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ISC Class XII Prelims 2025 : Computer Science (Central Modern School (CMS), Baranagar, Kolkata)

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CENTRAL MODERN SCHOOL, Baranagar Pre-Board Examination for ISC -2025 Class - XIl Time:3 hrs. Maximum Marks: 70 COMPUTER SCIENCE,Theory (Paper - I) F.M. :70 Time Allotted: Three Hours Reading Time: Additional Fifteen minutes Instructions to Candidates : You are allowed additional 15 minutes for only reading the question paper. You must NOT start writing during the reading time. > This question paper has 9 printed pages. It is divided into two parts and has 11 questions in all. > Part Iis compulsory and has two questions. Answer all questions. > Part Il is divided into three sections: A, B and C. While attempting Multiple Choice Questions in Part I, you are required to write oniy ONE option as the answer. Each section in Part Il has three questions. Any two questions have to be attempted from each section. > The intended marks for questions are given in brackets ]. PART -I [20 Marks] Answer allquestions. While answeringquestions in this Part, indicate briefly your working and reasoning, wherever required. QUESTION: 1 i) public class A{ public static void main(String[] args) [1] System.out.println(|] +'a' + +'a'); What is the probable output of the following? c) 418 b) Syntax error a) java i) Which of these is not a limitation of recursion? d) None of these (1] a) Occupies more space in the stack b) Execution time is more than that of recursion c) Minimum variables are used to depict the logic d) Results in stack overflow. ii) What is the worst case complexity for bubble sort? c) O(1) b) O(nlogn) a) On) d) O(n) iv) Since a major drawback of a single linked list is its unidirectional traversal. what [1] alternative can be used in its place? [1] c) Double Linked list d) Binary tree addrees v) Which of these components are used torsnaring common bus for a) Stack b) Dequeue transmission among the devices? a) Decoder b) Encoder XI, Computer Science (Theory) c) Multiplexer d) Adders [1] Page 1 of 7 vi) Assertion: The Boolean expression obtained on dualing (performing dualty) a given expression, is its complemented form. Reason: In dualof a expression (+) is replaced with (),and vice versa, 1gets replaced with Oand viceversa, keeping the variables and their complerments unchanged. [1] Which of the following options is correct? a) Both Assertion and Reason is true. andReason is the correct explanation for Assertion. b) Both Assertion and Reason is true, but Reason is not the correct explanation of Assertion. c) Assertion is True, but Reason is False. d) Assertion is False, but Reason is True vii) What do you mean by recursion ? vii) State the cardinal form of a 2 input XOR gate? ix) What is the function of indexof() ? x) For Big O notation, state the difference between O(n) and O(n). [1] [1] [1] [1] QUESTION:2 a) Convert the given expression from infix to prefix form: [3] (A+ B^C/X)+ (D*E/|+ F)+ S^Y b) A two dimensional array M[.....8][-4.....5]contains integer numbers. The base address of the array is 2000 bytes. The address at M[-3][5] is 2156 bytes. Assuming that the array is row major oriented, find the value of x, and the address at M2][3] c) How is overloading different from overriding ? [3] [1] d) Given code snippet for the class Test. Show the output for the following snippet. Also state the function of the function recs(int) apart from recursion. (2+1] class test public intrecs(intnum) if(num==0) return 0; else return (num + recs(num-1); public void main() inti,r; for( =0;i<5;i++) r=recs(): System.out.printin(i+"Mt+r); XI, Computer Science (Theory) Page 2 of 7 PART-Il [50 Marks] Answer six questions in this part, choosing two questions from Section A, two from Section B and two from Section C. SECTION-A Answer any two questions. QUESTION :3 i) Reduce the given expression W (A, B, C, D) using a 4 - variable Karnaugh Map. showing the groups (as pairs, quads and octal). Also draw the logical diagram of the reduced expression. Do not assume that the variables and their complements are [4+1] given. W(A, B, C, D) = E(0,2,3,5,6,7,8,9,10,11,12,13,15) ii) Draw the neat circuit showing a hexadecimal to binary encoder. Provide a truth table (2+2+1] for the same. State the working principle of an encoder. QUESTION : 4 [2] i) Drawa logic diagram using NOR gates only, for the expression: (A+B').(A'+B).(A'+B'+C) ii) Given expression as: (A+B'+C+D') Y= (A+B+C+D) (A+B+C'+D) (A+B'+C+D') (A+B'+C+D') (A+B'+C'+D) (A'+B'+C+D')(A+B'+C'+D)(A'+B+C+D)(A'+B+C+D) (A)Find the most simplified POS expression using K-map. (B) Drawa logic diagram using fundamental gates only. (C) Drawalogicdiagram using NOR gates only ii) State and prove DeMorgan's Theorem. [2] [2] [2] (2] QUESTION: 5 Afamily consists of afather, mother, a son and daughter. They want to builda voting machine according to the following rules: A motion is carried if: Father votes Yes. Mother votes Yes. Father and any child vote Yes. Mother and any child votes Yes. Allvote Yes. The inputs are: A: Denotes Father's vote. B: Denotes mother's vote. C: Denotes son's vote. (1 indicates YES, O indicates NO) (1 indicates YES, 0 indicates NO) (1 indicates YES,Oindicates NO) (1 indicates YES, Oindicates NO) D: Denotes daughter's vote. Output is: indicates YES, 0 indicates NO) (1 motion the of result the Denotes S: outputs given above, and write the SOP the and inputs the for table truth i) Draw the S(A,B,C,D),and also write the respective motion the of result the expression for [3+1] cardinal form. Page 3 of 7 Xl, Computer Science (Theory) i) Reduce the above expression using 4 variable Karnaugh Map, by grouping using [2] pairs, quads and octs, and write the reduced expression. ii) Draw a logicdiagram for the reduced expression using fundamental gates. Assume [2] that the variables and their conmplements are available to the user. iv) Draw the same logic circuit but using NAND gates, and show how they are equivalent (2] to each other. SECTION-B Answer any two questions. Each program should be written in such a way that it clearly depicts the logic of the problem. This can be achieved by using mnemonic names and comments in the program. (Flowcharts and Algorithms are not required.) The programs must be written in Java. [10] QUESTION:6 Fascinating Numbers: Some numbers of 3 digits or more exhibit a very interesting property. The property is such that, when the number is multiplied by 2 and 3, and both these products are concatenated with the original number, all digits from 1 to 9 are present exactly once, regardless of the number of zeroes. Let's understand the concept of Fascinating Number through the following example: Consider the number 192 192 x1= 192 192 x 2=384 192 x 3 = 576 Concatenating the results: 192 384 576 It could be observed that '192384576' consists of all digits from 1to 9 exactly once. Hence, it could be concluded that 192 is a Fascinating Number. Some examples of fascinating Numbers are: 192, 219, 273, 327, 1902, 1920, 2019 etc. Write a java program implementing as per the following instructions: Class Name: Data variables: number concatenated Fascinating Number To store the number to be checked A string to store the concatenated numbers Member methods: void concatenateNumbers(int) void containsAlIDigOnce(String) To store the number, its double and triple in concatenated form To check whether the concatenated string contains the digits 1 to 9, only once, using recursive technique Callthe above methods and check whether it is a Fascinating number or not method to accept the number and display the result. void isFascinating(int) Nowwrite the main() Xl, Computer Science (Theory) Page 4of7 QUESTION:7 Twomatrices are said to be equal if they have the same dimension and corresponding elements are equal. [10] their For example, the matrices given below are equal. MATRIXA MATRIXB 1 2 3 4 5 7 8 6 1 2 4 5 7 8 3 Design a class EgMat to check if twO matrices are equal or not. Some of the members of the class are given below: Class name: EqMat Data members/ Instance variables A0I To store the integer elements Tostore the number of rows m To store the number of columns Member functions: EqMat(int mm, int nn) Parameterized constructor to initialize the data members m=mm, and n= nn void readarray() Toenter the elements of the array Checks if the parameterized objects P and Q are equal and returns 1, else returns 0. int check(EqMat p, qMat Q) void print() Displays the array elements Define the class EqMat giving details of the constructir(), void readarray), int check(EqMat, EqMat) and void print(). Define a main() function to create objects and call the functions accordingly to enable the task. (10] A console works in suchaway that it first encodes astring, in a manner, that it replaces each letter by a letter at a fixed move ahead in the alphabet. QUESTION :8 For example: Given string COMPUTER and move ahead = 3, means which each character is replaced by a character which is three characters ahead in the alphabet. (NOTE: move ahead <= 26). Thus the new string stands: FRPSXWHU. Now the console removes all the vowels from the Encoded string and sorts the new token in alphabetical order of letters. Sample examples: Enter a string to encode: COMPUTER Enter the shift value (1 to 26): 3 Encoded String: FRPSXWHU String without vowels: FRPSXWH FHPRSWX Final sorted string: Sample examples: Enter a string to encode: ZEOLOGY XIl, Computer Science (Theory) Page 5 of 7 Enter the shift value (1 to 26):2 Encoded String: BGQNQIA String without vowels: BGQNQ Final sorted string: BGNQQ Write a Java program that implements such console performing the following operations: 1. Encode the String with a certain move ahead as input 2. Remove all the vowels in the encoded string 3. Sort the new string in alphabetical order and display the final result. SECTION -C (Answer any two questions) Each program should be written in such a way that it clearly depicts the logic of the problem stepwise. This can be achieved by using comments in the program and mnemonic names or pseudo codes for algorithms. The programs must be written in Java and the algorithms must be written in general / standard form, wherever required /specified. (Flowcharts are not required.) QUESTION:9 Dequeue is an entity which is similar to Queue data structure, but it allows insertion and deletion of elements from both the ends (front and rear). The details of the class are given below : [5] Class name Data members/ Instance variables Dequeue intDqll To store the elements of maximum size 200 intcapc To store the maximum capacity of the array Dql) int F int R Member functions To point the index of the front queue To point the rear index of the rear queue Dequeue) Constructor to assign 0 to Dql Constructor to assign c to capc, nf to F, and nr toR (nf and nr initially getsa value -1) Add the integer n to the rear of the Dequeue If Dequeue(int c, int nf, int nr) void pushAtRear(int n) posibe,else display the message "Dequeue Overflow" void pushAtFront(int n) Add the integer n to the front of the Dequeue If posibe,else display the message "Dequeue Overflow" intRemoveRear() Removes the integer from the front of the Dequeue, if not enmpty,otherwise return -9999 intRemoveFront() void DequeueDisplay() Removes the integer from the rear of the Dequeue, if not empty, otherwise return -9999 To display the elements of the dequeue, if dequeue is empty, display "Dequeue is underflow" constructors, and the methods vojd Specify the class Dequeue bygiving details of the need not be written. pUshAtRear(int), int RemoveFront(). The main() method XI,Computer Science (Theory) Page 6 of 7 QUESTION: 10 Asuper class Record has been defined to store the names and rank of 50 students. Define a subclass Rank to find the highest rank along with the name. The details of the both the classes are given below: Class name [5] Record Data members: Namel] Rnk) Member functions: To store the names of the students To store the ranks of the students Record() Constructor to initialize the data members void readvalues() void display() To store the names and ranks Class name Rank Displays the names along with the corresponding ranks Data members: index Member functions: Integer to store the index of the topmost rank Rank() void highest() Constructor to invoke the Base class Finds the index/ location of the topmost rank and stores it. Further it sorts the array containing the rank in ascending order (accordingly sort the names also), leaving out the topmost rank index from the array. Displays the name having the topmost rank, and then displays void display() the remaining sorted array along with their names. Assume that the base class Record has been defined. member methods Now specify the class Rank, implementing the constructors and the be written. using the concept of inheritance .The main() method need not QUESTION 11: a) A linked list is formed from the objects of the class: [3] class Node { int num; Node next; } Write an algorithmOR a method to reverse the given linked list, and print the same The method declaration is given below: void reverseandPrint(Node head) questions from the b) Answer the following below: diagram of the binary tree given i) Write the F post-order of the left-subtree of node B, including itself. nodes Rand M. number of ii) State the level R H p [1] N E X Science(Theory) Computer XIl, Page 7 of 7

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