1 All variables, constants and other identifiers must have meaningful names. (a) Identify the variable that you used to store the student’s answer in Task 1. Give the most appropriate data type for this variable. Explain how your program ensured that any data entered for the answer was valid. Variable … Data type … Validation … … … … [4] (b) Identify and give the data type of a different variable, that you could have used in Task 2. State the use of this variable in Task 2. Variable … Data type … Use … … [3] (c) Write an algorithm for Task 1, using either pseudocode, programming statements or a flowchart. … … … … … … … … … … … … … … … … … … … … … … … … … … … … … … … … … … … … … … … … … … … … … … … … … … … … … … [6] (d) Explain how your program completed Task 3. Include any programming statements that you have added to Task 1 and fully explain the purpose of each statement. … … … … … … … … … … … … … … … … … … … … … … … [4] (e) Explain how you could alter Task 1 to change the quiz to: • display three alternative answers for each question • allow the student to choose one of these answers … … … … … … … … … … … … … … … … … … … … … … … [3] Section B

1(a) Variable answer (example only) Data type integer/int Validation two distinct different points OR one point and an expansion One mark per mark point, max two – restricted input to positive numbers – checked if input was numeric – ensured that input was a whole number / integer – checked if a value was input Or one point and an expansion two marks, for example – restricted input to positive numbers (1) by using a range/limit check / REPEAT… UNTIL looping until value greater than zero (1) – checked if input was numeric (1) by using a type check (1) – ensured the value input was a whole number (1) any suitable method e.g. rounding to whole number – checked if a value was input (1) by using a presence check (1) 4 1(b) Variable noAttempts (example only) Data type integer/int Use storing the number of attempts a pupil has made on a question 3 1(c) One mark per mark point, max six MP1 initialisation (must include number of correct answers) MP2 input name and table number with prompts MP3 validate table number and reinput MP4 ensure each question uses a different multiplier MP5 display question MP6 input and validate answer MP7 check if answer correct MP8 update score appropriately MP9 repeat for 5 questions MP10 display score and name at end … MP11 …with an attempt to display an appropriate message dependent on score Example Score = 0 Multiplier[1] ← 2 Multiplier[2] ← 5 Multiplier[3] ← 7 Multiplier[4] ← 8 Multiplier[5] ← 11 OUTPUT "Multiplication Table Test" OUTPUT "Please enter your name" INPUT Name REPEAT OUTPUT "Please enter the table (2 to 12) you would like to be tested" INPUT Table UNTIL (Table >=2) AND (Table 0 AND Answer = INT(Answer) IF Answer = Multiplier[Count] * Table THEN Score ← Score + 1 ENDIF NEXT OUTPUT (Name, " your score is ", Score) IF Score = 5 THEN OUTPUT ("Well done full marks") ELSE OUTPUT ("Have another practice") ENDIF 6 1(d) Explanation One mark per mark point illustrated with a suitable programming statement, max four MP1 extra prompt and input to choose the number of questions and/or mixed set MP2 method of choosing number of questions and/or mixed set MP3 extra prompt and input for number of questions MP4 explanation of validation for either input MP5 how the end value for the question loop was changed if required MP6 how the program was changed to allow for mixed tables MP7 … how the program ensured that the test used more than one multiplication table 4 1(e) Explanation One mark per mark point, max three MP1 how to provide 3 answers, including the correct one MP2 how to ensure that all 3 answers are different MP3 how 3 answers are displayed e.g. output all 3 answers as a numbered list MP4 how to select the correct answer e.g. input the number of the correct MP5 how to ensure that the correct answer is not always in the same position 3 Section B (a) To earn marks, you must identify a suitable variable name (like 'answer'), state its data type as integer, and provide two distinct points about how input validation was performed (e.g., restricting to positive numbers and checking if numeric), or one point with a clear expansion. (b) You need to identify a different variable (like 'noAttempts'), state its integer data type, and explain its purpose in Task 2, such as storing the number of attempts.

1 All variables, constants and other identifiers must have meaningful names. (a) Identify and give the data type and use of one array that you could have used for Task 1. Array … Data type … Use … [3] (b) Describe two validation checks that could be used when inputting the number of tickets to buy for Task 2. For each validation check give one example of normal data and one example of erroneous data. Validation check 1 … … … Normal data … Erroneous data … Validation check 2 … … … Normal data … Erroneous data … [6] (c) Write an algorithm for the part of Task 2 that inputs the tickets required, calculates the total price for the ticket(s) purchased by a passenger including a group discount (if applicable) and updates the data structures used for the totals. Use either pseudocode, programming statements or a flowchart. … … … … … … … … … … … … … … … … … … … … … … … … … … … … … … … … … … … … … … … … … … … … … … … … … … … … [6] (d) Explain how your program completed Task 3. Include any programming statements that you have used and fully explain the purpose of each statement. … … … … … … … … … … … … … … … … … … … … … … … [5] Section B starts on page 8 Section B

Section A 1(a) Array TrainUpPassengers // TrainUpPassengers[] Data type Integer/int Use storing the number of passengers on the train journeys up Many correct answers, this is an example. 3 1(b) One mark for description, one mark for normal data and one mark for erroneous data for two checks Validation check (type check) to check that the number entered is a whole number / integer Normal data 34 Erroneous data two // 1.5 Validation check (range check) to check that the value of the number entered is between 1 and 80 / 480 inclusive Normal data 34 Erroneous data 99 // 500 Validation check (presence check) to check that a value has been entered Normal data 34 // any data entered Erroneous data “” // blank // no data entered Validation check (length check) to check that a value has 3 digits or fewer // between 1 and 3 digits Normal data 345 Erroneous data 3456 Many correct answers, the data are examples only. 6 1(c) Any six from: MP1 Input number of tickets MP2 Input train up mountain and train down mountain MP3 Suitable prompts seen for inputs that are included MP4 Check that tickets are available on selected train(s) MP5 If available calculate price of tickets … MP6 … calculation includes discount if required MP7 Update total passengers / seats available for a train MP8 Update total passengers / seats available for up train and down train MP9 Update total cost for a train MP10 Update total cost for up train and down train Example answers OUTPUT "How many tickets" INPUT NoTickets OUTPUT "Which Train up the mountain? 1, 2, 3 or 4" INPUT UpNumber OUTPUT "Which Train down the mountain? 1, 2, 3 or 4" INPUT DownNumber IF (DownNumber = 4 AND TrainUp[UpNumber] + NoTickets <= 480 AND TrainDown[DownNumber] + NoTickets <= 640) OR (TrainUp[UpNumber] + NoTickets <= 480 AND TrainDown[DownNumber] + NoTickets <= 480) THEN Cost ← (NoTickets – NoTickets DIV 10) * 50 TrainUp[UpNumber] ← TrainUp[UpNumber] + NoTickets TrainDown[DownNumber] ← TrainUp[DownNumber] + NoTickets TrainUpTotal[UpNumber] ← TrainUpTotal[UpNumber] + Cost / 2 TrainDownTotal[DownNumber] ← TrainDownTotal[DownNumber] + Cost / 2 ENDIF 6 1(c) Yes Yes START OUTPUT "Tickets" INPUT Tickets Cost ← (NoTickets – NoTickets DIV 10) * 50 TrainUp[UpNo] ← TrainUp[UpNo] + NoTickets TrainDown[DownNo] ← TrainUp[DownNo] + NoTickets TrainUpTotal[UpNo] ← TrainUpTotal[UpNo] + Cost / 2 TrainDownTotal[DownNo] ← TrainDownTotal[DownNo] + Cost / 2 END Is Tickets <= UpTickets[UpNo] AND Tickets <= DownTickets[DownNo]? No OUTPUT "Up Train" INPUT UpNo OUTPUT "Down Train" INPUT DownNo 1(d) Explanation Any five from: MP1 How the program displayed the number of passengers for a journey ... MP2 … how completed for all trains MP3 How the program displayed the amount of money taken for a journey … MP4 … how completed for all trains MP5 How the program calculated the total number of passengers MP6 How the program calculated the total money taken MP7 How the program attempted to select the train journey with the most passengers MP8 How the program attempted to dealt with more than one train being the most popular MP9 How the program displayed the results with suitable messages Programming statements must be given with each explanation. 5 Section B 2(a) Any six from: MP1 Initialisation of large and small variables e.g. Large ← 0 Small ← 1000 MP2 Use of a loop for 500 entries // or 499 if initialisation done on first correct entry MP3 Input with prompt MP4 Attempt at checking the range of 1 to 999 for input MP5 … working range check MP6 Checking for a whole number MP7 Selecting largest number MP8 Selecting smallest number MP9 Calculating the range MP10 Outputting the largest, smallest and range with message Large ← 0 Small ← 1000 FOR Count ← 1 TO 500 REPEAT OUTPUT "Enter a whole number between 1 and 999" INPUT Number UNTIL Number >= 1 AND Number Large THEN Large ← Number ENDIF NEXT Range ← Large – Small OUTPUT "Largest number is ", Large, " Smallest number is ", Small, " Range of numbers is ", Range 6 (a) To earn marks, you must identify a suitable array name (e.g., TrainUpPassengers), state its data type (Integer/int), and clearly explain its purpose (e.g., storing the number of passengers for train journeys). (b) For each of two validation checks, you need to describe the check (e.g., type check, range check), provide an example of normal data that would pass, and an example of erroneous data that would fail.

2 An algorithm has been written in pseudocode to: • input 25 positive whole numbers less than 100 • find and output the largest number • find and output the average of all the numbers 01 A ← 0 O2 B ← 0 03 C ← 0 04 REPEAT 05 REPEAT 06 INPUT D 07 UNTIL D > 0 AND D B 09 THEN 10 B ← D 11 ENDIF 12 C ← C + D 13 A ← A + 1 14 UNTIL A >= 25 15 E ← C / A 16 OUTPUT "Largest number is ", B 17 OUTPUT "Average is ", E (a) Give the line number for the statements showing: Totalling … Counting … Range check … Calculating the average … [4] (b) State an example for each type of test data needed to test the input of the number: Normal test data example … Erroneous/abnormal test data example … Extreme test data example … [3] (c) The algorithm needs to be changed to include finding and outputting the smallest number input. Describe how you would change the algorithm. … … … … … … … … … … [4]

2(a) – 12 – 13 – 07 – 15 4 2(b) – 27 (example many correct answers any whole number 1-99 inclusive) – 106 (example many correct answers) – 99/1 3 2(c) One mark per mark point, max four – new variable for minimum… – … set to first value/high value – … at start of program / before line 4 – test input / D for less than minimum – … replace value minimum if input less than – … after line 7 and before line 14 – new output for minimum (with appropriate message) – … at end of program // after line 14 4 (a) You earn marks by correctly identifying the line numbers for totalling (12), counting (13), range checking (07), and calculating the average (15). (b) To score, provide a valid normal test data example (e.g., 27), an erroneous/abnormal example (e.g., 106), and an extreme example (e.g., 99 or 1).

2 (a) Write an algorithm in pseudocode to input 500 positive whole numbers. Each number input must be less than 1000. Find and output the largest number input, the smallest number input and the range (difference between the largest number and smallest number). … … … … … … … … … … … … … … … … … … … … … … … … … [6] (b) Describe how the algorithm could be changed to make testing less time-consuming. … … … … [2]

Section B 2(a) Any six from: MP1 Initialisation of large and small variables e.g. Large ← 0 Small ← 1000 MP2 Use of a loop for 500 entries // or 499 if initialisation done on first correct entry MP3 Input with prompt MP4 Attempt at checking the range of 1 to 999 for input MP5 … working range check MP6 Checking for a whole number MP7 Selecting largest number MP8 Selecting smallest number MP9 Calculating the range MP10 Outputting the largest, smallest and range with message Large ← 0 Small ← 1000 FOR Count ← 1 TO 500 REPEAT OUTPUT "Enter a whole number between 1 and 999" INPUT Number UNTIL Number >= 1 AND Number Large THEN Large ← Number ENDIF NEXT Range ← Large – Small OUTPUT "Largest number is ", Large, " Smallest number is ", Small, " Range of numbers is ", Range 6 2(b) One mark for action required and one mark for method used Reduce the amount of numbers entered By decreasing the final value of the loop or Remove the need to input values By using random numbers / a previously populated array 2 3(a) Pseudocode statement Flowchart symbol IF Number = 20 PRINT Number Number ← Number + 1 3 3(b) IF Number = 20 selection PRINT Number output Number ← Number + 1 counting 3 (a) To score marks, your pseudocode must include initialising variables for largest and smallest numbers, using a loop for 500 entries, prompting for input, attempting and correctly implementing a range check (1 to 999) and a whole number check for the input, correctly selecting the largest and smallest numbers, calculating the range, and finally outputting the largest, smallest, and range with appropriate messages. (b) You earn marks by stating an action to reduce the number of inputs (e.g., reduce the number of entries or remove input entirely) and describing the method to achieve it (e.g., decrease loop's final value or use random numbers/pre-populated array).

2 An algorithm has been written in pseudocode to generate 50 positive random integers with values less than or equal to 100. These random integers are stored in the array RandNum[ ] The function Rand(X, Y) generates a random integer greater than or equal to X and less than Y. For example, Rand(1, 4) generates 1 or 2 or 3. 1 Count 0 2 REPEAT 3 RandNum[Counter] Rand(1, 100) 4 Count Count + 2 5 UNTIL Count <= 50 (a) Find the four errors in the pseudocode and write a correction for each error. Error 1 … Correction … … Error 2 … Correction … … Error 3 … Correction … … Error 4 … Correction … … … [4] (b) The pseudocode for this algorithm could be shortened by the use of a FOR … NEXT loop. Rewrite the algorithm using a FOR … NEXT loop. … … … … [3] (c) Identify another loop structure available in pseudocode. … [1]

Section B 2(a) Line 1 should be Counter ← 0 Line 3 RandNum[Counter] ← Rand(1, 100)should be RandNum[Counter] ← Rand(1, 101) Line 4 Counter ← Counter + 2 should be Counter ← Counter + 1 Line 5 UNTIL Count = 50 // UNTIL Counter = 50 1 Counter ← 0 2 REPEAT 3 RandNum[Counter} ← Rand(1, 100) 4 Counter ← Counter + 1 5 UNTIL Counter >= 50 Or Line 3 RandNum[Counter] should be RandNum[Count] Line 3 Rand(1, 100)should be Rand(1, 101) Line 4 Counter ← Counter + 2 should be Count ← Count + 1 Line 5 UNTIL Count = 50 // UNTIL Count = 50 1 Count ← 0 2 REPEAT 3 RandNum[Count} ← Rand(1, 100) 4 Count ← Count + 1 5 UNTIL Count >= 50 4 2(b) One mark for each correct line FOR Count ← 0 TO 49 // FOR Count ← 1 TO 50 RandNum[Count] ← Rand(1, 101) / Rand(0, 101) NEXT // NEXT Count 3 2(c) Precondition loop // WHILE … DO … ENDWHILE 1 (a) To earn marks, you must identify four specific errors in the pseudocode and provide the correct line of code for each. The errors relate to the initial value of the counter, the upper bound of the random number generation, the increment of the counter, and the condition for the loop termination. (b) To earn marks, you must correctly rewrite the algorithm using a FOR loop, including the correct loop bounds, the random number generation with the correct upper bound, and the NEXT statement. (c) To earn the mark, you must identify the type of loop as a 'Precondition loop' or specify 'WHILE ... DO ... ENDWHILE'.

Cambridge IGCSE Computer Science · 0478

IGCSE Computer Science (0478) Algorithm design and problem-solving past paper questions

Revise IGCSE Computer Science (0478) — Algorithm design and problem-solving with real Cambridge past-paper questions grouped by topic, each shown with its marking scheme. Working one topic at a time targets exactly the skill each question tests.

104 free questions from 2016–2021, each with its marking scheme. Open the full topical bank to filter by subtopic, paper, and year.

Algorithm design and problem-solving in IGCSE Computer Science 0478 exams, 2020–2025

Across 2020–2025, Algorithm design and problem-solving accounted for 164 questions worth 1,320 marks in Cambridge IGCSE Computer Science (0478) papers.