Hey!There

You can buy any textbook of computer science for class 12 as it is really hard to find specific computer science book for Bihar board.I am suggesting you book of CS for class 12th which is very popular,all you need is go through this textbook after having syllabus of Bihar board as lot of it's content won't be in your syllabus.So it will be better for you if you have syllabus of Bihar board before going to this book;

TEXTBOOK OF COMPUTER SCIENCE for class 12 BY SEEMA BHATNAGAR .

Ask if any query