ISC Class 12 Computer Science Board Exam Question Paper 2011 with Solutions

ISC Class 12 Computer Science Board Exam Question Paper with Solutions

COMPUTER SCIENCE
Paper - 2
(PRACTICAL)

Question 1

Write a program to input a natural number less than 1000 and display it in words.
Test your program for the given sample data and some random data.

Answer:
import java.util.Scanner;

public class NumberToWords {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        System.out.print("INPUT: ");
        int n = sc.nextInt();

        if (n < 1 || n >= 1000) {
            System.out.println("OUTPUT: OUT OF RANGE");
            return;
        }

        String[] units = {"", "ONE", "TWO", "THREE", "FOUR", "FIVE", "SIX", "SEVEN", "EIGHT", "NINE", "TEN", "ELEVEN", "TWELVE", "THIRTEEN", "FOURTEEN", "FIFTEEN", "SIXTEEN", "SEVENTEEN", "EIGHTEEN", "NINETEEN"};
        String[] tens = {"", "", "TWENTY", "THIRTY", "FORTY", "FIFTY", "SIXTY", "SEVENTY", "EIGHTY", "NINETY"};

        String word = "";
        int h = n / 100;
        int rem = n % 100;

        if (h > 0) {
            word = units[h] + " HUNDRED";
            if (rem > 0) {
                word = word + " AND ";
            }
        }

        if (rem > 0) {
            if (rem < 20) {
                word = word + units[rem];
            } else {
                int t = rem / 10;
                int u = rem % 10;
                word = word + tens[t];
                if (u > 0) {
                    word = word + " " + units[u];
                }
            }
        }

        System.out.println("OUTPUT: " + word);
    }
}

Teacher's Note:
a) Use string arrays for mapping digits to their corresponding word representations to simplify conversion logic.
b) Ensure boundary conditions such as numbers less than 1 and greater than or equal to 1000 are explicitly checked and flagged as out of range.

Question 2

Encryption is a technique of coding messages to maintain their secrecy. A String array of size 'n' where 'n' is greater than 1 and less than 10, stores single sentences (each sentence ends with a full stop) in each row of the array.
Write a program to accept the size of the array. Display an appropriate message if the size is not satisfying the given condition. Define a string array of the inputted size and fill it with sentences row-wise. Change the sentence of the odd rows with an encryption of two characters ahead of the original character. Also change the sentence of the even rows by storing the sentence in reverse order. Display the encrypted sentences as per the sample data given below:
Test your program on the sample data and some random data.

Answer:
import java.util.Scanner;

public class SentenceEncryption {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        System.out.print("Enter value of n: ");
        int n = sc.nextInt();
        sc.nextLine();

        if (n <= 1 || n >= 10) {
            System.out.println("OUTPUT: INVALID ENTRY");
            return;
        }

        String[] arr = new String[n];
        System.out.println("Enter " + n + " sentences:");
        for (int i = 0; i < n; i++) {
            arr[i] = sc.nextLine();
        }

        System.out.println("OUTPUT:");
        for (int i = 0; i < n; i++) {
            if (i % 2 == 0) {
                // Odd rows in 1-based indexing correspond to even indices (0, 2, ...)
                String s = arr[i];
                String enc = "";
                for (int j = 0; j < s.length(); j++) {
                    char ch = s.charAt(j);
                    if (Character.isLetter(ch)) {
                        ch = (char)(ch + 2);
                    }
                    enc = enc + ch;
                }
                System.out.println(enc);
            } else {
                // Even rows in 1-based indexing correspond to odd indices (1, 3, ...)
                StringBuffer sb = new StringBuffer(arr[i]);
                System.out.println(sb.reverse().toString());
            }
        }
    }
}

Teacher's Note:
a) Clarify whether array row numbers are 0-indexed or 1-indexed as per standard matrix convention; odd rows (1st, 3rd) map to array indices 0, 2.
b) Handle newline character left in the scanner buffer using sc.nextLine() immediately after reading integer inputs.

Question 3

Design a program which accepts your date of birth in dd mm yyyy format. Check whether the date entered is valid or not. If it is valid, display "VALID DATE", also compute and display the day number of the year for the date of birth. If it is invalid, display "INVALID DATE" and then terminate the program.
Test your program for the given sample data and some random data.

Answer:
import java.util.Scanner;

public class DateValidator {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        System.out.println("Enter your date of birth in dd mm yyyy format");
        int d = sc.nextInt();
        int m = sc.nextInt();
        int y = sc.nextInt();

        boolean isLeap = (y % 400 == 0) || (y % 4 == 0 && y % 100 != 0);
        int[] days = {0, 31, (isLeap ? 29 : 28), 31, 30, 31, 30, 31, 31, 30, 31, 30, 31};

        if (y < 1 || m < 1 || m > 12 || d < 1 || d > days[m]) {
            System.out.println("OUTPUT: INVALID DATE");
            return;
        }

        System.out.println("OUTPUT: VALID DATE");
        int dayNo = 0;
        for (int i = 1; i < m; i++) {
            dayNo += days[i];
        }
        dayNo += d;
        System.out.println(dayNo);
    }
}

Teacher's Note:
a) Account for leap year rules correctly when validating February days and calculating the day number.
b) Terminate execution immediately upon encountering an invalid date using return statements.