Thanks for the A2A.
As per your situation, it appears that you are still studying in school and/or haven’t joined college. So, I will suggest you to utilise the long vacation which you will get after finishing your 12th boards and entrance tests.
Take this time to join a good computer institute near you and learn the basics of computer programming. Also, learn programming in C/C++ language. They are very easy and even if you find it a bit tough initially, please remember that you will be taught the same thing again and when you learn them in your college for the second time, you will feel very comfortable then.
The rest of the syllabus would be still somewhat similar to the PCM subjects of school. Some topics will be repeated. So, it will be easy to pick up momentum of your college courses and you won’t feel much of a difference in the syllabus of your school and college at the beginning.
Slowly, new subjects will appear and around the third year, most of the new subjects related to your branch will be introduced. I believe, you might have got comfortable with the college and its syllabus by then.