“Error: ` cout ‘was not declared in this scope”

code is:
#include <iostream>
int main(int argc, char *argv[])
{
    cout << “hello world” << endl;
}
when compile the erro info is below:
[email protected] ~/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;
}
or
#include <iostream>
using namespace std;
int main(int argc, char *argv[])
{
     cout << “hello world” << endl;
}

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