[Use language = C++]
#include <iostream>
using namespace std;
 
class String
{
    int len;
    char *p;
 
    public:
        String ()
        {
            cout << "default constructor " << this << endl;
            len = 0;
            p = NULL;
        }
        String (const char *s)
        {
            cout << "String constructor called " << s << endl;
            len = strlen(s);
            p = new char[len + 1];
            strcpy(p, s);
        }
        String (const String &s)
        {
            cout << "Copy constructor invoked " << s.p << endl;;
            len = s.len;
            p = new char[len + 1];
            strcpy(p, s.p);
        }
        ~String ()
        {
             cout << "destructor invoked\n";
            delete p;
        }
        void display(void)
        {
            cout << p << "\t address of p = " << &p << "\tobject this = " <<  this << endl;
        }
        void operator = (const String &s)
        {
            cout << "assignment operator invoked\n";
            len = s.len;
            p = new char[len + 1];
            strcpy(p, s.p);
        }
        friend String operator + (const String &s, const String &t);
};
 
String operator + (const String &s, const String &t)
{
    String temp;
 
    temp.len = s.len + t.len;
    temp.p = new char[temp.len + 1];
    strcpy(temp.p, s.p);
    strcat(temp.p, t.p);
 
    cout << "temp = "; temp.display();
    return temp;
}
 
main()
{
    String s1("abcdefg"), s2("hijklmn ");
 
    String s3 = s2 + s1 ;
 
    cout << "S1 = "; s1.display();
    cout << "S2 = "; s2.display();
    cout << "S3 = "; s3.display();
 
    return 0;
}