Why is the size of an empty class not zero in C++?

The standard does not allow objects of size 0 since that would make it possible for two distinct objects to have the same memory address. That’s why even empty classes must have a size of (at least) 1 byte.

Example,

#include<iostream>
using namespace std;
class Test
{
 //empty class
};
int main()
{
    cout << sizeof(Test);
    return 0;
}

Output: 1