What is the size of an object of an empty class in C++?

The following is an example to find the size of object of an empty class.

Example

 Live Demo

#include <bits/stdc++.h>
using namespace std;
class p1 {
   public:
   void first() {
      cout << "\nThe parent class p1 function is called.";
   }
};
class p2
{ };
int main() {
   cout << "The size of non-empty class p1 = " << sizeof(p1);
   cout << "\nThe size of empty class p2 = " << sizeof(p2);
   p2 p;
   cout << "\nThe size of object of empty class p2 = " << sizeof(p);
   p1 o;
   cout << "\nThe size of object of non-empty class p1 = " << sizeof(o);
   return 0;
}

Output

The size of non-empty class p1 = 1
The size of empty class p2 = 1
The size of object of empty class p2 = 1
The size of object of non-empty class p1 = 1

In the above program, an empty class p2 is created.

class p2
{ };

The size of classes and objects is printed as follows −

cout << "The size of non-empty class p1 : " << sizeof(p1);
cout << "\nThe size of empty class p2 : " << sizeof(p2);
p2 p;
cout << "\nThe size of object of empty class : " << sizeof(p);
p1 o;
cout << "\nThe size of object of non-empty class p1 : " << sizeof(o);