As your query is not clear so I am assuming you are asking about the months between your 12th exam and B.Tech/B.E session so if you are planning to get admission in top branches like CS then I would say better to relax and enjoy this time because once you enter the college, the life would be tough because of strict study schedule and you will not get much time to relax. Apart from this, you can learn languages like C, C++, JAVA,PYTHON, Ruby, Perl, Smalltalk, Prolog, SQL etc.

Hope this helps!!!