Naming a Text file in C++

I am working on a small project, and I need to be able to let the user name there txt file. I have tried many things, none have worked.

Also, I'm not exactly the best C++ programmer, so if you could, please explain your answers with a lot of detail.

But what I want is:

char filename;
cin>>filename;
ifstream inputFile;
inputFile.open(filename, ".txt", ios::in);

Obviously, the last line of code is wrong, but thats what I would like to work. I have tried:

strcat(filename, ".txt");
inputFile.open(filename, ios::in);

And it did not work either.

>>12
The best thing about C++ is the STL, and strings.