Twenty complete mock papers for ISC Computer Science, Paper 1 (Theory), Class XII, written for the 2027 examination. Each paper follows the board pattern: 70 marks, 3 hours, a compulsory Part I and a Part II with Sections A, B and C and a choice of questions. Every solution shows the working the way an examiner wants to see it: K-map groupings, truth tables and circuit expressions, stack traces for infix, prefix and postfix conversions, tree traversals written out in full, and complete Java programs with sample input and output. A chapter on the ISC papers from 2017 to 2026 shows marks by topic, year by year. All questions are original, written for this book. Free sampler and PDF edition at codewithvinay.com. Independent practice papers, not affiliated with or endorsed by CISCE.