hi,

see the karnataka pre university conducts karnataka 12th board exam i.e 2nd puc, now this exam is equivalent with 10+2 course. 10+2 course certificate is mandatory to take admission in any courses as bachelors or integrated. unless you do not qualify in the higher secondary or 10+2 course exam, you will not eligible to take admission in bachelors level course.

BCA, or Bachelor of Computer Applications is a 3 year ug program in India which comprises  with the basics of software development and computer applications. From computer programming to computer networking, everything is included in the BCA syllabus. the eligibility criteria for bca course is applicants must secure  atleast  50% in Class 12 with English as a mandatory subject.

now some of the institute take admission based on 12th course, some have their own entrance test. so you must clear your puc 2nd to become eligible for bca.

another option for you is you may go for diploma in computer science engineering, which has similar concept of bca , but you can go for b.tech course after completing diploma in cse. for diploma course eligibility, candidates must pass 10th course with science subject from a recognized education board.

hope it would help.