alright, I'm using linux 9.0 and working in c++:
my question is:

if I use the code,
void Node::Read_In ( ifstream &Nin )
{
Nin.getline ( Kdata, 4, '\n' );
Kdata[4] = '\0';
}

I keep getting the error message for the Nin.getline ( Kdata, 4, '\n' ); line.

Node.cxx: In member function `void Node::Read_In(std::fstream&)':
Node.cxx:24: invalid use of undefined type `struct std::basic_fstream<char,
std::char_traits<char> >'
/usr/include/c++/3.2.2/iosfwd:92: declaration of `struct
std::basic_fstream<char, std::char_traits<char> >'

the file being passed in was opened by concatenating two strings together s1+=s2, then using the command
ifstream Fin;
Fin.open ( s1.c_str(), ios::in );

any ideas?

the Fin.open can be either ifstream or fstream, I'm getting the same message for both cases.