fseek() and ftell() work only for files < 2,147,483,647 bytes
fseeko64() and ftello64() from <stdio.h> can deal with files up to 18,446,744,073,709,552,000 bytes
the printf format for unsigned long long val is %I64d
eg. Obtaining the file dimension (this code was tested with GNU GCC compiler (MinGW/Cygwin) from code::blocks)