I am getting garbage value while using operator overloading

Question

I have got a question -

Write a c++ program to calculate Gross salary(net salary+DA+TDS) for 4 employees where overload the + operator for getting the total salary obtained by all the 4 employees. Also get the average salary of employees by operator overloading. display all the details of all four employees. Also display who is getting highest salary. Employee salary must be entered by the user at runtime.

#include<iostream>
#include<string>
using namespace std;
class Employee
{
    private:
        int net_salary, DA, TDA, Gross_salary;
    public:
        void SetData(int net, int da, int tda, int gross)
        {
            net_salary=net;
            DA=da;
            TDA=tda;
            Gross_salary=gross;
        }
        void GetData()
        {
            cout << "Enter net salary: "<<net_salary;
            DA = (15*net_salary)/100; //Declaring the value of DA as 15% and calculating the amount 
            //on basis of net salary of the employee
            TDA = (10*net_salary)/100; //Declaring the value of TDA as 10% and calculating the amount
            // of TDA on basis of net salary
            Gross_salary = net_salary+DA+TDA;
        }
        void DisplayData()
        {
            cout << "Total Gross Salary = "<<Gross_salary;
        }
        Employee operator +(Employee e)
        {
            Employee temp;
            temp.Gross_salary=Gross_salary+e.Gross_salary;
            return temp;
            }
};
int main()
{
    Employee e1,e2,e3,e4,e5;
    e1.GetData();
    e2.GetData();
    e3.GetData();
    e4.GetData();
    e5=e1+e2+e3+e4;
    e5.DisplayData();
    return 0;
}

Answer 1

The trouble comes from the absent initial values for the data members.

// ...
cout << "Enter net salary: " << net_salary;
DA = (15*net_salary)/100;
// ...

Here, in the GetData() member function, that is called after you have created five default initialized objects e1,e2,e3,e4,e5 of Employee type. The net_salary here is of built-in type and is default initialized by the implicitly defined default constructor, hence it has an undefined value. Then you assign this undefined value to the DA and so on in the body of the GetData().

You should not look toward the SetData() as a solution for this, since it should act as a setter method, a method used to modify an already initialized object. You will need to implement constructor(s) for your class, or you can at least supply in-class initializers for the members, like so:

// ...
int net_salary=0, DA=0, TDA=0, Gross_salary=0;
// ...

---

I can't help but notice that GetData() either has a confusing name or tries to do more than it is intended to do. It does some internal computation, which is ok for a GetSomething function, but it modifies internal data while does some prints.

Also, note the line (in the GetData()):

Enter net salary: 

Will be followed by an output, you won't be given a chance to input any data in the GetData(). I assume, you may want to create a constructor that takes input from a user, and then call a function to do all the needed computations.