c++ ifstream undeclared identifier

I am in Visual Studio and am getting 'ifstream undeclared identifier' with this code (same for ofstream)

#include开发者_如何学编程 <iostream>
#include <iomanip>
#include <fstream>
void main()
{
    ifstream infile("file.txt");
    ofstream outfile("out.txt");
}

do I need to include something else?

You need to scope it. Use using namespace std; or preface ifstream and ostream with std::

For example, std::ifstream

Currently, the compiler does not know where these structures are defined (since they are declared/defined within the std namespace). This is why you need to scope your structures/functions in this case.

You need to reference the standard namespace (std). Try this:

#include <iostream>
#include <iomanip>
#include <fstream>
void main()
{
    std::ifstream infile("file.txt");
    std::ofstream outfile("out.txt");
}

You can use

using namespace std;

instead of prefixing everyline with std::