Computer Science — Chapter-Wise Extended Response Questions (ERQs)

• 1 mark for reading the menu option using prompt().
• 4 marks (1 mark per case with break) for handling options 1, 2, 3, 4.
• 1 mark for the default branch displaying "Invalid Option Selected".
• 1 mark for reading n and checking if (n < 1).
• 2 marks for writing the for loop from 1 to n and reading each student's marks.
• 2 marks for accumulating total and computing average = total / n.
• 1 mark for displaying Total Marks and Average Marks in the required format.

let option = Number(prompt("Enter menu option number (1-4):"));
switch (option) {
    case 1:
        document.write("Add Record");
        break;
    case 2:
        document.write("Update Record");
        break;
    case 3:
        document.write("Delete Record");
        break;
    case 4:
        document.write("View Record");
        break;
    default:
        document.write("Invalid Option Selected");
}

let n = Number(prompt("Enter the number of students:"));
if (n < 1) {
    document.write("Invalid number of students");
} else {
    let total = 0;
    for (let i = 1; i <= n; i++) {
        let marks = Number(prompt("Enter marks for student " + i + ":"));
        total += marks;
    }
    let average = total / n;
    document.write("Total Marks: " + total + "<br>");
    document.write("Average Marks: " + average);
}

Examiner Commentary (Better Responses): Follow the reference model solution and step-by-step marking criteria.

• 1 mark for declaring correct variables.
• 1 mark for taking input.
• 1 mark for writing the correct condition of the while loop.
• 1 mark for writing the formula for calculating multiple.
• 1 mark for the increment in the counter variable.
• 1 mark for writing the output.
• 1 mark for taking input.
• 1 mark for printing output.
• 2 marks for checking vowel using if condition (five operators/cases required).
• 1 mark for checking a consonant.
• 1 mark for checking invalid character (default in switch).

#include <stdio.h>
int main()
{
    int num, range, i = 1, result;
    printf("Enter a number for table: ");
    scanf("%d", &num);
    printf("Enter range of the table: ");
    scanf("%d", &range);
    while (i <= range)
    {
        result = num * i;
        printf("%d * %d = %d\n", num, i, result);
        i = i + 1;
    }
    return 0;
}

let num = Number(prompt("Enter a number for table:"));
let range = Number(prompt("Enter range of the table:"));
let i = 1;
while (i <= range) {
    let result = num * i;
    document.write(num + " * " + i + " = " + result + "<br>");
    i++;
}

#include <stdio.h>
int main()
{
    char ch;
    printf("Enter an alphabet: ");
    scanf(" %c", &ch);
    if ((ch >= 'A' && ch <= 'Z') || (ch >= 'a' && ch <= 'z'))
    {
        if (ch == 'a' || ch == 'e' || ch == 'i' || ch == 'o' || ch == 'u' ||
            ch == 'A' || ch == 'E' || ch == 'I' || ch == 'O' || ch == 'U')
        {
            printf("%c is a vowel", ch);
        }
        else
        {
            printf("%c is a consonant", ch);
        }
    }
    else
    {
        printf("Invalid character");
    }
    return 0;
}

Examiner Commentary (Better Responses): Part (a): In better responses, candidates demonstrated a clear understanding of how to generate a multiplication table. They correctly took all required inputs, including the number and the range, applied the correct formula to calculate the multiplication of numbers as specified in the question, and successfully printed the times table in the expected format. Part (b): In better responses, candidates effectively checked whether the input character was a vowel, a consonant, or an invalid character. They applied the correct syntax of if-else statements and compared the input character through relational and logical operators accurately to construct appropriate conditions.

Authentic E-Marking Better Candidate Script:

• 1 mark for variable declaration (int year;).
• 1 mark for taking user input (scanf("%d", &year);).
• 2 marks for writing the correct leap-year condition (year % 4 == 0 or full Gregorian rule (year % 400 == 0) || (year % 4 == 0 && year % 100 != 0)).
• 2 marks for printing the appropriate output in both if and else blocks.
• 1 mark for declaring and initialising the first two terms (t1 = 0, t2 = 1) and loop variables.
• 2 marks for writing the for loop structure for 10 terms (for (i = 1; i <= 10; i++)).
• 2 marks for computing the next Fibonacci term (nextTerm = t1 + t2; t1 = t2; t2 = nextTerm;).
• 1 mark for printing the series output accurately.

#include <stdio.h>
int main()
{
    int year;
    printf("Enter a year: ");
    scanf("%d", &year);
    if ((year % 400 == 0) || (year % 4 == 0 && year % 100 != 0))
    {
        printf("%d is a leap year.\n", year);
    }
    else
    {
        printf("%d is not a leap year.\n", year);
    }
    return 0;
}

let year = Number(prompt("Enter a year:"));
if ((year % 400 === 0) || (year % 4 === 0 && year % 100 !== 0)) {
    document.write(year + " is a leap year.");
} else {
    document.write(year + " is not a leap year.");
}

#include <stdio.h>
int main()
{
    int i, n = 10, t1 = 0, t2 = 1, nextTerm;
    printf("First 10 numbers of Fibonacci series: ");
    for (i = 1; i <= n; i++)
    {
        printf("%d ", t1);
        nextTerm = t1 + t2;
        t1 = t2;
        t2 = nextTerm;
    }
    return 0;
}

let t1 = 0, t2 = 1, nextTerm;
for (let i = 1; i <= 10; i++) {
    document.write(t1 + " ");
    nextTerm = t1 + t2;
    t1 = t2;
    t2 = nextTerm;
}

Examiner Commentary (Better Responses): In better responses for Part (a), candidates used the modulus operator `%` to test divisibility by 4 (and 100/400) inside an `if-else` statement. For Part (b), better responses initialised `t1 = 0` and `t2 = 1`, ran a `for` loop 10 times, printed `t1`, and updated `nextTerm = t1 + t2; t1 = t2; t2 = nextTerm;`.

• 1 mark for declaring the correct variables.
• 1 mark for taking the input.
• 1 mark for writing each correct condition using correct operators (FOUR required).
• 1 mark for declaring correct variables.
• 1 mark for taking input.
• 1 mark for writing correct for loop.
• 1 mark for writing print statement inside loop.
• 1 mark for the formula for adding even numbers.
• 1 mark for writing the output.

#include <stdio.h>
int main()
{
    int years_of_service;
    char gender;
    printf("Enter Gender (M for Male, F for Female): ");
    scanf(" %c", &gender);
    printf("Enter Years of Service: ");
    scanf("%d", &years_of_service);

    if ((gender == 'M' || gender == 'm') && (years_of_service >= 5))
        printf("Your salary is 150000");
    else if ((gender == 'M' || gender == 'm') && (years_of_service < 5))
        printf("Your salary is 100000");
    else if ((gender == 'F' || gender == 'f') && (years_of_service >= 5))
        printf("Your salary is 200000");
    else if ((gender == 'F' || gender == 'f') && (years_of_service < 5))
        printf("Your salary is 150000");
    else
        printf("Invalid input");

    return 0;
}

let gender = prompt("Enter Gender (M for Male, F for Female):");
let years = Number(prompt("Enter Years of Service:"));
if ((gender === 'M' || gender === 'm') && years >= 5) {
    document.write("Your salary is 150000");
} else if ((gender === 'M' || gender === 'm') && years < 5) {
    document.write("Your salary is 100000");
} else if ((gender === 'F' || gender === 'f') && years >= 5) {
    document.write("Your salary is 200000");
} else if ((gender === 'F' || gender === 'f') && years < 5) {
    document.write("Your salary is 150000");
}

#include <stdio.h>
int main()
{
    int a, n, sum = 0, b = 2;
    printf("Enter number of even numbers required: ");
    scanf("%d", &n);
    for (a = 1; a <= n; a++)
    {
        printf("\n%d", b);
        sum += b;
        b += 2;
    }
    printf("\nSum of these numbers is %d", sum);
    return 0;
}

let n = Number(prompt("Enter number of even numbers required:"));
let sum = 0, b = 2;
for (let a = 1; a <= n; a++) {
    document.write(b + "<br>");
    sum += b;
    b += 2;
}
document.write("Sum of these numbers is " + sum);

Examiner Commentary (Better Responses): Part (a): In the better responses, the candidates effectively generated the desired output using proper variable declarations, input and output statements, and accurate conditional statements. Notably, the candidates demonstrated the ability to differentiate between character and numeric variable declaration. Part (b): In better responses, candidates successfully incorporated correct looping statements, a counter statement to calculate even numbers (`b += 2`), proper variable declarations (`sum = 0, b = 2`), and appropriate input and output statements.

Authentic E-Marking Better Candidate Script:

• 1 mark for inputting total number of items.
• 2 marks for loop inputting each item's price and accumulating Total Price.
• 1 mark for calculating Tax = Total Price * 0.13.
• 1 mark for calculating and printing Total Bill = Total Price + Tax.
• 2 marks for conditional check (Total Bill <= 10000 vs > 10000) and outputting Service Charges (250 or 500).
• 1 mark for inputting kilometres travelled (D).
• 2 marks for condition D <= 5 calculating fare = D * 30.
• 2 marks for condition D > 5 calculating fare = (5 * 30) + ((D - 5) * 25).
• 1 mark for adding fixed charges of 50 rupees.
• 1 mark for outputting the final bill.

10 CLS
20 SUM = 0
30 INPUT "Enter number of items purchased: "; N
40 FOR A = 1 TO N
50 INPUT "Enter price of item: "; P
60 SUM = SUM + P
70 NEXT A
80 TAX = SUM * 0.13
90 TB = SUM + TAX
100 PRINT "The Total Bill is: "; TB
110 IF TB >= 1 AND TB <= 10000 THEN SC = 250 ELSE SC = 500
120 PRINT "The Service Charges are: "; SC
130 END

let n = parseInt(prompt("Enter total number of items purchased:"));
let totalPrice = 0;
for (let i = 1; i <= n; i++) {
    let price = parseFloat(prompt("Enter price of item " + i + ":"));
    totalPrice += price;
}
let tax = totalPrice * 0.13;
let totalBill = totalPrice + tax;
document.write("Total Bill: " + totalBill + "<br>");
let serviceCharges = (totalBill <= 10000) ? 250 : 500;
document.write("Service Charges: " + serviceCharges);

10 CLS
20 INPUT "Enter total kilometres travelled: "; D
30 IF D <= 5 THEN SUBCOST = D * 30 ELSE SUBCOST = (5 * 30) + ((D - 5) * 25)
40 BILL = SUBCOST + 50
50 PRINT "Total Cab Service Bill = "; BILL
60 END

let d = parseFloat(prompt("Enter number of kilometres travelled:"));
let subCost;
if (d <= 5) {
    subCost = d * 30;
} else {
    subCost = (5 * 30) + ((d - 5) * 25);
}
let totalBill = subCost + 50;
document.write("Total Cab Bill: Rs. " + totalBill);

Examiner Commentary (Better Responses): Part (a): Better responses demonstrated application of various GW-BASIC concepts correctly such as input statement, loop syntax with initial and final values of counter variable, tax calculation and totaling, using GW-BASIC arithmetic and relational operators rather than mathematical operators, and IF…THEN statement with correct condition criteria. Few of these responses used array to store price of items. Part (b): Better responses were able to apply knowledge of GW-BASIC to write a program for the scenario of cab service given in the question. These responses wrote correct input statement, IF…ELSE statements for less than or equal to 5 kilometers and for greater than 5 kilometers, fare calculation according to the criteria given in the question, totaling statements, and output statements.

Authentic E-Marking Better Candidate Script:

• 2 marks for FOR loop running from 1 to 150.
• 2 marks for inputting the first four digits of each book's barcode.
• 3 marks for computing Step 1, Step 2, Step 3, and Step 4 (Remainder using MOD 10).
• 2 marks for IF-ELSE condition setting check digit to 0 or (10 - Remainder) and printing the check digit.
• 2 marks for declaring arrays A(15), B(15), and C(15).
• 2 marks for FOR loop running from 1 to 15.
• 2 marks for inputting values into A(T) and B(T).
• 2 marks for adding C(T) = A(T) + B(T).
• 1 mark for printing the elements of array C(T).

10 CLS
20 FOR B = 1 TO 150
30 INPUT "Enter 1st, 2nd, 3rd, and 4th digits of barcode: "; D1, D2, D3, D4
40 LET S1 = (D1 + D3) * 3
50 LET S2 = D2 + D4
60 LET S3 = S1 + S2
70 LET REMVAL = S3 MOD 10
80 IF REMVAL = 0 THEN CD = 0 ELSE CD = 10 - REMVAL
90 PRINT "Check digit for book "; B; " is: "; CD
100 NEXT B
110 END

for (let b = 1; b <= 150; b++) {
    let d1 = parseInt(prompt("Book " + b + " - Enter 1st digit:"));
    let d2 = parseInt(prompt("Book " + b + " - Enter 2nd digit:"));
    let d3 = parseInt(prompt("Book " + b + " - Enter 3rd digit:"));
    let d4 = parseInt(prompt("Book " + b + " - Enter 4th digit:"));
    let s1 = (d1 + d3) * 3;
    let s2 = d2 + d4;
    let rem = (s1 + s2) % 10;
    let checkDigit = (rem === 0) ? 0 : (10 - rem);
    document.write("Book " + b + " Check Digit: " + checkDigit + "<br>");
}

10 CLS
20 DIM A(15), B(15), C(15)
30 FOR T = 1 TO 15
40 INPUT "Enter value for Array A: "; A(T)
50 INPUT "Enter value for Array B: "; B(T)
60 C(T) = A(T) + B(T)
70 NEXT T
80 FOR T = 1 TO 15
90 PRINT "Sum at position "; T; " = "; C(T)
100 NEXT T
110 END

let A = new Array(15);
let B = new Array(15);
let C = new Array(15);
for (let i = 0; i < 15; i++) {
    A[i] = parseInt(prompt("Enter element " + (i + 1) + " for Array A:"));
    B[i] = parseInt(prompt("Enter element " + (i + 1) + " for Array B:"));
    C[i] = A[i] + B[i];
    document.write("C[" + i + "] = " + C[i] + "<br>");
}

Examiner Commentary (Better Responses): Part (a): Better responses demonstrated an excellent understanding of the given problem and wrote the correct FOR loop statement followed by input statement for four input digits and finally applied the different calculations, formulae and conditions given in this question. Part (b): Better responses depicted good understanding of the given problem and declared three arrays with appropriate names and subscript values followed by FOR loop statement with correct loop condition and the addition operation is performed on the values of arrays A and B and their answer is stored in array C. Finally, the output is displayed by printing the values of array C.

Authentic E-Marking Better Candidate Script:

• 1 mark for initialising SUM = 0 and MAX = 0.
• 2 marks for FOR loop running from 1 to 55 and inputting weight W.
• 2 marks for accumulating SUM = SUM + W and updating MAX using IF W > MAX THEN MAX = W.
• 1 mark for calculating AVG = SUM / 55.
• 1 mark for printing AVG and MAX.
• 1 mark for inputting Weight (W) and Height (H).
• 2 marks for calculating BMI = W / (H * H) or W / H^2.
• 4 marks for conditional statements checking the 4 BMI ranges and printing the respective Weight Category (1 mark per category).

10 CLS
20 SUM = 0 : MAX = 0
30 DIM W(55)
40 FOR I = 1 TO 55
50 INPUT "Enter weight of club member: "; W(I)
60 SUM = SUM + W(I)
70 IF W(I) > MAX THEN MAX = W(I)
80 NEXT I
90 AVG = SUM / 55
100 PRINT "Average Weight = "; AVG
110 PRINT "Maximum Weight = "; MAX
120 END

let W = new Array(55);
let sum = 0;
let max = -Infinity;
for (let i = 0; i < 55; i++) {
    W[i] = parseFloat(prompt("Enter weight of member " + (i + 1) + ":"));
    sum += W[i];
    if (W[i] > max) {
        max = W[i];
    }
}
let avg = sum / 55;
document.write("Average Weight: " + avg + "<br>");
document.write("Maximum Weight: " + max);

10 CLS
20 INPUT "Enter weight in kg: "; W
30 INPUT "Enter height in metres: "; H
40 BMI = W / (H ^ 2)
50 IF BMI >= 27.5 THEN PRINT "Obese"
60 IF BMI >= 23 AND BMI <= 27.4 THEN PRINT "Overweight"
70 IF BMI >= 18.5 AND BMI <= 22.9 THEN PRINT "Healthy"
80 IF BMI < 18.5 THEN PRINT "Underweight"
90 END

let W = parseFloat(prompt("Enter weight in kg (W):"));
let H = parseFloat(prompt("Enter height in metres (H):"));
let bmi = W / (H * H);
if (bmi >= 27.5) {
    document.write("Obese");
} else if (bmi >= 23 && bmi <= 27.4) {
    document.write("Overweight");
} else if (bmi >= 18.5 && bmi <= 22.9) {
    document.write("Healthy");
} else {
    document.write("Underweight");
}

Examiner Commentary (Better Responses): Part (a): Better responses demonstrated good application of the FOR loop and conditional statement for the given problem, using the correct range (1 to 55) to start and end the loop and tracking both the sum and maximum weight (either with scalar variables or a 55-element 1D array). Part (b): Better responses used proper GW-BASIC statements to take input weight and height values, correctly converted the given formula into a GW-BASIC expression (`BMI = W / H^2`), and used conditional statements with the correct range of BMI to display the weight category.

Authentic E-Marking Better Candidate Script:

• 6 marks for discussing six distinct threats to the PC (1 mark each).
• 2 marks for describing preventive steps to avoid virus infection.
• 3 marks for describing uses of AI in the defence industry.
• 3 marks for describing uses of AI in weather forecasting.
• 2 marks for stating at least two benefits of using AI in these fields.

Examiner Commentary (Better Responses): Part (a): Better responses described possible threats such as replication of folders due to viruses, failure of operating system, corruption of data and files, damaging the boot sector, changing the location of the file and making their shortcuts, and consuming hardware and software resources to make the system slow. Moreover, these responses wrote appropriate steps to prevent computer systems from viruses such as scan USB drive before opening it, install anti-virus software and keep it updated, avoid double click on USB drive because it may execute the virus in computer system, and run your anti-virus program regularly. Part (b): Better responses described relevant uses of artificial intelligence (AI) in the defence industry and weather forecasting such as unmanned drone attacks can be done via AI, quick and precise attacks on sensitive targets, and analyzing large sets of data to predict the weather better than any experienced weatherman. Moreover, these responses wrote benefits such as AI-based robots can fight in the battle without getting tired for 24×7, are more accurate than humans, can be sent to risky and dangerous places where a normal human cannot go, and AI-based systems can generate alarms to warn people in advance about a big storm.

Authentic E-Marking Better Candidate Script:

Examiner Commentary (Better Responses): Follow the reference model solution and step-by-step marking criteria.

• 2 marks for the explanation of each term (Worm, Adware, Trojan horse).
• 2 marks each for the description of Script Kiddie, Blue Hat Hacker, and Red Hat Hacker.

Examiner Commentary (Better Responses): Part (a): In better responses, candidates provided clear and well-structured explanations of the terms worm, adware, and Trojan horse. For example, a worm transmits itself over a network to infect other computers. Adware displays advertisements to users. Trojans are disguised as legitimate or desirable software to trick users into executing them. They accurately identified the key characteristics of each type of malware, elaborating on how they spread within systems and networks. Part (b): In better responses, candidates effectively defined the distinct characteristics of the three types of hackers. For example, a script kiddie lacks technical expertise or skills but uses pre-made scripts to conduct cyberattacks. Blue hat hacker is neither a white hat nor a black hat, either invited by organisations to test systems for bugs before launch or seeking revenge, while Red Hat hackers act as vigilantes who aggressively target and disable black hat hackers.

Authentic E-Marking Better Candidate Script:

• 1 mark each for the description of authentication and authorisation.
• 1 mark will be awarded for only stating authentication and authorisation.
• 1 mark for writing the names of authentication methods of 2FA (Any TWO required).
• 1 mark for describing each authentication method of 2FA (Any TWO required).
• 1 mark for each highlighted point of white hat hacker (Any TWO required).
• 1 mark for each highlighted point of black hat hacker (Any TWO required).
• 1 mark for each highlighted point of green hat hacker (Any TWO required).

Examiner Commentary (Better Responses): Part (a): In better responses, the candidates showed a good understanding of authentication methods and their significance in ensuring secure access to systems and data, including multimodal biometric verification and smart access cards combined with a PIN. Part (b): In better responses, candidates showed commendable understanding of the three types of hackers, providing accurate definitions and clear distinctions between each category: white hat hackers as ethical hackers, black hat hackers as criminals, and green hat hackers as learners of cybersecurity.

Authentic E-Marking Better Candidate Script:

• 1 mark for each valid positive impact of computers on society (up to 4 marks).
• 1 mark for each valid negative impact of computers on society (up to 4 marks).
• 1 mark for each valid point from the user's point of view (up to 4 marks).
• 1 mark for each valid point from the software owner's/developer's point of view (up to 4 marks).

Examiner Commentary (Better Responses): Part (a): Better responses revealed that they understood the question well. The positive impacts of computers on society included: computers are used for quick long distance communication and video calls which is time and cost efficient; new employment opportunities are created such as trend of freelancing and working online has increased due to which people can work from home for employers from any part of the world; paper is saved and pollution is reduced due to the replacement of paper work by the computerised systems; computers have made e-learning easy and cost effective due to which people can study from world class institutions while staying at home. Negative impacts described by such candidates included: using computers too long causes health problems such as it may affect eyesight or make the user obese due to less physical movement; people may become socially inactive; computers with the internet connection can be used to spread rumors, false information and fake news quickly; online immoral material and inappropriate websites may open. Part (b): Better responses demonstrated good understanding of importance of software licensing and mentioned that licensed software is free from any hidden virus or malware, user gets full support from the software company, owner of software gets paid by user for using licensed software, and no one else can steal the idea to develop same software.

Authentic E-Marking Better Candidate Script:

• 1 mark for defining a computer virus.
• 3 marks for describing any three ways viruses spread (1 mark each).
• 4 marks for writing any four steps to protect a computer system against viruses (1 mark each).
• 1 mark for defining hacking.
• 7 marks for suggesting seven distinct technical/security measures to avoid hacking (1 mark each).

Examiner Commentary (Better Responses): Part (a): Better responses defined the computer virus correctly and described the ways to spread viruses such as downloading and opening infected attachments in an email, downloading an infected file from the internet, infected removable media (USB flash drive, CD/DVD), and computer networks. Also, these responses wrote correct steps to protect a computer system such as keeping antivirus software up to date, not clicking untrusted email links, using a firewall, and scanning USB drives before opening. Part (b): Better responses showed good understanding about hacking and measures to avoid it, suggesting measures such as changing passwords periodically, installing a firewall on the computer system, updating the operating system frequently, installing anti-spyware/antivirus programs, and not logging into social media or bank accounts from public computers.

Authentic E-Marking Better Candidate Script:

• i. 1 mark each for any THREE valid reasons why computer security is vital for an online business (3 Marks).
• ii. 1 mark each for any THREE specific security measures/practices to protect the online store (3 Marks).
• i. 2 marks for accurately defining a computer virus (malicious program that attaches to host files and self-replicates when executed).
• ii. 1 mark each for any FOUR valid ways a virus spreads (4 Marks).

Examiner Commentary (Better Responses): In better responses for Part (a), candidates separated the business importance points (i) from the concrete technical safeguards (ii). For Part (b), candidates defined a virus as host-dependent self-replicating malware and explained four distinct transmission vectors.