Hello there!!
After 12th PCM with computer science, you are open to a lot of options. You should choose whatever suits your interests and skills. You can become an IT/CS engineer, you can also apply for NDA (All three forces), you can pursue Bsc in your related subjects, Bca, Barch. Apart from these you can apply for other Humanities or commerce related courses like BA and Bcom.
Hope this helps!
Good luck!