Hello dear,

first thing i want to clear with you is that for computer branch you didn't required any basic knowledge you can start it any time and in first year of b.tech all the syllabus is common for all branches.so, it is not required to you have a basic knowledge.

You can also check out following link to know more - 

https://www.careers360.com/computer-science-engineering-course

i hope this is helpfull to you.

Thank you for your query. 

In B. Tech first year, you will be oriented with each and every branch of engineering.

Its not that you will be straightaway taught high end programming. 

The eligibility criteria is to have 50% marks in ohysics, Chemistry and mathematics in boards and get a good total in JEE to get a good college. 

You can check out the following link to know more - 

https://www.careers360.com/computer-science-engineering-course