<iostream.h> or <iostream>?

**Yumin** · 01-28-2006

Here is a simple code:

Code:

        // abc.cpp 
         # include<iostream.h>
           void main()
          {
            int a=1,b=2,c;
            c=a+b;
            cout<<"c="<<c<<endl;
          }

in VC++6, it passed compling and linking all right. If use <iostream> to replace <iostream.h>, the vc6 prompts:

error C2065: 'cout' : undeclared identifier
error C2065: 'endl' : undeclared identifier

BUT in VC7, use <iostream.h>, it says:

fatal error cannot open include file 'iostream.h': no such file or directory.

If changed to <iostream>, it says:

Error c2065: 'cout': undeclared identifier.
Error c2065: 'endl': undeclared identifier.

What is the reason? How deal with?

**MadCow257** · 01-28-2006

the problem is namespacing

The simplest solution is to add "using namespace std" after "#include <iostream>"

Another bad thing is your use of void main, main should have type int

EDIT
Here is you code, nicely formatted and working

Code:

// abc.cpp 
# include<iostream>
using namespace std;
int main()
{
     int a=1,b=2,c;
     c=a+b;
     cout<<"c="<<c<<endl;
}

**SlyMaelstrom** · 01-28-2006

<iostream> (as well as all the conventional C++ libraries) is defined under the std namespace. Either use the appropriate using namespace line at the top of your program:

Code:

#include <iostream>

using namespace std;

or preceed all functions and identifiers from those libraries with its namespace.

Code:

std::cout << std::endl;

**7stud** · 01-28-2006

It's apparent that you are a beginner, so for now don't worry about what everything means, and just use this template for all your programs:

Code:

#include <iostream>
using namespace std;

int main()
{
 
     //your code here

     return 0;

}

Depending on what compiler you are using, you may need to add:

Code:

cin.get();

before the line:

Code:

return 0;

to keep the console window open so that you can see the output from your program.

**siavoshkc** · 01-28-2006

Or use iostream.h to know whats going on.

**SirCrono6** · 01-28-2006

» Or use iostream.h to know whats going on.
What do you mean by that?

**siavoshkc** · 01-28-2006

Just

Code:

#include<iostream.h>

And no need to specify a namespace. If it compiles then it's OK.

**SirCrono6** · 01-28-2006

No it's not.

**siavoshkc** · 01-28-2006

Don't post like that if so, i will answer: IT IS!

**SirCrono6** · 01-28-2006

And I will answer: <iostream.h> is a non-standard header in C++, so don't use it. Period. And if it compiles okay, throw out your compiler and get a new one.

**SlyMaelstrom** · 01-28-2006

I don't know a single modern C++ compiler that won't compile <iostream.h>.

They'll all give a warning though. It's a bad habit to use antiquated headers, as they might lose their functionality in the future. This is why you use <iostream>.

**SirCrono6** · 01-28-2006

Hmm, you're right. Well then, if it doesn't give a warning...

**siavoshkc** · 01-28-2006

>>And if it compiles okay, throw out your compiler and get a new one.
Then we should throw out the microsoft!!!

**laserlight** · 01-29-2006

Then we should throw out the microsoft!!!

No, you should throw out Microsoft Visual C++ 6. If you insist on using a Microsoft compiler, the one from Visual C++ 2005 Express should be fine, especially since the package is available as a free download till November this year, or something like that, and you can continue using it for free even after that.

**siavoshkc** · 01-29-2006

The cost of the IDE is not a problem for me (look where am i). But I don't have any problem with my compiler, I like it! I think it is not a problem for a compiler to compile a code, the problem is when it doesn't.