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

Cambridge IGCSE™(9–1) COMPUTER SCIENCE 0984/22 Paper 2 Problem-solving and Programming October/November 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. This document has 12 pages. Blank pages are indicated. DC (KS) 205005 © UCLES 2020 [Turn over * 4 5 5 4 4 3 4 9 7 6 *

2 0984/22/O/N/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 An online computer shop sells customised personal computers. Every computer sold includes a basic set of components costing $200 and additional items can be added from the table: Category Item code Description Price ($) Case A1 Compact 75.00 Case A2 Tower 150.00 RAM B1 8 GB 79.99 RAM B2 16 GB 149.99 RAM B3 32 GB 299.99 Main Hard Disk Drive C1 1 TB HDD 49.99 Main Hard Disk Drive C2 2 TB HDD 89.99 Main Hard Disk Drive C3 4 TB HDD 129.99 Solid State Drive D1 240 GB SSD 59.99 Solid State Drive D2 480 GB SSD 119.99 Second Hard Disk Drive E1 1 TB HDD 49.99 Second Hard Disk Drive E2 2 TB HDD 89.99 Second Hard Disk Drive E3 4 TB HDD 129.99 Optical Drive F1 DVD/Blu-Ray Player 50.00 Optical Drive F2 DVD/Blu-Ray Re-writer 100.00 Operating System G1 Standard Version 100.00 Operating System G2 Professional Version 175.00 As well as the basic set of components every computer must include one case, one RAM and one Main Hard Disk Drive from the table. A computer is supplied with or without an Operating System. Write and test a program or programs for the online computer 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 and ordering the main items. Write a program to: • use arrays to store the item code, description and price • allow a customer to choose one case, one RAM and one Main Hard Disk Drive • calculate the price of the computer using the cost of the chosen items and the basic set of components • store and output the chosen items and the price of the computer. Task 2 – Ordering additional items. Extend TASK 1 to: • allow a customer to choose whether to purchase any items from the other categories – if so, which item(s) • update the price of the computer • store and output the additional items and the new price of the computer. Task 3 – Offering discounts. Extend TASK 2 to: • apply a 5% discount to the price of the computer if the customer has bought only one additional item • apply a 10% discount to the price of the computer if the customer has bought two or more additional items • output the amount of money saved and the new price of the computer after the discount.

3 0984/22/O/N/20 © UCLES 2020 [Turn over 1 All variables, constants and other identifiers must have meaningful names. (a) (i) Identify one array you could have used for Task 1 and state its purpose. Array … Purpose … … … [2] (ii) Identify one variable you could have used for Task 2 and state its purpose. Variable … Purpose … … … [2] (iii) Identify one constant you could have used for Task 3 and state its purpose. Constant … Purpose … … … [2] (b) Explain the benefits of storing Price as a real data type. … … … … … … … [2]

4 0984/22/O/N/20 © UCLES 2020 (c) Write an algorithm to show how you completed Task 1, using either pseudocode, programming statements or a flowchart. It is not necessary to show initialisation or setting up of arrays in your answer. … … … … … … … … … … … … … … … … … … … … … … … … … … … …

5 0984/22/O/N/20 © UCLES 2020 [Turn over … … … … … … … … … … … … … … … … … … … … … … … … … … … … … [6]

6 0984/22/O/N/20 © UCLES 2020 (d) Explain how your program completes Task 3. Any programming statements used in your answer must be fully explained. … … … … … … … … … … … … … … … … … … … … … … … … … … … … [4]

7 0984/22/O/N/20 © UCLES 2020 [Turn over (e) Describe how you could alter your program to allow more than one computer to be bought. … … … … … … … … … … … … [2]

8 0984/22/O/N/20 © UCLES 2020 Section B 2 Tick (3) one box in each row to identify if the statement about subroutines is true or false. Statement true (3) false (3) A subroutine is called from within a program. A subroutine is not a complete program. A subroutine is a self-contained piece of code. A subroutine must return a value to the code from which it was called. [2] 3 This pseudocode algorithm is used as a validation check. PRINT "Input a number from 1 to 5000" REPEAT INPUT Number IF Number < 1 OR Number > 5000 THEN PRINT "Invalid number, please try again" ENDIF UNTIL Number >= 1 AND Number <= 5000 PRINT Number, " is within the correct range" Identify three different types of test data. For each type, give an example of the test data you would use to test this algorithm and state a reason for your choice of test. Type of test data 1 … Test data … Reason … … Type of test data 2 … Test data … Reason … … Type of test data 3 … Test data … Reason … … [6]

9 0984/22/O/N/20 © UCLES 2020 [Turn over 4 This pseudocode algorithm allows 5000 numbers to be entered and stored in an array called Number. FOR Count 1 TO 5000 INPUT Number[Count] NEXT Count Extend and re-write the algorithm using pseudocode to also count and output how many of the numbers stored in the array are greater than 500, using the variable Higher. Only output Higher once with an appropriate message. … … … … … … … … … … … … … … … … … … … … … … … [6]

10 0984/22/O/N/20 © UCLES 2020 5 This pseudocode represents an algorithm. REPEAT Flag 0 FOR Count 0 to 3 IF Num[Count] < Num[Count + 1] THEN Store Num[Count] Num[Count] Num[Count + 1] Num[Count + 1] Store Flag 1 ENDIF NEXT Count UNTIL Flag = 0 (a) The contents of the array at the start of the algorithm are: Num[0] Num[1] Num[2] Num[3] Num[4] 45 56 30 12 15 Complete the trace table for the algorithm using the data given in the array. Flag Count Num[0] Num[1] Num[2] Num[3] Num[4] Store 45 56 30 12 15 [5] (b) Describe the purpose of the algorithm. … … … … [2]

11 0984/22/O/N/20 © UCLES 2020 [Turn over 6 Draw a flowchart symbol to represent each of the following: Input/Output Decision [2] Question 7 starts on Page 12. 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.

12 0984/22/O/N/20 © UCLES 2020 7 The table AUDIOPARTS stores the part number, description, cost and quantity in stock of the items sold by a music shop. PartNum Description Cost Quantity A01 Compact Amplifier Case 50.00 15 A02 Deluxe Amplifier Case 75.00 1 A03 Amplifier Standard 79.99 48 A04 Amplifier Midrange 149.99 50 A05 Amplifier Megablaster 299.99 48 S01 Tweeter 59.99 10 S02 Midrange Woofer 99.99 0 S03 Subwoofer 139.99 16 S04 Tower Speaker Basic 159.99 25 S05 Tower Speaker Skyscraper 219.99 9 S06 Centre Speaker 149.99 25 S07 Soundbar 89.99 2 S20 Soundbar 129.99 0 S21 Ceiling Surround Speaker 75.00 15 S22 Ceiling Full Range Speaker 100.00 1 S25 Surround Speaker 100.00 60 T19 Speaker Stands (Pair) 75.00 60 (a) State the number of records in the table AUDIOPARTS … [1] (b) Identify the field that is most suitable to be a primary key and give a reason for your choice. Fieldname … Reason … … … [2] (c) Complete the query-by-example grid to show the items where the quantity in stock is fewer than 10. Show all the fields from the database table in descending order of cost. Field: Table: Sort: Show: Criteria: or: [4]

This document consists of 9 printed pages. © UCLES 2020 [Turn over Cambridge IGCSE™ (9–1) COMPUTER SCIENCE 0984/22 Paper 2 October/November 2020 MARK SCHEME Maximum Mark: 50 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 2020 series for most Cambridge IGCSE™, Cambridge International A and AS Level and Cambridge Pre-U components, and some Cambridge O Level components.

0984/22 Cambridge IGCSE (9–1) – Mark Scheme PUBLISHED October/November 2020 © UCLES 2020 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 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.

0984/22 Cambridge IGCSE (9–1) – Mark Scheme PUBLISHED October/November 2020 © UCLES 2020 Page 3 of 9 Question Answer Marks 1(a)(i) Any meaningful name for an array related to Task 1 – one mark e.g. SysStore SysPrice Correct purpose related to Task 1 – one mark e.g. …to store the system (components) that have been purchased …to store the (total) price of the system (being purchased) 2 1(a)(ii) Any meaningful name for a variable related to Task 2 – one mark e.g. Component TotalPrice Correct purpose related to Task 2 - one mark e.g. … to allow input of a component code … to store/calculate the running total price of the system 2 1(a)(iii) Any meaningful name for a constant related to Task 3 – one mark e.g. Offer5 Offer10 Correct purpose related to Task 3 - one mark e.g. … to store the one option discount rate … to store the two-option discount rate 2 1(b) Mark as either: Two distinct different points OR One point and an expansion Example answers: Real data can be used in calculations directly (which is required of the Price data) (1) Data can be stored with decimal places (1) Real numbers can be used in calculations (1) which is not possible with strings (1) 2

0984/22 Cambridge IGCSE (9–1) – Mark Scheme PUBLISHED October/November 2020 © UCLES 2020 Page 4 of 9 Question Answer Marks 1(c) Any six from: MP1 At least one input (case, RAM, HDD) MP2 All three inputs fully prompted MP3 An attempt at validation of input MP4 One complete validation of input with error message MP5 Finding the price for one chosen item MP6 Finding the prices of the other two chosen items correctly MP7 Calculation of price of the chosen items MP8 …add the basic components cost to the cost of the chosen items MP9 Storage of chosen items MP10 Output to show chosen items and price of the computer (with appropriate message) Example answer: OUTPUT "Which type of Case would you like? Input the Item Code" ComponentFlag ← False WHILE ComponentFlag = False INPUT CaseCode Count ← 0 WHILE Count<2 DO IF CaseCode = ComponentCode[Count] THEN CaseIndex ← Count ComponentFlag ← True Count ← 2 ENDIF Count ← Count + 1 ENDWHILE IF ComponentFlag = False THEN OUTPUT "Your case Item Code doesn’t exist, please try again" ENDIF ENDWHILE OUTPUT "Which type of RAM would you like? Input the Item Code" ComponentFlag ← False WHILE ComponentFlag = False INPUT RAMCode Count ← 2 WHILE Count<5 DO IF RAMCode = ComponentCode[Count] THEN RAMIndex ← Count ComponentFlag ← True Count ← 5 ENDIF Count ← Count + 1 ENDWHILE 6

0984/22 Cambridge IGCSE (9–1) – Mark Scheme PUBLISHED October/November 2020 © UCLES 2020 Page 5 of 9 Question Answer Marks 1(c) IF ComponentFlag = False THEN OUTPUT "Your RAM Item Code doesn’t exist, please try again" ENDIF ENDWHILE OUTPUT "Which type of Primary Hard Disk Drive would you like? Input the Item Code" ComponentFlag ← False WHILE ComponentFlag = False INPUT PHDDCode Count ← 5 WHILE Count<8 DO IF PHDDCode = ComponentCode[Count] THEN HDDIndex ← Count ComponentFlag ← True Count ← 8 ENDIF Count ← Count + 1 ENDWHILE IF ComponentFlag = False THEN OUTPUT "Your Primary HDD Item Code doesn’t exist, please try again" ENDIF ENDWHILE TotalPrice ← 200 + ComponentPrice[CaseIndex] + ComponentPrice[RAMIndex] + ComponentPrice[HDDIndex] OUTPUT "Your computer consists of ", Description[CaseIndex], " case, ", Description[RAMIndex], " RAM and ", Description[HDDIndex], " Primary Hard Disk Drive." OUTPUT "The total price of your computer is $", TotalPrice 1(d) Any four from: MP1 Explanation of how the number of additional parts is stored MP2 Explanation of counting of additional parts being added to the system MP3 Explanation of determination of additional parts being 1, or more than 1 MP4 Explanation of using the correct percentage discount MP5 Explanation of calculating the money saved and finding the new price MP6 Explanation of correct output of money saved and new price 4 1(e) Any two from: MP1 Prompt and input to ask buyer how many computers they wish to purchase (at the start) // When the first computer is complete, prompt and input to ask if they would like to purchase another computer MP2 Introduce an appropriate loop structure MP3 New storage for more than one computer // Enable the ordering of multiple computers of the same specification 2

0984/22 Cambridge IGCSE (9–1) – Mark Scheme PUBLISHED October/November 2020 © UCLES 2020 Page 6 of 9 Question Answer Marks Section B 2 Statement true () false () A subroutine is called from within a program.  A subroutine is not a complete program.  A subroutine is a self-contained piece of code.  A subroutine must return a value to the code from which it was called.  Two marks for four correct rows One mark for any two correct rows 2 Question Answer Marks 3 One mark for each correct type of test and one mark for each correct accompanying example of test data and reason (max six) e.g. • Extreme data • 5000 • to check it is accepted • Normal data • 300 • To check it is accepted • Abnormal data • 10000 • To check it is rejected 6

0984/22 Cambridge IGCSE (9–1) – Mark Scheme PUBLISHED October/November 2020 © UCLES 2020 Page 7 of 9 Question Answer Marks 4 Any six from: MP1 Initialisation of Higher to 0 before the loop MP2 Use of IF statement MP3 Correct condition in IF statement MP4 Correct counting statement inside loop MP5 OUTPUT/PRINT statement with correct reference to Higher MP6 Appropriate message in output MP7 Correct location of OUTPUT and IF statements Higher ← 0 FOR Count ← 1 TO 5000 INPUT Number[Count] IF Number[Count] > 500 THEN Higher ← Higher + 1 ENDIF NEXT Count OUTPUT "There are ", Higher, " values that are greater than 500" 6

0984/22 Cambridge IGCSE (9–1) – Mark Scheme PUBLISHED October/November 2020 © UCLES 2020 Page 8 of 9 Question Answer Marks 5(a) Flag Count Num [0] Num [1] Num [2] Num [3] Num [4] Store 45 56 30 12 15 0 0 45 56 1 45 1 2 3 12 15 12 0 0 1 2 3 One mark – Flag column One mark – Count column One mark – Num[0] and Num[1] columns One mark – Num[2], Num[3] and Num[4] columns One mark – Store column 5 5(b) Any two from: • The algorithm sorts/orders numbers • … into descending order / from largest to smallest 2 Question Answer Marks 6 Input/Output Decision One mark for each correct symbol 2

0984/22 Cambridge IGCSE (9–1) – Mark Scheme PUBLISHED October/November 2020 © UCLES 2020 Page 9 of 9 Question Answer Marks 7(a) 17 1 7(b) One mark for correct fieldname and one mark for correct reason PartNum The data stored in this field is unique for each record 2 7(c) Field: PartNum Description Cost Quantity Table: AUDIOPARTS AUDIOPARTS AUDIOPARTS AUDIOPARTS Sort: Descending Show:     Criteria: <10 or: One mark for correct field and table rows One mark for sort row One mark for show row One mark for correct criteria 4