Cambridge A Level Computer Science 9618 — 2023 May/June Paper 1 · Variant 3

This document has 16 pages. Any blank pages are indicated. [Turn over Cambridge International AS & A Level DC (KN/CT) 313485/2 © UCLES 2023 * 5 6 4 8 1 8 9 2 3 3 * COMPUTER SCIENCE 9618/13 Paper 1 Theory Fundamentals May/June 2023 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 9618/13/M/J/23 © UCLES 2023 1 (a) Write the logic expression for this truth table: A B C X 0 0 0 1 0 0 1 1 0 1 0 0 0 1 1 0 1 0 0 1 1 0 1 1 1 1 0 0 1 1 1 0 … [1] (b) Complete the truth table for this 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]

3 9618/13/M/J/23 © UCLES 2023 [Turn over 2 A university has two sites. Each site has several computer rooms. The computers are all connected as a WAN (wide area network). (a) Identify two differences between a WAN and a LAN (local area network). 1 … … 2 … … [2] (b) The network uses different topologies in different areas of the sites. In one building there are five computers connected in a mesh topology. (i) Describe what is meant by a mesh topology. … … … … [2] (ii) Give two advantages of using a mesh topology instead of a bus topology. 1 … … 2 … … [2] (c) The computers in one room are set up as thin-clients in a client-server model. Describe the role of the different computers in this model. … … … … [2]

4 9618/13/M/J/23 © UCLES 2023 (d) Students can connect their devices to the university network using cables or a wireless connection. Explain the benefits to the students of allowing them to use both wired and wireless connections. … … … … … … … … [4] (e) One site has split the network into several subnetworks. An IP address in a subnetwork is divided into two parts. Identify and describe the two parts of an IP address in a subnetwork. … … … … … … [3]

5 9618/13/M/J/23 © UCLES 2023 [Turn over 3 A mobile telephone is used to record a video. (a) The mobile telephone has a touchscreen. There are different types of touchscreen. Complete the description of the principal operation of touchscreens. A … touchscreen has two layers. When the user touches the screen, the layers touch and a … is completed. A … touchscreen has several layers. When the top layer is touched, there is a … in the electric current. A microprocessor identifies the … of the touch. [5] (b) The mobile telephone uses a built-in digital camera to record the video. The digital camera automatically focuses on the faces of people. Explain how Artificial Intelligence (AI) is used by the camera to automatically focus on the faces of people. … … … … … … … … [3] (c) The video includes a sound recording. (i) Describe how sound is represented in a computer. … … … … … … [3]

6 9618/13/M/J/23 © UCLES 2023 (ii) A second video is recorded. The sound in the second video needs to be more precise. Explain the reasons why increasing the sampling rate and the sampling resolution will improve the precision of the second recording. Sampling rate … … … … Sampling resolution … … … … [4]

7 9618/13/M/J/23 © UCLES 2023 [Turn over 4 A shop rents cars to customers. The shop uses a relational database to store information about the rentals. (a) Describe two ways in which a relational database addresses the limitations of a file-based approach. 1 … … … … 2 … … … … [4] (b) Complete the table by writing the missing term or description for each database feature. Term Description … … An object that data is stored about. Tuple … … … Secondary key … … … … … A field in one table that is linked to a primary key in another table. [4]

8 9618/13/M/J/23 © UCLES 2023 (c) The car rental database is not normalised. The current database design is: BOOKING(CarRegistration, StartDate, EndDate, CarModel, CarColour, CustomerFirstName) CUSTOMER(CustomerFirstName, CustomerLastName, EmailAddress, TelephoneNumber) Write a normalised database design for this database. All tables must be in Third Normal Form (3NF). Use the field names given and underline the primary key fields. … … … … … … … … … … [4] (d) The data is validated and verified when it is entered into the database. (i) The car registration number must be: 1 letter, followed by 3 numbers, followed by 2 letters. For example, A123AA is valid but A12AA is invalid. One way that a registration number can be validated is by using a presence check to make sure the registration number has been entered. Describe two other ways that the car registration number can be validated. 1 … … 2 … … [2]

9 9618/13/M/J/23 © UCLES 2023 [Turn over (ii) Describe two ways that the car registration number can be verified when it is entered into the database. 1 … … 2 … … [2] (iii) State why the car registration number might be incorrect even after it has been validated and verified. … … [1]

10 9618/13/M/J/23 © UCLES 2023 5 A programmer is developing a computer game in a high-level language to sell to the public. (a) The programmer uses both an interpreter and a compiler at different stages of the development of the program. (i) Explain the reasons why the programmer uses an interpreter while writing the program code. … … … … [2] (ii) Explain the reasons why the programmer uses a compiler when the program has been written. … … … … … … [3] (b) The programmer needs to publish the game under a software licence so that it can be sold to the public. Identify the most appropriate type of software licence for the game and justify your choice. Licence … Justification … … … … … … [4]

11 9618/13/M/J/23 © UCLES 2023 [Turn over 6 Data needs to be kept secure when stored on a computer and during transmission over a network. (a) Explain how a digital signature is used to authenticate a digital document during transmission over a network. … … … … … … … … … … [5] (b) Complete the table by identifying and describing two types of software that can be installed on a computer to prevent threats over a network. Type of software Description ……………………….. ……………………….. … … … ……………………….. ……………………….. … … … [2]

12 9618/13/M/J/23 © UCLES 2023 7 A computer stores data in binary form. (a) Draw one line from each description to its matching denary value. Description Denary value The smallest integer that can be represented in 8-bit two’s complement. The largest integer that can be represented in 8-bit two’s complement. The largest unsigned integer that can be represented in 8 bits. 127 −255 −128 −256 256 128 255 −127 [3] (b) The computer has a Control Unit (CU), system clock and control bus. Explain how the CU, system clock and control bus operate to transfer data between the components of the computer system. … … … … … … … … [4]

13 9618/13/M/J/23 © UCLES 2023 (c) Complete the table by writing the register transfer notation for each stage of the Fetch-Execute (F-E) cycle given in the table. Stage description Register transfer notation The Program Counter (PC) is incremented … The data in the address stored in the Memory Address Register (MAR) is copied to the Memory Data Register (MDR) … [2]

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16 9618/13/M/J/23 © UCLES 2023 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

This document consists of 11 printed pages. © UCLES 2023 [Turn over Cambridge International AS & A Level COMPUTER SCIENCE 9618/13 Paper 1 Theory Fundamentals May/June 2023 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 2023 series for most Cambridge IGCSE, Cambridge International A and AS Level and Cambridge Pre-U components, and some Cambridge O Level components.

9618/13 Cambridge International AS & A Level – Mark Scheme PUBLISHED May/June 2023 © UCLES 2023 Page 2 of 11 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 descriptors 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 2023 © UCLES 2023 Page 3 of 11 Question Answer Marks 1(a) NOT B 1 1(b) 1 mark for first 4 rows correct; 1 mark for second 4 rows correct A B C X 0 0 0 1 0 0 1 0 0 1 0 1 0 1 1 0 1 0 0 1 1 0 1 0 1 1 0 0 1 1 1 1 2 Question Answer Marks 2(a) 1 mark each to max 2  WAN covers a large geographical area and LAN covers a small geographical area  LAN connections between devices are usually physical, whereas the WAN connections are often virtual  A LAN has a high data transfer rate, whereas a WAN has a low data transfer rate  The ownership of a LAN is private; the ownership of a WAN can be private or public  LAN is usually more secure than a WAN because protection is easier to implement 2 2(b)(i) 1 mark each to max 2  All computers are connected to at least one other device  There are multiple routes between devices  The computers can act as relays, passing packets on towards the final destination 2

9618/13 Cambridge International AS & A Level – Mark Scheme PUBLISHED May/June 2023 © UCLES 2023 Page 4 of 11 Question Answer Marks 2(b)(ii) 1 mark each to max 2  If one line goes down there are more routes available  Improved security as not using one main line  No/fewer collisions  New nodes can be added without interruption or interfering with other nodes  More secure because data is sent over a dedicated connection 2 2(c) 1 mark each to max 2  Server performs all processes required by the task and/or data storage  Clients only sends requests to the server and displays the returned results 2 2(d) 1 mark each to max 4 Examples:  Some students might only have one sort of connection on their device  Wired provides better performance for the student's device  ... for example, enabling faster access to university databases  There will be less interference if students connect via a cable  Students can transmit private/confidential data/work securely  ... for example, their final dissertation  Wireless connection means that the students can use their devices in different rooms/sites/outside/anywhere more freely // student devices can be portable  Wireless connection enables the students to bring multiple devices // bring their own devices // change devices 4 2(e) 1 mark for identification  IP address is made up of a network ID and a host ID 1 mark each to max 2 for description  Each device in a subnetwork has the same network ID // Each subnetwork has a different network ID  Every device in each subnetwork has a different host ID but the same network ID // the host ID uniquely identifies the device within the subnetwork 3

9618/13 Cambridge International AS & A Level – Mark Scheme PUBLISHED May/June 2023 © UCLES 2023 Page 5 of 11 Question Answer Marks 3(a) 1 mark for each term  Resistive  Circuit  Capacitive  Change  Coordinates A resistive touchscreen has two layers. When the user touches the screen, the layers touch and a circuit is completed. A capacitive touchscreen has several layers. When the top layer is touched there is a change/increase/decrease in the electric current. A microprocessor identifies the coordinates of the touch. 5 3(b) 1 mark each to max 3 Examples:  Scans the scene in real time  Identifies if there are faces in the image  Uses facial recognition  ... uses image recognition  ... takes each frame individually  ... analyses the pixels  ... stores pattern for a face  ... looks for patterns that match/come close to the pattern for a face  Camera focuses on the pattern identified 3 3(c)(i) 1 mark each  The amplitude is recorded a set number of times a second  Each (instance of an) amplitude is given a corresponding binary number  The binary number (of each amplitude) is saved in sequence 3 3(c)(ii) 1 mark each; max 2 for rate and max 2 for resolution Sampling rate  There are smaller 'gaps' in the sound wave // sound is recorded more often  Digital waveform is closer to the analogue waveform  The quantisation errors are smaller Sampling resolution  There are more bits per sample // a wider range of amplitudes can be stored  Each binary amplitude/note (in the digital recording) is closer to the analogue amplitude/note  Digital waveform is closer to the analogue waveform  The quantisation errors are smaller 4

9618/13 Cambridge International AS & A Level – Mark Scheme PUBLISHED May/June 2023 © UCLES 2023 Page 6 of 11 Question Answer Marks 4(a) 1 mark for each bullet point. Mark in pairs. Max 2 for each description.  Reduces data redundancy  ... because linked tables mean that each data item is stored only once  Reduces program-data dependency  ... because the data is separate from the software so changes to the data do not require programs to be re-written  Reduces data inconsistency // improves data integrity  ... because by only storing data once it only needs to be updated once // changes in one table will automatically update in another // linked data cannot be entered differently in two tables  Complex queries are easier to run  Can provide different views  ….so users can only see specific aspects of the database 4 4(b) 1 mark each Term Description Entity An object that data is stored about. Tuple A row of data in a table about one instance of an object. Secondary key An additional/alternative key used as well as the primary key to locate specific data // a candidate key that has not been chosen as a primary key. Foreign key A field in one table that is linked to a primary key in another table. 4 4(c) 1 mark each  Only 3 tables with appropriate identifiers (i.e. one table for customer, one for booking and one for car)  Appropriate Primary key in each table underlined  Booking table includes Primary key from car and Primary key from customer as Foreign keys  All original fields are in correct tables Example answer: BOOKING(BookingID, CarRegistration, CustomerID, StartDate, EndDate) CAR(CarRegistration, CarModel, CarColour) CUSTOMER(CustomerID, CustomerFirstName, CustomerLastName, EmailAddress, TelephoneNumber) 4

9618/13 Cambridge International AS & A Level – Mark Scheme PUBLISHED May/June 2023 © UCLES 2023 Page 7 of 11 Question Answer Marks 4(d)(i) 1 mark each to max 2  Length check: the registration number must be 6 characters long  Format check: the registration number must be in the format letter- digit-digit-digit-letter-letter  Type check: the registration number must be alphanumeric 2 4(d)(ii) 1 mark each  Visual check: Manually compare the registration number entered with the source document  Double entry: Enter the registration number twice and the computer compares to check they are the same 2 4(d)(iii) The registration number on the original document might be in the correct format but may be the incorrect registration number for that car. 1 Question Answer Marks 5(a)(i) 1 mark each to max 2  Programmer can test sections of the code without every part working / being written  Programmer can debug in real time  … so that errors can be fixed and the program continued from that point  The effect of any changes made by the programmer can be seen immediately  To avoid dependent errors 2 5(a)(ii) 1 mark each to max 3  The compiler produces an executable file  ... so the user cannot access / edit / sell the code  ... and users do not need the translator to run the game  The game can be compiled for different hardware specifications  ... and then used to generate more income for the programmer  The program can be tested multiple times without having to retranslate each time 3

9618/13 Cambridge International AS & A Level – Mark Scheme PUBLISHED May/June 2023 © UCLES 2023 Page 8 of 11 Question Answer Marks 5(b) 1 mark for appropriate licence; 1 mark for each point to max 3  Commercial software licence  User has to pay for the product so the programmer can gain an income  Enables the program to be copyrighted  ... so the user cannot legally edit the program // the programmer retains control over product  … and can take legal action against people who attempt to illegally copy it /sell it on  Shareware licence  Enables the program to be copyrighted  The user cannot legally edit the program so the developer retains control over product  User can try the program for free and then pay for the full game which allows the programmer to gain an income  so more people can experience it and therefore be more likely to buy it 4 Question Answer Marks 6(a) 1 mark each to max 5  The sender hashes the document  ... to produce a digest  The sender encrypts the digest to create the digital signature  The message and the signature are sent to the 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 is authentic 5

9618/13 Cambridge International AS & A Level – Mark Scheme PUBLISHED May/June 2023 © UCLES 2023 Page 9 of 11 Question Answer Marks 6(b) 1 mark each for identification and appropriate description of 2 pieces of software, max 2 Type of software Description Antivirus  scans the computer for viruses and checks against a stored database of viruses, that needs to be updated regularly and then deletes / quarantines them  compares downloaded files to a database of known viruses and prevents the download continuing Antispyware  scans the computer for spyware and checks against a stored database of viruses, that needs to be updated regularly and then deletes / quarantines them  compares downloaded files to a database of known spyware and prevents the download continuing. Firewall  monitors incoming and outgoing traffic and compares it to criteria that are set by the user such as through a whitelist/blacklist/identifying allowed / blocked IP addresses  compares incoming and outgoing traffic to criteria blocks those that do not match criteria Antimalware  scans the computer for viruses and checks against a stored database of viruses, that needs to be updated regularly and then deletes / quarantines them  compares downloaded files to a database of known viruses and prevents the download continuing 2

9618/13 Cambridge International AS & A Level – Mark Scheme PUBLISHED May/June 2023 © UCLES 2023 Page 10 of 11 Question Answer Marks 7(a) 1 mark for each correct line Description Denary value The smallest integer that can be represented in 8-bit two's complement. 127 127 255 128 The largest integer that can be represented in 8-bit two's complement. 256 256 128 The largest unsigned integer that can be represented in 8 bits. 255 3 7(b) 1 mark each to max 4  The system clock gives out timing signals  … which are sent on the control bus  …to synchronise the other system components  The Control Unit initiates data transfer  …by generating signals that are sent on the control bus to other components 4

9618/13 Cambridge International AS & A Level – Mark Scheme PUBLISHED May/June 2023 © UCLES 2023 Page 11 of 11 Question Answer Marks 7(c) 1 mark for each Register transfer notation Stage description Register transfer notation The Program Counter (PC) is incremented PC  [PC] + 1 The data in the address stored in the Memory Address Register (MAR) is copied to the Memory Data Register (MDR) MDR  [[MAR]] 2