After completing 12th with commerce you have many options to go to higher studies. You can go Bachelor of commerce in Computers and you can also go B.Sc computer science.

Candidate should pass in Higher Secondary(10+2),not necessary science background.

If you want to do BSC in computer science than take admission in good college
Eg . Loyola college in Chennai
Oxford college of science,banglore
St .Xavier's college,mumbai

If you are interested in cse than btech is also a good opportunity after 12
Best of luck