C++: Why size of an empty class object is 1 byte ?

Question

Please explain with an example

Answer 1

Consider the following cases case of empty classes contained in another.

class Empty
{ };

class TwoEmpties
{
  Empty a;
  Empty b;
};

You may want the addresses of the two members, &TwoEmpties::a and &TwoEmpties::b, to be different. For this to happen they must have size > 1. (or the compiler would have to add padding between them, which would in turn complicate the rules for when and where the compiler can add padding to classes.)