Difference Between iostream and iostream.h in C++

Here we will see what are the differences between iostream and iostream.h in C++. The iostream.h was a header file used by the early 1990's I/O streams library. This was developed at AT&T for use with early C++. In that time C++ was not standardized.

iostream header file used by the C++ standard library. This is first published in 1998, to provide access to standard I/O streams.

There was never a C++ standard that made any mention of "iostream.h", but pre-standard references, such as Annotated C++ Reference Manual from 1990 did use that header file.