The long long type denotes an integral data type that is at least as large as a long int. On 32-bit architectures and 64-bit architectures, long long occupies 64 bits (eight bytes). Although long long is not defined by theANSI/ISO C++ standard yet, it is defined by the C9X draft standard and in practice, many platforms (Win32, Unix, Linux and others) already support it. As with other integral types, a long long can also be unsigned:
unsigned long long distance_to_star;
You can add the affixes "ll" and "LL" to a literal integer to indicate a long long type:
#define year_light_in_km 9460800000000LL
Similarly, you can add the affixes "ull" and "ULL" to a literal integer to indicate an unsigned long long type.