Oxford Cambridge and RSA - 2025
Wednesday 11 June 2025 – Morning
A Level Computer Science
H446/01 Computer systems
Time allowed: 2 hours 30 minutes
(Verified Question Paper With Mark
Scheme Combined June 2025)
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2025 OCR A Level Computer Science H446/01 Computer systems, Exams of Computer Science
2025 OCR A Level Computer Science H446/01 Computer systems Time allowed: 2 hours 30 minutes (Verified Question Paper With Mark Scheme Combined June 2025) INSTRUCTIONS •Use black ink. You can use an HB pencil, but only for graphs and diagrams. •Write your answer to each question in the space provided. If you need extra space use the lined pages at the end of this booklet. The question numbers must be clearly shown. •Answer all the questions. INFORMATION •The total mark for this paper is 140. •The marks for each question are shown in brackets [ ]. •Quality of extended response will be assessed in questions marked with an asterisk (*). •This document has 32 pages. ADVICE •Read each question carefully before you start your answer. OCR 2025 [601/4911/5] DC (PQ/CB) 340531/5 OCR is an exempt Charity Turn over BLANK PAGE DO NOT WRITE ON THIS PAGE
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Oxford Cambridge and RSA - 2025
Wednesday 11 June 2025 – Morning
A Level Computer Science
H446/01 Computer systems
Time allowed: 2 hours 30 minutes
(Verified Question Paper With Mark
Scheme Combined June 2025)
INSTRUCTIONS
- Use black ink. You can use an HB pencil, but only for graphs and diagrams.
- Write your answer to each question in the space provided. If you need extra space use the lined pages at the end of this booklet. The question numbers must be clearly shown.
- Answer all the questions. INFORMATION
- The total mark for this paper is 140.
- The marks for each question are shown in brackets [ ].
- Quality of extended response will be assessed in questions marked with an asterisk (*).
- This document has 32 pages. ADVICE
- Read each question carefully before you start your answer. © OCR 2025 [601/4911/5] DC (PQ/CB) 340531/ OCR is an exempt Charity (^) Turn over
© OCR Turn over 1 Charlie is about to study a computer games design course at university. He needs to purchase a computer to allow him to design and edit the graphics in his games, including video files. (a) Charlie’s computer contains a data bus, an address bus and a control bus. State the purpose of each of these three buses. Data bus ........................................................................................................................................... ............................................................................................................................................ .............. Address bus ..................................................................................................................................... ............................................................................................................................................ .............. Control bus ....................................................................................................................................... ............................................................................................................................................ .............. [3] (b) Charlie will need to use input and output devices when designing and editing his computer games. (i) State one input device and one output device that Charlie could use and give an example use of each. Input device Device name .................................................................................................................................... ............................................................................................................................................ .............. Example use .................................................................................................................................... ............................................................................................................................................ .............. Output device Device name ..................................................................................................................................... ............................................................................................................................................ ..............
© OCR Example use ..................................................................................................................................... ............................................................................................................................................ .............. [4]
© OCR (i) State which type of operating system Charlie will need to install. ............................................................................................................................................ .............. .................................................................................................................................. [1]
© OCR Turn over (ii) An operating system that Charlie is thinking about installing uses a multi-level feedback queue. Describe how a multi-level feedback queue works. ............................................................................................................................................ .............. ............................................................................................................................................ .............. ............................................................................................................................................ .............. ............................................................................................................................................ .............. ............................................................................................................................................ .............. .................................................................................................................................. [3] (iii) An operating system manages and installs device drivers. Explain why hardware devices require a device driver. ............................................................................................................................................ .............. ............................................................................................................................................ .............. ............................................................................................................................................ .............. .................................................................................................................................. [2] (e) Once Charlie has installed an operating system he will need to install utility software. State two utilities that Charlie could install and state the purpose of each. Utility 1 ............................................................................................................................................. ............................................................................................................................................ .............. Purpose .............................................................................................................................. .............. ............................................................................................................................................ .............. Utility 2
© OCR Turn over 2 OCR Consultants is designing a computer for a large company. (a) OCR Consultants is designing the architecture of the CPU. (i) Compare two differences between the Von Neumann architecture and the Harvard architecture. Difference 1 ...................................................................................................................................... ............................................................................................................................................ .............. ............................................................................................................................................ .............. ............................................................................................................................................ .............. Difference 2 ...................................................................................................................................... ............................................................................................................................................ .............. ............................................................................................................................................ .............. ............................................................................................................................................ .............. [4] (ii) OCR Consultants is considering using pipelining. State two benefits of using pipelining. Benefit 1 ........................................................................................................................................... ............................................................................................................................................ .............. Benefit 2 ........................................................................................................................................... ............................................................................................................................................ .............. [2]
© OCR (iii) OCR Consultants can base the CPU around a RISC architecture or a CISC architecture. Compare two differences between a RISC architecture and a CISC architecture. Difference 1 ...................................................................................................................................... ............................................................................................................................................ .............. ............................................................................................................................................ .............. ............................................................................................................................................ .............. Difference 2 ...................................................................................................................................... ............................................................................................................................................ .............. ............................................................................................................................................ .............. ............................................................................................................................................ .............. [4] (iv) Describe a benefit of making the CPU a multicore CPU. ............................................................................................................................................ .............. ............................................................................................................................................ .............. ............................................................................................................................................ .............. .................................................................................................................................. [2]
© OCR
© OCR Turn over
© OCR Turn over (c) Show the subtraction of these two floating point binary numbers. Both numbers are stored in a normalised floating point format, using 6 bits for the mantissa and 4 for exponent. You should show your result in the same format. Show your working out.
Working space .................................................................................................................................. ............................................................................................................................................ .............. ............................................................................................................................................ .............. ............................................................................................................................................ .............. ............................................................................................................................................ .............. ............................................................................................................................................ .............. ............................................................................................................................................ .............. ............................................................................................................................................ .............. ............................................................................................................................................ .............. ............................................................................................................................................ .............. ............................................................................................................................................ .............. ............................................................................................................................................ .............. ............................................................................................................................................ .............. ............................................................................................................................................ .............. ............................................................................................................................................
© OCR
................. Final 6-bit mantissa ............................................. Final 4-bit exponen t ............................................. [6]
© OCR 4 Kofi is a software engineer and has been asked to write some code using the Little Man Computer (LMC) instruction set. (a) State the LMC command that would be used for each description given in the table. Description LMC Command Load the value stored in the memory address into the accumulator Branch without checking the value in the accumulator Store the value from the accumulator into a memory address Branch if zero is in the accumulator Branch if zero or a positive number is in the accumulator [3] (b) Kofi has been asked to write a program that inputs two numbers and then outputs the largest of the two numbers. Write the code for this program using the LMC instruction set. You can assume that the two numbers will always be different. ............................................................................................................................................ .............. ............................................................................................................................................ .............. ............................................................................................................................................ .............. ............................................................................................................................................ .............. ............................................................................................................................................ .............. ............................................................................................................................................ .............. ............................................................................................................................................ .............. ............................................................................................................................................ ..............
© OCR Turn over