HCI 2025 H2 Computing Prelim Paper 1

Page 1 of 6 HWA CHONG INSTITUTION C2 PRELIMINARY EXAMINATION 2025 COMPUTING Higher 2 15 Sept 2025 Paper 1 (9569 / 01) 1400 -- 1700 hrs READ THESE INSTRUCTIONS FIRST An answer booklet will be provided with this question paper. You should follow the instructions on the front cover of the answer booklet. If you need additional answer paper ask the invigilator for a continuation booklet. Answer ALL questions. Approved calculators are allowed. The number of marks is given in brackets [ ] at the end of each question or part question. The total number of marks for this paper is 100. This document consists of 6 printed pages.

Page 2 of 6 1 (a) Describe the purpose of Internet Protocol (IP) and state the format of an IPv4 address. [2] (b) Describe one disadvantage of packet switching and how the problem can be handled. [2] (c) Explain the term Domain Name Server (DNS) and how it works. [5] 2 (a) An airline website is designed for customers to book air tickets. (i) State the purpose of data validation and give one example of how the website implements it on the customers’ date of birth. [2] (ii) State the purpose of data verification and give one example of how the website implements it on the bookings. [2] (iii) Describe two differences between a web application and a native application. [2] (b) Give two purposes of using digital signature and describe how it works. [8] (c) Describe how a firewall protects computer networks and one limitation of a firewall. [2] 3 A system processes user input and performs encoding and validation using character and number representations. (a) The ASCII code (in denary) for the character 'A' is 65. (i) Express 'D' in 7-bit binary. [1] (ii) Express 'D' as a hexadecimal value. [1] (iii) State the range of values that are common to both ASCII and Unicode. [1] (b) A user inputs the number 365, which must be stored in a 7-bit binary format. Explain the problem, and how this could be resolved. [2] (c) Give one example of a software or platform that relies on Unicode and explain its benefit in that context. [2]

Page 3 of 6 4 A collectible toy store sells Libaba figurines that come in many series. Each series is released in a different year, and within a series release, multiple toy figurines may be produced. The following unnormalised table is used to track sales of these toys: LibabaSale SaleID SaleDate ToyID ToyName SeriesName ReleaseYear NumSold S101 1/4/2025 T001 Polar Pixie Starborn 2024 1 T002 Misty Mewling Fairytails 2025 3 S102 3/4/2025 T003 Nutty Nimlet Arborealis 2023 1 S103 5/4/2025 T002 Misty Mewling Fairytails 2025 2 T004 Jungle Jinx Arborealis 2023 2 (a) State one data redundancy and one anomaly issue present in the LibabaSale table above. [2] (b) Identify one transitive dependency that exist in the table. [2] (c) Normalise the LibabaSales table into Third Normal Form (3NF) and draw the Entity-Relationship (E -R) diagram showing the relationships between the resulting tables. [3] (d) A table description can be expressed as: TableName (Attribute1, Attribute2, Attribute3, ...) The primary key is indicated by underlining one or more attributes. Foreign keys are indicated by using a dashed underline. Write table descriptions for the tables obtained from part (c). [4] (e) Write an SQL query to display each SeriesName and the total number of Libaba sold, grouped by series and ordered from highest to lowest total. [6] (f) Explain one advantage and one disadvantage of archiving sales data. Determine whether weekly archiving is appropriate. [4] (g) Explain what constitutes personal data under PDPA and give two examples of personal data that the toy shop may have of their customers. [2] (h) What should the toy shop do when attaining personal data from their customers? [2]

Page 4 of 6 5 A car dealership is building a system to manage its vehicle inventory. The company sells Internal Combustion Engine (ICE) vehicle and Electric Vehicles (EV) . They want to store and manage information about each car’s key specifications, and allow the system to estimate how far the car can travel based on its current fuel or charge level. For every vehicle, the following data is recorded: • BMY: the brand, model and year of manufacture of the car • mileage: total distance driven in kilometers • trip_mileage: distance driven since the engine was last started in kilometers • estimated_distance: distance which the vehicle can be driven. All vehicles reset the trip_mileage to zero when the engine of the vehicle starts. For an Internal Combustion Engine vehicle, the following data is recorded: • fuel_capacity: maximum capacity of fuel in liter • current_fuel: current capacity of fuel in liter • fuel_consumption: distance driven in kilometer per liter of fuel Each internal combustion engine vehicle resets the trip_mileage to zero when the engine of the vehicle starts. The vehicle computes the estimated_distance, based on the fuel_consumption and the current_fuel amount of the vehicle, when it is driven. For an electric vehicle, the following data is recorded: • battery_capacity: maximum energy the battery can store in kWh • current_charge: current battery level as a percentage of total • energy_consumption: energy used in kWh to travel one kilometer Each electric vehicle resets the trip_mileage to zero and check the current_charge value to ensure it is above certain threshold when the engine of the vehicle starts. The vehicle computes the estimated_distance, based on the energy_consumption and the current_charge value of the vehicle, when it is driven. (a) State the purpose of a superclass and subclass. [2] (b) State the purpose of polymorphism. Give one example of polymorphism from the vehicle inventory system. [2]

Page 5 of 6 (c) Draw a class diagram for the described situation, showing: • any derived classes and inheritance from the base class • the properties needed in the base and any derived classes • suitable methods, in each class, to support the system. [7] (d) State one reason for a method of a class to be private. Give one example from the vehicle inventory system. [2] 6 A hash function and associated hash table are commonly used when finding storage space for a new record and searching for a specific record within a data set. (a) State three features of an effective hash function. [3] (b) Explain the meaning of a collision in the context of finding storage space for a new record. [1] (c) A method of collision resolution is chaining. Explain what happens when a new record causes a collision and how the search operation works. [3] (d) Explain why the chains, used in chaining, are usually not sorted. [2] Each node in the chain of the hash table contains the following: • record – the value of the record • next – reference to the next node in the chain. The following pseudocode performs the search on the chain. FUNCTION find_value (head, target) current  head WHILE current <> NULL IF current.record = target THEN RETURN current.record ENDIF current  current.next ENDWHILE RETURN NULL ENDFUNCTION (e) Write in pseudocode the equivalent recursive function find_value_recursive(node, target) that performs the same task. [6] (f) State one advantage and disadvantage of using recursion in this context.