Cambridge A Level Computer Science 9618 — 2025 May/June Paper 1 · Variant 3

This document has 20 pages. Any blank pages are indicated. [Turn over Cambridge International AS & A Level COMPUTER SCIENCE 9618/13 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. * 8 5 2 6 4 4 3 9 7 8 * DC (PQ/FC) 341018/3 © UCLES 2025 ,










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2 9618/13/M/J/25 © UCLES 2025 1 (a) A student paints a picture in an art class. The student takes a photograph of the picture using a digital camera. The digital camera creates an image with a resolution of 2 million pixels and uses a bit depth of 16 bits. (i) Calculate the file size of the image created by the digital camera in megabytes (MB). Show your working. Working space … … … Answer … MB [2] (ii) The student takes a second photograph with a lower bit depth. Explain the effect of decreasing the bit depth on the image and on the image file. Effect on image … … … … Effect on image file … … … … [4] (b) A teacher records an audio file of the student playing the piano during a music lesson. Complete the table by giving the term for each description about sound representation on a computer. Description Term the number of times the amplitude is measured per time interval the number of bits used to store each amplitude measurement the type of sound wave before it is recorded by a computer [3] * 0000800000002 * ,










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3 9618/13/M/J/25 © UCLES 2025 [Turn over (c) The student types a report on a computer in a history lesson. (i) The computer uses the Unicode character set. Give two characteristics of the Unicode character set. 1 … … 2 … … [2] (ii) Some of the school’s computers use the extended ASCII character set. The table gives some characters from the extended ASCII character set, their denary, 8-bit binary and hexadecimal numbers. Complete the table by filling in the missing numbers. Character Denary 8-bit Binary Hexadecimal ! 33 21 L 01001100 4C ü 252 11111100 [3] * 0000800000003 * ,










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4 9618/13/M/J/25 © UCLES 2025 2 A computer has a processor. (a) The processor has a Control Unit (CU) and system clock. (i) Explain how the CU and the system clock work together. … … … … [2] (ii) The processor runs the Fetch-Execute (F-E) cycle. Write the stages of the F-E cycle using register transfer notation. … … … … … … [4] (b) The computer has cache memory. Describe one benefit of the computer using cache memory. … … … … [2] (c) The computer connects to a monitor using a High Definition Multimedia Interface (HDMI) cable that connects into an HDMI port. Explain how HDMI provides connection to peripheral devices. … … … … [2] * 0000800000004 * ,










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5 9618/13/M/J/25 © UCLES 2025 [Turn over BLANK PAGE * 0000800000005 * ,










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6 9618/13/M/J/25 © UCLES 2025 3 A programmer is writing a program in a high-level language. (a) Complete the description of compilers and interpreters by writing the missing words. A compiler checks all the code before attempting to translate the program. If any errors are found, they are all reported at the same time and the program does not translate or run. If there are no errors found, the compiler produces … which can run without access to the … . An interpreter translates one line of code and then runs it, before moving to the next line of code. If the line of code has an error, the interpreter … and displays the error. The programmer can correct the error … and then the interpreter continues translating from that point. [4] (b) The programmer needs to keep the program files secure on their computer and during electronic data transmission over the internet. The files are protected by a password. Complete the table by identifying one other method of keeping the files secure during electronic data transmission and one other method of keeping the files secure on the computer. State how each method protects the data. The methods must be different. Method How the method protects the data during transmission … … … … … on the computer … … … … … [4] * 0000800000006 * ,










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7 9618/13/M/J/25 © UCLES 2025 [Turn over (c) The computer program allows users to play a game in a virtual world. Users can play the game from any computer with internet access using a web browser. The game allows users to interact with other users. Explain the reasons why the statement ‘This computer game uses a client-server model’ is correct. … … … … … … … … [4] (d) Describe the possible consequences of the programmer not joining a professional ethical body. … … … … … … [3] * 0000800000007 * ,










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8 9618/13/M/J/25 © UCLES 2025 4 (a) Write the logic expressions for the following logic circuit. A B X Y C D X = … Y = … [2] * 0000800000008 * ,










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9 9618/13/M/J/25 © UCLES 2025 [Turn over (b) Complete the truth table for the logic expression: X = (A OR B) XOR (B OR C) XOR (NOT A NAND 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] * 0000800000009 * ,










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10 9618/13/M/J/25 © UCLES 2025 5 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 STO <address> Store the contents of ACC at the given address ADD #n/Bn/&n Add the number n to the ACC ADD <address> Add the contents of the given address to the ACC SUB <address> Subtract the contents of the given address from the ACC SUB #n/Bn/&n Subtract the number n from 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> CMP #n Compare the contents of ACC with number n 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 (a) The current contents of memory are: Address 50 51 52 Instruction 47 48 49 500 501 502 LDM #50 53 ... 50 DEC ACC CMP 51 503 JPE 505 JMP 501 504 STO 50 505 SUB #10 506 STO 51 507 END 508 * 0000800000010 * ,










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11 9618/13/M/J/25 © UCLES 2025 [Turn over (i) Trace the program currently in memory using the following trace table. Instruction address ACC Memory address 50 51 52 53 47 48 49 50 [3] * 0000800000011 * ,









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12 9618/13/M/J/25 © UCLES 2025 (ii) Complete the table by identifying and describing two modes of addressing that are not used in the program in part (a). Mode of addressing Description … … … … … … … … … … … … [4] * 0000800000012 * ,









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13 9618/13/M/J/25 © UCLES 2025 [Turn over (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> <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 Write the bit manipulation instructions that can be used to set only the most significant bit to 1 in an 8-bit register. The instructions need to work on a register that contains any 8-bit binary number. … … [2] * 0000800000013 * ,









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14 9618/13/M/J/25 © UCLES 2025 6 A shop sells pens to customers. Customers place an order with the shop and collect the items the next day. The shop uses a database to store the information about the orders. The database contains the following tables: CUSTOMER(CustomerID, CustomerName, Email) ORDER(OrderID, CustomerID, Date, Collected) ORDER_PRODUCT(OrderID, ProductID, Quantity) PRODUCT(ProductID, ProductName, QuantityInBox, Cost, SupplierID) SUPPLIER(SupplierID, SupplierName, SupplierEmail) The primary keys are underlined. (a) Complete the entity-relationship (E-R) diagram for the database. CUSTOMER ORDER SUPPLIER ORDER_PRODUCT PRODUCT [4] * 0000800000014 * ,









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15 9618/13/M/J/25 © UCLES 2025 [Turn over (b) A new product needs to be entered into the database. The product has the ID 002323, the product name ‘Blue ball point 2mm’, there are 50 in a box, the product costs $5.00 and the supplier has the ID SFX223. Write a Structured Query Language (SQL) script to enter the new product into the table PRODUCT. … … … … … … … … [4] (c) The attribute Collected in the table ORDER stores the Boolean value TRUE if the order has been collected and FALSE if the order has not been collected. Write an SQL script to return the customer name for each customer that has orders they have not collected. Include the number of orders each customer has not collected with an appropriate title. An example output might be: CustomerName NotCollected Jack Wright 2 Lin Cho 1 Santaya Yui 1 … … … … … … … … [4] * 0000800000015 * ,









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16 9618/13/M/J/25 © UCLES 2025 (d) The shop uses a Database Management System (DBMS). (i) One feature provided by a DBMS is a data dictionary. The data dictionary stores the attribute names, table names, foreign keys and primary keys in the database. Identify three other items stored in a data dictionary. 1 … 2 … 3 … [3] (ii) The DBMS provides a developer interface. Explain how a database designer can make use of the developer interface. … … … … … … [3] * 0000800000016 * ,









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17 9618/13/M/J/25 © UCLES 2025 7 (a) A computer can perform logical and arithmetic shifts. (i) Show the result of a logical left shift of 2 places on the two’s complement binary integer 11001010 … … [1] (ii) Show the result of an arithmetic right shift of 3 places on the two’s complement binary integer 10011110 … … [1] (b) Complete the following binary addition. Show your working. Include any overflow bit(s). 1 1 1 1 0 1 0 1 + 1 0 1 1 0 0 0 1 [1] (c) Subtract the binary number 00011110 from the binary number 01100100 using binary subtraction. Show your working. [2] * 0000800000017 * ,









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20 9618/13/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 9618/13 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.

9618/13 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.

9618/13 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

9618/13 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)(i) 1 mark for correct working: e.g. 2000000 * 16 / (8 * 1000 * 1000) 1 mark for answer: 4MB 2 1(a)(ii) 1 mark each Image: • There will be fewer shades of colour available • so the image does not match the original as detail is lost Image file: • Fewer bits are used to store each pixel • so less data is stored, therefore the file size is reduced 4 1(b) 1 mark for each correct term: Description Sound term the number of times the amplitude is measured per time interval Sampling rate the number of bits used to store each amplitude measurement Sampling resolution the type of sound wave before it is recorded by a computer Analogue 3 1(c)(i) 1 mark each to max 2 • 8 / 16 / 32 / bits per character • Represents 28 / 216 / etc. characters • Represents every language and other characters such as emojis 2 1(c)(ii) 1 mark for each correctly completed space Character Denary 8–bit Binary Hexadecimal ! 33 0010 0001 21 L 76 0100 1100 4C ü 252 1111 1100 FC 3

9618/13 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)(i) 1 mark each to max 2 - max 1 for each set of marks • The control unit synchronises the actions of the processor • by sending a command / signal on each timing signal produced by the system clock • using / along the control bus 2 2(a)(ii) 1 mark each • MAR  [PC] and PC  [PC] + 1 • MDR  [[MAR]] • CIR  [MDR] • Correct order • For example: • MAR  [PC] • PC  [PC] + 1 • MDR  [[MAR]] • CIR  [MDR] 4 2(b) 1 mark each • Using cache memory improves system performance • because cache is fast access memory close to the CPU • which stores frequently used instructions / data • so that they can be accessed faster than from RAM 2 2(c) 1 mark each to max 2 e.g. • HDMI transfers both audio and video using a single cable • HDMI has a high bandwidth • Data is transmitted in a stream • of uncompressed digital signals • HDMI uses a technology called Transition-Minimized Differential Signalling (TMDS) 2

9618/13 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 correctly completed term • an executable file/.exe • source/program code • stops • immediately/in real-time A compiler checks all of the code before attempting to translate the program. If any errors are found, they are all reported at the same time and the program does not translate or run. If there are no errors found, the compiler produces an executable file/.exe which can run without access to the source/program code. An interpreter translates one line of code and then runs it, before moving to the next line of code. If the line of code has an error, the interpreter stops and displays the error. The programmer can correct the error immediately/in real- time and then the interpreter continues translating from that point. 4 3(b) 1 mark for method and 1 mark for corresponding description During transmission e.g. • Encryption // by example such as VPN • Jumble / encode data so it cannot be decrypted/understood without the key On computer e.g. • Firewall / proxy • Filter incoming transmissions and stop any that could be attempting unauthorised access • Anti-malware • Find and delete or quarantine any malware that could delete the data / files • Encryption • Jumble / encode data so it cannot be decrypted / understood without the key • Physical method // by example • For example, the computer storing the data cannot be accessed without the key to the room 4

9618/13 Cambridge International AS & A Level – Mark Scheme PUBLISHED May/June 2025 © Cambridge University Press & Assessment 2025 Page 7 of 12 Question Answer Marks 3(c) 1 mark each to max 4 • A webserver stores all the data for each player • Each player is on a client computer // The player’s web browser is the client • that sends requests over the internet to the web server • the server performs the required action in the game • the server updates the data in the game • the server sends the results to the player 4 3(d) 1 mark each to max 3 e.g. • There is no / limited access to legal advice • in case action is taken against them • There are fewer networking opportunities • so they could miss out on contacts / jobs • There would be less access to training • There would be no clear laid out ethical guidelines • and / or people to discuss potential ethical problems with • possibly leading to inappropriate / unethical actions • which might lead to legal proceedings / recourse 3

9618/13 Cambridge International AS & A Level – Mark Scheme PUBLISHED May/June 2025 © Cambridge University Press & Assessment 2025 Page 8 of 12 Question Answer Marks 4(a) 1 mark for each correct statement X = B NOR (A NOR C) Y = (B AND C) XOR NOT D 2 4(b) 1 mark for 1st 4 rows 1 mark for 2nd 4 rows A B C Working space X 0 0 0 1 0 0 1 1 0 1 0 1 0 1 1 0 1 0 0 0 1 0 1 1 1 1 0 1 1 1 1 1 2

9618/13 Cambridge International AS & A Level – Mark Scheme PUBLISHED May/June 2025 © Cambridge University Press & Assessment 2025 Page 9 of 12 Question Answer Marks 5(a)(i) 1 mark for each shaded section Instruction address ACC Memory address 50 51 52 53 47 48 49 50 500 50 501 49 502 504 501 48 502 503 505 48 506 38 507 38 3 5(a)(ii) 1 mark for addressing mode, 1 mark for matching description • Direct • The operand is the address of the data • Indirect • The operand points to the memory location which is the address of the data • Indexed • The address of the data is formed by adding the contents of the Index Register (IX) to the operand 4 5(b) 1 mark for each correct instruction e.g. AND B00000000 / #0 / &0 OR B10000000 / #128 / &80 2

9618/13 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) 1 mark for each correct relationship 4 6(b) 1 mark each • INSERT INTO PRODUCT • VALUES with opening and closing brackets • Inserting ProductID, ProductName and SupplierID correctly as strings including quotation marks into correct fields • Inserting quantity and cost correctly into correct fields Example 1: INSERT INTO PRODUCT VALUES ("002323", "Blue ball point 2 mm", 50, 5.00, "SFX223"); Example 2: INSERT INTO PRODUCT (ProductID, ProductName, QuantityInBox, Cost, SupplierID) VALUES ("002323", "Blue ball point 2 mm", 50, 5.00, "SFX223"); 4 CUSTOMER ORDER ORDER_PRODUCT SUPPLIER PRODUCT

9618/13 Cambridge International AS & A Level – Mark Scheme PUBLISHED May/June 2025 © Cambridge University Press & Assessment 2025 Page 11 of 12 Question Answer Marks 6(c) 1 mark each • Selection of customer name and counting any field from ORDER as an appropriate identifier • Joining tables ORDER and CUSTOMER • AND (or WHERE) clause: Collected = FALSE • Grouping by customer ID or customer name Example 1: SELECT CustomerName, COUNT(OrderID) AS NotCollected FROM ORDER, CUSTOMER WHERE ORDER.CustomerID = CUSTOMER.CustomerID AND Collected = FALSE GROUP BY CUSTOMER.CustomerID Example 2: SELECT CustomerName, COUNT(OrderID) AS NotCollected FROM ORDER INNER JOIN CUSTOMER ON ORDER.CustomerID = CUSTOMER.CustomerID WHERE Collected = FALSE GROUP BY CUSTOMER.CustomerID 4 6(d)(i) 1 mark each to max 3 e.g. • Relationships • Views • Data types • Validation rules 3 6(d)(ii) 1 mark each to max 3 e.g. • To create / modify / delete database objects • To create a form for data input • To add tools to a form • for example, drop-down boxes / buttons etc. • To design a report to show the output in an organised manner • To add a menu to enable users to choose different actions / run different queries 3

9618/13 Cambridge International AS & A Level – Mark Scheme PUBLISHED May/June 2025 © Cambridge University Press & Assessment 2025 Page 12 of 12 Question Answer Marks 7(a)(i) 1 mark for 0010 1000 1 7(a)(ii) 1 mark for 1111 0011 1 7(b) 1 mark for 1 1 1 1 0 1 0 1 +1 11 01 11 1 0 0 01 1 (1) 1 0 1 0 0 1 1 0 Answer: (1) 1010 0110 1 7(c) 1 mark for showing binary subtraction (any method) Direct subtraction: 0 1 1 10 10 11 10 0 -0 0 01 11 11 11 1 0 0 1 0 0 0 1 1 0 Adding the two’s complement: 0 1 1 0 0 1 0 0 +1 11 11 1 0 0 0 1 0 (1) 0 1 0 0 0 1 1 0 1 mark for answer 0100 0110 2