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

Answer: 
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.
Use the operator `sizeof`, it will give you the size of a type expressed in byte. One byte is eight bits. See the following program:

```
#include <iostream>

int main(int,char**)
{
 std::cout << "unsigned long long " << sizeof(unsigned long long) << "\n";
 std::cout << "unsigned long long int " << sizeof(unsigned long long int) << "\n";
 return 0;
}

```