I have created a file called untitled1.cpp in dev-cpp with the following script:
#include <iostream.h>
using namespace std;
int main(){
cout << "C++";
return 0;
}
But the compiler shows errors like:
1 F:\Dev-Cpp\include\c++\3.4.2\backward\iostream.h:31,
from F:\Dev-Cpp\Untitled1.cpp In file included from
include/c++/3.4.2/backward/iostream.h:31, from
F:\Dev-Cpp\Untitled1.cpp 32:2
F:\Dev-Cpp\include\c++\3.4.2\backward\backward_warning.h #warning This
file includes at least one deprecated or antiquated header. Please
consider using one of the 32 headers found in section 17.4.1.2 of the
C++ standard. Examples include substituting the header for the
header for C++ includes, or instead of the deprecated
header . To disable this warning use -Wno-deprecated.
What is the error that I have? How do I fix it?
In C++ you import the standard library without using the .h suffix.
#include <iostream>
So your fixed example:
#include <iostream>
int main(int argc, char **argv) {
std::cout << "C++";
return 0;
}
Your code is not standard C++. You should say #include <iostream> (no ".h"!). Whatever source you have been learning this from is about 25 years out of date, and you should consider getting some more modern material.
(The "iostreams.h" header was part of a very early non-standard library in the early 1990s, and so it's being kept around for "compatibility" reasons, or to catch very inert programmers and give them a helpful hint.)
Use header file as #include<iostream> instead of #include<iostream.h>
Include iostream instead of iostream.h
This is just a warning.
I think that you could try to include iostream instead of iostream.h in order to fix it.
It says that the header, in this case, iostream.h is deprecated or antiquated. (You only have one header, so that's the one! Just read the error message!)
So you'll have to use iostream, not iostream.h.
You've posted the reason in your question already!
This file includes at least one deprecated or antiquated header.
The real question should therefore be: "Which one is antiquated, how do I replace it?", not "What's the error". Answer: Use <iostream>. The <*.h> versions are pre-standard, legacy headers.
So: Read error messages, people.
Related
I have included stdio.h into my C++ project, why am I still getting this error? Also, after I added #include , printf(), in my code, was no longer underlined in red to suggest that there was any error.
Also, I would like to use the function, format(). Which library is that found in?
you must include stdio.h instead of cstdio.h
#include <stdio.h>
Use #include< cstdio>
using namespace std;
after that you can use printf()
I'm using turboc++ 4.0 and Visual studio 2013. I just started learning programming. when I write the code.
#include<iostream.h>
#include<conio.h>
int main()
{
cout<<"hello!";
getch();
return 0;
}
it works well in turbo, but visual stdio shows an error
fatal error C1083: Cannot open include file: 'iostream.h': No such file or directory.
and when I use
using namespace std;
it shows another error about using getch();.
Does every compiler have its own syntax?
"Does every compiler have it's own syntax?"
No, there's a standard every compiler needs to implement.
Turbo-C++ was made before any standards were established and is merely the only compiler still around, that doesn't implement them.
The standard compliant way to write your program looks like:
#include <iostream>
int main() {
std::cout<<"hello!" << std::endl;
char dummy;
std::cin >> dummy;
}
Note: You shouldn't use using namespace std;, but explicitly put the std:: scope when needed, or use using std::cout cout;, etc.
Turbo C++ is from the middle or early 1990's, before the standardization of C++.
At that time the effective standard for C++ was the ARM, the Annotated Reference Manual by Bjarne Stroustrup and Margaret Ellis (IIRC), and it used <iostream.h>.
With the first standardization in 1998 <iostream.h> was dropped, and replaced with just <iostream>. The standard header places cin and cout in namespace std, so you can't just change the header name. It's not guaranteed, but you may possibly be able to make your code work by writing
#include <iostream>
using namespace std;
I am at the absolutely newest level of new when it comes to C++. It may seem like a noob mistake, but I think I'm missing something with my first program, "Hello World!".
I'm running from Ubuntu (not sure if this is any different from working with Windows), and I'm using a book called Teach Yourself C++ in 21 Days.
The code I'm resembling looks exactly like this:
#include <iostream.h>
int main()
{
cout <<"Hello World!\n";
return 0;
}
I have this exactly in my text editor, but I keep getting greeted by the same error whenever I try to compile it!
first.cpp:2:22: fatal error: iostream.h: No such file or directory
compilation terminated.
I'm pretty distressed as this is literally the first step in my coding career! I'm not sure if ubuntu needs to be treated differently than Windows (which is what the book is using as reference).
Help!
There are two problems here:
You need to omit the .h suffix:
#include <iostream>
Also, cout is an unqualified name, and needs to be qualified with the std namespace since you are not using namespace std:
std::cout << "Hello World!\n";
There shouldn't be any iostream.h it's simply called iostream and should look like this:
#include <iostream>
int main()
{
std::cout <<"Hello World!\n";
return 0;
}
(also notice the std:: before the cout, since it means that it's from the standard namespace.)
You want just iostream
#include <iostream>
I suspect the book is very old. Names are qualified in the std namespace, so you may want to add
using namespace std;
For now at least.
use
#include <iostream>
in general STL header file don't have a .h
you need to compile using g++ compiler, not by gcc
g++ hello.cpp
So, I have this question. Why does cout throws
error C2065: 'cout' : undeclared identifier
I am using Visual Studio 2012 as an IDE and I am writing a school project. I have everything done except an example file. So I am trying to write something on the screen like this:
#include "iostream"
#include "stdafx.h"
using namespace std;
int main()
{
cout<<"example";
return 0;
}
So the problem is with cout... printf works fine, but I want to use cout.
EDIT:
I've changed "" to <> but it is not helping. Also I am using this code only for example... This is not the whole project.
stdafx.h shall be the first include directive in your source file.
Switch files and convert the second include to <>, as other suggested.
#include "stdafx.h"
#include <iostream>
See this post for more information.
First of all:
#include <iostream>
instead of #include "iostream"
Secondly, it is generally considered bad practice to write using namespace std;, even though most courses start with that. It is better to only use what you actually need, in your case:
using std::cout;
#include "iostream"
should be
#include <iostream>
Quoting from this post:difference-between-iostream-and-iostream-quotes-in-include
By courtesy of #Jerry Coffin's answer:
When you use < >, the compiler only looks in the system-designated directory/directories (e.g., whatever you've set in the include environment variable) for the header.
When you use " ", the compiler looks in the local directory first, and if that fails, re-searches just like you'd used < >. Technically, (i.e., according to the standard) that doesn't have to be the "local" directory, but that's how it works in essentially every compiler of which I'm aware).
EDIT:
However, the root cause is that stdafx.h is a precompiled header. Visual C++ will not compile anything before the #include "stdafx.h" in the source file, unless the compile option /Yu'stdafx.h' is unchecked (by default); it assumes all code in the source up to and including that line is already compiled. However, it is still better to use <> with iostream not to confuse reader of the code.
If you use #include <iostream> with the <> instead of "" then it should work. Right now, the compiler doesn't know where to find the iostream library.
Also, you might want to change cout<<"example"; to cout<<"example"<<endl; for a new line so that it formats correctly.
Came across this issue while trying to build a Dynamic Linked Library. Make sure that instead of the #include stdafx.h you specify the following include on the first line of your .cpp file:
#include "pch.h"
This should also be the case for VS2017 or earlier.
This error also occurred in the Visual Studio 2017 IDE. Moving stdafx.h to the top solved the error.
For more on stdafx.h, see What's the use for "stdafx.h" in Visual Studio?
I have the following source code. Which compiles fine in visual studios and g++ 3.4.6; but not with g++ 4.4.3 (on a newer ubuntu machine). The newer compiler requires that I explicitly include to use atoi. I am just trying to figure out what might have changed to cause this behavior. Is it sstream header file previously included cstdlib and no longer does so. Or is it the compiler behavior that has changed.
#include <sstream>
int main()
{
char str1[]="123";
int i = atoi(str1);
printf ("value = %d",i);
return 0;
}
You also need to include <cstdio> for printf().
Technically, if you include the headers of the form <cname> instead of <name.h>, you also need to qualify the names from the standard library using std::. A lot of standard library implementations are relaxed when it comes to this, though, and also put the names into the global namespace.
It's implementation-dependent which headers are included by which other headers, so you should always be sure to include all the headers that you need and not assume that they will be included automatically.
I'm using GCC 4.4.5 on Debian, and the headers have changed so you will not bring in the headers necessary. You need to #include <cstdlib> and #include <cstdio> to get atoi and printf, as the compiler complained about both being missing.
#include <sstream>
#include <cstdio>
#include <cstdlib>
int main()
{
char str1[]="123";
int i = std::atoi(str1);
std::printf ("value = %d",i);
return 0;
}
Well yes. That is common. You should always include ALL headers that you are directly using and not depend on the fact that those headers are already included.
Compiler behavior is what would have changed... the <sstream> doesn't use atoi.
Arguably you should have always done #include <cstdlib>, and you'd gotten lucky with your previous compilers.
As James McNeillis points out, you should also #include <cstdio> in order to use the printf function.