How many bytes is unsigned long long?

Question

How many bytes is unsigned long long? Is it the same as unsigned long long int ?

Answer 1

It must be at least 64 bits. Other than that it's implementation defined.

Strictly speaking, unsigned long long isn't standard in C++ until the C++0x standard. unsigned long long is a 'simple-type-specifier' for the type unsigned long long int (so they're synonyms).

The long long set of types is also in C99 and was a common extension to C++ compilers even before being standardized.