File is not creating if not exist.

[prakhargvp]

fstream file;
file.open(fname.c_str(),fstream::out | fstream::in);

[prakhargvp]

fstream::in does not create file. So file open the file in out mode then in input and out mode.

fstream file;
file.open(fname.c_str(),fstream::out, fstream::app);

[rishabhgupta1322]

what does c_str function do and how does it work?

[prakhargvp]

@rishabhgupta1322 c_str is a method in string object. It convert string type object into c string (character array).
Since so many function accept character string as argument not string type object.
SO that's why we are using stringObject.c_str() method to get character array.