title: error C2039: 'string' : is not a member of 'std', header file problem
body: <p>I am having problems with a class I am writing. I have split the class into a .h file that defines the class and an .cpp file that implements the class.</p>
  
  <p>I receive this error in Visual Studio 2010 Express:</p>
  
  <p>error C2039: 'string' : is not a member of 'std'</p>
  
  <p>This is the header FMAT.h</p>
  
  <pre><code>class string;
  
  class FMAT {
  public:
      FMAT(); 
  
      ~FMAT(); 
  
      int session();              
  
  private:
      int manualSession();    
      int autoSession();      
  
      int     mode;       
      std::string instructionFile;    
  
  };
  </code></pre>
  
  <p>This is the implementation file FMAT.cpp</p>
  
  <pre><code>#include &lt;iostream&gt;
  #include &lt;string&gt;
  #include "FMAT.h"
  
  FMAT::FMAT(){
  
      std::cout &lt;&lt; "manually (1) or instruction file (2)\n\n";
      std::cin &gt;&gt; mode;
      if(mode == 2){
          std::cout &lt;&lt; "Enter full path name of instruction file\n\n";
          std::cin &gt;&gt; instructionFile;
      }
  
  }
  
  int FMAT::session(){
  
      if(mode==1){
          manualSession();
      }else if(mode == 2){
          autoSession();
      }
  
      return 1;
  }
  
  int FMAT::manualSession(){
      //more code
      return 0;
  }
  </code></pre>
  
  <p>this is the main file that uses this class</p>
  
  <pre><code>#include "FMAT.h"
  
  int main(void)
  {
      FMAT fmat;      //create instance of FMAT class
  
      fmat.session();     //this will branch to auto session or manual session
  
  }
  </code></pre>
  
  <p>My inability to fix this error is probably a result of me not understanding how to properly structure a class into separate files. Feel free to provide some tips on how to handle multiple files in a c++ program.</p>