Cambridge IGCSE Computer Science (9-1) 0984 — 2020 May/June Paper 2 · Variant 1

Cambridge IGCSE™(9–1) COMPUTER SCIENCE 0984/21 Paper 2 Problem-solving and Programming May/June 2020 1 hour 45 minutes You must answer on the question paper. No additional materials are needed. INSTRUCTIONS ● Answer all questions. ● Do not attempt Tasks 1, 2 and 3 in the copy of the pre-release material on page 2; these are for information only. ● Use a black or dark blue pen. You may use an HB pencil for any diagrams or graphs. ● 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. ● Calculators must not be used in this paper. INFORMATION ● The total mark for this paper is 50. ● 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. * 7 4 4 1 4 2 6 0 7 5 * This document has 16 pages. Blank pages are indicated. DC (RW) 198787 © UCLES 2020 [Turn over

2 0984/21/M/J/20 © UCLES 2020 Section A You are advised to spend no longer than 40 minutes answering this section. Here is a copy of the pre-release material. DO NOT attempt Tasks 1, 2 and 3 now. Use the pre-release material and your experience from attempting the tasks before the examination to answer Question 1. Pre-release material A shop sells a range of mobile devices, SIM cards and accessories as shown in the table: Category Item code Description Price ($) Phone BPCM Compact 29.99 Phone BPSH Clam Shell 49.99 Phone RPSS RoboPhone – 5-inch screen and 64 GB memory 199.99 Phone RPLL RoboPhone – 6-inch screen and 256 GB memory 499.99 Phone YPLS Y-Phone Standard – 6-inch screen and 64 GB memory 549.99 Phone YPLL Y-Phone Deluxe – 6-inch screen and 256 GB memory 649.99 Tablet RTMS RoboTab – 8-inch screen and 64 GB memory 149.99 Tablet RTLM RoboTab – 10-inch screen and 128 GB memory 299.99 Tablet YTLM Y-Tab Standard – 10-inch screen and 128 GB memory 499.99 Tablet YTLL Y-Tab Deluxe – 10-inch screen and 256 GB memory 599.99 SIM card SMNO SIM Free (no SIM card purchased) 0.00 SIM card SMPG Pay As You Go (SIM card purchased) 9.99 Case CSST Standard 0.00 Case CSLX Luxury 50.00 Charger CGCR Car 19.99 Charger CGHM Home 15.99 Write and test a program or programs for this shop. • Your program or programs must include appropriate prompts for the entry of data; data must be validated on entry. • Error messages and other output need to be set out clearly and understandably. • All arrays, variables, constants and other identifiers must have meaningful names. You will need to complete these three tasks. Each task must be fully tested. Task 1 – Setting up the system. Write a program to: • use appropriate data structures to store the item code, description and price information for the mobile devices, SIM cards and accessories • allow the customer to choose a specific phone or tablet • allow phone customers to choose whether the phone will be SIM Free or Pay As You Go • allow the customer to choose a standard or luxury case • allow the customer to choose the chargers required (none, one or both may be purchased) • calculate the total price of this transaction • output a list of the items purchased and the total price. Task 2 – Allow a customer to order multiple mobile devices. Extend Task 1 to: • offer the customer the opportunity to purchase an additional mobile device • if required, perform bulleted steps 2 to 7 of Task 1 for each additional mobile device and calculate a running total for the customer • once no further devices are required, output the total the customer will need to pay. Task 3 – Offering discounts. Extend the program to allow a discount of 10% off the price of every additional phone or tablet purchased. Output the new total the customer will need to pay and the amount of money saved.

3 0984/21/M/J/20 © UCLES 2020 [Turn over 1 All variables, constants and other identifiers must have meaningful names. (a) (i) Identify two arrays you could have used for Task 1 and, in each case, state its purpose. Array 1 … Purpose … … … Array 2 … Purpose … … … [4] (ii) Identify two variables you could have used for Task 1 and, in each case, state its purpose. Variable 1 … Purpose … … … Variable 2 … Purpose … … … [4] (b) Explain why the item code data could not be stored as a real data type and identify the most suitable data type for the item code data. … … … … … … [2]

4 0984/21/M/J/20 © UCLES 2020 (c) Write an algorithm to show how you input your choice of mobile device and SIM card (part of Task 1), using either pseudocode, programming statements or a flowchart. It is not necessary to show initialisation or setting up of arrays containing product details. … … … … … … … … … … … … … … … … … … … … … … … … … …

5 0984/21/M/J/20 © UCLES 2020 [Turn over … … … … … … … … … … … … … … … … … … … … … … … … … … … … [5]

6 0984/21/M/J/20 © UCLES 2020 (d) Explain how your program completes Task 3. Any programming statements used in your answer must be fully explained. … … … … … … … … … … … … … … … … … … … … … … … … … … [5]

7 0984/21/M/J/20 © UCLES 2020 [Turn over Section B starts on page 8.

8 0984/21/M/J/20 © UCLES 2020 Section B 2 Tick (ü) one box in each row to identify if the statement about structure diagrams is true or false. Statement True (ü) False (ü) A structure diagram is a piece of code that is available throughout the structure of a program. A structure diagram shows the hierarchy of a system. A structure diagram is another name for an array. A structure diagram shows the relationship between different components of a system. [2] 3 Programs can perform validation and verification checks when data is entered. (a) Give the names of two different validation checks and state the purpose of each one. Check 1 … Purpose … … … Check 2 … Purpose … … … [4] (b) Give the name of one verification check. … [1] (c) Describe the difference between validation and verification. … … … … [2]

9 0984/21/M/J/20 © UCLES 2020 [Turn over 4 The pseudocode algorithm shown should allow numbers to be entered and should allow 50 numbers to be stored in an array. Count ← 0 REPEAT INPUT Values[Count] Count ← Count + 1 UNTIL Count = 0 (a) Explain why the algorithm will never end. … … … … … [2] (b) Re-write the original pseudocode so that it terminates correctly and also prevents numbers below 100 from being stored in the array Values[ ] … … … … … … … … … … [4] (c) Describe how you could change your pseudocode in part (b) so that it prevents numbers below 100 and above 200 from being stored in the array Values[ ] … … … … [2]

10 0984/21/M/J/20 © UCLES 2020 5 The flowchart represents an algorithm. The predefined function DIV gives the value of the result of integer division, for example, y ← 9 DIV 4 gives y a value of 2 An input value of –1 ends the algorithm. START INPUT Value Yes Yes No No IS Value = -1 ? Calc1 Value DIV 2 END No OUTPUT Value IS Calc1 = Value / 2 ? IS Calc2 = Value / 3 ? Calc2 Value DIV 3 Yes

11 0984/21/M/J/20 © UCLES 2020 [Turn over (a) Complete the trace table for the input data: 50, 33, 18, 15, 30, –1, 45, 12, 90, 6 Value Calc1 Calc2 OUTPUT [4] (b) Describe the purpose of the algorithm. … … … [2]

12 0984/21/M/J/20 © UCLES 2020 6 A garden centre sells garden tools and stores details of these in a database table named TOOLS. Code is the primary key in the TOOLS table. Code Description Price ($) Quantity_Stock Quantity_Ordered GFLG Garden Fork 50.00 1 50 GSLG Garden Spade 50.00 11 0 GHLG Garden Hoe 45.00 8 0 HFSM Hand Fork 9.99 42 0 HSSM Hand Spade 9.99 40 0 HWSM Hand Weeder 9.99 11 0 HS20 Hose (20 metres) 45.00 10 0 HS35 Hose (35 metres) 60.00 2 0 HS50 Hose (50 metres) 75.00 20 60 YBLG Yard Brush 24.99 100 0 LMHD Lawn Mower 99.99 5 0 LMBT Lawn Mower (Battery) 249.99 7 0 LMPT Lawn Mower (Petrol) 349.99 10 25 TRBT Edge Trimmer (Battery) 79.99 15 0 TRPT Edge Trimmer (Petrol) 59.99 20 0 SHSM Shears 40.00 40 0 HCSM Hedge Clippers 40.00 45 0 (a) State the purpose of the primary key in the TOOLS table. … … … [1]

13 0984/21/M/J/20 © UCLES 2020 (b) List the output from the data shown in the table TOOLS that would be given by this query-by- example. Field: Code Description Price ($) Quantity_Stock Quantity_Ordered Table: TOOLS TOOLS TOOLS TOOLS TOOLS Sort: Descending Show: ü ü ü Criteria: >40 >0 >0 or: … … … … … … [3] (c) Complete the query-by-example grid to output the tools where the quantity in stock is below 25. Only show the Code, Description and Quantity_Stock fields in ascending order of Code. Field: Table: Sort: Show: Criteria: or: [3]

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16 0984/21/M/J/20 © UCLES 2020 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 2020 [Turn over Cambridge IGCSE™ (9–1) COMPUTER SCIENCE 0984/21 Paper 2 May/June 2020 MARK SCHEME Maximum Mark: 50 Published Students did not sit exam papers in the June 2020 series due to the Covid-19 global pandemic. This mark scheme is published to support teachers and students and should be read together with the question paper. It shows the requirements of the exam. The answer column of the mark scheme shows the proposed basis on which Examiners would award marks for this exam. Where appropriate, this column also provides the most likely acceptable alternative responses expected from students. Examiners usually review the mark scheme after they have seen student responses and update the mark scheme if appropriate. In the June series, Examiners were unable to consider the acceptability of alternative responses, as there were no student responses to consider. Mark schemes should usually be read together with the Principal Examiner Report for Teachers. However, because students did not sit exam papers, there is no Principal Examiner Report for Teachers for the June 2020 series. Cambridge International will not enter into discussions about these mark schemes. Cambridge International is publishing the mark schemes for the June 2020 series for most Cambridge IGCSE™ and Cambridge International A & AS Level components, and some Cambridge O Level components.

0984/21 Cambridge IGCSE (9–1) – Mark Scheme PUBLISHED May/June 2020 © UCLES 2020 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.

0984/21 Cambridge IGCSE (9–1) – Mark Scheme PUBLISHED May/June 2020 © UCLES 2020 Page 3 of 10 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.

0984/21 Cambridge IGCSE (9–1) – Mark Scheme PUBLISHED May/June 2020 © UCLES 2020 Page 4 of 10 Question Answer Marks 1(a)(i) Any meaningful array related to Task 1 – one mark (max two) e.g. ItemCode Description Correct purpose for each array related to Task 1 – one mark (max two) e.g. …to store the item codes …to store the descriptions of the items for sale 4 1(a)(ii) Any meaningful variable related to Task 1 – one mark (max two) e.g. PurchaseItem TotalPrice Correct purpose for each variable related to Task 1 - one mark (max two) e.g. … to allow input of an item/code for purchase … to store/calculate the total price of the transaction 4 1(b) Any one correct statement e.g. • The Code data is made up of letters/alphabetic characters/not numbers • Real data must have numerical value/would not be used in calculations One mark for: • String 2

0984/21 Cambridge IGCSE (9–1) – Mark Scheme PUBLISHED May/June 2020 © UCLES 2020 Page 5 of 10 Question Answer Marks 1(c) Any five from • Input with message to allow choice of mobile device • Attempt to validate input to check for valid item code • Accurate validation of input to check for valid item code • Determination of whether device is phone or tablet • Restriction to only allow input for SIM card required if mobile device is a phone • Input with message to find out if a SIM card is required Example answer OUTPUT "Which type of phone or tablet would you like? Input the Item Code" DeviceFlag ← False WHILE DeviceFlag = False INPUT DeviceCode Count ← 0 WHILE Count<10 DO IF DeviceCode = ItemCode[Count] THEN IF Count < 6 THEN DeviceType ← "Phone" ELSE DeviceType ← "Tablet" ENDIF DeviceFlag ← True Count ← 10 ENDIF Count ← Count + 1 ENDWHILE IF DeviceFlag = False THEN 5

0984/21 Cambridge IGCSE (9–1) – Mark Scheme PUBLISHED May/June 2020 © UCLES 2020 Page 6 of 10 Question Answer Marks 1(c) OUTPUT "Your code doesn’t exist, please try again" ENDIF ENDWHILE IF DeviceType ← "Phone" THEN OUTPUT "Would you like a SIM Card? (Answer Y or N)" INPUT SimRequired ENDIF 1(d) Any five from • Explanation of finding if more than one device is purchased • Explanation of application of device discount • Explanation of calculating the discount(s) and finding the new price • Explanation of outputting new total • Explanation of outputting amount saved • Explanation of messages used 5 Question Answer Marks 2 Statement True () False () A structure diagram is a piece of code that is available throughout the structure of a program.  A structure diagram shows the hierarchy of a system.  A structure diagram is another name for an array.  A structure diagram shows the relationship between different components of a system.  Two marks for four correct rows. One mark for three correct rows. 2

0984/21 Cambridge IGCSE (9–1) – Mark Scheme PUBLISHED May/June 2020 © UCLES 2020 Page 7 of 10 Question Answer Marks 3(a) One mark for each correct validation check (max two) • Range • Length • Type • Check Digit One mark for each correct related purpose (max two) e.g. • To make sure the data entered falls within a specific set of values • To make sure the data entered is no longer than specified • To make sure the data entered follows rules related to whether it is numbers of letters • To make sure an identification code entered is genuine or possible 4 3(b) One mark for correct verification check (max one) • Double (data) entry • Visual check 1 3(c) Any two correct statements (max two) e.g. • Validation checks if the data entered is possible/it cannot check if data has been entered correctly. • Verification checks if the data entered matches the data submitted for entry/ it does not check if data matches set criteria. 2 Question Answer Marks 4(a) Any two correct statements (max two) e.g. • The value of the variable Count begins as 0 … • … and is incremented by 1 before it is tested by the loop condition • Count will never be 0 at the end of the loop 2

0984/21 Cambridge IGCSE (9–1) – Mark Scheme PUBLISHED May/June 2020 © UCLES 2020 Page 8 of 10 Question Answer Marks 4(b) Count ← 0 REPEAT INPUT Number IF Number >= 100 THEN Values[Count] ← Number ENDIF Count ← Count + 1 UNTIL Count = 50 One mark – separate INPUT statement One mark – IF statement attempted One mark – IF statement completely correct One mark – termination of loop updated 4 4(c) Any two correct statements (max two) e.g. • Alter the IFstatement/add a second IF statement/comparison that’s already there … • … so that additional criteria set an upper limit of <=200 2

0984/21 Cambridge IGCSE (9–1) – Mark Scheme PUBLISHED May/June 2020 © UCLES 2020 Page 9 of 10 Question Answer Marks 5(a) Value Calc1 Calc2 OUTPUT 50 25 16 33 16 11 18 9 6 18 15 7 5 30 15 10 30 -1 One mark for each correct column (max four) 4 5(b) Any two correct statements e.g. • The program outputs a value • That is divisible by 6 // 2 and 3 2

0984/21 Cambridge IGCSE (9–1) – Mark Scheme PUBLISHED May/June 2020 © UCLES 2020 Page 10 of 10 Question Answer Marks 6(a) To uniquely identify a product (in TOOLS) 1 6(b) HS50 Hose (50 metres) 60 GFLG Garden Fork 50 LMPT Lawn Mower (Petrol) 25 One mark for correct data One mark for correct format One mark for data in correct order 3 6(c) Field: Code Description Quantity_Stock Table: TOOLS TOOLS TOOLS Sort: Ascending Show:      Criteria: <25 or: One mark for each completely correct column (max three) 3