iostream.h vs iostream

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In this code if i write iostream.h then it will give me output without any error, but if i write only
iostream in place of iostream.h then i will have to use namespace std statement ,then what is the use of iostream.h headerfile ?

C++

#include <iostream>
#include <conio.h>

//using namespace std;
int main()
{
    //std::cout<<"Hello";
    
    cout<<"Hello";
    getch();
    return 0;
}

Posted 21-Oct-11 12:53pm

Ashutosh_g

Updated 23-Oct-11 9:03am

Emilio Garavaglia

v5

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Sergey Alexandrovich Kryukov 21-Oct-11 21:59pm

The code you show will not compile, but this is because you need to escape <>. Also, put it all in <pre lang="c++">....</pre>.
--SA

2 solutions

Solution 1

You say it like namespace-qualified names or "using namespace std" is something bad. :-)

This is good! What do you think name spaces are designed for?

The background on "extensionless" "<iostream>" vs. "<iostream.h>" is explained in detail here: http://members.gamedev.net/sicrane/articles/iostream.html[^].

—SA

Posted 21-Oct-11 16:05pm

Sergey Alexandrovich Kryukov

Updated 22-Oct-11 15:29pm

v3

Comments

Espen Harlinn 23-Oct-11 19:24pm

Good points :)

Sergey Alexandrovich Kryukov 23-Oct-11 20:11pm

Thank you, Espen.
--SA

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Maximilien · Accepted Answer · 2011-10-21T16:08:00

#include <iostream.h>

is the now obsolete header file for the iostream stuff.

Now, you juste need to include

C++

#include <iostream>

the iostream without the .h is the standardized header for the iostreams.

All new standard c++ header use the .h-less names.

#include <vector>
#include <algorithm>
...

Today all (most?) STL and standard C++ code are in the std namespace.

You can either use

using namespace std;

to let the compiler (?) know to look in the std namespace if it cannot find the declaration in the global namespace. (probably a bad wording).

or just use std:: in front of the STL and standard c++ functions and method.

so you'll have

C++

...
using namespace std;
cout << "hello" << endl;

or

C++

...
std::cout << "hello" << std::end;