2025 VJC H2 Computing Prelim Paper 1

This document consists of 10 printed pages and 2 blank pages. © NYJC/TJC/VJC 2025 [Turn over VICTORIA JUNIOR COLLEGE JC 2 PRELIMINARY EXAMINATION Higher 2 COMPUTING 9569/01 Paper 1 Written 17 September 2025 3 hours 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.

2 9569/01/2025 1 A programmer is writing a program to manage and search for records. The records include phone numbers, which comprise 8 decimal digits. (a) Convert the phone number 62842281 to: (i) Hexadecimal representation [2] (ii) ASCII value for each digit. ('0' has an ASCII value of 48 and '9' has an ASCII value of 57.) [2] (b) The programmer’s supervisor suggests a binary search tree instead of a sorted array for managing phone numbers. Suggest two reasons for the supervisor’s advice. [2]

3 9569/01/2024 [Turn over 2 A recursive function countPaths is designed to find the number of different possible paths from the top-left corner to the bottom-right corner of a grid. The function can only move right or down at each step. For example, in a 2×2 grid, where row = 2 and col = 2, there are two possible paths from the top-left corner to the bottom-right corner of the grid: • Right → Down • Down → Right The function is defined as follows: 01 FUNCTION countPaths(row : INTEGER, col : INTEGER) RETURNS INTEGER 02 IF row = 1 OR col = 1 THEN 03 RETURN 1 04 ENDIF 05 RETURN countPaths(row - 1, col) + countPaths(row, col - 1) 06 ENDFUNCTION (a) An example of a trace tree diagram showing countPaths(2,2) is shown as follows: Use the above example to create a trace tree diagram for the recursive function call countPaths(3,2). [4] (b) Explain how the base case in lines 02 to 03 prevents infinite recursion. [2] (c) Write an iterative version of the original countPaths function. [5] countPaths(2,2) countPaths(1,2) countPaths(2,1) Return 1 Return 1 Return 1+1=2

4 9569/01/2025 3 A software company is developing a print server that handles print jobs from multiple users. Each print job has a job ID and number of pages. The system needs to handle both regular and priority print jobs. (a) The regular print jobs use a linear queue data structure. Explain why a linear queue would be appropriate for regular print jobs. [2] (b) The company decides to implement the queue as a circular queue using a static array of size 5. State one difference between a linear queue and a circular queue. [2] (c) Draw a diagram showing the state of a circular queue after the following operations, showing the positions of front and rear pointers: 1. Enqueue jobs: 101, 102, 103, 104 2. Dequeue two jobs 3. Enqueue jobs: 105, 106 [3] (d) Explain one disadvantage of using a circular queue instead of a linear queue for this implementation. [2] (e) The print server keeps a history of completed print jobs in a stack data structure. (i) Explain how a stack data structure would be appropriate for implementing an "undo" feature that allows the system administrator to restore recently completed print jobs back to the queue. [2] (ii) Write pseudocode for a procedure restoreJobs that takes three parameters: the stack object, historyStack, the queue object, printQueue and an integer N. The pseudocode should restore the N most recently completed jobs from the historyStack back to the printQueue, maintaining their original print order. [6]

5 9569/01/2024 [Turn over 4 Most applications require data entry as an essential step for processing and output. (a) During data entry, validation and verification are commonly applied. (i) State the purpose of validation. [1] (ii) State the purpose of verification. [1] (b) The image below shows the password change dialog box for a web application. The flowchart below shows the process for changing a user’s password. (c) Redraw the flowchart to include, for the new password: • one suitable validation technique • one suitable verification technique [6] (d) State two ways the password change interface can be improved using suitable usability principles. [2] Display prompt Is current password correct? Is new password different? Password changed Yes Yes No No Input current password and new password Display error message Display error message

6 9569/01/2025 5 A company, ImageMaps, wishes to develop an application that scans a user's device for photographs, detect the associated location, and display the images on a map using the associated locations. (a) State the actions ImageMaps must take to secure critical business data such as user data against catastrophic hardware failure. [4] (b) State the consequences, should ImageMaps suffer such a hardware failure. [2] (c) ImageMaps needs to store a large quantity of data that will not be frequently accessed. State how they can reduce costs while doing so. [2] (d) State two actions the company must take regarding the collection and use of personal user data to comply with Singapore’s Personal Data Protection Act (PDPA). [4] (e) State whether a native or web application is more suitable for ImageMaps’s application. Explain your answer. [3]

7 9569/01/2024 [Turn over 6 A commercial bank is strengthening its cybersecurity framework after experiencing multiple security breaches. (a) Compare between a Trojan horse and a worm in terms of how they spread and how they are executed in the targeted network or device. [2] (b) Describe two characteristics that make ransomware particularly dangerous to financial institutions. [2] (c) The bank has deployed a firewall and Intruder Protection System (IPS). Explain why implementing both a firewall and IPS provides better security than using either system alone. [2] (d) Describe the complete process of generating and verifying a digital signature for an electronic funds transfer request. [3] (e) The bank must choose between biometric authentication and security tokens for employee access to sensitive systems. Evaluate which method would provide better security, giving two reasons for your choice. [3]

8 9569/01/2025 7 A packet switching network breaks data into packets, which are sent independently across the network and reassembled at the destination. (a) Describe how networking protocols address the following problems: (i) Data packets may arrive out of order and require reassembly [2] (ii) Data packets may be corrupted in transit. [2] (b) State and explain the time complexity of the following operations: (i) Adding an item to a sorted array [2] (ii) Adding an item to a balanced binary search tree (BST). [2] (c) A data structure is used to hold data packets that are being reassembled. Describe one advantage and one disadvantage of each of the following data structures for packet reassembly. (i) Statically allocated array [2] (ii) Dynamically allocated BST. [2]

9 9569/01/2024 [Turn over 8 A software company is writing a program for a vehicle hire business. Both cars and vans are available for hire. For all vehicles, the data that will be stored include: Vehicle Registration Number (VRN) Total distance travelled (km) Date hired Date of return Cost per day Available for hire For cars, the additional data stored include: Fuel type (petrol, diesel, electric, hybrid) For vans, the additional data stored include: