解决问题 “error: `cout' was not declared in this scope”

最新推荐文章于 2024-08-24 22:20:06 发布

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本文介绍了一个常见的C++编程错误：使用cout和endl时出现的未声明错误，并提供了两种解决方案：一是通过显式地使用std命名空间的成员；二是引入using namespace std;来简化代码。

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code is:
#include <iostream>

int main(int argc, char *argv[])
{
cout << "hello world" << endl;
}

when compile the erro info is below:

test@HuiT43 ~/sutdy $ g++ scat.cpp -o scat
scat.cpp: In function `int main(int, char**)':
scat.cpp:12: error: `cout' was not declared in this scope
scat.cpp:12: error: `endl' was not declared in this scope

the reason is :

This is becuase C++ 1998 requires cout and endl be called 'std::cout' and 'std::endl', or that a proper using directives such as 'using namespace std;' be used.

#include <iostream>

int main(int argc, char *argv[])
{
std::cout << "hello world" << std::endl;
}

#include <iostream>

using namespace std;

int main(int argc, char *argv[])
{
cout << "hello world" << endl;
}