Нужно разобраться в коде

include <iostream>
 
using namespace std;
 
class ComplexNumbers {
private:
    double a, b, i;
 
public:
 
    ComplexNumbers(double A = 0, double B = 0) {
        a = A;
        b = B;
        i = 1;
    }
 
    ComplexNumbers(const ComplexNumbers& complex) : a(complex.a), b(complex.b) {}
 
    void seta(double A) {
        a = A;
    }
 
    void setb(double B) {
        b = B;
    }
 
    void setab(double A, double B) {
        a = A;
        b = B;
    }
 
    double geta() {
        return a;
    }
 
    double getb() {
        return b;
    }
 
    double LengthComplex() {
        return abs(sqrt((a * a) + (b * b)));
    }
 
    friend ComplexNumbers operator+(const ComplexNumbers& c1, const ComplexNumbers& c2) {
        return ComplexNumbers(c1.a + c2.a, c1.b + c2.b);
    }
 
    friend ComplexNumbers operator-(const ComplexNumbers& c1, const ComplexNumbers& c2) {
        return ComplexNumbers(c1.a - c2.a, c1.b - c2.b);
    }
 
    friend ComplexNumbers operator*(const ComplexNumbers& c1, const ComplexNumbers& c2) {
        return ComplexNumbers(((c1.a * c2.a) + (c1.b * c2.b) * -1), ((c1.b * c2.a) + (c1.a * c2.b)));
    }
 
    friend ComplexNumbers operator/(const ComplexNumbers& c1, const ComplexNumbers& c2) {
        return ComplexNumbers((((c1.a * c2.a) + (c1.b * c2.b)) / ((c2.a * c2.a) + (c2.b * c2.b))), (((c1.b * c2.a) - (c1.a * c2.b)) / ((c2.a * c2.a) + (c2.b * c2.b))));
    }
 
    bool operator>(ComplexNumbers& complex) {
        return LengthComplex() > complex.LengthComplex();
    }
 
    bool operator<(ComplexNumbers& complex) {
        return LengthComplex() < complex.LengthComplex();
    }
 
    bool operator==(ComplexNumbers& complex) {
        return LengthComplex() == complex.LengthComplex();
    }
 
    bool operator!=(ComplexNumbers& complex) {
        return LengthComplex() != complex.LengthComplex();
    }
 
    friend ostream& operator<<(ostream& out, const ComplexNumbers& complex) {
        if (complex.i == 0) {
            if (complex.a == 0 && complex.b == 0) out << "0\n";
            else if (complex.a == 0) out << complex.b << endl;
            else if (complex.b == 0) out << complex.a << endl;
            else if (complex.b > 0) out << complex.a << " + " << complex.b << endl;
            else out << complex.a << " " << complex.b << endl;
        }
        else {
            if (complex.a == 0 && complex.b == 0) out << "0\n";
            else if (complex.a == 0) out << complex.b << "*i\n";
            else if (complex.b == 0) out << complex.a << endl;
            else if (complex.b > 0) out << complex.a << " + " << complex.b << "*i\n";
            else out << complex.a << " " << complex.b << "*i\n";
        }
        return out;
    }
 
    friend istream& operator>> (istream& is, ComplexNumbers& complex) {
        is >> complex.a >> complex.b;
        return is;
    }
 
};
 
 
 
 
int main() {
 
 
    ComplexNumbers c1{ 1,3 }, c2;
 
    cin >> c2;//{4,-5}
 
    cout << "Com1: " << c1 << "Com2: " << c2;
 
    cout << "Sum: ";
    cout << c1 + c2;
 
    c1.setab(-2, 1);
    c2.setab(3, 5);
 
    cout << endl << "Com1: " << c1 << "Com2: " << c2;
 
    cout << "Sub: ";
    cout << c1 - c2;
 
    c1.setab(1, -1);
    c2.setab(3, 6);
 
    cout << endl << "Com1: " << c1 << "Com2: " << c2;
 
    cout << "Multi: ";
    cout << c1 * c2;
 
    c1.setab(13, 1);
    c2.setab(7, -6);
 
    cout << endl << "Com1: " << c1 << "Com2: " << c2;
 
    cout << "Div: ";
    cout << c1 / c2;
 
    c1.setab(2, 2);
    c2.setab(3, 2);
 
    cout << "Large: ";
    cout << (c1 > c2) << endl;
 
    cout << "Less: ";
    cout << (c1 < c2) << endl;
 
    c1.setab(2, 2);
    c2.setab(2, 2);
 
    cout << endl << "Com1: " << c1 << "Com2: " << c2;
 
    cout << "Equally: ";
    cout << (c1 == c2) << endl;
 
    cout << "Not equally: ";
    cout << (c1 != c2) << endl;
 
 
 
}