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Wednesday 11 June 2025 – Morning
A Level Computer Science
H446/01 Computer systems
Time allowed: 2 hours 30 minutes You can use: • a ruler (cm/mm)
- an HB pencil Do not use: • a calculator
Please write clearly in black ink. Do not write in the barcodes. Centre number Candidate number
First name(s) Last name
OCR A Level Computer Science H446/01 Computer systems
QP&MS Summer 2025
Oxford Cambridge and RSA
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.
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BLANK PAGE
DO NOT WRITE ON THIS PAGE
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(ii) Charlie will need to store a large collection of files containing high definition images and high definition videos that he will use during his course. State a type of secondary storage device that Charlie could use and give a reason why. Type of storage ................................................................................................................................. .......................................................................................................................................................... Reason.............................................................................................................................................. .......................................................................................................................................................... [2]
(c) In addition to the Central Processing Unit (CPU), Charlie will purchase a Graphical Processing Unit (GPU) that will be used to process and display the graphics in his games. (i) Tick (✓) one box on each row to indicate if each statement is referring to a CPU or a GPU. Statement CPU GPU Suited to performing simple operations in parallel on larger data sets Suited to performing complex operations on smaller data sets [2] (ii) State two benefits of using a GPU to process and display the graphics in computer games. Benefit 1 ........................................................................................................................................... .......................................................................................................................................................... Benefit 2 ........................................................................................................................................... .......................................................................................................................................................... [2]
(d) Charlie will require an operating system that will allow him to have several applications open at the same time. (i) State which type of operating system Charlie will need to install. ..........................................................................................................................................................
. .................................................................................................................................................................... [1]
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(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 ............................................................................................................................................. .......................................................................................................................................................... Purpose ............................................................................................................................................ .......................................................................................................................................................... [4]
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(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]
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**(b) *** The employees of the large company work remotely from home and use large databases that store a lot of sensitive data. They need to be able to use the databases to search and sort data quickly. OCR Consultants is considering two approaches:
- thin client approach – this is where the database is stored virtually on a remote server. All of the data processing is also completed on a remote server on virtual machines. The employees’ computers are only used to capture the data input and display the results from the virtual machines
- thick client approach – this is where most of the processing is done on the employees’ computer using specialised software to access the remote database. Discuss the benefits and drawbacks of each of these approaches. You should include the following in your answer:
- • what is meant by virtual machines and virtual storagethe benefits and drawbacks of a thin client and thick client approach described in the question
- a conclusion justifying which approach would be most suitable for this scenario. [9] .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... ..........................................................................................................................................................
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(a) (i) Convert the denary number 189 into an 8-bit binary number. .......................................................................................................................................................... .......................................................................................................................................................... ..........................................................................................................................................................
. ................................................................................................................................................. [1] (ii) Convert the denary number 189 into a hexadecimal value. .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... . ................................................................................................................................................. [1] (iii) Convert the hexadecimal value E4 into a denary number. .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... . ................................................................................................................................................. [1] (b) Explain the effect that a right shift of three places will have on a positive binary number. .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... . ................................................................................................................................................. [2]
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(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 .................................................................................................................................. .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... Final 6-bit mantissa ............................................. Final 4-bit exponen t ............................................. [6]
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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. .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... ..........................................................................................................................................................
. ................................................................................................................................................. [4]
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**(c) *** Kofi is working on a number of projects. These include:
- project 1 – Writing a mobile phone app to look at the news
- project 2 – Writing software to send temperature readings from an embedded heat sensor to other devices
- project 3 – Writing an image editing application for a desktop computer
- project 4 – Writing software to calculate the results of a physics experiment that produces terabytes of data
- project 5 – Writing a new device driver for a new piece of hardware. Discuss which of these projects should be written in a high level programming language and which should be written in a low level language. You should include the following in your answer:
- what is meant by high level programming language and low level language
- which projects are suitable for high level and which are suitable for low level languages
- a conclusion that justifies why these different languages are needed. [12] .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... ..........................................................................................................................................................
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5 This diagram shows the logic circuit for a half adder.
A B
(a) Complete the truth table for this half adder circuit.
S
C (Out)
A B S C (Out) 0 0 0 1 1 0 1 1 [4] (b) Describe the difference between a half adder circuit and a full adder circuit. .......................................................................................................................................................... .......................................................................................................................................................... ..........................................................................................................................................................
. ................................................................................................................................................. [2]
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(c) The diagram below shows a partially completed logic circuit for a full adder. The full adder circuit contains three inputs:
- A – represents the first input
- B – represents the second input
- C(in) – represents the carry bit from the previous stage of the addition. The full adder circuit contains two outputs:
- Sum – represents the result of adding the three inputs A , B and C(in)
- C(out) – represents the carry that is passed to the next stage of the addition. Complete the logic circuit to represent a full adder.
A
B
C(in)
Sum
C(out)
[4]
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6 DCC Software is a company that creates a wide range of software products for home computers. Its products include image, video and sound editing software. (a) DCC Software makes significant use of software libraries. Explain the benefits of using software libraries to create software. .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... ..........................................................................................................................................................
. ................................................................................................................................................. [4] (b) Once DCC Software has written a piece of software, they use translators to translate the programming code. (i) The table shows different stages of code compilation labelled A , B , C and D. A Lexical analysis B Syntax analysis C (^) Code generation D Code optimisation In each box write the letter of the stage that matches each description. Converts the high level code into low level instructions Examines the code and improves the efficiency of it without affecting the functionality Removes comments and whitespace and then converts the high level code into tokens Identifies syntax errors and creates an abstract syntax tree [4]
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(ii) DCC Software is considering the benefits of both an interpreter and a compiler. State two benefits of using an interpreter. Benefit 1 ........................................................................................................................................... .......................................................................................................................................................... Benefit 2 ........................................................................................................................................... .......................................................................................................................................................... [2] (iii) State two benefits of using a compiler. Benefit 1 ........................................................................................................................................... .......................................................................................................................................................... Benefit 2 ........................................................................................................................................... .......................................................................................................................................................... [2] (c) DCC software uses a database table called TblSoftware to store details about all of their products. ProductID Name Type Price DCC01 DCCPhotos Image £129. DCC02 DCCDraw Image £119. DCC03 DCCAnimate Image £99. DCC04 DCCMovie Video £189. DCC05 DCCEffects Video £99. DCC06 DCCAudio Sound £119. TblSoftware
