run/executed (1) but the interpreter translates each line/statement as it reads it (1)
• The interpreter translates one line/statement at a time (1) and the compiler translates the whole program/source code together (1)

Accept the compiler point and the interpreter point in either order.

Do not accept responses about object code/executable files, when the translated code is executed, how errors are reported, or speed/memory use.

Do not accept 'the interpreter executes/runs each line' on its own, without saying that it translates one line/statement at a time.

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

• Sends outgoing email from the client to the mail server (1) so it can be forwarded/relayed to the recipient's mail server (1)
• Transfers email between mail servers (1) so it reaches the destination server (1)
• Pushes/sends the email message (1) because it handles outgoing mail while POP3/IMAP handle incoming mail (1)

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

Do not accept receiving/downloading email or storing email on the server, which is POP3/IMAP.

Indicative content

How files become fragmented

• A file is saved into free blocks on the disk, so as files are deleted and new ones saved, one file can end up split across blocks in different places.
• Large files are more likely to become fragmented because they may not fit into one free space.
• The more the disks are used, the more fragmented they become, so the read/write head has to move to more locations to read all the parts of a file.
• Fragmentation is the reason that files on the college's computers take a long time to open.

What defragmentation software does

• It reorganises the blocks of each file so that they are stored together (contiguously) on the disk.
• It collects the free space into one block so that new files are written in one piece and are less likely to be fragmented.
• It is a housekeeping utility that is often supplied with the operating system, and it reorganises data that is already on the disk.
• It does not change the contents of any file, it only changes where the blocks of the file are stored.

Benefits of running it

• Files and programs open faster because the read/write head makes fewer movements, so the older computers feel quicker without the college buying new hardware.
• Free space in one block means new files are written in one piece, so the improvement lasts for a while.
• Running it may mean the college can keep using the older computers for longer instead of replacing them.

Drawbacks of running it

• It can take a long time to run, so it should be scheduled for when the room is not in use, such as overnight or at weekends.
• It causes a lot of disk activity, so running it too often puts unnecessary strain on the disks.
• It does not free up any space, as no files are deleted, so the disks will still be almost full.
• It only reorganises files that are intact, so it cannot recover a corrupted file, and a backup is still needed.

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 how files become fragmented and what defragmentation software does, with at least one benefit or drawback applied to the college's computers. An answer that only states what the software does and one benefit, with no explanation of how files became fragmented and no drawback, is Level 1 (2 marks).

Do not accept: defragmentation software compresses files, frees up storage space, deletes unused files, repairs corrupted files, or speeds up the processor or internet connection.