bash shell, c (string library), data structures (array, linked lists, trees, graphs), c++ (vectors, constructors and destructors, inheritance, polymorphism, copy constructor, assignment operator), debugging (gdb), coding basics (theoretical knowledge on various topics; viz. stack and queue)

1. C++ concepts such as polymorphism, virtual functions, inheritance, operator overloading, initializer lists, pointers, references. 2. conceptual questions have more weightage.