Dear Aspirant

To get into the computer science stream you must complete the JEE Main entry level exam.The cut off marks in the JEE MAIN vary according to the category as you asked,

JEE MAIN 2017 - General category:81

OBC:49

SC:32

ST:27

JEE MAIN 2018 - General:85

OBC:50

SC:35

ST:30

The cut off marks vary basing on the factors of paper difficulty ,seats available etc for every year.

Not only JEE MAIN you can also go with the CET exam conducted with respect to your state.

All the best for your Future...