What is the différence between #include and #include ?

Question

What is the difference between

#include <iostream.h>

and

#include <iostream>

?

score 18 · Accepted Answer · answered Mar 28 '13 at 11:14

18

Before C++ was even standardised, the I/O library was developed as <iostream.h>. However, that header has never been a standard C++ header. Some older compilers continued to distribute the <iostream> header also as <iostream.h>. Use <iostream> because it is guaranteed by the standard to exist.

It's worth noting that the only standard headers that end with .h are the C standard library headers. All C++ standard library headers do not end with .h.

answered Mar 28 '13 at 11:14

Joseph Mansfield

108,238
20
242
324

1

During the transition period, there were compilers which delivered a `` which included `` (plus a number of `using`, so that you didn't need `std::`); there were others whose `` included `` (and the compiler was hacked to make `std::` the same as `::`). – James Kanze Mar 28 '13 at 11:47
Extra question about naming conventions: why it is named `` instead of ``? Or vice versa: why it is named `` instead of ``? – pmor Jun 23 '22 at 13:55

score 4 · Answer 2 · answered Mar 28 '13 at 11:15

4

<iostream> is the usual header

<iostream.h> is the old header, not longer supported by some compilers

answered Mar 28 '13 at 11:15

StepUp

36,391
15
88
148

score 0 · Answer 3 · edited Sep 23 '21 at 06:44

0

It just depends on the name of the file provided by your toolchain. Some (old) compilers use .h files. Modern compilers usually use <iostream> (without the .h extension).

edited Sep 23 '21 at 06:44

ecm

2,583
4
21
29

answered Mar 28 '13 at 11:13

Claudio

10,614
4
31
71

What is the différence between #include and #include ?

3 Answers3