C++ Class example

class.cpp

#include <iostream>
using namespace std;

class Add
{ public: short S1;
  int f(int x)
    { return S1 + ++x;}
  int A(short a, short b);
} K1;
int Add::A(short a, short b)
{
  this->S1 += a*b;
  return this->S1;
};

int main() {
    K1.S1 = 2;
    K1.f(2);
    K1.A(0, 1);
    cout << K1.S1;    // Result is 2
    return 0;
}