OCR A LEVEL Computer Science H446/01 Official MARK SCHEME for JUNE 2025: Computer systems, Exams of Computer Science

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OCR Oxford Cambridge and RSA GCE Computer Science H446/01: Computer systems A Level Mark Scheme for June 2025 OCR (Oxford Cambridge and RSA) is a leading UK awarding body, providing a wide range of qualifications to meet the needs of candidates of all ages and abilities. OCR qualifications include AS/A Levels, Diplomas, GCSEs, Cambridge Nationals, Cambridge Technicals, Functional Skills, Key Skills, Entry Level qualifications, NVQs and vocational qualifications in areas such as IT, business, languages, teaching/training, administration and secretarial skills. It is also responsible for developing new specifications to meet national requirements and the needs of students and teachers. OCR is a not-for-profit organisation; any surplus made is invested back into the establishment to help towards the development of qualifications and support, which keep pace with the changing needs of today’s society. This mark scheme is published as an aid to teachers and students, to indicate the requirements of the examination. It shows the basis on which marks were awarded by examiners. It does not indicate the details of the discussions which took place at an examiners’ meeting before marking commenced. All examiners are instructed that alternative correct answers and unexpected approaches in candidates’ scripts must be given marks that fairly reflect the relevant knowledge and skills demonstrated. Mark schemes should be read in conjunction with the published question papers and the report on the examination. H446/01 Mark Scheme June 2025 t Multiple Choice Question Responses When a multiple choice question has only a single, correctresponse and a candidate provides two responses (evenif one of th ese responses is correct), then no mark should be awarded (as it is not possible to determine which was the first response selected by the candidate). When a question requires candidates to select more than one option/multiple options, then local marking arrangements need to ensure consistency of approach. Contradictory Responses When a candidate provides contradictory responses, then no mark should be awarded, even if one of the answers is correct. ‘Short Answer Questions (requiring only a list by way of a response, usually worth only one mark per response) Where candidates are required to provide a set number of short answer responses then only the set number of responses should be marked. The response space should be marked fromleftto righton each line and then line by line until the required number of responses have been considered. The remaining responses should not then be marked. Examiners will have to apply judgement as to whether a ‘second response’ on a line is adevelopment of the ‘first response’, rather than a separate, discrete response. (The underlying assumptionis that the candidate is attempting to hedge their bets and therefore getting undue benefit rather than engaging with the question and giving the most relevant/correct responses.) Short Answer Questions (requiring a more developed response, worth two or more marks) If the candidates are required to provide a description of, say, three items or factors and fouritems or factors are provided, then mark on a similar basis — that is downwards (as it is unlikely in this situation that a candidate will provide more than one response in each section of the response space.) Longer Answer Questions (requiring a developed response) Where candidates have provided two (or more) responses to a medium or high tariff question which only required a single (deve loped) response and not crossed out the first response, then only the first response should be marked. Examiners will need to apply professional judgement as to whether the second (or a subsequent) response is a ‘new start’ or simply a poorly expressed continuation of the first response. Always check the pages (and additional objects if present) at the end of the response in case any answers have been continued there. Ifthe candidate has continued an answer there, then add a tick to confirm that the work has been seen. There is a NR (No Response) option. Award NR (No Response): - if there is nothing written at all in the answer space - OR if there is a comment which does not in any way relate to the question (e.g., ‘can’t do’ , ‘don’t know’) 3 446/01 Mark Scheme June 2025 - ORiif there is a mark (e.g., a dash, a question mark) which is not an attempt at the question. Note: Award 0 marks — for an attempt that earns no credit (including copying out the question). 8. The RM Assessor comments box is used by your team leader to explain the marking of the practice responses. Please refer to these comments when checking your practice responses. Do not use the comments box for any other reason. If you have any questions or comments for your team leader, use the phone, the RM Assessor messaging system, or e-mail. 9. Assistant Examiners will send a brief report on the performance of candidates to their Team Leader (Supervisor) via email by the end of the marking period. The report should contain notes on particular strengths displayed as well as common errors or weaknesses. Constructive criticism of the question paper/mark scheme is also appreciated. 10. For answers marked by levels of response: a. To determine the level — start at the highest level and work down until you reach the level that matches the answer b. To determine the mark within the level, consider the following Descriptor Award mark On the borderline of this level and the one below | At bottom of level Just enough achievement on balance for this Above bottom and either below middle or at middle of level (depending on number of marks level available) Meets the criteria but with some slight Above middle and either below top of level or at middle of level (depending on number of marks inconsistency available) Consistently meets the criteria for this level At top of level H446/01 Mark Scheme 12. Subject Specific Marking Instructions June 2025 Question Answer Mark Guidance 1 |i 1 mark max for each correct bus to max 3. Data bus © Transmits/carries data/instructions (between the hardware components / between CPU and memory). Address bus o Transmits/carries the (memory) address/location (where data will be sent to/retrieved from). Control bus © Transmits/carries (control) signal(s) (to control/coordinate CPU operations). H446/01 Mark Scheme June 2025 Question Answer Mark Guidance 1 | (b) i) 4 mark for input device with a suitable example and 1 mark for output device with suitable example to max 4 €.9.: Input Device ‘© Keyboard * _...Allow him to enter the game instructions / test the game « Mouse... * _...Allow him to select/manipulate objects in graphics programs © Graphics tablet... . Allow him to draw the characters in his game @ Microphone... * _...Allows him to record game narration/ instructions Output Device @ Monitor.. ...Display images / graphics he is working on for the game @ Speakers... e ...Allows him to edit/hear sound effects in the game The devices and examples must be relevant to something Charlie could be doing when doing computer game design/editing/testing. If device name is wrong, ignore example. If device name given in example space (and no device name has been stated) allow both marks. H446/01 Mark Scheme June 2025 Question Answer Mark Guidance (c) (i) | 4 mark for each correct row. 9 Ignore rows with a tick in both boxes. Statement CPU GPU Suited to performing simple v Allow alternative marks to a tick e.g. operations in parallel on ‘yes’ larger data sets. Suited to complex operations v on smaller data sets. (il) | 4 mark for each to max 2, e.9.: 2 Must be relevant to graphics in gameplay © More responsive gameplay © Shorter loading times/rendering Ignore general points about a «@ More realistic/immersive graphics GPU/multiple cores or reverse points © Higher frame rates/smoother gameplay about benefit for CPU © Higher resolutions/HD/4k graphics © Better multiplayer experience Only mark first benefit given per answer space 1 (d) Oo) ¢ = Multi-Tasking 1 1 (d) (ii) | 1 mark for each to max 3, e.g.: 3 © Puts processes into different categories/ queues Each queue has a different priority/quantum/scheduling approach * Processes can move between queues. e ...based on their behaviour/priority e Designed to minimise I/O bottle necks _...balances longer and shorter processes H446/01 Mark Scheme June 2025 Question Answer Mark Guidance 1 | (d) (ili) 2 marks for valid explanation. Allows the operating-system/software to communicate/interface with external hardware Translates operating-system instructions into a form that devices can use Allows peripherals from different manufacturers to work with different OS Abstracts hardware complexity (the OS and software don’t need to know specific commands) 1 Je 4 mark for suitable utility software and 1 mark for purpose to max 4, €.9.: . . . . . . ec ceecee Defragmentation... puts fragmented files in consecutive storage locations Encryption ...scrambles data so it cannot be understood Compression ...reduces the amount of storage space files take up/creates more storage space File repair.. repairs damaged/corrupt files Backup... ...copies data to another storage device Security/anti-virus... protects the computer against threats / malware/hacking etc. System clean-up... ...femoves files that are no longer needed ‘Accept firewall, file management, disk management with reasonable purpose H446/01 Mark Scheme June 2025 Question Answer Mark Guidance 2 (a) 2 marks for each difference to max 4. 4 Must be a full comparison for 2 marks to be given. CISC has a larger instruction set RISC has a smaller instruction set CISC requires more complex hardware/ requires cooling RISC requires less complex hardware/ requires little cooling CISC takes multiple clock cycles to execute an instruction RISC takes one clock cycle to execute an instruction CISC tends to use more energy RISC tends to use less energy CISC has more addressing modes RISC has fewer addressing modes CISC uses less RAM RISC uses more RAM CISC is difficult to pipeline RISC is easier to pipeline Each comparison must be comparing the same feature. 446/01 Mark Scheme June 2025 Question Answer Mark Guidance 2 (a) (iv) | 4 mark for each to max 2. 2 Allow ‘FDE Cycles’ for MP1 e Multiple instructions/threads can be processed at the same time © Improves multi-tasking Enables parallel processing * Increases the performance of the computer 2 (b) Mark Band 3 — High level (7-9 marks) 9 Answers may include, but are not limited to, some The candidate demonstrates a thorough knowledge and understanding of virtual machines. The material is generally accurate and detailed. The candidate is able to apply their knowledge and understanding directly and consistently to the context provided. Evidence/examples will be explicitly relevant to the explanation. The candidate provides a thorough discussion which is well balanced. Evaluative comments are consistently relevant and well-considered There is a well-developed line of reasoning which is clear and logically structured. The information presented is relevant and substantiated. Mark Band 2 — Mid level (4-6 marks) The candidate demonstrates reasonable knowledge and understanding of virtual machines. The material is generally accurate but at times underdeveloped. of the points below: AQ1 Virtual Machines: * Amachine that exists as software « Behaves as another program or piece of hardware * Needs areal machine to run on «For the user it will be indistinguishable Virtual Storage « Afile will be visible to a virtual machine as secondary storage * Remote storage that is mounted locally to seem like local storage * Stored on remote servers. Thick/Thin client: * Thick client involves all the processing being completed on the client. This can result in minimal use for a server, possibly only storing common data H446/01 Mark Scheme June 2025 Question Answer Mark Guidance Thick client approach: @ The computers have their own processing power to run complex processing locally. © Often has offline functionality as they can continue to work without an internet connection Devices can be customised to meet the user's needs. ® Possibly less secure (than thin client) as the security software on the devices needs to be managed. © May need more advanced devices so therefore will increase the upfront costs. AO3 Evaluation © There are cost savings to using thin client approaches The ability to dynamically allocate resources would benefit users who have unusually large processing jobs as they will not cause unacceptable wait times. * As the users are mobile, they are reliant on network access or mobile access. © May not allow 3rd party access. © Mobile data access may be slow or even non-existent. «If auser has a fully powered laptop in case of connectivity issues it will remove the cost saving advantages © If there is slow network access the user could be subject to unacceptable waits due to latency issues. 446/01 Mark Scheme June 2025 Question Answer Mark Guidance 3 (a) (i) | 10111104 1 (a) (i) | BD 1 (a) (iit) | 228 1 (b) 1 mark for each to max 2 Ps Allow: multiplies by 2° or % or 0.125 (1) © Divides... © .by 8/23 (c) 4 mark for each to max 6 6 Correct answer with valid binary working for © Both exponents converted 0011 =3 0010 =2 « Both mantissas shifted 0110.10 010.010 © Align mantissas: 0110.10 010.010 e Binary subtraction: 02 0110.400 0010,010 0100.010 Correct mantissa 010001 © Correct exponent 0011 calculation = full marks. Where denary working is clearly used to calculate the answer, do not allow MP4 Example of 2’s complement addition Convert 2"4 mantissa to 2's comp e.g.: 010.010 >> 101.11 0110.10 + 1101.11 4.0100.01 1111 H446/01 Mark Scheme June 2025 Question Answer Mark Guidance 4 {a) 4 correct answer = 1 mark 2 correct answers = 2 marks 5 correct answers = 3 marks Description Command Load the value stored in the memory address into the accumulator. LDA/ LOAD Branch without checking the value in the accumulator. BRA/ BR Store the value from the accumulator into the memory address. STA/STO Branch if zero is in the accumulator. BRZ/BZ Branch if zero or a positive number is in the accumulator. BRP/ BP H446/01 Mark Scheme June 2025 Question Answer Mark Guidance 4 (b) 1 mark for each to max 4: 4 Accept alternative mnemonics from the spec: STO, © Correctly inputting two values and storing at least one value Correctly subtracting one number from the other © Correct use of branch © Correct output for each path LOAD, BR, BZ, BP, IN, INPUT, COB, END If labels used must be a corresponding DAT location for MP1 POSSIBLE SOLUTION: INP STA FIRST INP STA SECOND suB FIRST BRP OUTPUTSECOND LDA ‘FIRST our HLT OQUTPUTSECOND LDA SECOND our HLT FIRST DAT SECOND DAT 0