Tech Mahindra interview questions

In the technical interview, they asked me one question about what is circular reference?

questions from eletronics and basic data structure. antenna, modulation, heap sort, sql queries (very basic group by) basic difference in CDMA and GSM, function overloading, overridding, abstract class, work of constructors were covered in interview.. if you understand basic concepts of your subject then it is a peice of cake but the written is tough. no IT related questions but aptitude from R S agarwal would help. English is medium. time is just appropriate for exam so be fast.