ISC 2025 Computer Science Question Paper for Class 12

About this paper

This is ISC Class 12 Computer Science Paper 1 (Theory), code 868A, from the 2025 board examination. It carries 70 marks and three hours, plus fifteen minutes to read the paper. There are 11 questions on 15 printed pages. Part I, worth 20 marks, is compulsory and uses multiple-choice and assertion–reason items. Part II, worth 50 marks, has three sections, and any two questions are attempted from each. Section A includes an access-control truth table, Karnaugh maps drawn with NAND gates, and an encoder. Section B is Java: pernicious numbers, column sums of two matrices, and flipping the halves of a word. Section C is a circular queue, a flight fare with tax, a linked list and a binary tree. This copy has the questions only.

Exam

ISC Class 12

Subject

Computer Science

Year

2025

Paper code

868A

Maximum marks

70

Time allowed

3 hours + 15 min reading

Questions

11

Pages

16

Answers included

No, questions only

Paper pattern

• Part I

  20 marks

  Questions 1 and 2, all compulsory: multiple-choice and assertion–reason items, a postfix conversion and two Java methods

• Section A

  20 marks

  Questions 3–5, ten marks each; answer any two. An access truth table reduced with NOR gates, Karnaugh maps and an octal encoder

• Section B

  20 marks

  Questions 6–8, ten marks each; answer any two. Java classes for a pernicious number, column sums and flipping a word

• Section C

  10 marks

  Questions 9–11, five marks each; answer any two. A circular queue, flight-fare inheritance, a linked list and a binary tree

Topics covered

• Boolean algebra and duality
• Propositional logic
• Karnaugh maps
• Encoders and decoders
• Recursion and Big O notation
• Matrices
• Number systems
• Strings
• Inheritance
• Circular queues
• Linked lists and binary trees

Questions from this paper

1. Convert the infix expression (A − B / C) + (D * E / F) * G to postfix form.
2. A pernicious number, written in binary, has at least two digits and a prime number of 1s. 101 and 10110 are pernicious; 1111 is not. Design a class Perni to test one.
3. Class Colsum checks whether two matrices of the same size have equal sums down each corresponding column.
4. Class Flipgram swaps the left and right halves of a word that is not a heterogram, leaving the middle letter in place when the length is odd. BETTER becomes TERBET, and NEVER becomes ERVNE.
5. A superhero may enter a secure facility with Avengers membership and a high-security badge, or with a S.H.I.E.L.D. permit and that badge. Draw the truth table and write the POS expression for X(A, S, C, L).
6. Subclass Passenger calculates tax as 5% of the base fare and the total amount as base fare plus tax.