what are iostream and stdio.h

header files iostream is used in c++ n stdio.h in c

what is the main function of header

to include std libraries

sir, while using header files, there's nothing like main functions or there may not be any global functions at all of but yes if you want to ask the particular most used functions and objects then stdio.h- gets(),scanf(),printf() iostream - it has two particularly used objects namely "cout" and "cin", please note that there several member functions of those two objects and yes cout and cin are objects not function, they have some functions like flush(), get(), put(), etc that have usage in stream operations.... the implementation of objects is one of the major characteristic of C++ ask if you aren't satisfied?

iostream is derived class/buffer from ios class, in c++ we are using direct buffer to print or scan the data, hence iostream is used