Cambridge A Level Computer Science 9618 — 2021 May/June Paper 1 · Variant 2

This document has 16 pages. Any blank pages are indicated. Cambridge International AS & A Level COMPUTER SCIENCE 9618/12 Paper 1 Theory Fundamentals May/June 2021 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. DC (LK) 205797/1 © UCLES 2021 [Turn over * 3 0 1 4 9 9 4 8 4 1 *

2 9618/12/M/J/21 © UCLES 2021 1 Raj owns houses that other people rent from him. He has a database that stores details about the people who rent houses, and the houses they rent. The database, HOUSE_RENTALS, has the following structure: CUSTOMER(CustomerID, FirstName, LastName, DateOfBirth, Email) HOUSE(HouseID, HouseNumber, Road, Town, Bedrooms, Bathrooms) RENTAL(RentalID, CustomerID, HouseID, MonthlyCost, DepositPaid) (a) Give the definition of the following database terms, using an example from the database HOUSE_RENTALS for each definition. Term Definition and example Field … … … Entity … … … Foreign key … … … [6] (b) Tick (3) one box to identify whether the database HOUSE_RENTALS is in Third Normal Form (3NF) or not in 3NF. Justify your choice using one or more examples from the database HOUSE_RENTALS. In 3NF Not in 3NF Justification … … … … [2]

3 9618/12/M/J/21 © UCLES 2021 [Turn over (c) Example data from the table RENTAL are given: RentalID CustomerID HouseID MonthlyCost DepositPaid 1 22 15B5L 1000.00 Yes 2 13 3F 687.00 No 3 1 12AB 550.00 Yes 4 3 37 444.50 Yes (i) Complete the following Data Definition Language (DDL) statement to define the table RENTAL. CREATE … … ( RentalID INTEGER NOT NULL, CustomerID INTEGER NOT NULL, HouseID … (5) NOT NULL, MonthlyCost … NOT NULL, DepositPaid BOOLEAN NOT NULL, … (RentalID) ); [4] (ii) Write a Data Manipulation Language (DML) script to return the first name and last name of all customers who have not paid their deposit. … … … … … … [4]

4 9618/12/M/J/21 © UCLES 2021 2 Aisha manages a team of software developers. (a) Explain the reasons why it is important that Aisha acts ethically in relation to her team members. … … … … [2] (b) The team are developing a computer game where the user plays a board game (such as chess) against the computer. Describe how the computer would use Artificial Intelligence (AI) to play the board game. … … … … … … [3] (c) The final game will be released under a licence. Tick (3) one or more boxes in each row to identify the licence(s) each statement describes. Statement Free Software Foundation Open Source Initiative Shareware Commercial Software The user can edit the source code The user must always pay before being able to use the software The user can redistribute the software The user always gets a trial period [4]

5 9618/12/M/J/21 © UCLES 2021 [Turn over 3 A logic expression is given: S = (A AND B AND C) OR (B XOR C) (a) Draw the logic circuit for the given expression. A B C S [4] (b) Complete the truth table for the logic expression: S = (A AND B AND C) OR (B XOR C) A B C Working space S 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]

6 9618/12/M/J/21 © UCLES 2021 4 The table shows part of the instruction set for a processor. The processor has one general purpose register, the Accumulator (ACC), and an Index Register (IX). Instruction Explanation Opcode Operand LDM #n Immediate addressing. Load the number n to ACC LDD <address> Direct addressing. Load the contents of the location at the given address to ACC STO <address> Store contents of ACC at the given address ADD <address> Add the contents of the given address to 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) CMP <address> Compare the contents of ACC with the contents of <address> JPE <address> Following a compare instruction, jump to <address> if the compare was True JPN <address> Following a compare instruction, jump to <address> if the compare was False JMP <address> Jump to the given address 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 # denotes a denary number, e.g. #123 The current contents of the main memory and selected values from the ASCII character set are: Address Instruction ASCII code table (selected codes only) 70 IN ASCII code Character 71 CMP 100 65 A 72 JPE 80 66 B 73 CMP 101 67 C 74 JPE 76 68 D 75 JMP 80 76 LDD 102 77 INC ACC 78 STO 102 79 JMP 70 80 LDD 102 81 DEC ACC 82 STO 102 83 JMP 70 … 100 68 101 65 102 100

7 9618/12/M/J/21 © UCLES 2021 [Turn over (a) Complete the trace table for the program currently in main memory when the following characters are input: A D Do not trace the program any further when the third input is required. Instruction address ACC Memory address 100 101 102 68 65 100 [4]

8 9618/12/M/J/21 © UCLES 2021 (b) Some bit manipulation instructions are shown in the table: Instruction Explanation Opcode Operand AND #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 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 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 address or a symbolic address # denotes a denary number, e.g. #123 The contents of the memory address 300 are shown: Bit Number 7 6 5 4 3 2 1 0 300 0 1 1 0 0 1 1 0 (i) The contents of memory address 300 represent an unsigned binary integer. Write the denary value of the unsigned binary integer in memory address 300. … [1] (ii) An assembly language program needs to test if bit number 2 in memory address 300 is a 1. Complete the assembly language instruction to perform this test. … #4 [1] (iii) An assembly language program needs to set bit numbers 4, 5, 6 and 7 to 0, but keep bits 0 to 3 with their existing values. Write the assembly language instruction to perform this action. … … [2]

9 9618/12/M/J/21 © UCLES 2021 [Turn over 5 Seth uses a computer for work. (a) Complete the following descriptions of internal components of a computer by writing the missing terms. The … transmits the signals to coordinate events based on the electronic pulses of the … . The … carries data to the components, while the … carries the address where data needs to be written to or read from. The … performs mathematical operations and logical comparisons. [5] (b) Describe the ways in which the following factors can affect the performance of his laptop computer. Number of cores … … … … Clock speed … … … … [4]

10 9618/12/M/J/21 © UCLES 2021 (c) Seth accesses both software and data using cloud computing. (i) Give two benefits of storing data using cloud computing. 1 … … 2 … … [2] (ii) Give two drawbacks of Seth using cloud computing. 1 … … 2 … … [2]

11 9618/12/M/J/21 © UCLES 2021 [Turn over (d) Draw one line from each term to its most appropriate description. Term Description Public IP address Private IP address Dynamic IP address Static IP address It is only visible to devices within the Local Area Network (LAN) It increments by 1 each time the device connects to the internet A new one is reallocated each time a device connects to the internet It can only be allocated to a router It is visible to any device on the internet It does not change each time a device connects to the internet [4]

12 9618/12/M/J/21 © UCLES 2021 6 A computer uses the ASCII character set. (a) State the number of characters that can be represented by the ASCII character set and the extended ASCII character set. ASCII … Extended ASCII … [2] (b) Explain how a word such as ‘HOUSE’ is represented by the ASCII character set. … … … … [2] (c) Unicode is a different character set. The Unicode value for the character ‘1’ is denary value 49. (i) Write the hexadecimal value for the Unicode character ‘1’. … [1] (ii) Write the denary value for the Unicode character ‘5’. … [1]

13 9618/12/M/J/21 © UCLES 2021 [Turn over 7 Jennifer is writing a computer program for her A Level homework. (a) Jennifer uses a program library to help her write her computer program. Describe how a program library can be used while writing a computer program. … … … … [2] (b) Jennifer uses an Integrated Development Environment (IDE) to write her computer program. (i) The IDE allows Jennifer to use both an interpreter and a compiler while creating her computer program. Describe the ways in which Jennifer can use both a compiler and an interpreter while developing the program. … … … … … … … … [4] (ii) Identify two debugging tools that a typical IDE can provide. 1 … … 2 … … [2]

14 9618/12/M/J/21 © UCLES 2021 8 A company has several security measures in place to prevent unauthorised access to the data on its computers. (a) Describe the difference between the security and privacy of data. … … … … [2] (b) Each employee has a username and password to allow them to log onto a computer. An employee’s access rights to the data on the computers is set to either read-only, or read and write. Identify one other software-based measure that could be used to restrict the access to the data on the computers. … … [1] (c) The company is also concerned about threats posed by networks and the internet. Identify two threats to the data that are posed by networks and the internet. Threat 1 … … Threat 2 … … [2]

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16 9618/12/M/J/21 © UCLES 2021 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 the Cambridge Assessment Group. Cambridge Assessment is the brand name of the University of Cambridge Local Examinations Syndicate (UCLES), which itself is a department of the University of Cambridge. BLANK PAGE

This document consists of 10 printed pages. © UCLES 2021 [Turn over Cambridge International AS & A Level COMPUTER SCIENCE 9618/12 Paper 1 Theory Fundamentals May/June 2021 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 2021 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 May/June 2021 © UCLES 2021 Page 2 of 10 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 May/June 2021 © UCLES 2021 Page 3 of 10 Question Answer Marks 1(a) 1 mark for definition, 1 mark for appropriate example in each Term Definition and example Field A column/attribute in a table e.g. CustomerID in the table CUSTOMER Entity Anything that data can be stored about e.g. A customer or a house Foreign Key A field in one table that is linked to a Primary Key in another table e.g. CustomerID / HouseID in table RENTAL 6 1(b) 1 mark per bullet point to max 2 • All fields in all tables are dependant fully on the PK and on no other fields • for example all fields in Customer table are fully dependent on CustomerID 2 1(c)(i) 1 mark for each correctly completed line CREATE TABLE RENTAL( RentalID INTEGER NOT NULL, CustomerID INTEGER NOT NULL, HouseID VARCHAR (5) NOT NULL, MonthlyCost REAL/CURRENCY NOT NULL, DepositPaid BOOLEAN NOT NULL, PRIMARY KEY (RentalID) ); 4 1(c)(ii) 1 mark per bullet point • Select FirstName and LastName • From both tables • Where DepositPaid = No • Joining tables (either AND, or INNER JOIN) Example script: SELECT FirstName, LastName FROM CUSTOMER, RENTAL WHERE DepositPaid = No AND RENTAL.CustomerID = CUSTOMER.CustomerID; 4

9618/12 Cambridge International AS & A Level – Mark Scheme PUBLISHED May/June 2021 © UCLES 2021 Page 4 of 10 Question Answer Marks 2(a) 1 mark per bullet point to max 2 • To make sure the team members feel valued • To get the best work out of the team • To enable them to work well together • To enable them to create the best product for the client 2 2(b) 1 mark per bullet point to max 3 • The rules / past moves / decision making algorithms of the game will be stored • The AI program is trained, by playing many times • AI will look (ahead) at possible moves • ... and/or analyse the pattern of past choices • … and choose the move most likely to be successful • Computer could learn how to improve // learn from previous mistakes • … by storing the positive/negative result of choices • ... and changing its future choices 3 2(c) 1 mark for each correct column Statement Free Software Foundation Open Source Initiative Shareware Commercial Software The user can edit the source code   The user must always pay before being able to use the software  The user can redistribute the software    The user always gets a trial period  4

9618/12 Cambridge International AS & A Level – Mark Scheme PUBLISHED May/June 2021 © UCLES 2021 Page 5 of 10 Question Answer Marks 3(a) 1 mark for each correct gate, with correct inputs 4 3(b) 1 mark for each half (shaded) A B C Working space S 0 0 0 0 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

9618/12 Cambridge International AS & A Level – Mark Scheme PUBLISHED May/June 2021 © UCLES 2021 Page 6 of 10 Question Answer Marks 4(a) 1 mark for each shaded section / bullet point • Load 65 into ACC • Load 100 into ACC, increment and store in 102 • Load 68 into ACC • Load 101 into ACC, decrement and store in 102 Instruction address ACC Memory address 100 101 102 68 65 100 70 65 71 72 73 74 76 100 77 101 78 101 79 70 68 71 72 80 101 81 100 82 100 83 (70) 4 4(b)(i) 102 1 4(b)(ii) AND 1

9618/12 Cambridge International AS & A Level – Mark Scheme PUBLISHED May/June 2021 © UCLES 2021 Page 7 of 10 Question Answer Marks 4(b)(iii) 1 mark for AND, 1 mark for #15 AND #15 2 Question Answer Marks 5(a) 1 mark for each term correctly inserted The control unit/bus transmits the signals to coordinate events based on the pulses of the (system) clock. The data bus carries data to components, while the address bus carries the address where data is being written to or read from. The arithmetic logic unit/ALU performs mathematical operations and logical comparisons. 5 5(b) 1 mark per bullet point to max 3 per factor. max 4 overall. Number of cores: • Each core processes one instruction per clock pulse • More/multiple cores mean that sequences of instructions can be split between them • … and so more than one instruction is executed per clock pulse // more sequences of instructions can be run at the same time • More cores decreases the time taken to complete task Clock speed: • Each instruction is executed on a clock pulse // one F-E cycle is run on each clock pulse • ... so the clock speed dictates the number of instructions that can be run per second • The faster the clock speed the more instructions can be run per second 4 5(c)(i) 1 mark per bullet point to max 2 • Cloud storage can be free (for small quantities ) • No need for separate (high capacity) storage devices // saves storage on existing devices • Can access data from any computer with internet access • Most cloud data services will have in-built backup/disaster recovery • Security could be better • Can easily increase capacity • Data can be easily shared 2

9618/12 Cambridge International AS & A Level – Mark Scheme PUBLISHED May/June 2021 © UCLES 2021 Page 8 of 10 Question Answer Marks 5(c)(ii) 1 mark per bullet point to max 2: • Can only access (the cloud) with internet access • Security may not be strong // no control over security • There may not be any backups // no control over backups • It can take a long time to upload/download the data • It can be more expensive in the long term • There could be a limit to the amount of storage unless paid for • There could be compatibility/access issues • There could be issues with the company offering cloud services 2 5(d) 1 mark for each correct line 4 Question Answer Marks 6(a) 1 mark for each correct answer ASCII = 128 // 27 Extended ASCII = 256 // 28 2 6(b) 1 mark per bullet point to max 2 • Each character has its own unique code • Each character in the word is replaced by its code • The codes are stored in the order in the word 2

9618/12 Cambridge International AS & A Level – Mark Scheme PUBLISHED May/June 2021 © UCLES 2021 Page 9 of 10 Question Answer Marks 6(c)(i) 31 1 6(c)(ii) 53 1 Question Answer Marks 7(a) 1 mark per bullet point to max 2 • Program libraries store pre-written functions and routines • The program library can be referenced/imported • the functions/routines can be called in her own program 2 7(b)(i) 1 mark per bullet point to max 4; max 3 from each section Interpreter: • Use an interpreter while writing the program • … to test/debug the partially completed program • … because errors can be corrected and processing continue from where the execution stopped // errors can be corrected in real time // errors are identified one at a time Compiler: • Use the compiler after the program is complete • … to create an executable file • Use the compiler to repeatedly test the same (completed) section • … without having to re-interpret every time // compiler not needed at run- time 4 7(b)(ii) 1 mark per correct tool to max 2 e.g. • Breakpoints • Single stepping • Report windows 2 Question Answer Marks 8(a) 1 mark per bullet point • Security protects data against loss • Privacy protects data against unauthorised access 2 8(b) 1 mark for a correct answer • Two factor authentication • Biometric passwords • Key Card Access • Firewall 1

9618/12 Cambridge International AS & A Level – Mark Scheme PUBLISHED May/June 2021 © UCLES 2021 Page 10 of 10 Question Answer Marks 8(c) 1 mark per correct answer to max 2 • Malware // viruses // spyware // by example • Hacking • Phishing • Pharming 2