Write a program to overload binary '+' operator.

 here's an example program to overload the binary + operator:

#include <iostream>
using namespace std;
class Number {
    int num;
public:
    Number(int n=0) {
        num = n;
    }
    Number operator+(Number const &obj) {
        Number res;
        res.num = num + obj.num;
        return res;
    }
    void display() {
        cout << "Number: " << num << endl;
    }
};
int main() {
    Number n1(10);
    Number n2(20);
    Number n3 = n1 + n2; // using overloaded '+' operator
    n3.display();
    return 0;
}

In the above program, we have created a class named Number with one data member num. We have defined a constructor with a default argument of 0. We have also overloaded the binary + operator using the operator+ function.

In the operator+ function, we have created a Number object named res. We have added the num values of the two Number objects (this->num and obj.num) and assigned the result to res.num. Finally, we have returned the res object.

In the main function, we have created two Number objects n1 and n2 with values 10 and 20 respectively. We have added these two objects using the overloaded + operator and assigned the result to a third Number object n3. Finally, we have displayed the value of n3 using the display function. The output of the program will be:

Number: 30