Cambridge A Level Computer Science 9618 — 2023 Oct/Nov Paper 1 · Variant 2

This document has 16 pages. Any blank pages are indicated. [Turn over * 0 1 3 3 1 4 9 7 0 1 * Cambridge International AS & A Level DC (DE/FC) 318301/3 © UCLES 2023 COMPUTER SCIENCE 9618/12 Paper 1 Theory Fundamentals October/November 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 9618/12/O/N/23 © UCLES 2023 1 A factory makes chocolate bars. The factory uses a conveyor belt that moves the products from one stage of production to the next stage. (a) An automated system counts the number of chocolate bars made at the end of production. The system includes a sensor positioned above the conveyor belt. Identify one appropriate type of sensor that can be used. … [1] (b) A second automated system removes chocolate bars with an incorrect weight from the production line. Describe the role of an actuator in this second system. … … … … [2] (c) The factory has many different machines with embedded systems. (i) Identify two features of embedded systems. 1 … … 2 … … [2] (ii) Identify one drawback of embedded systems. … … [1]

3 9618/12/O/N/23 © UCLES 2023 [Turn over BLANK PAGE

4 9618/12/O/N/23 © UCLES 2023 2 (a) State what is meant by the following terms in a relational database model. Entity … … … Primary key … … … Referential integrity … … … [3] (b) Authentication is one method a Database Management System (DBMS) can use to improve the security of a database. Describe other methods that a DBMS can use to improve the security of a database. … … … … … … … … [4]

5 9618/12/O/N/23 © UCLES 2023 [Turn over (c) The following database table is not normalised. StudentName DateOfBirth TutorGroup Subject SubjectCode Yuwei Chen 01/09/2004 SMH English, Maths, Computer Science EN, MA, CS Claudia Raj 23/02/2005 JMB Maths, Physics, Art MA, PY, AR Aamil Akram 24/01/2005 KMB Art, Design, English language AR, DE, EN Areeba Faraz 21/12/2004 SMH English language, Chemistry, Design EN, CH, DE Explain how to modify the table to put it into First Normal Form (1NF). … … … … … … … … [4]

6 9618/12/O/N/23 © UCLES 2023 3 (a) State one difference between a kibibyte and a megabyte. … … [1] (b) (i) Convert the denary value into a 12-bit two’s complement binary integer. −196 Answer … [1] (ii) Convert the Binary Coded Decimal (BCD) into denary. 100001100101 Answer … [1] (iii) Convert the unsigned binary integer into denary. 000111010110 Answer … [1] (c) Identify one practical application of BCD and justify why BCD is used in this application. Application … … Justification … … … … [2]

7 9618/12/O/N/23 © UCLES 2023 [Turn over 4 (a) Write the Boolean expression that corresponds to the following logic circuit. A B C X … … [3] (b) Complete the truth table for the logic expression: X = A XOR (B AND (A NAND B) AND NOT 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]

8 9618/12/O/N/23 © UCLES 2023 5 (a) State the meaning of privacy of data. … … [1] (b) State the meaning of integrity of data. … … [1] (c) Describe the following threats to a computer system. Phishing email … … … … Spyware … … … … [4]

9 9618/12/O/N/23 © UCLES 2023 [Turn over 6 (a) A real-time video of a music concert needs to be streamed to subscribers. Tick (✓) one box to identify the most appropriate type of compression and justify your answer. Lossy Lossless Justification … … … … … … [3] (b) Explain the impact of changing the sampling resolution on the accuracy of a sound recording. … … … … … … [3] (c) A bitmap image has a resolution of 2048 pixels wide and 1024 pixels high. The image has a bit depth of 10 bits per pixel. Estimate the file size of the bitmap image in mebibytes. Show your working. Working … … … … … … Estimated file size in mebibytes … [2]

10 9618/12/O/N/23 © UCLES 2023 7 A Local Area Network (LAN) contains four devices: • a router • two laptop computers • a server. (a) The server has the IP address 192.168.3.2 Explain why this is not an IPv6 address. … … … … [2] (b) (i) The LAN is set up as a star topology. Draw a diagram of the topology of the LAN. [2] (ii) Explain how data is transmitted between the two laptops in the LAN. … … … … [2]

11 9618/12/O/N/23 © UCLES 2023 [Turn over (iii) Subnetting can be used to separate a network into logical segments. Describe two other reasons why subnetting is used in a network. 1 … … … … 2 … … … … [4] (c) State three tasks performed by devices to deal with collisions when using the Carrier Sense Multiple Access / Collision Detection (CSMA/CD) protocol in a network. 1 … … 2 … … 3 … … [3]

12 9618/12/O/N/23 © UCLES 2023 (d) The following incomplete table contains types of IP addresses and their descriptions. Complete the table by writing the missing types of IP addresses and the missing descriptions. Type of IP address Description … … an IP address that is assigned to a device to allow direct access on the internet static IP address … … … … … … an IP address used for internal LAN communication only dynamic IP address … … … … [4]

13 9618/12/O/N/23 © UCLES 2023 [Turn over 8 A computer has an Operating System (OS). (a) State one purpose of the Operating System. … … [1] (b) The Operating System has utility software. The purpose of some utility software is to improve security. Identify one example of utility software that is not intended to improve security. Explain why this software is needed. Utility software … Explanation … … … … … [3] (c) An optical disc reader/writer is connected to the computer. (i) Give the name of one port that can provide a connection for the optical disc reader/writer. … [1] (ii) Describe the roles of the address bus, the data bus and buffers in the process of writing data to the optical disc reader/writer. … … … … … … [3]

14 9618/12/O/N/23 © UCLES 2023 9 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 LDD <address> Direct addressing. Load the contents of the location at the given 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 STO <address> Store the contents of ACC at the given address ADD #n Add the denary number n to the ACC JMP <address> Jump to the given address INC <register> Add 1 to the contents of the register (ACC or IX) CMP <address> Compare the contents of ACC with the contents of <address> CMI <address> Indirect addressing. The address to be used is at the given address. Compare the contents of ACC with the contents of this second address JPE <address> Following a compare instruction, jump to <address> if the compare was True IN Key in a character and store its ASCII value in ACC OUT Output to the screen the character whose ASCII value is stored in ACC END Return control to the operating system <address> can be an absolute or a symbolic address # denotes a denary number, e.g. #123 (a) The instructions in the processor’s instruction set can be grouped according to their function. Identify the instruction group for each of the following opcodes. IN … ADD … JPE … CMI … [4] (b) The current contents of main memory and selected values from the ASCII character set are given on page 15. Trace the program currently in memory using the trace table when the input is ‘1’.

15 9618/12/O/N/23 © UCLES 2023 Address Instruction 10 LDR #0 11 IN 12 STO 101 13 LDX 110 14 CMP 100 15 JPE 21 16 LDD 101 17 ADD #16 18 INC IX 19 STO 100 20 JMP 13 21 OUT 22 END ... 100 0 101 0 ... 110 51 111 65 ASCII value Character 49 1 50 2 51 3 52 4 ... 65 A 66 B 67 C 68 D Instruction address ACC IX Memory address Output 100 101 110 111 0 0 51 65 [4]

16 9618/12/O/N/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 9618/12 Paper 1 Theory Fundamentals October/November 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 October/November 2023 series for most Cambridge IGCSE, Cambridge International A and AS Level components, and some Cambridge O Level components.

9618/12 Cambridge International AS & A Level – Mark Scheme PUBLISHED October/November 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.

9618/12 Cambridge International AS & A Level – Mark Scheme PUBLISHED October/November 2023 © UCLES 2023 Page 3 of 11 Question Answer Marks 1(a) 1 mark for: • infra-red / proximity (sensor) 1 1(b) 1 mark for each bullet point (max 2) • Actuator generates a signal / causes an action / converts electrical energy into a mechanical force • ... to push an arm // to open a trap door // to pick up the chocolate bar with the incorrect weight 2 1(c)(i) 1 mark for each feature (max 2) • Dedicated to a single task // limited number of functions • Built into a larger system // integrated into a larger system • An embedded system must contain a processor, memory and an I/O capability // Dedicated hardware 2 1(c)(ii) 1 mark for each bullet point (max 1) • Difficult to change / update the firmware by the user // Difficult to upgrade devices to take advantage of new technology • Cannot be easily adapted for another task • Troubleshooting faults/upgrading is a specialist task • Devices are often thrown away rather than repaired as difficult to upgrade or repair 1 Question Answer Marks 2(a) 1 mark for each term (max 3) Entity: • An object about which data can be stored Primary key: • The unique attribute / combination of attributes used to identify the record / tuple Referential integrity: • Makes sure that if data is changed in one place the change is reflected in all related records - cascading update/delete • Makes sure that data that does not exist cannot be referenced • Ensures that every foreign key has a corresponding primary key // A logical dependency of a foreign key on a primary key • Ensures that the data in the database is consistent / up to date • Prevents records from being added/deleted/modified incorrectly • Makes sure any queries return accurate and complete results 3

9618/12 Cambridge International AS & A Level – Mark Scheme PUBLISHED October/November 2023 © UCLES 2023 Page 4 of 11 Question Answer Marks 2(b) 1 mark for each bullet point (max 4) Max 2 if no descriptions • Backup / recovery procedures • … automatically takes copies of the database and store off site on a regular basis / weekly, etc. • ... so that the data can be recovered if lost • Use of access rights • … some users are given different access permissions to different tables • ... read/write, read only, full access, etc. • Views • … different users are able to see different parts of the database • ... only see what users need to see // by example • Record and table locking • … prevents simultaneous access to data • ... so updates are not lost // data is not overwritten • Encryption • ... the data is turned into ciphertext • ... so it cannot be understood without a decryption key 4 2(c) 1 mark for each bullet point (max 4) • Identify repeating groups of attributes ... • ... Subject and SubjectCode • Ensure each field is atomic • ... StudentName should be split into e.g. FirstName and LastName • Identify the primary key for the table 4 Question Answer Marks 3(a) 1 mark for: Either • kibibyte = 1,024 bytes // 210 bytes and megabyte = 1000 kilobytes //1 000 000 bytes // 103 kilobytes // 106 bytes Or • kibi is binary prefix and mega is denary prefix 1 3(b)(i) 1111 0011 1100 1 3(b)(ii) 865 1 3(b)(iii) 470 1

9618/12 Cambridge International AS & A Level – Mark Scheme PUBLISHED October/November 2023 © UCLES 2023 Page 5 of 11 Question Answer Marks 3(c) 1 mark for a correct application 1 mark for a corresponding justification • An application that performs financial / banking calculations • ... because it is difficult to represent decimal values exactly in normal binary and financial transactions use only two decimal places and must be accurate, no accumulating errors Or • Electronic displays, e.g. calculators, digital clocks • ... because visual displays only need to show individual digits • ... because conversion between denary and BCD is easier Or • The storage of the date and time in the BIOS of a PC • ... because conversion with denary is easier 2 Question Answer Marks 4(a) 1 mark for each bullet point • A NAND B • NOT(B XOR C) • Final NAND X = A NAND B NAND (NOT(B XOR C)) 3 4(b) 1 mark for each set of rows (shaded) A B C X 0 0 0 0 0 0 1 0 0 1 0 1 0 1 1 0 1 0 0 1 1 0 1 1 1 1 0 1 1 1 1 1 2 5(a) 1 mark for: Either • Ensuring data can only be accessed by / disclosed to authorised persons Or • Ensuring data cannot be accessed by / disclosed to unauthorised persons 1

9618/12 Cambridge International AS & A Level – Mark Scheme PUBLISHED October/November 2023 © UCLES 2023 Page 6 of 11 Question Answer Marks 5(b) 1 mark for each bullet point (max 1) • Ensuring the accuracy / completeness / consistency of data (during / after processing) • Ensuring the data is up to date 1 5(c) 1 mark for each bullet point. Phishing email (max 2) • The email pretends to be from an official body • ... persuading individuals to disclose private information // by example such as bank details • ... or requesting authentication by redirecting to an unofficial/unauthorised website // inviting a user to click a link Spyware (max 2) • Malware downloaded without the user’s knowledge • ... which secretly records the user’s actions / keystrokes on the computer • ... and sends logs of the actions to a third party 4 Question Answer Marks 6(a) 1 mark for each bullet point (max 3) Lossy compression (ticked) • Loss of quality will not be noticed • Needs to be viewed in real time so less bandwidth needed if file size smaller • Smaller file sizes will reduce buffering so the video will play more smoothly • Viewers may watch on different devices, so may not need high quality resolution Lossless compression (ticked) • Original recording may not have been made in high resolution • Could be streaming to high bandwidth devices • The reduction in the file size is sufficient for the receiving device • Viewers do not want any loss of quality 3

9618/12 Cambridge International AS & A Level – Mark Scheme PUBLISHED October/November 2023 © UCLES 2023 Page 7 of 11 Question Answer Marks 6(b) 1 mark for each bullet point (max 3) Increase sampling resolution • … the number of bits used for each sample is increased • … there will be more values available to represent each sample // more amplitudes can be represented • ... each binary amplitude/note in the digital recording is closer to the analogue amplitude/note • … quantisation errors are reduced • … the digital soundwave is closer to the original analogue soundwave Decrease sampling resolution • … the number of bits used for each sample is decreased • … there will be fewer values available to represent each sample // fewer amplitudes can be stored • ... each binary amplitude/note in the digital recording is further from the analogue amplitude/note • … quantisation errors are increased • … the digital soundwave is less like the original analogue soundwave 3 6(c) 1 mark for answer, 1 mark for working Answer: 2.5 mebibytes Working: (2048  1024  10) / (8  1024  1024) 2 Question Answer Marks 7(a) 1 mark for each bullet point (max 2) • Only has four groups of digits // IPv6 has eight groups • Uses dotted notation instead of colons • Because it is a 32 bit / 4 byte address // IPv6 is 128 bits / 16 bytes 2 7(b)(i) 1 mark for server only connected to router 1 mark for two laptop computers connected only to router 2

9618/12 Cambridge International AS & A Level – Mark Scheme PUBLISHED October/November 2023 © UCLES 2023 Page 8 of 11 Question Answer Marks 7(b)(ii) 1 mark for each bullet point (max 2) • The data from the sending laptop is transmitted to the router • The data has address of recipient • The router determines recipient’s destination address • ... by using a routing table • The router transmits data directly / only to recipient 2 7(b)(iii) 1 mark for each use (max 2) and 1 mark for corresponding expansion (max 2) • To improve the security of the LAN • … so that devices do not receive unintended data • … so that a compromised device does not expose the whole network • ... so not all devices can access all segments • To make the network management easier • … because faults can be isolated more efficiently • ... by appropriate example • To make the network easier to expand // For better control of network growth • … by allowing for greater range of IP addresses to be available • To improve network performance • To reduce network congestion • … by localising network communications // by dividing data between segments • … so that devices are not flooded with data • … because data sent between devices on the same subnet stays within the subnet 4 7(c) 1 mark for each bullet point (max 3) • To monitor the communications channel • To send data only when there is no data being transmitted / the line is quiet / idle • To detect a collision and then stop transmissions of further data // transmit a jamming signal • To calculate a random wait time / back-off time • ... then retransmit the data after that random wait time • Increase random time if multiple collisions 3

9618/12 Cambridge International AS & A Level – Mark Scheme PUBLISHED October/November 2023 © UCLES 2023 Page 9 of 11 Question Answer Marks 7(d) 1 mark for each highlighted area Type of IP address Description public IP address an IP address that is assigned to a device to allow direct access on the internet static IP address an IP address that is fixed / doesn’t change each time a device re-joins a LAN / network private IP address an IP address used for internal LAN communication only dynamic IP address an IP address that may be refreshed / changed each time a device re-joins a LAN / network 4 Question Answer Marks 8(a) 1 mark for each bullet point (max 1) • To hide the complexities of the hardware from the user • To provide a platform for software to run • To provide a user interface 1 8(b) 1 mark for the name of the utility software 2 marks for the explanation • Defragmentation software • … because over time saving and deleting of small files fragments the disk • ... the software makes (individual) files contiguous • … so access time to the files is improved • … because head movement is reduced • Disk contents analysis/disk repair software • … to identify and mark bad sectors • ... to restore corrupted files • ... to recover lost data (due to hardware failure) • File compression • … to reduce the size of files • ... which saves storage and memory space // by example • ... and reduces transmission time // by example • Disk formatter • … to prepare a disk for use // set up the file system • ... to partition the disc • ... to delete all the data from the disc 3

9618/12 Cambridge International AS & A Level – Mark Scheme PUBLISHED October/November 2023 © UCLES 2023 Page 10 of 11 Question Answer Marks 8(c)(i) 1 mark for each bullet point (max 1) • USB / Universal Serial Bus • HDMI 1 8(c)(ii) 1 mark for each component (max 3) Buffers • A buffer temporarily holds data until it is ready to be transmitted to the device Address Bus • The address of the data to be written to the device (in RAM) is carried on the address bus Data Bus • All data to be written to the device / buffer is carried on the data bus 3 Question Answer Marks 9(a) 1 mark for each bullet point • IN - Input and output of data • ADD - Arithmetic operations • JPE - Unconditional and conditional instructions • CMI - Compare instructions 4

9618/12 Cambridge International AS & A Level – Mark Scheme PUBLISHED October/November 2023 © UCLES 2023 Page 11 of 11 Question Answer Marks 9(b) 1 mark for each set of shaded rows Instruction address ACC IX Memory address Output 100 101 110 111 0 0 51 65 10 0 11 49 12 49 13 51 14 15 16 49 17 65 18 1 19 65 20 13 65 14 15 21 A 22 4