blocks|key|321478|text|在开始这个程序之前，去掉所有的代码，在main中做一个简单的hello+world。仅包括iostream和使用命名空间%25+std；。一点一点地添加到它中，以找到您的问题。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|321479|cout+<<+"hi"+<<+endl;|code-block|syntax|javascript|321480|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

before you begin this program get rid of all the code and do a simple hello world inside of main. Only include iostream and using namespace std;.
Little by little add to it to find your issue.

<pre><code>cout &lt;&lt; "hi" &lt;&lt; endl;
</code></pre>

blocks|key|323949|text|下面的代码为我编译并正常运行，使用的是gcc。尝试复制/粘贴它，看看它是否有效。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|323950|#include+<iostream>
using+namespace+std;

int+bob+(int+a)+{+cout+<<+"hey"+<<+endl;+return+0;+};

int+main+()+{
++++int+a+=+1;
++++bob(a);
++++return+0;
}|code-block|syntax|javascript|323951|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

The code below compiles and runs properly for me using gcc. Try copy/pasting this and see if it works. 

<pre><code>#include &lt;iostream&gt;
using namespace std;

int bob (int a) { cout &lt;&lt; "hey" &lt;&lt; endl; return 0; };

int main () {
 int a = 1;
 bob(a);
 return 0;
}
</code></pre>

blocks|key|3288554|text|如果您唯一包含的文件是iostream，但它仍然显示未定义，那么iostream可能没有包含它应该包含的内容。有没有可能你的项目中有一个名为"iostream“的空文件？|type|unstyled|depth|inlineStyleRanges|entityRanges|data|3288555|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|D|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|E|8|@]|9|@]|A|$]]]|C|$]]

If the only file you include is iostream and it still says undefined, then maybe iostream doesn't contain what it's supposed to. Is it possible that you have an empty file coincidentally named "iostream" in your project?

blocks|key|321499|text|您确定它正在编译为C%2B%2B吗？检查你的文件名(应该以.cpp结尾)。检查您的项目设置。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|321500|您的程序没有任何问题，而且cout是在namespace+std中。你安装的VS2010Beta2是有缺陷的，我认为不仅仅是你的安装有问题。|321501|我认为VS2010还没有为C%2B%2B做好准备。标准的"Hello，World“程序在Beta1上不起作用。我刚刚尝试创建一个测试Win32控制台应用程序，生成的test.cpp文件没有main()函数。|321502|我对VS2010有一种非常非常不好的预感。|321503|entityMap^0|P|4|0|D|4|J|D|0|26|8|2I|6|0|0^^$0|@$1|2|3|4|5|6|7|N|8|@$9|O|A|P|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|Q|8|@$9|R|A|S|B|C]|$9|T|A|U|B|C]]|D|@]|E|$]]|$1|H|3|I|5|6|7|V|8|@$9|W|A|X|B|C]|$9|Y|A|Z|B|C]]|D|@]|E|$]]|$1|J|3|K|5|6|7|10|8|@]|D|@]|E|$]]|$1|L|3|-4|5|6|7|11|8|@]|D|@]|E|$]]]|M|$]]

Are you sure it's compiling as C++? Check your file name (it should end in <code>.cpp</code>). Check your project settings.

There's simply nothing wrong with your program, and <code>cout</code> is in <code>namespace std</code>. Your installation of VS 2010 Beta 2 is defective, and I don't think it's just your installation.

I don't think VS 2010 is ready for C++ yet. The standard "Hello, World" program didn't work on Beta 1. I just tried creating a test Win32 console application, and the generated <code>test.cpp</code> file didn't have a <code>main()</code> function.

I've got a really, really bad feeling about VS 2010.

blocks|key|3288567|text|我有VS2010，Beta1和Beta2(一个在我的工作机器上，一个在家里)，我已经使用了很多std，没有出现问题。尝试键入：|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|3288568|std::|code-block|syntax|javascript|3288569|看看Intellisense能不能给你带来什么。如果它提供了除cout之外的常见内容(abort、abs、acos等)，那么，这就相当令人困惑了。在这种情况下，一定要查看您的C%2B%2B标头。|3288570|除此之外，我只想补充一下，以确保您正在运行常规的空项目(而不是CLR，因为在CLR中，Intellisense是残缺的)，并且您至少尝试过一次构建该项目。正如我在一条评论中提到的，一旦添加了include，VS2010就会解析文件；可能是某些东西卡住了解析器，它没有立即“找到”cout。(在这种情况下，尝试重新启动VS可能？)|3288571|entityMap^0|1B|3|0|0|V|4|17|5|1D|3|1H|4|0|2N|7|3V|4|0^^$0|@$1|2|3|4|5|6|7|Q|8|@$9|R|A|S|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|T|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|U|8|@$9|V|A|W|B|C]|$9|X|A|Y|B|C]|$9|Z|A|10|B|C]|$9|11|A|12|B|C]]|D|@]|E|$]]|$1|M|3|N|5|6|7|13|8|@$9|14|A|15|B|C]|$9|16|A|17|B|C]]|D|@]|E|$]]|$1|O|3|-4|5|6|7|18|8|@]|D|@]|E|$]]]|P|$]]

I have VS2010, Beta 1 and Beta 2 (one on my work machine and one at home), and I've used <code>std</code> plenty without issues. Try typing:

<pre><code>std::
</code></pre>

And see if Intellisense gives you anything. If it gives you the usual stuff (<code>abort</code>, <code>abs</code>, <code>acos</code>, etc.), except for <code>cout</code>, well then, that is quite a puzzler. Definitely look into your C++ headers in that case.

Beyond that, I would just add to make sure you're running a regular, empty project (not CLR, where Intellisense is crippled), and that you've actually attempted to build the project at least once. As I mentioned in a comment, VS2010 parses files once you've added an <code>include</code>; it could be that something stuck the parser and it didn't "find" <code>cout</code> right away. (In which case, try restarting VS maybe?)

blocks|key|323963|text|当我在C%2B%2B代码中使用.c文件扩展名时，我看到过类似的事情。除此之外，我不得不同意每个人关于buggy安装的看法。如果你尝试用VS的早期版本编译这个项目，它能起作用吗？试试VC%2B%2B+Express2008吧。在msdn上是免费的。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|323964|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|D|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|E|8|@]|9|@]|A|$]]]|C|$]]

I've seen similar things happen when I was using the .c file extension with C++ code. Other than that, I'd have to agree with everyone about a buggy installation. Does it work if you try to compile the project with an earlier release of VS? Try VC++ Express 2008. Its free on msdn.

blocks|key|323389|text|type|unstyled|depth|inlineStyleRanges|entityRanges|data|323390|是编译器的问题--我现在使用的是Eclipse+Galileo，这个程序运行起来简直是个奇迹|323391|323392|entityMap^0|0|0|0^^$0|@$1|2|3|-4|4|5|6|F|7|@]|8|@]|9|$]]|$1|A|3|B|4|5|6|G|7|@]|8|@]|9|$]]|$1|C|3|-4|4|5|6|H|7|@]|8|@]|9|$]]|$1|D|3|-4|4|5|6|I|7|@]|8|@]|9|$]]]|E|$]]

<hr>

It was the compiler - I'm now using Eclipse Galileo and the program works like a wonder

<hr>

blocks|key|3075209|text|通常存储在C:\Program+Files\Microsoft+Visual+Studio+8\VC\include文件夹中。首先检查它是否还在那里。然后选择Tools+%2B+Options，Projects+and+Solutions，VC%2B%2B+Directories，在"Show+Directories+for“组合框中选择"Include+files”，然后仔细检查$(VCInstallDir)include是否在列表的顶部。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|3075210|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|D|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|E|8|@]|9|@]|A|$]]]|C|$]]

is normally stored in the C:\Program Files\Microsoft Visual Studio 8\VC\include folder. First check if it is still there. Then choose Tools + Options, Projects and Solutions, VC++ Directories, choose "Include files" in the "Show Directories for" combobox and double-check that $(VCInstallDir)include is on top of the list.

blocks|key|323984|text|当我从头开始一个ms+c%2B%2B+2010项目时，我遇到了同样的问题-我删除了由ms生成的所有头文件，但使用了：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|323985|#include+"stdafx.h"
#include+<iostream>
using+namespace+std;

int+main()+{
+++cout+<<+"hey"+<<+endl;
+++return+0;
}|code-block|syntax|javascript|323986|我不得不包含stdafx.h，因为它导致了不包含它的错误。|offset|length|style|CODE|323987|entityMap^0|0|0|6|8|0^^$0|@$1|2|3|4|5|6|7|O|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|P|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|Q|8|@$I|R|J|S|K|L]]|9|@]|A|$]]|$1|M|3|-4|5|6|7|T|8|@]|9|@]|A|$]]]|N|$]]

I had the same issue when starting a ms c++ 2010 project from scratch - I removed all of the header files generated by ms and but used:

<pre><code>#include "stdafx.h"
#include &lt;iostream&gt;
using namespace std;

int main() {
 cout &lt;&lt; "hey" &lt;&lt; endl;
 return 0;
}
</code></pre>

I had to include <code>stdafx.h</code> as it caused an error not having it in.

blocks|key|3075243|text|我已经看到，如果你使用|type|unstyled|depth|inlineStyleRanges|entityRanges|data|3075244|#include+<iostream.h>|code-block|syntax|javascript|3075245|然后你就会有问题了。|3075246|如果您使用|3075247|#include+<iostream>++|3075248|(注意-没有.h)|3075249|那么你就不会得到你提到的问题了。|3075250|entityMap^0|0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|S|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|T|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|U|8|@]|9|@]|A|$]]|$1|I|3|J|5|6|7|V|8|@]|9|@]|A|$]]|$1|K|3|L|5|D|7|W|8|@]|9|@]|A|$E|F]]|$1|M|3|N|5|6|7|X|8|@]|9|@]|A|$]]|$1|O|3|P|5|6|7|Y|8|@]|9|@]|A|$]]|$1|Q|3|-4|5|6|7|Z|8|@]|9|@]|A|$]]]|R|$]]

I have seen that if you use

<pre><code>#include &lt;iostream.h&gt;
</code></pre>

then you will get the problem.

If you use 

<pre><code>#include &lt;iostream&gt; 
</code></pre>

(notice - without the .h)

then you will not get the problem you mentioned.

blocks|key|326183|text|试一下，它会起作用的。我在Windows+XP，Visual+Studio+2010学习版中检查了它。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|326184|#include+"stdafx.h"
#include+<iostream>
using+namespace+std;

void+main(+)+
{
+++int+i+=+0;
+++cout+<<+"Enter+a+number:+";
+++cin+>>+i;
}|code-block|syntax|javascript|326185|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

Try it, it will work. I checked it in Windows XP, Visual Studio 2010 Express.

<pre><code>#include "stdafx.h"
#include &lt;iostream&gt;
using namespace std;

void main( ) 
{
 int i = 0;
 cout &lt;&lt; "Enter a number: ";
 cin &gt;&gt; i;
}
</code></pre>

blocks|key|326187|text|如果您开始了一个需要#include+"stdafx.h"行的项目，请将它放在第一位。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|326188|entityMap^0|A|J|0^^$0|@$1|2|3|4|5|6|7|H|8|@$9|I|A|J|B|C]]|D|@]|E|$]]|$1|F|3|-4|5|6|7|K|8|@]|D|@]|E|$]]]|G|$]]

If you started a project requiring the <code>#include "stdafx.h"</code> line, put it first.

blocks|key|3075326|text|把代码拿来|type|unstyled|depth|inlineStyleRanges|entityRanges|data|3075327|#include+<iostream>
using+namespace+std;|code-block|syntax|javascript|3075328|在您的.cpp文件之外，创建一个头文件并将其放入.h文件中。然后添加|3075329|#include+"whatever+your+header+file+is+named.h"|3075330|在您的.cpp代码的顶部。然后再运行一次。|3075331|entityMap^0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|O|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|P|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|Q|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|R|8|@]|9|@]|A|$E|F]]|$1|K|3|L|5|6|7|S|8|@]|9|@]|A|$]]|$1|M|3|-4|5|6|7|T|8|@]|9|@]|A|$]]]|N|$]]

Take the code 

<pre><code>#include &lt;iostream&gt;
using namespace std;
</code></pre>

out of your .cpp file, create a header file and put this in the .h file. Then add

<pre><code>#include "whatever your header file is named.h"
</code></pre>

at the top of your .cpp code. Then run it again.

blocks|key|321580|text|写这段代码，它工作得很好..|type|unstyled|depth|inlineStyleRanges|entityRanges|data|321581|#include+"stdafx.h"
#include+<iostream>

using+namespace+std;

int+main()
{
+cout<<"Hello+World!";
++return+0;
}|code-block|syntax|javascript|321582|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

write this code, it works perfectly..

<pre><code>#include "stdafx.h"
#include &lt;iostream&gt;

using namespace std;

int main()
{
 cout&lt;&lt;"Hello World!";
 return 0;
}
</code></pre>

blocks|key|3075454|text|我在Visual+Studio+C%2B%2B+2010上也遇到了同样的问题。这很容易修复。在main()函数上面，只需用下面的代码替换标准的include行，但是在include前面用井号。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|3075455|#+include+"stdafx.h"
#+include+<iostream>
using++namespace+std;|code-block|syntax|javascript|3075456|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

I had same problem on Visual Studio C++ 2010. It's easy to fix. Above the main() function just replace the standard include lines with this below but with the pound symbol in front of the includes.

<pre><code># include "stdafx.h"
# include &lt;iostream&gt;
using namespace std;
</code></pre>

blocks|key|3288901|text|在刚刚安装了VS2010之后，我遇到了这个错误，只是试图让一个几乎相同的程序正常工作。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|3288902|我以前在unix风格的机器上做过普通的C编码，决定自己尝试一下。|3288903|我尝试的第一个程序是：|3288904|#include+"stdafx.h"


int+_tmain(int+argc,+_TCHAR*+argv[])
{
++++cout+<<+"Hello+World!";
++++return+0;
}|code-block|syntax|javascript|3288905|这里需要注意的一件事是……如果你曾经做过C语言编程，|3288906|int+_tmain(int+argc,+_TCHAR*+argv[])|3288907|看起来很奇怪。它应该是：|3288908|int+main(+int+argc,+char+**+argv+)|3288909|在我的示例中，我只是将程序更改为：|3288910|#include+<iostream>
using+namespace+std;

int+main()
{
+++++cout+<<+"Hello+world+from++VS+2010!\n";
+++++return+0;
}|3288911|它运行得很好。|3288912|注意:使用CTRL+%2B+F5可以让控制台窗口保持不动，这样您就可以看到结果了。|3288913|entityMap^0|0|0|0|0|0|0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|12|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|13|8|@]|9|@]|A|$]]|$1|D|3|E|5|6|7|14|8|@]|9|@]|A|$]]|$1|F|3|G|5|H|7|15|8|@]|9|@]|A|$I|J]]|$1|K|3|L|5|6|7|16|8|@]|9|@]|A|$]]|$1|M|3|N|5|H|7|17|8|@]|9|@]|A|$I|J]]|$1|O|3|P|5|6|7|18|8|@]|9|@]|A|$]]|$1|Q|3|R|5|H|7|19|8|@]|9|@]|A|$I|J]]|$1|S|3|T|5|6|7|1A|8|@]|9|@]|A|$]]|$1|U|3|V|5|H|7|1B|8|@]|9|@]|A|$I|J]]|$1|W|3|X|5|6|7|1C|8|@]|9|@]|A|$]]|$1|Y|3|Z|5|6|7|1D|8|@]|9|@]|A|$]]|$1|10|3|-4|5|6|7|1E|8|@]|9|@]|A|$]]]|11|$]]

I ran across this error after just having installed vs 2010 and just trying to get a nearly identical program to work. 

I've done vanilla C coding on unix-style boxes before, decided I'd play with this a bit myself. 

The first program I tried was:

<pre><code>#include "stdafx.h"


int _tmain(int argc, _TCHAR* argv[])
{
 cout &lt;&lt; "Hello World!";
 return 0;
}
</code></pre>

The big thing to notice here... if you've EVER done any C coding, 

<pre><code>int _tmain(int argc, _TCHAR* argv[])
</code></pre>

Looks weird. it should be:

<pre><code>int main( int argc, char ** argv )
</code></pre>

In my case I just changed the program to:

<pre><code>#include &lt;iostream&gt;
using namespace std;

int main()
{
 cout &lt;&lt; "Hello world from VS 2010!\n";
 return 0;
}
</code></pre>

And it worked fine.

Note: Use CTRL + F5 so that the console window sticks around so you can see the results.

blocks|key|323543|text|创建项目时，没有正确设置“使用预编译头”。在属性->C/C%2B%2B->预编译头中更改它。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|323544|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|D|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|E|8|@]|9|@]|A|$]]]|C|$]]

When you created your project, you did not set 'use precompiled headers' correctly. Change it in properties->C/C++->precompiled headers.

blocks|key|3288950|text|在Visual+studio中，使用"stdafx.h“下的所有头文件。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|3288951|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|D|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|E|8|@]|9|@]|A|$]]]|C|$]]

In Visual studio use all your header filer below "stdafx.h".

blocks|key|3075582|text|include+"stdafx.h"正常|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|3075583|但除非包含using+namespace+std，否则不能使用cout|3075584|如果没有包含名称空间标准，则必须编写std::cout而不是简单cout|3075585|entityMap^0|0|I|0|5|J|V|4|0|I|9|W|4|0^^$0|@$1|2|3|4|5|6|7|L|8|@$9|M|A|N|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|O|8|@$9|P|A|Q|B|C]|$9|R|A|S|B|C]]|D|@]|E|$]]|$1|H|3|I|5|6|7|T|8|@$9|U|A|V|B|C]|$9|W|A|X|B|C]]|D|@]|E|$]]|$1|J|3|-4|5|6|7|Y|8|@]|D|@]|E|$]]]|K|$]]

The <code>include "stdafx.h"</code> is ok

But you can't use <code>cout</code> unless you have included <code>using namespace std</code> 

If you have not included namespace std you have to write <code>std::cout</code> instead of simple <code>cout</code>

blocks|key|326422|text|在Visual+Studio中，你必须对cpp文件的第一个包含项进行#include+"stdafx.h"和be+。例如：：|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|BOLD|entityRanges|data|326423|这些将不会工作。|326424|#include+<iostream>
using+namespace+std;
int+main+()+{
++++cout+<<+"hey"+<<+endl;
++++return+0;
}




#include+<iostream>
#include+"stdafx.h"
using+namespace+std;
int+main+()+{
++++cout+<<+"hey"+<<+endl;
++++return+0;
}|code-block|syntax|javascript|326425|这个就行了。|326426|#include+"stdafx.h"
#include+<iostream>
using+namespace+std;
int+main+()+{
++++cout+<<+"hey"+<<+endl;
++++return+0;
}|326427|Here+is+a+great+answer+on+what+the+stdafx.h+header+does.|326428|entityMap|0|LINK|mutability|MUTABLE|url|https://stackoverflow.com/a/4726838/2528907^0|Y|J|1L|4|0|0|0|0|0|0|1K|0|0^^$0|@$1|2|3|4|5|6|7|11|8|@$9|12|A|13|B|C]|$9|14|A|15|B|D]]|E|@]|F|$]]|$1|G|3|H|5|6|7|16|8|@]|E|@]|F|$]]|$1|I|3|J|5|K|7|17|8|@]|E|@]|F|$L|M]]|$1|N|3|O|5|6|7|18|8|@]|E|@]|F|$]]|$1|P|3|Q|5|K|7|19|8|@]|E|@]|F|$L|M]]|$1|R|3|S|5|6|7|1A|8|@]|E|@$9|1B|A|1C|1|1D]]|F|$]]|$1|T|3|-4|5|6|7|1E|8|@]|E|@]|F|$]]]|U|$V|$5|W|X|Y|F|$Z|10]]]]

In Visual Studio you must <code>#include "stdafx.h"</code> and be the first include of the cpp file. For instance:

These will not work.

<pre><code>#include &lt;iostream&gt;
using namespace std;
int main () {
 cout &lt;&lt; "hey" &lt;&lt; endl;
 return 0;
}




#include &lt;iostream&gt;
#include "stdafx.h"
using namespace std;
int main () {
 cout &lt;&lt; "hey" &lt;&lt; endl;
 return 0;
}
</code></pre>

This will do.

<pre><code>#include "stdafx.h"
#include &lt;iostream&gt;
using namespace std;
int main () {
 cout &lt;&lt; "hey" &lt;&lt; endl;
 return 0;
}
</code></pre>

<a href="https://stackoverflow.com/a/4726838/2528907">Here is a great answer on what the stdafx.h header does.</a>

blocks|key|3288983|text|只要使用printf就可以了！|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|3288984|在printf的stdafx.h头文件中包含stdio.h。|3288985|entityMap^0|4|6|0|1|6|8|8|M|7|0^^$0|@$1|2|3|4|5|6|7|J|8|@$9|K|A|L|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|M|8|@$9|N|A|O|B|C]|$9|P|A|Q|B|C]|$9|R|A|S|B|C]]|D|@]|E|$]]|$1|H|3|-4|5|6|7|T|8|@]|D|@]|E|$]]]|I|$]]

Just use <code>printf</code>!

Include <code>stdio.h</code> in your <code>stdafx.h</code> header file for <code>printf</code>.

blocks|key|3289003|text|我来这里是因为我有同样的问题，但当我执行#include+"stdafx.h"时，它说它找不到那个文件。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|3289004|给我带来好处的是：#include+<algorithm>。|3289005|我使用Microsoft+Visual+Studio+2008。|3289006|这些都是你可以使用的东西，包括。‘'count'：Link|3289007|entityMap|0|LINK|mutability|MUTABLE|url|http://www.cplusplus.com/reference/algorithm/^0|K|J|0|9|K|0|0|P|4|0|0^^$0|@$1|2|3|4|5|6|7|T|8|@$9|U|A|V|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|W|8|@$9|X|A|Y|B|C]]|D|@]|E|$]]|$1|H|3|I|5|6|7|Z|8|@]|D|@]|E|$]]|$1|J|3|K|5|6|7|10|8|@]|D|@$9|11|A|12|1|13]]|E|$]]|$1|L|3|-4|5|6|7|14|8|@]|D|@]|E|$]]]|M|$N|$5|O|P|Q|E|$R|S]]]]

I came here because I had the same problem, but when I did <code>#include "stdafx.h"</code> it said it did not find that file. 
What did the trick for me was: <code>#include &lt;algorithm&gt;</code>. 
I use Microsoft Visual Studio 2008. 
These are the things that you can use then, incl. 'count': <a href="http://www.cplusplus.com/reference/algorithm/" rel="nofollow noreferrer">Link</a>

blocks|key|3289018|text|通过在代码顶部插入以下行来包含std库：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|3289019|using+namespace+std;|code-block|syntax|javascript|3289020|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

Include the std library by inserting the following line at the top of your code:

<pre><code>using namespace std;
</code></pre>

blocks|key|3289033|text|在我的例子中，这是一个愚蠢的解决方案：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|3289034|//+Example+a
#include+<iostream>++++
#include+"stdafx.h"|code-block|syntax|javascript|3289035|上面是按照示例a排序的，当我将其更改为类似于下面的示例b时…|3289036|//+Example+b
#include+"stdafx.h"
#include+<iostream>++|3289037|我的代码编译得很棒。试试看，保证有效。|3289038|entityMap^0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|O|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|P|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|Q|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|R|8|@]|9|@]|A|$E|F]]|$1|K|3|L|5|6|7|S|8|@]|9|@]|A|$]]|$1|M|3|-4|5|6|7|T|8|@]|9|@]|A|$]]]|N|$]]

Such a silly solution in my case:

<pre><code>// Example a
#include &lt;iostream&gt; 
#include "stdafx.h"
</code></pre>

The above was odered as per example a, when I changed it to resemble example b below...

<pre><code>// Example b
#include "stdafx.h"
#include &lt;iostream&gt; 
</code></pre>

My code compiled like a charm. Try it, guaranteed to work.

blocks|key|323597|text|在VS2017中，stdafx.h似乎被pch.h取代参见this+article，|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|323598|所以使用：|323599|#include+"pch.h"
#include+<iostream>

using+namespace+std;

int+main()+{
++++cout+<<+"Enter+2+numbers:"+<<+endl;|code-block|syntax|javascript|323600|entityMap|0|LINK|mutability|MUTABLE|url|https://social.msdn.microsoft.com/Forums/vstudio/en-US/10b0f517-5086-45ac-96b3-1d7c79985915/cannot-open-source-file-quotstdafxhquot?forum=vcgeneral^0|9|8|K|5|T|C|0|0|0|0^^$0|@$1|2|3|4|5|6|7|U|8|@$9|V|A|W|B|C]|$9|X|A|Y|B|C]]|D|@$9|Z|A|10|1|11]]|E|$]]|$1|F|3|G|5|6|7|12|8|@]|D|@]|E|$]]|$1|H|3|I|5|J|7|13|8|@]|D|@]|E|$K|L]]|$1|M|3|-4|5|6|7|14|8|@]|D|@]|E|$]]]|N|$O|$5|P|Q|R|E|$S|T]]]]

In VS2017, <code>stdafx.h</code> seems to be replaced by <code>pch.h</code> see <a href="https://social.msdn.microsoft.com/Forums/vstudio/en-US/10b0f517-5086-45ac-96b3-1d7c79985915/cannot-open-source-file-quotstdafxhquot?forum=vcgeneral" rel="nofollow noreferrer">this article</a>,

so use:

<pre><code>#include "pch.h"
#include &lt;iostream&gt;

using namespace std;

int main() {
 cout &lt;&lt; "Enter 2 numbers:" &lt;&lt; endl;
</code></pre>

blocks|key|324187|text|有这个问题，当头文件声明“使用命名空间std;”时，似乎让GNU编译器感到困惑；不管怎样，这是糟糕的风格！|type|unstyled|depth|inlineStyleRanges|entityRanges|data|324188|解决方案是提供std::cout+...并将"using+namespace+std“移至实现文件。|324189|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|F|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|G|8|@]|9|@]|A|$]]|$1|D|3|-4|5|6|7|H|8|@]|9|@]|A|$]]]|E|$]]

Had this problem, when header files declared &quot;using namespace std;&quot;, seems to be confusing for GNU compiler;
anyway is bad style!
Solution was providing std::cout ... in headers and moving &quot;using namespace std&quot; to the implementation file.

I am working on the 'driver' part of my programing assignment and i keep getting this absurd error:

<blockquote>
 error C2065: 'cout' : undeclared identifier
</blockquote>

I have even tried using the std::cout but i get another error that says: IntelliSense: namespace "std" has no member "cout" when i have declared using namespace std, included iostream + i even tried to use ostream

I know it's a standard noob question but this has stumped me and I'm a novice (meaning: I've programed before...)

<pre><code>#include &lt;iostream&gt;
using namespace std;

int main () {
 cout &lt;&lt; "hey" &lt;&lt; endl;
 return 0;
}
</code></pre>

I'm using Visual Studio 2010 and running Windows 7. All of the .h files have "using namespace std" and include iostream and ostream.

error C2065: 'cout' : undeclared identifier

翻译质量差，导致语言生硬或混乱。

没有提供实际的解决方法或示例。

解答不清晰，无法理解或解决问题。

页面排版不美观，阅读体验差。

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我正在做我的编程任务中的“驱动”部分，我总是收到这个荒谬的错误：错误C2065：'cout‘：未声明的标识符我甚至尝试过使用命名空间std：：cout，但我收到另一个错误消息：IntelliSense:命名空间"std“没有成员"cout"当我已经使用命名空间std声明了时，包括iostream +我甚至尝试使用ost...

问错误C2065：'cout‘：未声明的标识符
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问错误C2065：'cout‘：未声明的标识符EN