It all depends on what level, or OS you really want to target.
1. High level - C++
If you just want to Open/Create files for reading/writing - you can simply use
C filehandling or C++ streams (fstream, ifstream, ofstream)
Note these do not do stuff related to file attributes/security/permissions or any OS related stuff like that.
These function are portable.
You will find information on C/C++ I/O and File Handling in any C/C++ programming book.
2. Operating System function calls.
All OS have function calls for file/directeory handling. They also have function for dealing with file permissions/security/attributes etc.
These calls are OS dependent so are not portable.
You will need a book on the particular OS to get this type of information.
3. At an even Lower level -
Creating and implementing FileSystems.
We are into serious Device Driver territory on this one.