Hello,

First of all you have to decide what course you want to pursue related to Computer Science field. There are many Undergraduate Programmes are available that are related to Computer Science,  I am listing a few of them

1. B.Sc (Bachelor's in Science) in Computer Science-

This a three years Undergraduate Course. For this course you must have Studied Physics Chemistry and Mathematics as you main Subjects in 12th. You must have scored minimum 50 percent in 12th (depends on the University you're willing to take admission into)

2. BCA (Bachelor's of Computer Application)

This is also a three years Undergraduate Programme. To take admission into this course you must have Studied Mathematics as one of your Subjects in 12th. It doesn't matter what was your stream, if you Studied Mathematics, then you are eligible for this course. You must have scored minimum 45-50 percent in 12th (depends on the University you're willing to take admission into).

3. B.Tech (Bachelor's of Technology) Computer Science and Engineering-

This a four years Engineering degree programme. To take admission into this course you will have to appear for some National level, state level or University level entrance exams such as JEE MAINS, JEE ADVANCED, VITEEE, SRM JEE, BITSAT. Minimum 50-60 percent in 12th is mandatory to be eligible for any of the Entrance exams.

Good Luck.