2. Do we need to study any mainframe/ testing/ .NET, etc?

For fresher, absolutely no need for computer courses. More practice in Quantitative analysis , C , C++ is more than sufficient to clear the software test papers also the recruiters do not expect professional experience from the fresh graduates. A good guidance is hundred times better than a computer course.
If you are graduated before 2004 and if you feel that you don't have sufficient knowledge in any of the software languages, try to join some computer courses like testing/ mainframe/ .NET, meanwhile u can try similar projects at your lab or home so that you can include it as a work experience even though you are not employed anywhere. This is a tip given by the expertise because in many of the interviews, the candidate will not be asked about the work experience rather he will be asked technically.

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General faqs