is it useful to take computer science as main subject instead of hindi in class 12 for biology students?
It's completely your choice which subject you prefer over another. If you choose computer science it's absolutely fine. You will gain programming knowledge which will definitely help you in future. You already know Hindi, there is nothing to learn more in it. But there is a ocean in computer science to dive into. If you feel that force inside yourself, go for computer science. You can do a B.Tech or B.Sc. in computer science after 12th. In that condition the knowledge you gain now will help a lot.
So, think twice before choosing. Best of luck.