2022 HKDSE Information and Communication Technology Practice Paper | DSE Mock

Which of the following 8-bit binary representations represents the decimal number -58 in two's complement representation?

In a school database, there are two tables: STUDENT and CLASS.\nSTUDENT table: StudentID (Primary Key), Name, ClassID\nCLASS table: ClassID (Primary Key), ClassTeacher\nWhich of the following database operations will violate referential integrity?

Which register stores the memory address of the next instruction to be fetched and executed by the CPU?

Which of the following statements about compilers and interpreters is correct?

An IP address of a host is 192.168.10.45, and its subnet mask is 255.255.255.240. What is the network ID (subnet address) of the network to which this host belongs?

In public key cryptography, if Alice wants to send a confidential message to Bob, which key should Alice use to encrypt the message to ensure that only Bob can read it?

Which of the following is an advantage of Radio Frequency Identification (RFID) technology over traditional barcodes?

Consider the following pseudocode:\n\n```\nSet count = 0\nFor i From 1 To 4\n For j From i To 4\n count = count + (i * j)\n Next j\nNext i\n```\n\nWhat is the final value of `count` after executing the pseudocode?

A photographer publishes their photo under a 'CC BY-NC-ND' Creative Commons license. Which of the following acts is permitted under this license without obtaining additional permission?

There is a database table `SALES` with the following columns: `SalespersonID`, `SaleAmount`, and `Region`.\nWhich of the following SQL statements finds the `Region` where the total sales amount exceeds 50000?

In an 8-bit two's complement representation system, what is the result of adding the binary numbers representing the denary values \(-75\) and \(-85\)?

An IoT smart thermometer requires memory to store the following three items: (1) The bootloader program (startup code), (2) Real-time temperature logs collected over the last 24 hours, (3) The configured target temperature set by the user (which must persist even if the power is cut off). Which of the following combinations of memory types is the most suitable for storing each of these items respectively?

A computer user notices that when they open too many large applications simultaneously, the hard disk activity light blinks constantly, and the system response becomes extremely slow. This phenomenon is known as 'thrashing'. Which of the following is the primary cause of thrashing?

Consider two database tables: STUDENT (Student_ID, Name, Class, Club_ID) and CLUB (Club_ID, Club_Name, Teacher_In_Charge). 'Student_ID' and 'Club_ID' are the primary keys of STUDENT and CLUB respectively. 'Club_ID' in STUDENT is a foreign key referencing CLUB. Which of the following statements about referential integrity in this database is/are correct? (1) A new student record cannot be inserted with a Club_ID that does not exist in the CLUB table. (2) A club record cannot be deleted from the CLUB table if there are students currently registered with that Club_ID (assuming 'Restrict delete' is enforced). (3) A student's Club_ID can be set to NULL if joining a club is optional.

A database table SALES has records with schema: SALES (Transaction_ID, Product_Category, Amount, Salesperson). The records are: ('T101', 'Electronics', 1500, 'Alice'), ('T102', 'Furniture', 800, 'Bob'), ('T103', 'Electronics', 400, 'Alice'), ('T104', 'Clothing', 200, 'Charlie'), ('T105', 'Furniture', 1200, 'Bob'), ('T106', 'Electronics', 150, 'Charlie'). What is the output of the query: SELECT Salesperson, SUM(Amount) FROM SALES GROUP BY Salesperson HAVING COUNT(Transaction_ID) >= 2 AND AVG(Amount) > 500;

Which of the following statements about MAC (Media Access Control) addresses and IP (Internet Protocol) addresses is correct?

In secure online transactions, asymmetric encryption is widely used. Which of the following correctly describes the main purpose of using a digital signature?

A school is developing a customized student portfolio system. Instead of purchasing physical servers, they decide to use a cloud service where they rent virtual machines with a pre-installed operating system and database management system, allowing their IT teachers to focus entirely on writing the system code and deploying the database. Which cloud service model are they using?

Consider the following algorithm: A is an array of integers [3, 8, 2, 7, 5]; N = 5; X = A[0]; Y = A[0]; For i from 1 to N - 1 do: If A[i] > X then X = A[i] Else if A[i] < Y then Y = A[i] End If End For; Print X - Y. What is the printed output of this algorithm?

Consider the following Python code to calculate the average of three test scores: score1 = 80; score2 = 90; score3 = 85; average = score1 + score2 + score3 / 3; print('The average is: ' + average). The programmer encounters two errors: (1) The calculated average is mathematically incorrect due to operator precedence, (2) The program crashes with a TypeError during runtime because of an attempt to concatenate a string and a float. Which of the following correctly classifies these two errors?

What is the 8-bit two's complement representation of the decimal number \(-37\)?

A database designer wants to ensure that a student record in the 'Student' table cannot be deleted if the student has already enrolled in any course in the 'Enrollment' table. Which integrity constraint should be applied?

During the Fetch-Decode-Execute cycle, which register is used to store the address of the next instruction to be fetched from memory, and which register holds the instruction currently being decoded?

A computer has an IP address of '192.168.10.45' and a subnet mask of '255.255.255.240'. Which of the following is the network address (subnet address) of this host?

To achieve both confidentiality and authenticity (non-repudiation) when Alice sends a message to Bob using public key cryptography, which of the following processes should Alice use?

Consider the following pseudocode which processes an array A of 6 elements: '[3, 8, 2, 7, 5, 10]':

N = 6
FOR i = 0 TO N-2
FOR j = i+1 TO N-1
IF A[i] < A[j] THEN
temp = A[i]
A[i] = A[j]
A[j] = temp
ENDIF
ENDFOR
ENDFOR

What is the content of array A immediately after the outer loop finishes its first iteration (where i = 0)?

A database table STUDENT has the attributes StudentID, Name, Class, Gender, and Score. Which of the following SQL statements correctly displays the Class and the number of female students for classes with more than 5 female students?

An illustrator shares their digital artwork under a Creative Commons license. The terms of the license allow others to copy, distribute, and display the work, and also allow others to modify or build upon the work. However, any commercial use is forbidden, and any modified works must be shared under the same license terms. Which of the following Creative Commons licenses did the illustrator apply?

Which of the following statements about Virtual Memory is/are correct?

(1) Virtual memory uses a portion of secondary storage (such as a hard disk or SSD) to simulate additional RAM.
(2) Increasing the size of virtual memory can speed up CPU instruction execution as effectively as increasing physical RAM.
(3) A "page fault" occurs when the requested memory page is not currently located in the physical RAM and needs to be fetched from secondary storage.

A web form requires users to enter a Hong Kong Identity Card (HKID) number. The system performs several validation checks on the input:
(1) Check if the input is not left blank.
(2) Check if the input format matches one or two uppercase letters, followed by six digits, and a single digit/letter in parentheses.
(3) Calculate and verify the check digit using a weighted formula based on the preceding characters.
Which of the following correctly identifies these validation checks?

If an 8-bit register uses 2's complement representation, what is the 8-bit binary result of the subtraction \(01001100_2 - 10110101_2\), and does overflow occur?

Which of the following statements about cache memory in a computer system are correct?
(1) It stores frequently used data and instructions to reduce the average time to access memory.
(2) It has a faster access speed than registers.
(3) It resides inside or very close to the CPU chip.

Consider two database tables: `STUDENT(StudentID, Name, ClassID)` and `CLASS(ClassID, ClassTeacher, RoomNo)`. `StudentID` and `ClassID` are the primary keys of the respective tables. `ClassID` in `STUDENT` is a foreign key referencing `CLASS`. Which of the following operations will be rejected by the DBMS in order to maintain referential integrity?
(1) Inserting a new record into `STUDENT` with a `ClassID` that does not exist in `CLASS`.
(2) Deleting a record from `CLASS` whose `ClassID` is currently assigned to some students in `STUDENT`.
(3) Deleting a record from `STUDENT`.

A subnet of a school network has the IP address `192.168.10.32` with a subnet mask of `255.255.255.240`. Which of the following is/are valid IP address(es) for host computers on this subnet?
(1) `192.168.10.35`
(2) `192.168.10.45`
(3) `192.168.10.47`

Alice wants to send an encrypted and digitally signed email to Bob. She wants to ensure confidentiality (only Bob can decrypt and read it) and authenticity (Bob can verify the email was sent by Alice). Which keys should Alice use to encrypt the email message and to create the digital signature respectively?

Consider the following pseudocode algorithm:
```
A = 45
B = 12
COUNT = 0
While A >= B Do
A = A - B
COUNT = COUNT + 1
EndWhile
```
What are the values of `A` and `COUNT` after the execution of the algorithm?

A school registration system requires users to enter a student's date of birth in the format `DD/MM/YYYY`. Which of the following validation checks can be applied to verify the correctness of the input?
(1) Format check to ensure the input contains forward slashes at correct positions.
(2) Range check to ensure the month `MM` is between 1 and 12.
(3) Verification check by double entry of the date of birth.

In an operating system, what is the main purpose of "paging" in virtual memory management?

A programmer wants to release their software under a Creative Commons license. They want to allow others to copy, distribute, and display the software, but only if they give the programmer proper credit, do not use it for commercial purposes, and do not make any derivative works (no modifications). Which combination of Creative Commons terms should the programmer choose?

Consider a database table `SALES(SalesID, ProductID, Region, Amount)`. Which SQL query can find the regions where the total sales amount exceeds 50,000?

A digital temperature monitoring system in a vaccine cold room logs temperatures and security codes.

(a) The sensor records temperature in 8-bit two's complement representation.
(i) Express the binary representation 11110100 in decimal. (2 marks)
(ii) What is the range of integers (in decimal) that can be represented using 8-bit two's complement? (2 marks)

(b) The system logs security codes in hexadecimal format.
(i) Convert the denary number 213 into a 2-digit hexadecimal number. (2 marks)
(ii) State one reason why system administrators prefer hexadecimal representation over binary representation. (2 marks)

(c) When transmitting data, the system uses ASCII encoding with an even parity bit.
(i) The character 'A' has the ASCII value of 65 in denary. Write down the 8-bit byte (with the parity bit as the most significant bit) to transmit 'A'. (2 marks)
(ii) Explain a limitation of using a single parity bit for error detection. (2 marks)

A school library database management system contains two tables: BOOKS and LOANS.

BOOKS (BookID, Title, Author, Category)
LOANS (LoanID, BookID, MemberID, LoanDate, ReturnDate)

(a) State the relationship between BOOKS and LOANS. Explain how this relationship is implemented in the schema. (2 marks)
(b) Explain the importance of referential integrity in this database using BookID as an example. (2 marks)
(c) Write an SQL query to retrieve the Title and Author of all books under the 'Science' category. (2 marks)
(d) Write an SQL query to find the BookID and the total number of loans for each book that has been borrowed more than 5 times. (3 marks)
(e) Explain why the Title of the book should not be stored in the LOANS table. (3 marks)

Mr. Chan is setting up a local area network (LAN) for his new office.

(a) He is choosing network hardware to connect 15 computers.
(i) Explain why a network switch is preferred over a network hub in terms of network transmission performance. (2 marks)
(ii) Explain why a network switch is more secure than a network hub. (2 marks)

(b) The office router uses DHCP.
(i) State the full form of DHCP and describe its main function. (2 marks)
(ii) If a client computer fails to connect to the DHCP server, it might assign itself an APIPA address. Can this computer access the Internet? Explain your answer. (2 marks)

(c) Mr. Chan wants to protect his network from external threats.
(i) Distinguish between packet filtering and application-level gateway (proxy) firewalls. (2 marks)
(ii) Give an example of a rule that can be configured in a packet-filtering firewall to allow only web traffic (HTTP) to reach the internal web server. (2 marks)

The following algorithm is designed to find the second largest number in an array A of size N (where N >= 2). Assume all elements in array A are distinct.

```
largest = A[1]
second_largest = -999999
For i = 2 To N Do
If A[i] > largest Then
second_largest = [ (i) ]
largest = [ (ii) ]
Else If [ (iii) ] Then
second_largest = A[i]
End If
End For
```

(a) Complete the algorithm by writing down the code for blanks (i), (ii), and (iii). (4 marks)

(b) If N = 4 and A = [12, 15, 8, 14], trace the algorithm by showing the values of variables i, largest, and second_largest after each iteration. (4 marks)

(c) How many comparisons between array elements (i.e. involving A[i]) are made in the worst-case scenario for an array of size N using the above algorithm? Explain your answer. (2 marks)

(d) Briefly explain how you would modify this algorithm to find the second smallest number in array A. (2 marks)

A city is deploying IoT-enabled smart streetlights equipped with traffic cameras, environmental sensors, and wireless communication links.

(a) Describe two advantages of using IoT-enabled smart streetlights over traditional streetlights. (2 marks)

(b) The traffic cameras capture continuous real-time video to analyze traffic flow.
(i) State two potential privacy concerns raised by citizens regarding this system. (2 marks)
(ii) Suggest two technical or administrative measures that the government can adopt to address these privacy concerns. (2 marks)

(c) The streetlights upload historical environmental data to a central cloud server.
(i) State one advantage of using cloud storage instead of local storage within each streetlight. (2 marks)
(ii) State two risks of completely relying on a centralized cloud service for managing this critical city infrastructure. (2 marks)

(d) Explain how "Edge Computing" can be applied in this system to reduce network bandwidth usage. (2 marks)

A boutique pet hotel uses a relational database to manage room reservations. The database includes the following tables:\n\nPET (PetID, PetName, Species, OwnerName, ContactNo)\nROOM (RoomNo, Category, DailyRate)\nBOOKING (BookingID, PetID, RoomNo, StartDate, EndDate, ActualCost)\n\n(a) Database Concepts:\n(i) Explain why the combination of PetID and RoomNo cannot be used as the primary key of the BOOKING table. (2 marks)\n(ii) State the referential integrity constraint that must hold between the BOOKING table and the PET table. (2 marks)\n\n(b) Normalisation:\nThe hotel manager initially designed a flat file to record invoice details:\nINVOICE (InvoiceNo, PetID, OwnerName, OwnerAddress, CheckInDate, CheckOutDate, RoomNo, RoomType, Rate)\nNote: An invoice can contain multiple rooms if the owner books several rooms for different pets under the same invoice.\n(i) Explain why this relation is not in the First Normal Form (1NF). (1 mark)\n(ii) Normalise the relation step-by-step into the Third Normal Form (3NF). State the primary keys and foreign keys clearly. (4 marks)\n\n(c) SQL Queries:\n(i) Write an SQL statement to find the total revenue (ActualCost) generated by each RoomNo in the year 2023. (3 marks)\n(ii) Write an SQL statement to list the PetID and PetName of pets who have never booked a room with the Category 'Deluxe'. (3 marks)

A school is designing a web-based student council voting platform.\n\n(a) Session Management & Security:\n(i) Contrast the security of storing login states using cookies versus sessions. (2 marks)\n(ii) The system developer decides to enforce HTTPS for the connection. Briefly explain how HTTPS protects the credentials of voters in transit, and state the cryptographic technique used to establish the initial secure connection. (2 marks)\n\n(b) Client-Side vs Server-Side:\nThe system needs to validate two things:\nValidation 1: Checking if the format of the student ID entered matches the regular expression ^S[0-9]{5}$.\nValidation 2: Checking if the student has already voted.\n(i) State whether Validation 1 and Validation 2 should be implemented on the client side or the server side. Explain your choices. (4 marks)\n\n(c) AJAX and Data Interchanges:\nThe platform uses AJAX to display live results without requiring a full page refresh.\n(i) Describe how AJAX works in this scenario to fetch and display the live results dynamically. (3 marks)\n(ii) Compare XML and JSON formats for transmitting these live results in terms of data transmission size and the ease of processing within client-side JavaScript. (4 marks)

An algorithm needs to be developed to process and analyze data.\n\n(a) Consider the following recursive function solve(n, k):\n\n```\nfunction solve(n, k)\n if n == 0 or k == 0 then\n return 1\n else if n < k then\n return solve(n, n)\n else\n return solve(n - 1, k) + solve(n, k - 1)\n end if\nend function\n```\n\n(i) State the base cases of this recursive function. (1 mark)\n(ii) Draw a recursion tree or state the evaluation steps to find the final return value of solve(2, 2). (4 marks)\n\n(b) Algorithmic Efficiency:\nConsider an array A of size N containing distinct integers. A programmer wants to find the 2nd smallest element in the array.\nMethod 1: Sort the array in ascending order using Bubble Sort, then return the element at index 1 (the second element).\nMethod 2: Use a single pass loop to keep track of the smallest and second smallest elements.\n\n(i) State the worst-case time complexity, in Big-O notation, of Method 1 and Method 2. (2 marks)\n(ii) Write the pseudocode for Method 2. (5 marks)\n(iii) Explain why Method 2 is much more suitable than Method 1 when N is extremely large (e.g., \(N = 10^6\)). (3 marks)