Question

Having code:

int** a = new int*[2];
a[0] = new int(1);
a[1] = new int(2);
cout << "a[0] " << a[0] << '\n';
cout << "a[1] " << a[1] << '\n';
cout << "a[2] " << a[2] << '\n';
cout << "a[0] + 1 " << a[0] + 1 << '\n';//WHY THIS ISN'T == a[1] ?
cout << "*(a + 1): " << *(a + 1) << '\n'; //WHY THIS IS == a[1] ?
cout << "a[0] - a[1] " << static_cast<int>(a[0] - a[1])<< '\n';//WHY THIS IS == 16 not 4?

cout << sizeof(int**);

Questions are included right next to relevant lines in code.

Answer 1

a[0] + 1 means that 1 is added to the value stored in a[0]

*(a + 1) means that 1 * sizeof(int) is added to the memory address of a, and then the value at that location is accessed, meaning you get a[1]

Read more about pointers here.

As for your last question, there is no guarantee it will print any specific value, since the two memory addresses do not have to be contiguous. For me it prints -4 for example.