One note: there is the concept of a large file. These are files that exceed the capacity of the number of bytes a 32 bit file pointer can access. i.e., more than ~4.2GB of data.

This depends on your OS and sometimes the filesystems. If there is a problem with large files the fopen man page may mention how to deal with them. Frequently there is a call - maybe named like "fopen64" - that deals with largefiles. Check your man pages.