MCA

There must be many good college in ccu itself for mca.find out

Its better for u go MCA. Because with MCA u can get job easily, as well as Teaching or Research, what ever field as ur assumptions n interest or emergency all of the fields have always the greater benefit n honour also. All the Best.

Yes sure you can do the MCA after the B.Sc course. Those students who have done the 12th class or graduation with the math subject then they are eligible to apply. The admission in the MCA course is through the entrance exam which is conducted at the national & state level every year.
If you have good command on the programming language then you should move on this side otherwise not.

As per my view
Delhi School of E-Learning - http://www.dsel.shtr.org/
IGNOU - www.ignou.ac.in/
Annamalai University - Directorate of Distance Education (DDE) Study Centers - www.annauniv.edu/cde/
ICFAI - www.icfaiuniversity.in/
Sikkim Manipal university - Distance Education - www.smude.edu.in/
I have mentioned the websites of thse institutes/universities, you can check the websites for detailed information.
you can view my answer and try to think for your future.

go for MBA It. . try VGU Jaipur

MCA you can get jobs in software. and related areas.MBA suitable to all industries. based on your interest you can pursue the course.