Cambridge A Level Computer Science 9618 — 2025 May/June Paper 1 · Variant 1

This document has 20 pages. Any blank pages are indicated. [Turn over Cambridge International AS & A Level COMPUTER SCIENCE 9618/11 Paper 1 Theory Fundamentals May/June 2025 1 hour 30 minutes You must answer on the question paper. No additional materials are needed. INSTRUCTIONS ● Answer all questions. ● Use a black or dark blue pen. ● Write your name, centre number and candidate number in the boxes at the top of the page. ● Write your answer to each question in the space provided. ● Do not use an erasable pen or correction fluid. ● Do not write on any bar codes. ● You may use an HB pencil for any diagrams, graphs or rough working. ● Calculators must not be used in this paper. INFORMATION ● The total mark for this paper is 75. ● The number of marks for each question or part question is shown in brackets [ ]. ● No marks will be awarded for using brand names of software packages or hardware. * 5 0 8 2 3 3 9 5 5 9 * DC (SL/FC) 341015/3 © UCLES 2025 ,










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2 9618/11/M/J/25 © UCLES 2025 1 (a) Write the logic expressions for the following logic circuit. P Q X Y R S X = … Y = … [2] * 0000800000002 * ,










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3 9618/11/M/J/25 © UCLES 2025 [Turn over (b) Complete the truth table for the following logic circuit. A B X C A B C Working space X 0 0 0 0 0 1 0 1 0 0 1 1 1 0 0 1 0 1 1 1 0 1 1 1 [2] * 0000800000003 * ,










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4 9618/11/M/J/25 © UCLES 2025 2 Programmers in a software development company take part in live video conferences to discuss their work. The live video conferences take place using real‑time bit streaming. The video is compressed before it is transmitted. (a) Explain how data is transferred using real‑time bit streaming. … … … … … … … … [4] (b) (i) Explain the reasons why a video is compressed before it is transmitted using real‑time bit streaming. … … … … … … … … [4] * 0000800000004 * ,










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5 9618/11/M/J/25 © UCLES 2025 [Turn over (ii) Identify whether the lossy or lossless compression method is more appropriate for real‑time bit streaming. Justify your answer. Compression method … Justification … … … … … … [3] (c) The video conference is accessed over the internet. Complete the table by stating how modems and dedicated lines are used when data is transmitted over the internet. Hardware Use modems … … dedicated lines … … [2] * 0000800000005 * ,










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6 9618/11/M/J/25 © UCLES 2025 3 A computer stores images and text files. (a) One of the images is a bitmapped image. Complete the table by writing the answer for each statement. Statement Answer the term for the smallest element that makes up an image the largest number of different colours that can be represented with a bit depth of 8 bits the term for the dots per inch (dpi) when an image is displayed [3] (b) The text in the files is stored using the Unicode character set. (i) Give two advantages of using the Unicode character set instead of using the ASCII character set. 1 … … 2 … … [2] (ii) The Unicode character '❮' has the binary value: 0010 0111 0110 1110 Convert the binary value for the character '❮' into denary. … [1] (iii) The Unicode character '⅀' has the hexadecimal value 2140 Convert the hexadecimal code for the character '⅀' into denary. … [1] * 0000800000006 * ,










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7 9618/11/M/J/25 © UCLES 2025 [Turn over 4 A shop installs a new system that allows users to purchase items without going through a manual checkout. The new system: • identifies customers when they enter the shop and matches them to their account • prevents a customer from walking through the automatic barriers if they do not have an account • automatically detects the items that a customer has taken from a shelf and charges these to the customer’s account. (a) The new system uses digital cameras and Artificial Intelligence (AI) to identify the customers. Explain how the new system uses AI to identify each customer. … … … … … … … … … … [4] (b) The new system uses sensors to identify the items taken from a shelf. Identify one type of sensor that can be used in this new system. State how the sensor can be used to identify the items taken from a shelf. Sensor … Use … … [2] * 0000800000007 * ,










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8 9618/11/M/J/25 © UCLES 2025 5 A company builds and sells furniture to customers. The company stores data about customers, their payment cards and their furniture orders in a database. The database, FURNITURE, has the following tables: CUSTOMER(CustomerID, Name, Phone) CUSTOMER_CARD_DATA(CardID, CustomerID, CardType, CardNumber, EndDate) ORDER(OrderID, CustomerID, TotalCost, Paid, OrderDate, Complete) ORDER_ITEM(OrderItemID, OrderID, Type, Height, Width, Depth, Details) The primary keys are underlined in each table. The attribute Complete in the table ORDER stores the Boolean value TRUE if the order has been built and FALSE if the order has not been built. (a) Complete the entity‑relationship (E‑R) diagram for the database. CUSTOMER_CARD_DATA CUSTOMER ORDER_ITEM ORDER [3] (b) Identify one attribute in the table CUSTOMER_CARD_DATA that could be a candidate key. … [1] (c) Identify two tables in the database that contain one or more foreign keys. Give one attribute that is a foreign key in each table. Table Foreign key 1 2 [2] * 0000800000008 * ,










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9 9618/11/M/J/25 © UCLES 2025 [Turn over (d) Explain the reasons why the data in the table ORDER_ITEM cannot be stored in the table ORDER … … … … … … [3] (e) Write an Structured Query Language (SQL) script to output the customer ID, the customer’s name and the total cost of the customer’s orders that have not been paid. The output of the total cost must have an appropriate title. … … … … … … … … [4] * 0000800000009 * ,










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10 9618/11/M/J/25 © UCLES 2025 6 A programmer is buying a new computer. (a) The programmer is considering the following two computers: Computer 1 Quad‑core 2.2 GHz processor 16‑bit architecture 1 GB Random Access Memory (RAM) 500 GB magnetic hard disk Computer 2 Dual‑core 3.8 GHz processor 32‑bit architecture 2 GB RAM 500 GB solid state drive (SSD) (i) Computer 1 has a magnetic hard disk. Complete the description of the principal operation of a magnetic hard disk by writing the missing words. The magnetic hard disk has one or more … that can be magnetised. These are mounted on a … and rotate at high speed. A … is moved across the surface on an arm. When data is read, the changes in the … produce a change in the electric current. [4] (ii) The two computers have different amounts of RAM. Explain how different amounts of RAM affect the performance of a computer. … … … … … … [3] * 0000800000010 * ,










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11 9618/11/M/J/25 © UCLES 2025 [Turn over (iii) The two computers have different bus widths. Explain how different bus widths affect the performance of a computer. … … … … [2] (b) Both computers have an Operating System (OS). Describe the purpose of an OS in a computer. … … … … … … … … … … [5] * 0000800000011 * ,









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12 9618/11/M/J/25 © UCLES 2025 7 A banker stores personal data on their work computer. (a) The banker needs to transfer confidential data across the internet. Identify and describe one method of restricting the risks posed by an unauthorised person intercepting the data whilst it is being transferred across the internet. Method … Description … … … … … [3] (b) The banker receives confidential data across the internet. The data includes a digital signature. Explain how a digital signature can make sure the data has not been changed during transmission. … … … … … … … … … … [5] * 0000800000012 * ,









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13 9618/11/M/J/25 © UCLES 2025 [Turn over (c) The data that is transferred can also be verified using a checksum. Explain how data can be verified using a checksum. … … … … … … [3] * 0000800000013 * ,









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14 9618/11/M/J/25 © UCLES 2025 8 (a) The following table shows part of the instruction set for a processor. The processor has two registers: the Accumulator (ACC) and an Index Register (IX). Instruction Explanation Opcode Operand LDM #n Immediate addressing. Load the number n to ACC LDD <address> Direct addressing. Load the contents of the location at the given address to ACC LDI <address> Indirect addressing. The address to be used is at the given address. Load the contents of this second address to ACC INC <register> Add 1 to the contents of the register (ACC or IX) STO <address> Store the contents of ACC at the given address ADD #n/Bn/&n Add the number n to the ACC DEC <register> Subtract 1 from the contents of the register (ACC or IX) JMP <address> Jump to the given address CMP <address> Compare the contents of ACC with the contents of <address> JPE <address> Following a compare instruction, jump to <address> if the compare was True END Return control to the operating system ACC denotes Accumulator <address> can be an absolute or a symbolic address # denotes a denary number, e.g. #123 B denotes a binary number, e.g. B01001010 & denotes a hexadecimal number, e.g. &4A * 0000800000014 * ,









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15 9618/11/M/J/25 © UCLES 2025 [Turn over The current contents of memory are: address 80 81 82 Instruction 10 8 80 200 201 202 LDD 81 83 ... 81 INC ACC STO 83 203 LDI 82 CMP 83 204 JPE 209 205 LDD 83 206 ADD #10 207 JMP 210 208 DEC ACC 209 STO 81 210 END 211 Trace the program currently in memory using the following trace table. Instruction address ACC Memory address 80 81 82 83 10 8 80 81 [4] * 0000800000015 * ,









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16 9618/11/M/J/25 © UCLES 2025 (b) The table shows part of the instruction set for a processor. The processor has one register: the Accumulator (ACC). Instruction Explanation Opcode Operand AND #n/Bn/&n Bitwise AND operation of the contents of ACC with the operand AND <address> Bitwise AND operation of the contents of ACC with the contents of <address> XOR #n/Bn/&n Bitwise XOR operation of the contents of ACC with the operand XOR <address> Bitwise XOR operation of the contents of ACC with the contents of <address> OR #n/Bn/&n Bitwise OR operation of the contents of ACC with the operand OR <address> Bitwise OR operation of the contents of ACC with the contents of <address> LSL #n Bits in ACC are shifted logically n places to the left. Zeros are introduced on the right‑hand end LSR #n Bits in ACC are shifted logically n places to the right. Zeros are introduced on the left‑hand end <address> can be an absolute or symbolic address # denotes a denary number, e.g. #123 B denotes a binary number, e.g. B01001010 & denotes a hexadecimal number, e.g. &4A * 0000800000016 * ,









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17 9618/11/M/J/25 © UCLES 2025 (i) Write the bit manipulation instruction that can be used to set the least significant bit to 1 in an 8‑bit register. All other bits must remain unchanged. The instruction needs to work on a register that contains any 8‑bit binary number. … [1] (ii) The ACC currently contains the following binary value. 0 1 0 1 0 1 0 1 Write the result after the instruction XOR &FE is run. [1] (iii) The ACC currently contains the following binary value. 0 1 1 0 1 0 1 1 Write the result after the instruction LSR #5 is run. [1] * 0000800000017 * ,









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18 9618/11/M/J/25 © UCLES 2025 BLANK PAGE * 0000800000018 * ,









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19 9618/11/M/J/25 © UCLES 2025 BLANK PAGE * 0000800000019 * ,









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20 9618/11/M/J/25 © UCLES 2025 Permission to reproduce items where third‑party owned material protected by copyright is included has been sought and cleared where possible. Every reasonable effort has been made by the publisher (UCLES) to trace copyright holders, but if any items requiring clearance have unwittingly been included, the publisher will be pleased to make amends at the earliest possible opportunity. To avoid the issue of disclosure of answer‑related information to candidates, all copyright acknowledgements are reproduced online in the Cambridge Assessment International Education Copyright Acknowledgements Booklet. This is produced for each series of examinations and is freely available to download at www.cambridgeinternational.org after the live examination series. Cambridge Assessment International Education is part of Cambridge Assessment. Cambridge Assessment is the brand name of the University of Cambridge Local Examinations Syndicate (UCLES), which is a department of the University of Cambridge. BLANK PAGE * 0000800000020 * ,










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This document consists of 12 printed pages. © Cambridge University Press & Assessment 2025 [Turn over Cambridge International AS & A Level COMPUTER SCIENCE 9618/11 Paper 1 Theory Fundamentals May/June 2025 MARK SCHEME Maximum Mark: 75 Published This mark scheme is published as an aid to teachers and candidates, to indicate the requirements of the examination. It shows the basis on which Examiners were instructed to award marks. It does not indicate the details of the discussions that took place at an Examiners’ meeting before marking began, which would have considered the acceptability of alternative answers. Mark schemes should be read in conjunction with the question paper and the Principal Examiner Report for Teachers. Cambridge International will not enter into discussions about these mark schemes. Cambridge International is publishing the mark schemes for the May/June 2025 series for most Cambridge IGCSE, Cambridge International A and AS Level components, and some Cambridge O Level components.

9618/11 Cambridge International AS & A Level – Mark Scheme PUBLISHED May/June 2025 © Cambridge University Press & Assessment 2025 Page 2 of 12 Generic Marking Principles These general marking principles must be applied by all examiners when marking candidate answers. They should be applied alongside the specific content of the mark scheme or generic level descriptions for a question. Each question paper and mark scheme will also comply with these marking principles. GENERIC MARKING PRINCIPLE 1: Marks must be awarded in line with: • the specific content of the mark scheme or the generic level descriptors for the question • the specific skills defined in the mark scheme or in the generic level descriptors for the question • the standard of response required by a candidate as exemplified by the standardisation scripts. GENERIC MARKING PRINCIPLE 2: Marks awarded are always whole marks (not half marks, or other fractions). GENERIC MARKING PRINCIPLE 3: Marks must be awarded positively: • marks are awarded for correct/valid answers, as defined in the mark scheme. However, credit is given for valid answers which go beyond the scope of the syllabus and mark scheme, referring to your Team Leader as appropriate • marks are awarded when candidates clearly demonstrate what they know and can do • marks are not deducted for errors • marks are not deducted for omissions • answers should only be judged on the quality of spelling, punctuation and grammar when these features are specifically assessed by the question as indicated by the mark scheme. The meaning, however, should be unambiguous. GENERIC MARKING PRINCIPLE 4: Rules must be applied consistently, e.g. in situations where candidates have not followed instructions or in the application of generic level descriptors. GENERIC MARKING PRINCIPLE 5: Marks should be awarded using the full range of marks defined in the mark scheme for the question (however; the use of the full mark range may be limited according to the quality of the candidate responses seen). GENERIC MARKING PRINCIPLE 6: Marks awarded are based solely on the requirements as defined in the mark scheme. Marks should not be awarded with grade thresholds or grade descriptors in mind.

9618/11 Cambridge International AS & A Level – Mark Scheme PUBLISHED May/June 2025 © Cambridge University Press & Assessment 2025 Page 3 of 12 Annotations guidance for centres Examiners use a system of annotations as a shorthand for communicating their marking decisions to one another. Examiners are trained during the standardisation process on how and when to use annotations. The purpose of annotations is to inform the standardisation and monitoring processes and guide the supervising examiners when they are checking the work of examiners within their team. The meaning of annotations and how they are used is specific to each component and is understood by all examiners who mark the component. We publish annotations in our mark schemes to help centres understand the annotations they may see on copies of scripts. Note that there may not be a direct correlation between the number of annotations on a script and the mark awarded. Similarly, the use of an annotation may not be an indication of the quality of the response. The annotations listed below were available to examiners marking this component in this series. Annotations Annotation Meaning Correct Incorrect To indicate where a key word/phrase/code is missing. Not relevant or used to separate parts of an answer. Indicates a part of the answer that is incorrect. Highlighter To draw attention to a particular aspect or to indicate where parts of an answer have been combined. Too vague. Repetition No examples or not enough. Benefit of Doubt. Not Answered Question. Indicates that work or a page has been seen including blank answer spaces and blank pages. Follow through. Ignore

9618/11 Cambridge International AS & A Level – Mark Scheme PUBLISHED May/June 2025 © Cambridge University Press & Assessment 2025 Page 4 of 12 Question Answer Marks 1(a) 1 mark each: X = Q AND (NOT P OR R) Y = S XOR (Q NOR R) 2 1(b) 1 mark for first 4 rows, 1 mark for second 4 rows A B C Working space X 0 0 0 1 0 0 1 1 0 1 0 0 0 1 1 1 1 0 0 0 1 0 1 0 1 1 0 1 1 1 1 1 2

9618/11 Cambridge International AS & A Level – Mark Scheme PUBLISHED May/June 2025 © Cambridge University Press & Assessment 2025 Page 5 of 12 Question Answer Marks 2(a) 1 mark each to max 4 • Video is transmitted continuously • as a series of bits • The video is uploaded to a media server • The users download from the media server • On download, the media server sends the data to a buffer on the user's device • buffer is used when there is a difference in speed between transmission and receipt • Buffer stores data from server until recipient can receive it • Recipient views bit stream from the buffer 4 2(b)(i) 1 mark each to max 4 e.g. • Video is data-intensive • The file size needs reducing in order to • reduce the amount of bandwidth used • and reduce buffering • This means people are not behind in the conversation • and people with lower bandwidth can still take part 4 2(b)(ii) No mark for choice but lossy is most appropriate 1 mark each to max 3 e.g. • Reduces file size more than lossless • so significantly less bandwidth / data is needed • so buffering is reduced even more than with lossless • Data can be removed which cannot be seen • reducing quality without impacting experience • for example, because resolution of video can be reduced // sample rate of audio can be reduced 3 2(c) 1 mark each modems: • Converts digital data into analogue for transmission down phone lines // Converts analogue data into digital after transmission down phone lines dedicated lines: • Used to provide a direct / private connection which therefore provides faster transmission 2

9618/11 Cambridge International AS & A Level – Mark Scheme PUBLISHED May/June 2025 © Cambridge University Press & Assessment 2025 Page 6 of 12 Question Answer Marks 3(a) 1 mark for each correct answer Statement Answer The term for the smallest element that makes up an image. pixel The largest number of different colours that can be represented with a bit depth of 8 bits. 256 // 28 The term for the dots per inch (dpi) when an image is displayed. Screen resolution 3 3(b)(i) 1 mark each to max 2 • A wider range of characters can be represented • so characters from more languages can be represented • and symbols such as emojis can be used 2 3(b)(ii) 1 mark for: 10,094 1 3(b)(iii) 1 mark for: 8,512 1

9618/11 Cambridge International AS & A Level – Mark Scheme PUBLISHED May/June 2025 © Cambridge University Press & Assessment 2025 Page 7 of 12 Question Answer Marks 4(a) 1 mark each to max 4 e.g. • Uses image recognition / facial recognition • Measures the distance between facial features of the customer • and stores the values in a database of user information • An image is captured using the digital camera • the AI identifies that the image is a face • by analysing the pixels to find patterns • the distance between features is calculated and compared to those in database 4 4(b) 1 mark for sensor, 1 mark for corresponding use e.g. Sensor Use Pressure Detects when the pressure of an item is removed from a shelf / put back on a shelf Infrared Detects when the beam is broken for an item removed / added 2

9618/11 Cambridge International AS & A Level – Mark Scheme PUBLISHED May/June 2025 © Cambridge University Press & Assessment 2025 Page 8 of 12 Question Answer Marks 5(a) 1 mark for each relationship. Max 2 if any extra 3 5(b) 1 mark for: CardNumber 1 5(c) 1 mark per row to max 2 Table Foreign key ORDER_ITEM OrderID ORDER CustomerID CUSTOMER_CARD_DATA CustomerID 2 5(d) 1 mark each to max 3 e.g. • Each order would only be able to have one item • or the database would not be normalised • it would not be in 1NF • due to repeated groups of attributes • in the ORDER table 3

9618/11 Cambridge International AS & A Level – Mark Scheme PUBLISHED May/June 2025 © Cambridge University Press & Assessment 2025 Page 9 of 12 Question Answer Marks 5(e) 1 mark each • Selecting the customer ID, customer name and sum of TotalCost with appropriate identifier • FROM clause with suitable join of tables (ON or WHERE) • ORDER.Paid = FALSE condition (with correct key word) • GROUP BY condition e.g. SELECT CUSTOMER.CustomerID, CUSTOMER.Name, Sum(ORDER.TotalCost) AS TotalOwed FROM CUSTOMER INNER JOIN ORDER ON CUSTOMER.CustomerID = ORDER.CustomerID WHERE ORDER.Paid = FALSE GROUP BY CUSTOMER.CustomerID; Alternative JOIN Statement SELECT CUSTOMER.CustomerID, CUSTOMER.Name, Sum(ORDER.TotalCost) AS TotalOwed FROM CUSTOMER,ORDER WHERE CUSTOMER.CustomerID = ORDER.CustomerID AND ORDER.Paid = FALSE GROUP BY CUSTOMER.CustomerID; 4

9618/11 Cambridge International AS & A Level – Mark Scheme PUBLISHED May/June 2025 © Cambridge University Press & Assessment 2025 Page 10 of 12 Question Answer Marks 6(a)(i) 1 mark for each correctly completed space • platters • spindle • read/write head • magnetic field The magnetic hard disk has one or more platters that can be magnetised. These are mounted on a spindle and rotate at high speed. A read/write head is moved across the surface on an arm. When data is read the changes in the magnetic field produce a change in the electric current. 4 6(a)(ii) 1 mark each to max 3 • More RAM means more currently running data and instructions can be stored • without needing to use virtual memory • without having to fetch the data from secondary storage first • which has a slower access time • Less latency / delay waiting for instructions / data 3 6(a)(iii) 1 mark each to max 2 e.g. • Wider data bus means more data can be transferred between components at a time • there is less delay / latency when fetching data for a running process • Wider address bus means larger memory addresses can be used • allowing more memory locations to be accessed directly • so less likely to run out of memory 2 6(b) 1 mark each to max 5 e.g. • To provide a user interface • so that the user is able to communicate with the hardware • To manage memory • so that data can be stored and accessed • and multitasking is possible • To manage files • allowing the user to create, edit, update and delete files and folders • To manage inputs and outputs from hardware/peripherals • To handle processes • to make sure each process has fair access 5

9618/11 Cambridge International AS & A Level – Mark Scheme PUBLISHED May/June 2025 © Cambridge University Press & Assessment 2025 Page 11 of 12 Question Answer Marks 7(a) 1 mark for a correct method: 1 mark each to max 2 for a corresponding description Method: Encryption Description: • Data is encoded/scrambled using a key to create cipher text • if intercepted it cannot be understood • without being decrypted using a key 3 7(b) 1 mark each to max 5 • The sender hashes the document / message • to produce a digest • The sender encrypts the digest to create the digital signature • The message and the signature are sent to the banker / receiver • The receiver decrypts the signature to reproduce the digest • The receiver uses the same hashing algorithm on the document received to produce a second digest • The receiver compares this digest with the one from the digital signature • If both of the receiver’s digests are the same the document has not changed 5 7(c) 1 mark each to max 3 • The data is put through an algorithm to create a checksum value • The data and checksum are sent to the receiver • The receiver performs the same algorithm on the data • if both checksums match the data is verified 3

9618/11 Cambridge International AS & A Level – Mark Scheme PUBLISHED May/June 2025 © Cambridge University Press & Assessment 2025 Page 12 of 12 Question Answer Marks 8(a) 1 mark for each shaded section Instruction address ACC Memory address 80 81 82 83 10 8 80 81 200 8 201 9 202 9 203 10 204 206 9 207 19 208 210 19 4 8(b)(i) 1 mark for: OR B0000 0001 // OR #1 // OR &1 1 8(b)(ii) 1 mark for: 1010 1011 1 8(b)(iii) 1 mark for: 0000 0011 1