This is the official Sample Question Paper realesed by CISCE for ISC Computer Science, 2013.
To improve yourself and and to extract maximum benefit from these sample papers, choose a suitable time for yourself, and have 3 hours in your hand. Then try to solve this paper in the time limit given at the head of the paper taking 15 minutes extra for reading the paper.
Any queries regarding answer to any of the questions can be posted as a comment.
The moment you start solving these sample papers in the above described way, you will see a huge change in the way, you start preparing for your Computer Exams, and it will ultimately make you better and better.