As per as my knowledge, maximum MNCs and top companies requires minimum 60% marks in the through out the career. If you have minimum 60% marks in 12th and there is no problem, but if you have less then 60% marks, then it will affect you in near future.

But don’t worry, you can apply in the off campus placements to top companies, in off campus placement there is no minimum marks criteria only skills and knowledge matters to them. You can also apply for following short term, courses which will help you in getting job:

C++
Java
.net
O level etc.