A simple demonstration of inheritance

inheritance.cpp

#include <iostream>

struct Superclass {
  int x{};
};

struct Subclass : public Superclass {
 public:
  int y{};
  int foo() { return x + y; }
};

int main() {
  Subclass sub;
  sub.x = 2;
  sub.y = 2;
  std::cout << sub.foo();
}