Cambridge A Level Computer Science 9618 — 2024 Oct/Nov Paper 1 · Variant 3

[Turn over Cambridge International AS & A Level This document has 20 pages. Any blank pages are indicated. DC (WW/SW) 337423/4 © UCLES 2024 COMPUTER SCIENCE 9618/13 Paper 1 Theory Fundamentals October/November 2024 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. * 2 3 6 5 3 1 7 0 9 4 * ,










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2 9618/13/O/N/24 © UCLES 2024 1 (a) Describe the operation of a 2-input XOR gate. … … [1] (b) Write the logic expression for the following logic circuit. C X B A X = … … [2] (c) Draw the logic circuit for the logic expression: X = ((NOT A AND (B AND C)) OR (B NAND C)) AND NOT A X C B A [2] * 0000800000002 * ,










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3 9618/13/O/N/24 © UCLES 2024 [Turn over 2 A memory buffer uses Dynamic RAM (DRAM). (a) Identify two differences between DRAM and Static RAM (SRAM). Difference 1 … … … Difference 2 … … … [2] (b) Explain how a memory buffer is used when a computer is transferring data to its magnetic hard disk drive. … … … … … … … … [4] * 0000800000003 * ,










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4 9618/13/O/N/24 © UCLES 2024 3 A car has an automatic braking system. A sensor is used to measure the distance to objects that are in front of the car. The car automatically brakes if an object is too close to the front of the car or the distance between the car and the object is decreasing too quickly. The closer the object is to the front of the car, the harder the car brakes so that the car slows down more quickly. Explain the reasons why the automatic braking system of the car is a control system. … … … … … … [3] * 0000800000004 * ,










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5 9618/13/O/N/24 © UCLES 2024 [Turn over 4 A company makes ice cream and sells it to shops. The ice cream is made in batches: a large quantity of one type and flavour of ice cream that is then split into smaller quantities for sale. The company’s owner has designed a relational database, ICECREAM, to store data about their ice cream and customers. Some of the tables in the database are given. The database is not normalised. BATCH(BatchID, Type, Flavour, Size, SellingPrice, EndDate) CUSTOMER(CustomerID, CompanyName, EmailAddress, TelephoneNumber) SALE(SaleID, BatchID, CustomerID, Quantity, Date) (a) Identify two foreign keys in the table SALE and the table that each foreign key references. Foreign key 1 … Table name 1 … Foreign key 2 … Table name 2 … [2] (b) Write an SQL script to return the total quantity of ice cream sold to the customer with the ID of 0034E in the year 2023. … … … … … … [3] * 0000800000005 * ,










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6 9618/13/O/N/24 © UCLES 2024 (c) The table definition for BATCH is repeated here: BATCH(BatchID, Type, Flavour, Size, SellingPrice, EndDate) Sample data for the table BATCH is given: BatchID Type Flavour Size SellingPrice EndDate KlV12 Plain Vanilla 1 2.20 12/12/2024 RlC14 Plain Chocolate 0.5 1.80 12/12/2024 TYL1 Non-dairy Lemon 0.5 2.10 01/02/2025 FYV2 Non-dairy Vanilla 0.25 1.50 02/02/2025 BIV13 Plain Vanilla 1 2.20 02/02/2024 (i) Write an SQL script to define the table BATCH. Include constraints (restrictions) on the data that can be entered into each field where appropriate. … … … … … … … … … … [5] * 0000800000006 * ,










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7 9618/13/O/N/24 © UCLES 2024 [Turn over (ii) The table BATCH is not normalised. Normalise the database table BATCH. Write the table definitions for your new tables. Identify any primary and foreign keys in your tables. Do not change or include the tables CUSTOMER and SALE. … … … … … … … … [4] (d) Complete the following table by defining each database term. Database term Definition Entity … … … Attribute … … … [2] * 0000800000007 * ,










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8 9618/13/O/N/24 © UCLES 2024 (e) A Database Management System (DBMS) supports data integrity. Explain how a DBMS supports data integrity. … … … … … … [3] * 0000800000008 * ,










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9 9618/13/O/N/24 © UCLES 2024 [Turn over 5 A computer programmer writes programs that are distributed with a software licence. (a) Complete the table by writing the type of software licence each statement describes. Statement Software licence A fee is charged for the software. The source code cannot be accessed. Users do not get a free trial. … … Users can try the software before buying it. Users may not be able to access all features during the trial. … … Software is usually free of charge. Users can access the source code and alter the program to their needs. … … [3] (b) Explain the reasons why it is important for the computer programmer to join a professional ethical body. … … … … … … [3] * 0000800000009 * ,










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10 9618/13/O/N/24 © UCLES 2024 6 A computer system stores text, images and sound. (a) A character set is used to represent characters in a computer. Identify and describe one character set. Character set … Description … … [2] (b) The colour of each pixel in a bitmapped image is represented by 8 bits. (i) State the largest number of different colours that can be represented by 8 bits. … [1] (ii) State one drawback of increasing the number of bits that represents each pixel in the bitmap image. … … [1] (iii) A bitmap image can be compressed using lossy compression. Explain the reasons why lossy compression is often suitable for a bitmap image. … … … … [2] * 0000800000010 * ,










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11 9618/13/O/N/24 © UCLES 2024 [Turn over (c) (i) Explain how an analogue sound wave is converted into digital data. … … … … [2] (ii) Describe one method of compressing a sound file using lossy compression. … … … … [2] * 0000800000011 * ,









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12 9618/13/O/N/24 © UCLES 2024 7 The following table shows part of the instruction set for a processor. The processor has two registers, the Accumulator (ACC) and the 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 LDX <address> Indexed addressing. Form the address from <address> + the contents of the index register. Copy the contents of this calculated address to ACC LDR #n Immediate addressing. Load the number n to IX ADD #n/Bn/&n Add the number n to the ACC ADD <address> Add the contents of the given address to the ACC SUB #n/Bn/&n Subtract the number n from the ACC SUB <address> Subtract the contents of the given address from the ACC INC <register> Add 1 to the contents of the register (ACC or IX) DEC <register> Subtract 1 from the contents of the register (ACC or IX) <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 * 0000800000012 * ,









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13 9618/13/O/N/24 © UCLES 2024 [Turn over (a) The current contents of memory are shown: Address Data 50 54 51 55 52 50 53 52 54 100 55 25 56 50 The current contents of the ACC and IX are shown: ACC 50 IX 45 Complete the table by writing the content of the ACC after each program has run. Instructions ACC content 1 LDD 50 ADD #4 ADD 54 2 LDI 53 DEC ACC ADD 56 3 LDM #55 SUB #5 [3] * 0000800000013 * ,









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14 9618/13/O/N/24 © UCLES 2024 (b) The instruction set also includes these bit manipulation instructions: 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 Explain how bit manipulation can be used to clear the data in an 8-bit register. Write the bit manipulation instruction that will be used. Explanation … … … … … Instruction … [3] * 0000800000014 * ,









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15 9618/13/O/N/24 © UCLES 2024 [Turn over 8 (a) Convert the hexadecimal number 1FAB into denary. Working … … … Denary value … [1] (b) Explain how to convert the two’s complement integer 10011111 into denary. Give the denary value after conversion. Explanation … … … … … Denary value … [3] (c) Describe the difference between a right logical binary shift and a right arithmetic binary shift. … … … … [2] * 0000800000015 * ,









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16 9618/13/O/N/24 © UCLES 2024 9 A computer is connected to a Local Area Network (LAN) that connects to a Wide Area Network (WAN). (a) Describe the characteristics of a WAN. … … … … [2] (b) Copper cable can be used to transmit data in a network. Complete the table by identifying and describing two other transmission media that can be used to transfer data in the WAN. Transmission medium Description … … … … … … … … … … … … [4] * 0000800000016 * ,









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17 9618/13/O/N/24 © UCLES 2024 (c) The computer on the LAN is used for real-time video conferences, where people connected to the internet communicate in real-time using video and audio. Explain how bit streaming is used in a real-time video conference. … … … … … … … … [4] (d) The LAN has a router. The router has a public IP address and a private IP address. (i) State the purpose of a public IP address and a private IP address. Public IP address … … Private IP address … … [2] (ii) The LAN uses subnetting. Describe the purpose of subnetting in a network. … … … … [2] * 0000800000017 * ,









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18 9618/13/O/N/24 © UCLES 2024 BLANK PAGE * 0000800000018 * ,









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19 9618/13/O/N/24 © UCLES 2024 BLANK PAGE * 0000800000019 * ,









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20 9618/13/O/N/24 © UCLES 2024 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 9 printed pages. © Cambridge University Press & Assessment 2024 [Turn over Cambridge International AS & A Level COMPUTER SCIENCE 9618/13 Paper 1 Theory Fundamentals October/November 2024 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 October/November 2024 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 October/November 2024 © Cambridge University Press & Assessment 2024 Page 2 of 9 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 October/November 2024 © Cambridge University Press & Assessment 2024 Page 3 of 9 Question Answer Marks 1(a) 1 mark for: Output is only 1 if one input is 1 and the other is 0 // Output is only 1 if both inputs are different // Output is only 0 if both inputs are the same 1 1(b) 1 mark each: • ((A NOR B) AND (A OR B)) • NAND (B AND C) X = ((A NOR B) AND (A OR B)) NAND (B AND C) 2 1(c) 1 mark for NOT gate, 2 correct AND gates and the NAND gate 1 mark for OR gate and the final AND gate 2 Question Answer Marks 2(a) 1 mark for each difference e.g. • DRAM requires constant refreshing, but SRAM does not need to be constantly refreshed • DRAM generally has greater capacities per chip, but SRAM generally has lower capacities per chip • DRAM has slower access times than SRAM 2 2(b) 1 mark for each bullet point (max 4) • The computer and the hard disk drive transmit and receive at different speeds // The computer transfers data faster than the HDD can receive • The buffer is used for temporary storage • … so that the computer can transfer data to the buffer at the higher speed • ... and is not held up waiting for data to transfer • … and so that data is transferred to hard disk drive from the buffer at the slower rate 4

9618/13 Cambridge International AS & A Level – Mark Scheme PUBLISHED October/November 2024 © Cambridge University Press & Assessment 2024 Page 4 of 9 Question Answer Marks 3 1 mark for each bullet point (max 3) • The system uses feedback • The system acts independently • Input data causes the car to brake • … braking decreases the/changes the distance to the object • … this new distance is used to determine whether/how hard the car needs to brake 3 Question Answer Marks 4(a) 1 mark each: • Foreign key: BatchID, table BATCH • Foreign key: CustomerID, table CUSTOMER 2 4(b) 1 mark each: • SELECT SUM(Quantity) • FROM SALE WHERE and one correct condition • AND with remainder correct conditions e.g. SELECT SUM(Quantity) FROM SALE WHERE CustomerID = "0034E" AND Date >= #01/01/2023# AND Date <= #31/12/2023#; 3 4(c)(i) 1 mark for each bullet point • Create table BATCH with opening and closing brackets, all statements within brackets • BatchID, Type and Flavour as varchar or equivalent • …with suitable constraint(s) • Size as decimal, SellingPrice as currency, EndDate as date (or equivalent) • Primary key identified as BatchID e.g. CREATE TABLE BATCH( BatchID VARCHAR(6) NOT NULL, Type VARCHAR (20) NOT NULL, Flavour VARCHAR (20) NOT NULL, Size FLOAT, SellingPrice CURRENCY, EndDate DATE, PRIMARY KEY(BatchID) ); 5

9618/13 Cambridge International AS & A Level – Mark Scheme PUBLISHED October/November 2024 © Cambridge University Press & Assessment 2024 Page 5 of 9 Question Answer Marks 4(c)(ii) 1 mark for each bullet point each (max 4) e.g. • Ice cream table with an appropriate name • … containing type, flavour, size, selling price • … with suitable primary key • … foreign key identified in BATCH that links to the primary key in ICECREAM Example table definitions – not example answer: BATCH(BatchID, IceCreamID, EndDate) ICE_CREAM(IceCreamID, Type, Flavour, Size, SellingPrice) 4 4(d) 1 mark for each definition Entity: • A real-life object that is represented as a table Attribute: • An item of data about an entity 2 4(e) 1 mark for each bullet point each (max 3) • Referential integrity is enforced • … such as cascade update/delete // if the data is changed in one place it is updated in every other place • ... and ensures each foreign key has a corresponding primary key 3 Question Answer Marks 5(a) 1 mark for each correct licence Statement Software Licence A fee is charged for the software. The source code cannot be accessed. Users do not get a free trial. Commercial Users can try the software before buying it. Users may not be able to access all features during the trial. Shareware Software is usually free of charge. Users can access the source code and alter the program to their needs. Open Source // Free software 3

9618/13 Cambridge International AS & A Level – Mark Scheme PUBLISHED October/November 2024 © Cambridge University Press & Assessment 2024 Page 6 of 9 Question Answer Marks 5(b) 1 mark for each bullet point (max 3) e.g. • The professional ethical body has ethical guidelines to follow • … so clients/other staff know the standards being applied • … so the computer programmer does not have to decide what is ethical it's written down • Clients/staff know the computer programmer is reputable • … there may be a test/requirement for entry • … giving recognition of the computer programmer's skills/knowledge • The professional ethical body provides help and support • … for example, if the computer programmer needs legal advice • The professional ethical body runs training courses • … to keep the computer programmer's skills up to date 3 Question Answer Marks 6(a) 1 mark for identification 1 mark for matching description e.g. • ASCII • 7/8 bits per character // represents 128/256 characters // represents all characters from Latin alphabet • UNICODE • 8/16/32 bits per character // represents 256/65536+ characters // represents all characters in all languages 2 6(b)(i) 1 mark for: 256 // 28 1 6(b)(ii) 1 mark for: Increased file size 1 6(b)(iii) 1 mark for each bullet point (max 2) e.g. • The change may not be noticeable // Data removed is usually not noticed by the human eye • … for example, changes in shade/detail • It produces a larger decrease in file size compared to lossless // Lossy decreases file size considerably 2 6(c)(i) 1 mark for each bullet point (max 2) • Value/magnitude/size of the analogue sound wave is measured a set number of times each second/time / at set intervals • Each sample/reading/measurement is given the binary number and stored in sequence 2

9618/13 Cambridge International AS & A Level – Mark Scheme PUBLISHED October/November 2024 © Cambridge University Press & Assessment 2024 Page 7 of 9 Question Answer Marks 6(c)(ii) 1 mark for each correct point and 1 mark for matching expansion e.g. • Decrease sample rate • … fewer samples/readings/measurements stored per second // fewer bits per second stored • Decrease sample resolution • … fewer bits per sample/reading/measurement // each sample has fewer bits • Sound outside of set/human hearing range is removed • … fewer measurements are stored / decreases the number of possible binary values so fewer bits are stored 2 Question Answer Marks 7(a) 1 mark each: Instructions ACC content 1 LDD 50 ADD #4 ADD 54 158 2 LDI 53 DEC ACC ADD 56 99 3 LDM #55 SUB #5 50 3 7(b) 1 mark for each bullet point for the explanation 1 mark for correct instruction • A bit manipulation operation is required to set all the bits to zero • Compare the result of the masking with 0 • … the result of comparison will be true if the register is cleared • AND B00000000 / #00 / &00 3 Question Answer Marks 8(a) 1 mark for: Denary value: 8107 1

9618/13 Cambridge International AS & A Level – Mark Scheme PUBLISHED October/November 2024 © Cambridge University Press & Assessment 2024 Page 8 of 9 Question Answer Marks 8(b) 1 mark for each bullet point for the method (max 2) e.g. • Flip each bit then add 1 … • … method of converting the new binary number into denary • Most significant 1 bit is treated as the corresponding negative denary value … • … add the other positive corresponding denary values 1 mark for correct conversion Denary value: −97 3 8(c) 1 mark each: • A logical shift moves all bits to the right and inserts zeros in the appropriate leftmost bits • An arithmetic shift moves all bits to the right but copies the sign bit into the Most Significant Bit (MSB) 2 Question Answer Marks 9(a) 1 mark for each bullet point (max 2) • A WAN covers a large geographical area • External/public infrastructure is used • Non-dedicated hardware 2 9(b) 1 mark for correct media 1 mark for matching description e.g. • Fibre optic • Transmits data as pulses of light • Radio waves / microwaves • Transmits electromagnetic waves on different frequencies 4 9(c) 1 mark for each bullet point (max 4) • Data is compressed before transmitting • The video and audio are transmitted continuously as a series of bits • The video is uploaded to a media server • On download, the media server sends the data to a buffer • The buffer stores data from server until the receiving device can process it • The receiving device receives the bit stream from the buffer 4

9618/13 Cambridge International AS & A Level – Mark Scheme PUBLISHED October/November 2024 © Cambridge University Press & Assessment 2024 Page 9 of 9 Question Answer Marks 9(d)(i) 1 mark for public IP address and 1 mark for private IP address: Public IP address: • So that the router is visible to the Internet/external network/WAN Private IP address: • So that the router is identified to computers within the LAN 2 9(d)(ii) 1 mark for each bullet point (max 2) • It allows the network to be divided into smaller networks • … which reduces traffic in some parts of the network // reduces congestion • … because traffic only travels through the parts necessary • … which hides the complexity of network • … and allows for easier maintenance of the network 2