Hello.,

It totally depend upon college but in most of the college admission done directly once you pass your class 12th .

In few college admission taken on the basis of entrance exam mostly in government colleges. You are eligible for getting admission in bca in most college once you pass your 12th + 2 with science , commerce or art stream.

Mainly bca create for students who can't do b.tech due to commerce and arts stream. Some college asked for mathematics as subject in 10+2 .

All the best!!