JPJC 2025 H2 Computing Prelim Paper 1

Name:____________________________________ Class:_____________ JURONG PIONEER JUNIOR COLLEGE JC2 Year – End Examination 2025 COMPUTING 9569/01 Higher 2 17 September 2025 Paper 1 (Written) 3 hours Additional materials: 12-page Answer Booklet Answer all the questions. Approved calculators are allowed. You are reminded of the need for clear presentation in your answers. Answer papers will be provided with the question paper. Write your name and civics class on all the work that you hand in. Write in dark blue or black pen on both sides of the paper. You may use an HB pencil for any diagrams or graphs. Do not use staples, paper clips, glue or correction fluid. Write your answers to every question on a fresh page of paper. 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 9 printed pages and 3 blank pages. [Turn over

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3 1 JPCAR operates a car -sharing network across Singapore. Users can rent cars from docking stations using a mobile app. The company maintains two types of data storage: Relational Database (RDBMS): Stores structured data like user accounts, cars, stations, and rentals. NoSQL Database (Document Store): Stores unstructured data like real -time Global Positioning System (GPS) coordinates of bicycles and usage logs from Internet of Things (IoT) devices. Anyone who wishes to use the car -sharing network needs to sign up to be a user of the JPCAR. The company wants to store data in a relational database with the following requirements: • Each user has a unique userID that corresponds to a name, email, and phoneNo. • Each car has a carID that is linked to a stationID (where it is parked), and status (Available or In Use). • Each station has a stationID that corresponds to a stationName, and location. It is given that whenever a user rents an available car parked at the station, the car’s status will be set to “In Use” immediately, and the rental date and rental start time will be recorded by the system. Upon returning, the returned car’s status will be changed to “Available”. Rental end time, total rental cost, and information on the station the car was returned to will also be determined and recorded. (a) JPCAR wants to use a relational database to store and manage the data for the system. (i) A database requires several tables to store the data. Draw an entity-relationship (ER) diagram to show the tables in third normal form (3NF) and the relationship(s) between them. [2] [Turn over

4 (ii) 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 an asterisk (*). Write table descriptions for the tables identified in part (a)(i), using the information given. (b) Using tables created, write SQL statements for the following queries: (i) display all the available cars parked at the location “Desker Road”. (ii) display every userID, and the total number of car rentals the user has made. (iii) display the top three users who spent the highest total cost on car rentals, sorted from highest to lowest. (c) Explain how double -booking conflicts on a particular car between two or more users can be prevented. (d) Explain two key differences between a backup file and an archive file. [4] [2] [2] [2] [2] [2] (e) The real-time locations of cars are stored in a NoSQL document database (e.g., MongoDB) using the following document structure: { "carID": "C1001", "location": { "lat": 1.283, "lon": 103.860 }, "battery%": 85, "lastUpdate": "2025-07-15T13:45:00Z" } (i) Write a MongoDB query to find all bicycles with battery < 20% (ii) Explain one advantage of using NoSQL over SQL for storing GPS tracking data. (iii) Describe one scenario where the relational database design is still preferable for JPCAR. [2] [2] [2]

5 2 A start-up company is developing a ride -hailing application called JRide. The system will have different types of vehicles, such as car and motorbike, that share common attributes and behaviours but also have some unique features. The company wants to use Object-Oriented Programming (OOP) to model this situation. The system needs to: • Store details of the driver’s name, vehicle registration number, and maximum passenger capacity. • Motorbike can only carry one passenger while Car can carry up to seven passengers. • The fare is calculated differently depending on the type of vehicle. For example, Car calculates fare based on distance and a base fee, while Motorbike calculates fare based only on distance with a lower rate. (a) 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. [6] (b) The company has decided to introduce a Driver class to store details of the driver’s name, license number, and years of experience. Describe how you would update the class diagram to include this new class. [3] It is common for the properties of a class to be private. (c) Explain what encapsulation means in OOP. [2] (d) Describe how it could be applied to this situation. [2] [Turn over

6 3 A college is launching an online e -Assessment portal. Teachers record the marks in spreadsheets and upload them to the portal. The spreadsheets must be verified for both authenticity and integrity. Additionally, the portal must be protected from the public Internet. (a) Explain how a digital signature works in this situation. [5] (b) State one key difference between encrypting a file and digitally signing a file. [1] (c) Propose a firewall policy to protect the e-Assessment server that is reachable over HTTPS from the Internet but administered only from the IT office. [2] 4 A school maintains a Binary Search Tree (BST) of locker IDs to support quick allocation, deallocation and look -ups. Each node stores a unique integer key (the locker ID), and pointers left and right. Unless stated otherwise, assume no duplicate keys and that the BST property holds: all keys in the left subtree < key, all keys in the right subtree > key. (a) The following locker IDs are inserted into an initially empty BST in the following order: 42, 18, 60, 12, 35, 50, 70, 63, 72 (i) Draw the resulting BST. (ii) Write the in-order traversal output of your tree as a comma-separated list. [2] [1] Assume each node has fields: key, left, right. (b) Write a recursive pseudocode for InOrder(root) that displays the keys in ascending order. (c) Describe an iterative algorithm for BST_Search(root, k) that returns TRUE if found or FALSE if not found. [4] [5]

7 (d) State and justify the worst -case time complexity of searching in a BST using an iterative algorithm. [2] (e) Explain why you would store the ordered locker IDs in a BST rather than an ordered array. [2] The school’s allocation service buffers locker assignment requests in a fixed -capacity circular queue before processing them against the BST. The queue is implemented as an array that stores up to 50 integers. (f) Write the pseudocode for DEQUEUE()which returns the integer stored at the front of queue or -1 if the queue is empty. [6] (g) Explain one advantage of a circular queue over a linear queue in this situation. [2] [Turn over

8 5 A smart thermostat stores the current temperature setpoi