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ISC Class XII Prelims 2025 : Computer Science (Euro School, Bangalore)

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Pranav
Euro School, Bangalore
11th to 12th PCMC

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COMPUTER SCIENCE PAPER 1 (THEORY) PRELIMINARY EXAM - 1(2024-25) PRACTICE PAPER GRADE: XII Maximum Marks: 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 13 printed pages. It is divided into two parts and has 11 questions in all. Part I is compulsory and has two questions. Answer all questions. Part II is divided into three sections: A, B and C. While attempting Multiple Choice Questions in Part I, you are required to write only ONE option as the answer. Each section in Part II has three questions. Any two questions have to be attempted from each section. The intended marks for questions are given in brackets [ ]. ISC This Paper consists of 13 printed pages 1 PART I (20 MARKS) Answer all questions. While answering questions in this Part, indicate briefly your working and reasoning, wherever required. Question 1 (i) According to De Morgan's law (a + b + c')' will be equal to: (a) a' + b' + c' (b) a' + b' + c (c) a' . b' . c (d) a' . b' . c (ii) When a sequence of OR, NOT, NOR are connected in series, the logic gate obtained is: (a) AND (b) NOT (c) OR (d) XOR (iii) If ( x ~y ) then, its inverse will be: [1] [1] [1] (a) x y (b) y x (c) ~y x (d) ~x y (iv) The reduced expression of the Boolean function F=A(B+C(AB+AC)') is: (a) (b) (c) (d) (v) [1] 1 AB 0 A C+AB C The complement of the Boolean expression (P' Q) + (R S') is: (a) (P' + Q) (R' + S) (b) (P + Q') (R' + S) (c) (P + Q) (R + S') (d) (P+ Q') (R + S') 2 [1] (vi) Assertion (A): The protected members will have their accessibility limited only to [1] base and derived classes. Reason (R): These members of base class are used as private members for the same class and thus they can be accessed directly into the derived class. Based on the above discussion, choose an appropriate statement from the options given below: (a) Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of Assertion (A). (b) Both Assertion (A) and Reason (R) are true and Reason (R) is not the correct explanation of Assertion(A). (c) Assertion (A) is true but Reason (R) is false. (d) Assertion (A) is false but Reason (R) is true. (vii) Assertion (A): In stack, the data which has entered at last will come out first and viceversa. Reason (R): It follows the principle of FIFO. Based on the above discussion, choose an appropriate statement from the options given below: (a) Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of Assertion (A). (b) Both Assertion (A) and Reason (R) are true and Reason (R) is not the correct explanation of Assertion(A). (c) Assertion (A) is true but Reason (R) is false. (d) Assertion (A) is false but Reason (R) is true. [1] (viii) Assertion: Linked List is a nonlinear data structure. Reason: It allows the user to avail the facilities of storing various data items in randomly available/empty memory locations and linking them together. Based on the above discussion, choose an appropriate statement from the options given below: (a) Both Assertion and Reason are true, and Reason is the correct explanation for the Assertion. (b) Both Assertion and Reason are true, but Reason is not the correct explanation for the Assertion. (c) Assertion is true but Reason is false. (d) Assertion is false but Reason is true. [1] (ix) [1] Write the minterm of F(A, B, C, D) when A = 1, B = 0, C = 0 and D = 1. 3 (x) A full adder needs five gates and those are 3 AND gates, 1 OR gate and 1 XOR gate. When a full adder is constructed using 2 half adders, it also requires 5 gates. State the names along with the quantity those gates. [1] Question 2 (i) Convert the following infix notation to prefix notation. (A - B)/C*(D + E) [2] (ii) An array ARR [ - 5 ..... 15, 10 ..... 20] stores elements in Row Major Wise with each element requiring 2 bytes of storage. Find the address of ARR [10] [15] when the base address is 2500. [2] (iii) The following function is a part of some class. Assume x' and y' are positive integers, greater than 0. Answer the given questions along with dry run/working. void someFun(int x, int y) { if(x > 1) { if(x%y==0) { System.out.print(y+" "); someFun(x/y, y); } else someFun(x, y+1); } } (a) What will be returned bysomeFun(24, 2)? [2] (b) State in one line what does the function some fun() do, apart from recursion? [1] 4 (iv) The following is a function of some class .. There are some places in the code marked by ?1?, ?2?, ?3? which may be replaced by a statement/expression so that the function works properly. int gcd(int a, int b) { int r; while(?1?) { r=?2?; b=?3?; a=r; } if(a==0) return b; else return -1; } (i) What is the statement or expression at ?1? (ii) What is the statement or expression at ?2? (iii) What is the statement or expression at ?3? 5 [1] [1] [1] PART II (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) To be recruited as the Principal in a renowned College, a candidate must satisfy any one of the following criteria: The candidate must be a Postgraduate and should either possess a B.Ed. degree or a teaching experience of more than 15 years. OR The candidate must be an employee of the same college with a teaching experience of more than 15 years. OR The candidate must be a Postgraduate but not an employee of the same college and should have a teaching experience of more than 15 years. The inputs are: INPUTS P S E B [5] Candidate is a Postgraduate Candidate is an employee of the same college Candidate has a teaching experience of more than 15 years Candidate possesses a B.Ed. degree (In all the above cases, 1 indicates yes and 0 indicates no ) Output: X - Denotes eligibility of a candidate [ 1 indicates eligibility and 0 indicates ineligibility in all cases] Draw the truth table for the inputs and outputs given above and write the SOP expression for X (P, S, E, B). (ii) Reduce the above expression X(P,S,E,B) by using 4-variable Karnaugh map, showing the various groups (i.e. octal, quads and pairs). Draw the logic gate diagram for the reduced expression. Assume that the variables and their complements are available as inputs. 6 [5] Question 4 (i) Given the Boolean function for F(P,Q,R,S) = (2,3,4,5,11,12,13) (a) Reduce the above expression by using 4-variable Karnaugh map, showing the various groups (i.e. octal, quads and pairs). (ii) [4] (b) Draw the logic gate diagram for the reduced expression. Assume that the variables and their complements are available as inputs. [1] (a) From the logic circuit diagram given below, name the parts (1),(2),(3) and finally derive the Boolean expression and simplify it: [4] (b) What is the principle of duality? [1] Question 5 (i) How is a half adder different from a full adder? Draw the truth table and derive the SUM and CARRY expression for a full adder. Also, draw the logic diagram for a full adder. (ii) Show that X v (iii) Draw conclusion from the premises a b and b c that infers a c (Y ^ X) is a tautology. 7 [5] [2] [3] 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. Question 6 A class SortAlpha has been defined to sort the words in the sentence in alphabetical [10] order. Example: Input: THE SKY IS BLUE Output: BLUE IS SKY THE The details of the members of the class are given below: Class name : SortAlpha Data members/instance variables: sent : to store a sentence n : integer to store the number of words in a sentence Methods/Member functions: SortAlpha() : default constructor to initialise data members with legal initial values void acceptsent() : to accept a sentence in UPPER CASE void sort(SortAlpha P) : sorts the words of the sentence of object P in alphabetical order and stores the sorted sentence in the current object void display() : displays the original sentence along with the sorted sentence by invoking the method sort() Specify the class SortAlpha giving details of the constructor(), void acceptsent(), void sort(SortAlpha) and void display(). Define a main/function to create an object and call the functions accordingly to enable the task. 8 Question 7 Design a class BinSearch to search for a particular value in an array. The details of the members of the class are given below: Class name : BinSearch Data members/instance variables: arr[] : to store integer elements n : integer to store the size of the array Methods/Member functions: BinSearch(int nn) : parameterized constructor to initialize n=nn void fillarray() : to enter elements in the array void sort() : sorts the array elements in ascending order using any standard sorting technique int bin_search(int l,int u,int v) : searches for the value 'v using binary search and recursive technique and returns its location if found, otherwise returns -1 Define the class BinSearch giving details of the constructor(), void fillarray(), void sort() and int bin_search(int,int,int). Define the main() function to create an object and call the functions accordingly to enable the task. 9 [10] Question 8 A disarium number is a number in which the sum of the digits to the power of their respective position is equal to the number itself. Example: 135=11 +32+53 Hence, 135 is a disarium number. Design a class Disarium to check if a given number is a disarium number or not. The details of the members of the class are given below: Class name : Disarium Data members/instance variables: int num : stores the number int size : stores the size of the number Methods/Member functions: Disarium(int nn) : parameterized constructor to initialize the data members n = nn and size = 0 void countDigit() : counts the total number of digits and assigns it to size int sumofDigits(int n, int p) : returns the sum of the digits of the number(n) to the power of their respective positions(p) using recursive technique void check() : checks whether the number is a disarium number and displays the result with an appropriate message Specify the class Disarium giving the details of the constructor(), void countDigit(), int sumofDigits(int, int) and void check(). Define the main() function to create an object and call the functions accordingly to enable the task. 10 [10] 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 WordPile is an entity which can hold maximum of 20 characters. The restriction is that a character can be added or removed from one end only. The details of the members of the class are given below: Class name : WordPile Data members/instance variables: ch[] : character array to hold the character elements capacity : integer variable to store the maximum capacity top : to point to the index of the topmost element Methods/Member functions: WordPile(int cap) : constructor to initialise the data member capacity = cap, top = -1 and create the WordPile void pushChar(char v) : adds the character to the top of WordPile if possible, otherwise output "WordPile is full" char popChar() : returns the deleted character from the top of the WordPile if possible. Otherwise it returns '\\' (i) Specify the class WordPile giving details of the functions void pushChar(char) [4] and char popChar(). Assume that the other functions have been defined. The main( ) function and algorithm need NOT be written. (ii) Name the entity described above and state its principle. 11 [1] Question 10 A super class Godown has been defined to store the details of the stock of a retail store. Define a subclass Update to store the details of the items purchased with the new rate and update the stock. Some of the members of both the classes are given below: Class name : Godown Data members/instance variables: item : to store the name of the item qty : to store the quantity of an item in stock rate : to store the unit price of an item amt : to store the net value of the item in stock Member functions/methods: Godown (...) : parameterized constructor to assign value to the data members void display() : to display the stock details Class name : Update Data members/instance variables: pur_qty : to store the purchase quantity pur_rate : to store the unit price of the purchased item Member functions / methods: Update(...) void update() void display() : parameterized constructor to assign values to the datamembers of both the classes : to update the stock by adding the previous quantity by the purchased quantity and replace the rate of the item if there is a difference in the purchase rate. Also update the current stock value as: (quantity * unit price) : to display the stock details before and after updating Assume that the super class Godown has been defined. Using the concept of inheritance, specify the class Update giving details of the constructor, void update () and void display(). The super class, main function and algorithm need NOT be written. 12 [5] Question 11 (i) A linked list is formed from the objects of the class: class Node { int num; Node next; } Write an Algorithm OR a Method to insert a node at the beginning of an existing linked list. The method declaration is as follows: void InsertNode( Node startPtr, int n ) (ii) Answer the following questions from the diagram of a Binary Tree given below: (a) Write the post-order traversal of the left subtree of the above structure. (b) State the degree of the Nodes E and H. (c) Mention the external nodes of the right subtree. ******************* 13 [2] [3]

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