Normally we write iostream.h but in this app it is writen iostream so that's correct or not ?

Answer 1

iostream.h is deprecated in current (since 2002) C++ standard compliant compilers.  The new version fixes a reliability problem that exists in the old version.

Answer 2

maybe, I don't understand your question... iostream.h is a c++ library. It adds to your code features to manage stream, doesn't open any stream itself. With iostream.h features you can open your own stream and redurect standard output and standard error also on a different stream. You can create multiple streams at time also.